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The development of vascularized scaffolds remains one of the major challenges in tissue engineering, and co-culturing with endothelial cells is known as one of the possible approaches for this purpose. In this approach, optimization of cell culture conditions, scaffolds, and fabrication techniques is needed to develop tissue equivalents that will enable in vitro formation of a capillary network. Prevascularized equivalents will be more physiologically comparable to the native tissues and potentially prevent insufficient vascularization after implantation. This study aimed to culture human umbilical vein endothelial cells (HUVECs), alone or in co-culture with fibroblasts, on collagen scaffolds prepared by simple fabrication approaches for in vitro prevascularization. Different concentrations and ratios of HUVECs and fibroblasts seeded on collagen gel and sponge scaffolds under several culture conditions were examined. Cell viability, scaffolds morphology, and structure were analyzed. Collagen gel scaffolds showed good cell proliferation and viability, with higher proliferation rates for cells cultured in a 2:1 (fibroblasts: HUVECs) ratio and kept in endothelial cell growth medium. However, these matrices were unable to support endothelial cell sprouting. Collagen sponges were highly porous and showed good cell viability. However, they became fragile over time in culture, and they still lack signs of vascularization. Collagen scaffolds were a good platform for cell growth and viability. However, under the experimental conditions of this study, the HUVEC/fibroblast-seeded scaffolds were not suitable platforms to generate in vitro prevascularized equivalents. Our findings will be a valuable starting point to optimize culture microenvironments and scaffolds during fabrication of prevascularized scaffolds.
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Ingeniería de Tejidos , Andamios del Tejido , Humanos , Andamios del Tejido/química , Ingeniería de Tejidos/métodos , Células Endoteliales de la Vena Umbilical Humana , Colágeno , Fibroblastos , Neovascularización FisiológicaRESUMEN
PURPOSE: The SHILLA™ Growth Guidance system is a stainless-steel rod and screw system used for Early Onset Scoliosis which incorporates a unique flanged set screw designed to capture the rod, while allowing it to slide as the patient grows. Concomitant with this design is the potential for generation of wear debris and for an inflammatory host response. We hypothesized that the magnitude of the host response adjacent to the unlocked screws and rods would be greater than the host response to the locked rod/screws. METHODS: Seven tissue samples adjacent to locked (3) and unlocked screws (4) from three SHILLA patients (mean implantation time of 19 post-operative months) with infantile idiopathic scoliosis were obtained as part of an explant analysis protocol during a PMDA-approved clinical trial in Japan. Gross appearance, high-resolution radiographs, and histology were assessed. ISO Standard 10993 Part 6 was used to assess the host response. RESULTS: All three locked screw had no metallosis. In contrast, metallosis for unlocked screw tissue samples were rated as "ubiquitous" (2/4), "focal" (1/4), or "absent" (1/4). Microscopic metallic debris was found intracellularly and within interstices of fibrous connective tissues more frequently adjacent to unlocked screws compared to locked screws. Cell type and population scoring consistently showed a modestly larger inflammatory response (macrophages) in the unlocked tissue samples. CONCLUSIONS: The peri-prosthetic tissue response to the unlocked rods/screws had a higher reactivity grade (slight reaction, Δ = 4.0) per ISO 10993 Part 6 compared to the locked screws in three patients with the SHILLA™ Growth Guidance scoliosis system.
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Escoliosis , Fusión Vertebral , Tornillos Óseos/efectos adversos , Humanos , Japón , Radiografía , Escoliosis/cirugía , Fusión Vertebral/efectos adversos , Fusión Vertebral/métodos , Acero InoxidableRESUMEN
Articular cartilage has unique load-bearing properties but has minimal capacity for intrinsic repair. Here, we used three-dimensional weaving, additive manufacturing, and autologous mesenchymal stem cells to create a tissue-engineered, bicomponent implant to restore hip function in a canine hip osteoarthritis model. This resorbable implant was specifically designed to function mechanically from the time of repair and to biologically integrate with native tissues for long-term restoration. A massive osteochondral lesion was created in the hip of skeletally mature hounds and repaired with the implant or left empty (control). Longitudinal outcome measures over 6 months demonstrated that the implant dogs returned to normal preoperative values of pain and function. Anatomical structure and functional biomechanical properties were also restored in the implanted dogs. Control animals never returned to normal and exhibited structurally deficient repair. This study provides clinically relevant evidence that the bicomponent implant may be a potential therapy for moderate hip osteoarthritis.
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BACKGROUND: The objective of this study was to evaluate the host response to an interspinous process device [Device for Intervertebral Assisted Motion (DIAM®)] based on a series of nine spine explants with a mean post-operative explant time of 35 months. METHODS: Explanted periprosthetic tissues were processed for histology and stained with H&E, Wright-Giemsa stain, and Oil Red O. Brightfield and polarized light microscopy were used to evaluate the host response to the device and the resultant particulate debris. The host response was graded per ASTM F981-04. Quantitative histomorphometry was used to characterize particle size, shape, and area per ASTM F1877-05. The presence or absence of bone resorption was also evaluated when bony tissue samples were provided. RESULTS: Periprosthetic tissues demonstrated a non-specific foreign body response composed of macrophages and foreign body giant cells to the DIAM® device in most of the accessions. The foreign body reaction was not the stated reason for explantation in any of the accessions. Per ASTM F981-04, a "very slight" to "mild" to "moderate" chronic inflammatory response was observed to the biomaterials and particulate, and this varied by tissue sample and accession. Particle sizes were consistent amongst the explant patients with mean particle size on the order of several microns. Osteolysis, signs of toxicity, necrosis, an immune response, and/or device related infection were not observed. CONCLUSIONS: Cyclic loading of the spine can cause wear in dynamic stabilization systems such as DIAM®. The fabric nature of the DIAM® device's polyethylene terephthalate jacket coupled with the generation of polymeric particulate debris predisposes the device to a foreign body reaction consisting of macrophages and foreign body giant cells. Although not all patients are aware of symptoms associated with a foreign body reaction to a deeply implanted device, surgeons should be aware of the host response to this device.
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BACKGROUND: The effects of recombinant human bone morphogenetic protein-2 (rhBMP-2) on pedicle screw pullout force and its potential to improve spinal fixation have not previously been investigated. rhBMP-2 on an absorbable collagen sponge (ACS) carrier was delivered in and around cannulated and fenestrated pedicle screws in a sheep lumbar spine instability model. Two control groups (empty screw and ACS with buffer) were also evaluated. We hypothesized that rhBMP-2 could stimulate bone growth in and around the cannulated and fenestrated pedicle screws to improve early bone purchase. METHODS: Eight skeletally mature sheep underwent destabilizing laminectomies at L2-L3 and L4-L5 followed by stabilization with pedicle screw and rod constructs. An ACS carrier was used to deliver 0.15 mg of rhBMP-2 within and around the cannulated and fenestrated titanium pedicle screws. Biomechanics and histomorphometry were used to evaluate the early term results at 6 and 12 postoperative weeks. RESULTS: rhBMP-2 was unable to improve bony purchase of the cannulated and fenestrated pedicle screws compared to both control groups. Although rhBMP-2 groups had pullout forces that were less than both control groups, both rhBMP-2 groups had pullout force values exceeding 2,000 N, which was comparable to previously published results for unmodified pedicle screws. Significant differences in the percentages of bone in peri-screw tissues was not observed amongst the four treatment groups. Microradiography and quantitative histomorphometry showed that at 6 weeks, rhBMP-2 induced peri-screw remodeling regions containing peri-implant bone which was hypodense with respect to surrounding native trabeculae. A moderate correlation between biomechanical pullout variables and histomorphometry data was observed. CONCLUSIONS: The design of the cannulated and fenestrated pedicle screw was able to facilitate new bone formation to achieve high pullout forces. However, delivery of rhBMP-2 should be carefully controlled to prevent excessive bone remodeling which could cause early screw loosening.
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BACKGROUND CONTEXT: Opioid use is prevalent in the management of pre- and postoperative pain in patients undergoing spinal fusion. There is evidence that opioids downregulate osteoblasts in vitro, and a previous study found that morphine delays the maturation and remodeling of callus in a rat femur fracture model. However, the effect of opioids on healing of spinal fusion has not been investigated before. Isolating the effect of opioid exposure in humans would be limited by the numerous confounding factors that affect fusion healing. Therefore, we have used a well-established rabbit model to study the process of spinal fusion healing that closely mimics humans. PURPOSE: The objective of this work was to study the effect of systemic opioids on the process of healing of spinal fusion in a rabbit posterolateral spinal fusion model. STUDY DESIGN/SETTING: This is a preclinical animal study. MATERIALS AND METHODS: Twenty-four adult New Zealand white rabbits were studied in two groups after approval from the Institutional Animal Care and Use Committee (IACUC). The opioid group (n=12) received 4 weeks' preoperative and 6 weeks' postoperative transdermal fentanyl. Serum fentanyl levels were measured just before surgery and 4 weeks postoperatively to ensure adequate levels. The control group (n=12) received only perioperative pain control as necessary. All animals underwent a bilateral L5-L6 posterolateral spinal fusion using iliac crest autograft. Animals were euthanized at the 6-week postoperative time point, and assessment of fusion was done by manual palpation, plain radiographs, microcomputed tomography (microCT), and histology. RESULTS: Twelve animals in the control group and 11 animals in the opioid group were available for analysis at the end of 6 weeks. The fusion scores on manual palpation, radiographs, and microCT were not statistically different. Three-dimensional microCT morphometry found that the fusion mass in the opioid group had a lower bone volume (p=.09), a lower trabecular number (p=.02), and a higher trabecular separation (p=.02) compared with the control group. Histologic analysis found areas of incorporation of autograft and unincorporated graft fragments in both groups. In the control group, there was remodeling of de novo woven bone to lamellar organization with incorporation of osteocytes, formation of mature marrow, and relative paucity of hypertrophied osteoblasts lining new bone. Sections from the opioid group showed formation of de novo woven bone, and hypertrophied osteoblasts were seen lining the new bone. There were no sections showing lamellar organization and development of mature marrow elements in the opioid group. Less dense trabeculae on microCT correlated with histologic findings of relatively immature fusion mass in the opioid group. CONCLUSIONS: Systemic opioids led to an inferior quality fusion mass with delay in maturation and remodeling at 6 weeks in this rabbit spinal fusion model. These preliminary results lay the foundation for further research to investigate underlying cellular mechanisms, the temporal fusion process, and the dose-duration relationship of opioids responsible for our findings.
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Analgésicos Opioides/efectos adversos , Fusión Vertebral/métodos , Cicatrización de Heridas/efectos de los fármacos , Analgésicos Opioides/uso terapéutico , Animales , Trasplante Óseo/efectos adversos , Trasplante Óseo/métodos , Vértebras Lumbares/cirugía , Conejos , Fusión Vertebral/efectos adversos , Trasplante Autólogo/efectos adversos , Trasplante Autólogo/métodosRESUMEN
BACKGROUND CONTEXT: Adipokines are secreted by white adipose tissue and have been associated with fracture healing. Our goal was to report the temporal expression of adipokines during spinal fusion in an established rabbit model. PURPOSE: Our goal was to report the temporal expression of adipokines during spinal fusion in an established rabbit model. STUDY DESIGN: The study design included a laboratory animal model. METHODS: New Zealand white rabbits were assigned to either sham surgery (n=2), unilateral posterior spinal fusion (n=14), or bilateral posterior spinal fusion (n=14). Rabbits were euthanized 1-6 and 10 weeks out from surgery. Fusion was evaluated by radiographs, manual palpation, and histology. Reverse transcription-polymerase chain reaction on the bone fusion mass catalogued the gene expression of leptin, adiponectin, resistin, and vascular endothelial growth factor (VEGF) at each time point. Results were normalized to the internal control gene, glyceraldehyde-3-phosphate dehydrogenase (GAPDH) (2^ΔCt), and control bone sites (2^ΔΔCt). Quantitative data were analyzed by two-factor analysis of variance (p<.05). RESULTS: Manual palpation scores, radiograph scores, and histologic findings showed progression of boney fusion over time (p<.0003). The frequency of fusion by palpation after 4 weeks was 68.75%. Leptin expression in decortication and bone graft sites peaked at 5 weeks after the fusion procedure (p=.0143), adiponectin expression was greatest 1 week after surgery (p<.001), VEGF expression peaked at 4 weeks just after initial increases in leptin expression (p<.001), and resistin decreased precipitously 1 week after the fusion procedure (p<.001). CONCLUSIONS: Leptin expression is likely associated with the maturation phase of bone fusion. Adiponectin and resistin may play a role early on during the fusion process. Our results suggest that leptin expression may be upstream of VEGF expression during spinal fusion, and both appear to play an important role in bone spinal fusion.
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Adipoquinas/metabolismo , Trasplante Óseo/efectos adversos , Vértebras Lumbares/metabolismo , Complicaciones Posoperatorias/metabolismo , Fusión Vertebral/efectos adversos , Adipoquinas/genética , Animales , Gliceraldehído-3-Fosfato Deshidrogenasa (Fosforilante)/genética , Gliceraldehído-3-Fosfato Deshidrogenasa (Fosforilante)/metabolismo , Leptina/genética , Leptina/metabolismo , Vértebras Lumbares/cirugía , Conejos , Factor A de Crecimiento Endotelial Vascular/genética , Factor A de Crecimiento Endotelial Vascular/metabolismoRESUMEN
OBJECTIVE This study was designed with the following research objectives: 1) to determine the efficacy of facet fusion with recombinant human bone morphogenetic protein-2 (rhBMP-2) on an absorbable collagen sponge (ACS) in an ovine lumbar facet fusion model; 2) to radiographically and histologically compare the efficacy of lumbar facet fusion with rhBMP-2/ACS to facet fusion with an iliac crest bone graft (ICBG); and 3) to biomechanically compare lumbar facet fusion with rhBMP-2/ACS to lumbar posterolateral fusion (PLF) with ICBG. METHODS The efficacies of the 3 treatments to induce fusion were evaluated in an instrumented ovine lumbar fusion model. Eight sheep had 10 cm3/side ICBG placed as an onlay graft for PLF at L2-3. At the adjacent L3-4 level, 0.5 cm3/side ICBG was placed for facet fusion. Finally, 0.5 cm3/side rhBMP-2/ACS (0.43 mg/ml) was placed for facet fusion at L4-5. CT scans were obtained at 2, 4, and 6 months postoperatively with 2 reviewers conducting an evaluation of the 6-month results for all treated spinal levels. All 8 sheep were killed at 6 months, and all posterolateral instrumentation was removed at this time. The spines were then sectioned through L3-4 to allow for nondestructive unconstrained biomechanical testing of the L2-3 and L4-5 segments. All treated spinal levels were analyzed using undecalcified histology with corresponding microradiography. Statistical comparisons were made between the treatment groups. RESULTS The PLF with ICBG (ICBG PLF group) and the rhBMP-2 facet fusion (rhBMP-2 Facet group) treatment groups demonstrated similar levels of stiffness, with the rhBMP-2 Facet group having on average slightly higher stiffness in all 6 loading directions. All 8 levels in the autograft facet fusion treatment group demonstrated CT radiographic and histological fusion. All 8 levels in the rhBMP-2 Facet group showed bilateral CT radiographic and histological fusion. Six of 16 rhBMP-2/ACS-treated facet defects demonstrated small intraosseous hematomas or seromas. Four of the 8 levels (50%) in the ICBG PLF treatment group demonstrated bilateral histological fusion. Three of 8 levels in the ICBG PLF treatment group showed unilateral fusion. One of the 8 levels in the ICBG PLF treatment group demonstrated bilateral histological nonfusion. CONCLUSIONS Both rhBMP-2/ACS and autograft demonstrated 100% efficacy when used for facet fusion in the instrumented ovine model. However, the ICBG PLF treatment group only demonstrated a 50% bilateral fusion rate. Biomechanically, the ICBG PLF and rhBMP-2 Facet groups demonstrated similar stiffness in all 6 loading directions, with the rhBMP-2 Facet group having on average slightly higher stiffness in all directions.
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Conservadores de la Densidad Ósea/administración & dosificación , Proteína Morfogenética Ósea 2/administración & dosificación , Trasplante Óseo , Ilion/trasplante , Vértebras Lumbares/cirugía , Fusión Vertebral/métodos , Factor de Crecimiento Transformador beta/administración & dosificación , Implantes Absorbibles , Animales , Fenómenos Biomecánicos , Trasplante Óseo/efectos adversos , Colágeno , Implantes de Medicamentos , Femenino , Vértebras Lumbares/diagnóstico por imagen , Vértebras Lumbares/efectos de los fármacos , Microrradiografía , Modelos Animales , Proteínas Recombinantes/administración & dosificación , Ovinos , Fusión Vertebral/efectos adversos , Tomografía Computarizada por Rayos X , Resultado del TratamientoRESUMEN
BACKGROUND: Recombinant human bone morphogenetic protein-2 (rhBMP-2) is a powerful osteoinductive morphogen capable of stimulating the migration of mesenchymal stem cells (MSCs) to the site of implantation and inducing the proliferation and differentiation of these MSCs into osteoblasts. Vertebral end-plate and vertebral body resorption has been reported after interbody fusion with high doses of rhBMP-2. In this study, we investigated the effects of 2 rhBMP-2 doses on peri-implant bone resorption and bone remodeling at 7 time points in an end-plate-sparing ovine interbody fusion model. METHODS: Twenty-one female sheep underwent an end-plate-sparing discectomy followed by interbody fusion at L2-L3 and L4-L5 using a custom polyetheretherketone (PEEK) interbody fusion device. The PEEK interbody device was filled with 1 of 2 different doses of rhBMP-2 on an absorbable collagen sponge (ACS): 0.13 mg (1×) or 0.90 mg (7×). Bone remodeling and interbody fusion were assessed via high-resolution radiography and histological analyses at 1, 2, 3, 4, 8, 12, and 20 weeks postoperatively. RESULTS: Peri-implant bone resorption peaked between 3 and 8 weeks in both the 1× and the 7× rhBMP-2/ACS-dose group. Osteoclastic activity and corresponding peri-implant bone resorption was dose-dependent, with moderate-to-marked resorption at the 7×-dose level and less resorption at the 1×-dose level. Both dose (p < 0.0007) and time (p < 0.0025) affected bone resorption significantly. Transient bone-resorption areas were fully healed by 12 weeks. Osseous bridging was seen at all but 1 spinal level at 12 and at 20 weeks. CONCLUSIONS: In the ovine end-plate-sparing interbody fusion model, rhBMP-2 dose-dependent osteoclastic resorption is a transient phenomenon that peaks at 4 weeks postoperatively. CLINICAL RELEVANCE: Using the U.S. Food and Drug Administration (FDA)-approved rhBMP-2 concentration and matching the volume of rhBMP-2/ACS with the volume of desired bone formation within the interbody construct may limit the occurrence of transient bone resorption.
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Proteína Morfogenética Ósea 2/farmacología , Remodelación Ósea/efectos de los fármacos , Fusión Vertebral/métodos , Factor de Crecimiento Transformador beta/farmacología , Animales , Proteína Morfogenética Ósea 2/uso terapéutico , Discectomía , Relación Dosis-Respuesta a Droga , Femenino , Vértebras Lumbares/cirugía , Modelos Animales , Osteogénesis/efectos de los fármacos , Proteínas Recombinantes/farmacología , Proteínas Recombinantes/uso terapéutico , Ovinos , Factor de Crecimiento Transformador beta/uso terapéutico , Resultado del TratamientoRESUMEN
OBJECTIVE The objective of this study was to evaluate bone grafts consisting of rhBMP-2 on an absorbable collagen sponge with a ceramic composite bulking agent, rhBMP-2, directly on a ceramic-collagen sponge carrier or iliac crest bone graft (ICBG) in combination with local bone graft to effect fusion in a multisegmental instrumented ovine lumbar intertransverse process fusion model. METHODS Thirty-six sheep had a single treatment at 3 spinal levels in both the right and left intertransverse process spaces. Group 1 sheep were treated with 7.5 cm3 of autograft consisting of ICBG plus local bone for each intertransverse process space. For Groups 2-4, 4 cm3 of local bone was placed within the intertransverse process space followed by 4.5-5 cm3 of the rhBMP-2 graft material. Group 2 animals received 1.5 mg/cm3 rhBMP-2 on an absorbable collagen sponge with a commercial bone void filler consisting of Type I lyophilized collagen with a biphasic hydroxyapatite/ß-tricalcium phosphate ceramic with local bone. Group 3 animals received 0.75 mg/m cm3 of rhBMP-2 on a collagen ceramic sponge carrier with local bone. Group 4 animals received 1.35 mg/cm3 of rhBMP-2 on the same collagen ceramic sponge carrier with local bone. Sheep were euthanized 6 months postoperatively. Manual palpation, biomechanical testing, CT, radiography, and undecalcified histology were performed to assess the presence of fusion associated with the treatments. RESULTS All animals in Groups 2-4 that received grafts containing rhBMP-2 achieved radiographic and CT fusion at all 3 levels. In Group 1 (bone autograft alone), only 19% of the levels demonstrated radiographic fusion, 14% resulted in possible radiographic fusion, and 67% of the levels demonstrated radiographic nonfusion. Biomechanical testing showed that Groups 2-4 demonstrated similar stiffness of the L2-5 segment in all 6 loading directions, with each of the 3 groups having significantly greater stiffness than the autograft-only group. In Group 1, only 2 of 18 levels were rated as achieving bilateral histological fusion, with an additional 3 levels showing a unilateral fusion. The majority of the treated levels (13/18) in Group 1 were scored as histological nonfusions. There were no histological nonfusions in Groups 2 through 4. All 18 levels in Group 2 were rated as bilateral histological fusions. A majority (34/36) of the levels in Group 3 were rated as bilateral histological fusions, with 2 levels showing a unilateral fusion. A majority (35/36) of the levels in Group 4 were rated as bilateral histological fusions, with 1 level showing a unilateral fusion. CONCLUSIONS In the ovine multilevel instrumented intertransverse process fusion model, rhBMP-2 was able to consistently achieve CT, radiographic, biomechanical, and histological fusion. Compared with ICBG, the gold standard for bone grafting, rhBMP-2 was statistically superior at achieving radiographic and histological fusion.
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Proteína Morfogenética Ósea 2/administración & dosificación , Trasplante Óseo/métodos , Vértebras Lumbares/cirugía , Fusión Vertebral/métodos , Factor de Crecimiento Transformador beta/administración & dosificación , Trasplante Autólogo/métodos , Animales , Fenómenos Biomecánicos , Trasplante Óseo/instrumentación , Cerámica , Colágeno , Vértebras Lumbares/diagnóstico por imagen , Vértebras Lumbares/patología , Vértebras Lumbares/fisiopatología , Microrradiografía , Osteogénesis/efectos de los fármacos , Proteínas Recombinantes/administración & dosificación , Ovinos , Fusión Vertebral/instrumentación , Tapones Quirúrgicos de Gaza , Tomografía Computarizada por Rayos X , Trasplante Autólogo/instrumentaciónRESUMEN
The experiments reported here were designed to replicate and extend McCabe, Roediger, and Karpicke's (2011) finding that retrieval in category cued recall involves both controlled and automatic processes. The extension entailed identifying whether distinctive encoding affected 1 or both of these 2 processes. The first experiment successfully replicated McCabe et al., but the second, which added a critical baseline condition, produced data inconsistent with a 2 independent process model of recall. The third experiment provided evidence that retrieval in category cued recall reflects a generate-recognize strategy, with the effect of distinctive processing being localized to recognition. Overall, the data suggest that category cued recall evokes a generate-recognize retrieval strategy and that the subprocesses underlying this strategy can be dissociated as a function of distinctive versus relational encoding processes.
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Señales (Psicología) , Recuerdo Mental , Humanos , Modelos Psicológicos , Pruebas Psicológicas , Reconocimiento en PsicologíaRESUMEN
STUDY DESIGN: Fusion success with rhBMP-2 and autograft in titanium or PEEK corpectomy devices was evaluated in a sheep lumbar corpectomy model. The 6 treatment groups included titanium mesh or PEEK corpectomy devices filled with rhBMP-2 on a compression-resistant matrix (CRM) carrier; rhBMP-2 in a morselized absorbable collagen sponge (ACS) carrier combined with resorbable ceramic granules; and autograft. OBJECTIVE: The aim of this study was to determine fusion rates associated with 2 different preparations of rhBMP-2 as well as autograft in an instrumented ovine lumbar corpectomy model 6 months postoperatively. SUMMARY OF BACKGROUND DATA: Vertebral reconstruction with corpectomy devices requires bone graft. Bone graft substitutes have the potential to avoid a second operation, donor site pain, and attendant morbidity associated with autograft. METHODS: Twenty-four sheep in 6 treatment groups underwent lumbar corpectomy via a retroperitoneal trans-psoas approach. Spines were reconstructed with autograft, rhBMP-2 on a CRM, or rhBMP-2 on an ACS mixed with ceramic granules. Grafting materials were placed in either a titanium mesh or PEEK conduit in spines with internal fixation. Computed tomographic (CT) scans were evaluated for fusion. Undecalcified histology was used to evaluate for fusion as well as the amount and extent of graft incorporation and graft resorption. RESULTS: Regardless of corpectomy device used, rhBMP-2/CRM or rhBMP-2/ACS with MASTERGRAFT resulted in a 100% fusion rate. The autograft group had a lower (75%) radiographic fusion rate. Using either preparation of rhBMP-2 resulted in the length of the defect filling with solid bone. Autograft fragments and ceramic granules were incorporated into the fusion masses with much of the ceramic granules being resorbed by 6 months. CONCLUSION: Both of the rhBMP-2 formulations have the potential to effect bony fusion and vertebral reconstruction within the corpectomy devices.
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Autoinjertos/trasplante , Proteína Morfogenética Ósea 2/farmacología , Colágeno/farmacología , Fusión Vertebral , Columna Vertebral , Factor de Crecimiento Transformador beta/farmacología , Animales , Benzofenonas , Cerámica/farmacología , Femenino , Cetonas/farmacología , Polietilenglicoles/farmacología , Polímeros , Diseño de Prótesis , Proteínas Recombinantes/farmacología , Ovinos , Fusión Vertebral/instrumentación , Fusión Vertebral/métodos , Fusión Vertebral/estadística & datos numéricos , Columna Vertebral/diagnóstico por imagen , Columna Vertebral/efectos de los fármacos , Columna Vertebral/patología , Columna Vertebral/cirugíaRESUMEN
Mechanisms of restenosis in type 2 diabetes mellitus (T2DM) are incompletely elucidated, but advanced glycation end-product (AGE)-induced vascular remodeling likely contributes. We tested the hypothesis that AGE-related collagen cross-linking (ARCC) leads to increased downstream vascular resistance and altered in-stent hemodynamics, thereby promoting neointimal hyperplasia (NH) in T2DM. We proposed that decreasing ARCC with ALT-711 (Alagebrium) would mitigate this response. Abdominal aortic stents were implanted in Zucker lean (ZL), obese (ZO), and diabetic (ZD) rats. Blood flow, vessel diameter, and wall shear stress (WSS) were calculated after 21 days, and NH was quantified. Arterial segments (aorta, carotid, iliac, femoral, and arterioles) were harvested to detect ARCC and protein expression, including transforming growth factor-ß (TGF-ß) and receptor for AGEs (RAGE). Downstream resistance was elevated (60%), whereas flow and WSS were significantly decreased (44% and 56%) in ZD vs. ZL rats. NH was increased in ZO but not ZD rats. ALT-711 reduced ARCC and resistance (46%) in ZD rats while decreasing NH and producing similar in-stent WSS across groups. No consistent differences in RAGE or TGF-ß expression were observed in arterial segments. ALT-711 modified lectin-type oxidized LDL receptor 1 but not RAGE expression by cells on decellularized matrices. In conclusion, ALT-711 decreased ARCC, increased in-stent flow rate, and reduced NH in ZO and ZD rats through RAGE-independent pathways. The study supports an important role for AGE-induced remodeling within and downstream of stent implantation to promote enhanced NH in T2DM.
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Aorta Abdominal/efectos de los fármacos , Diabetes Mellitus/metabolismo , Oclusión de Injerto Vascular/metabolismo , Neointima/metabolismo , Obesidad/metabolismo , Stents , Estrés Mecánico , Tiazoles/farmacología , Resistencia Vascular/efectos de los fármacos , Animales , Aorta Abdominal/metabolismo , Colágeno/efectos de los fármacos , Colágeno/metabolismo , Productos Finales de Glicación Avanzada/efectos de los fármacos , Productos Finales de Glicación Avanzada/metabolismo , Masculino , Neointima/prevención & control , Ratas , Ratas Zucker , Receptor para Productos Finales de Glicación Avanzada/efectos de los fármacos , Receptor para Productos Finales de Glicación Avanzada/metabolismo , Resistencia al Corte , Factor de Crecimiento Transformador beta/efectos de los fármacos , Factor de Crecimiento Transformador beta/metabolismoRESUMEN
BACKGROUND: Total disc replacement was clinically introduced to reduce pain and preserve segmental motion of the lumbar and cervical spine. Previous case studies have reported on the wear and adverse local tissue reactions around artificial prostheses, but it is unclear how design and biomaterials affect clinical outcomes. QUESTIONS/PURPOSES: Which design and material factors are associated with differences in clinical wear performance (implant wear and periprosthetic tissue response) of (1) lumbar and (2) cervical total disc replacements? METHODS: We performed a systematic review on the topics of implant wear and periprosthetic tissue response using an advanced search in MEDLINE and Scopus electronic databases. Of the 340 references identified, 33 were retrieved for full-text evaluation, from which 16 papers met the inclusion criteria (12 on lumbar disc replacement and five on cervical disc replacement; one of the included studies reported on both lumbar and cervical disc replacement), which involved semiquantitative analysis of wear and adverse local tissue reactions along with a description of the device used. An additional three papers were located by searching bibliographies of key articles. There were seven case reports, three case series, two case-control studies, and seven analytical studies. The Methodological Index for Non-randomized Studies (MINORS) Scale was used to score case series and case-control studies, which yielded mean scores of 10.3 of 16 and 17.5 of 24, respectively. In general, the case series (three) and case-control (two) studies were of good quality. RESULTS: In lumbar regions, metal-on-polymer devices with mobile-bearing designs consistently generated small and large polymeric wear debris, triggering periprosthetic tissue activation of macrophages and giant cells, respectively. In the cervical regions, metal-on-polymer devices with fixed-bearing designs had similar outcomes. All metal-on-metal constructs tended to generate small metallic wear debris, which typically triggered an adaptive immune response of predominantly activated lymphocytes. There were no retrieval studies on one-piece prostheses. CONCLUSIONS: This review provides evidence that design and biomaterials affect the type of wear and inflammation. However, clinical study design, followup, and analytical techniques differ among investigations, preventing us from drawing firm conclusions about the relationship between implant design and wear performance for both cervical and lumbar total disc replacement.
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Materiales Biocompatibles , Vértebras Cervicales/cirugía , Disco Intervertebral/cirugía , Vértebras Lumbares/cirugía , Reeemplazo Total de Disco/instrumentación , Fenómenos Biomecánicos , Vértebras Cervicales/fisiopatología , Reacción a Cuerpo Extraño/etiología , Humanos , Disco Intervertebral/fisiopatología , Vértebras Lumbares/fisiopatología , Metales , Polímeros , Diseño de Prótesis , Falla de Prótesis , Estrés Mecánico , Reeemplazo Total de Disco/efectos adversos , Resultado del TratamientoRESUMEN
STUDY DESIGN: We used a nonhuman primate lumbar intertransverse process arthrodesis model to evaluate biological cascade of bone formation using different carrier preparation methods with a single dose of recombinant human bone morphogenetic protein-2 (rhBMP-2) at early time points. OBJECTIVE: To examine early-term/mid-term descriptive histologic and computerized tomographic events in single-level uninstrumented posterolateral nonhuman primate spinal fusions using rhBMP-2/absorbable collagen sponge (ACS) combined with ceramic bulking agents in 3 different configurations. SUMMARY OF BACKGROUND DATA: rhBMP-2 on an ACS carrier alone leads to consistent posterolateral lumbar spine fusions in lower-order animals; however, these results have been difficult to replicate in nonhuman primates. METHODS: Twelve skeletally mature, rhesus macaque monkeys underwent single-level posterolateral arthrodesis at L4-L5. A hydroxyapatite/ß-tricalcium phosphate ceramic bulking agent in 3 formulations was used in the treatment groups (n=3). When used, rhBMP-2/ACS at 1.5 mg/cm (3.0 mg rhBMP-2) was combined with 2.5 cm of ceramic bulking agent per side. Animals were euthanized at 4 and 12 weeks postoperative. Computerized tomography scans were performed immediately postoperatively and every 4 weeks until they were euthanized. Sagittal histologic sections were evaluated for bone histogenesis and location, cellular infiltration of the graft/substitute, and bone remodeling activity. RESULTS: Significant histologic differences in the developing fusion appeared between the 3 rhBMP-2/ACS treatment groups at 4 and 12 weeks. At 4 weeks, bone formation appeared to originate at the transverse process and the intertransverse membrane. Cellular infiltration was greatest in granular ceramic groups compared with matrix ceramic group. Minimal to no residual ACS was identified at the early time point. At 12 weeks, marked ceramic remodeling was observed with continued bone formation noted in all carrier groups. CONCLUSIONS: At the early time period, histology showed that bone formation appeared to originate at the transverse processes and the intertransverse membrane, indicating that the dorsal muscle bed may not be the only location for bone formation. Histology also showed that the collagen carrier for rhBMP-2 is mostly resorbed by 4 weeks. Our results and previous literature indicate that ceramic bulking agents are needed to provide resistance to compression caused by paraspinal muscles on the fusion bed in the posterolateral environment. Histology showed that ceramic bulking agents may offer long-term scaffolding and a structure to supporting bone formation of the developing fusion mass.
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Proteína Morfogenética Ósea 2/farmacología , Trasplante Óseo , Cerámica/farmacología , Colágeno/química , Vértebras Lumbares/efectos de los fármacos , Vértebras Lumbares/cirugía , Macaca mulatta/fisiología , Fusión Vertebral/métodos , Factor de Crecimiento Transformador beta/farmacología , Animales , Materiales Biocompatibles/farmacología , Humanos , Vértebras Lumbares/anatomía & histología , Vértebras Lumbares/diagnóstico por imagen , Modelos Animales , Osteogénesis/efectos de los fármacos , Proteínas Recombinantes/farmacología , Tomografía Computarizada por Rayos XRESUMEN
BACKGROUND: Osteogenesis imperfecta is a heterogeneous genetic disorder characterized by bone fragility. Previous research suggests that impaired collagen network and abnormal mineralization affect bone tissue properties, however, little data is yet available to describe bone material properties in individuals with this disorder. Bone material properties have not been characterized in individuals with the most common form of osteogenesis imperfecta, type I. METHODS: Bone tissue elastic modulus and hardness were measured by nanoindentation in eleven osteotomy specimens that were harvested from children with osteogenesis imperfecta during routine surgeries. These properties were compared between osteogenesis imperfecta types I (mild, n=6) and III (severe, n=5), as well as between interstitial and osteonal microstructural regions using linear mixed model analysis. FINDINGS: Disease severity type had a small but statistically significant effect on modulus (7%, P=0.02) and hardness (8%, P<0.01). Individuals with osteogenesis imperfecta type I had higher modulus and hardness than did those with type III. Overall, mean modulus and hardness values were 13% greater in interstitial lamellar bone regions than in osteonal regions (P<0.001). INTERPRETATION: The current study presents the first dataset describing bone material properties in individuals with the most common form of osteogenesis imperfecta, i.e., type I. Results indicate that intrinsic bone tissue properties are affected by phenotype. Knowledge of the material properties of bones in osteogenesis imperfecta will contribute to the ability to develop models to assist in predicting fracture risk.
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Fémur/patología , Modelos Lineales , Ensayo de Materiales/métodos , Modelos Biológicos , Osteogénesis Imperfecta/patología , Tibia/patología , Adolescente , Algoritmos , Niño , Preescolar , Módulo de Elasticidad , Femenino , Fémur/química , Fémur/fisiopatología , Dureza , Osteón/patología , Humanos , Masculino , Osteogénesis Imperfecta/fisiopatología , Tibia/química , Tibia/fisiopatologíaRESUMEN
Coarctation of the aorta (CoA) is associated with substantial morbidity despite treatment. Mechanically induced structural and functional vascular changes are implicated; however, their relationship with smooth muscle (SM) phenotypic expression is not fully understood. Using a clinically representative rabbit model of CoA and correction, we quantified mechanical alterations from a 20-mmHg blood pressure (BP) gradient in the thoracic aorta and related the expression of key SM contractile and focal adhesion proteins with remodeling, relaxation, and stiffness. Systolic and mean BP were elevated for CoA rabbits compared with controls leading to remodeling, stiffening, an altered force response, and endothelial dysfunction both proximally and distally. The proximal changes persisted for corrected rabbits despite >12 wk of normal BP (~4 human years). Computational fluid dynamic simulations revealed reduced wall shear stress (WSS) proximally in CoA compared with control and corrected rabbits. Distally, WSS was markedly increased in CoA rabbits due to a stenotic velocity jet, which has persistent effects as WSS was significantly reduced in corrected rabbits. Immunohistochemistry revealed significantly increased nonmuscle myosin and reduced SM myosin heavy chain expression in the proximal arteries of CoA and corrected rabbits but no differences in SM α-actin, talin, or fibronectin. These findings indicate that CoA can cause alterations in the SM phenotype contributing to structural and functional changes in the proximal arteries that accompany the mechanical stimuli of elevated BP and altered WSS. Importantly, these changes are not reversed upon BP correction and may serve as markers of disease severity, which explains the persistent morbidity observed in CoA patients.
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Coartación Aórtica/metabolismo , Coartación Aórtica/fisiopatología , Procedimientos Quirúrgicos Cardiovasculares , Proteínas Contráctiles/metabolismo , Endotelio Vascular/fisiopatología , Hemodinámica/fisiología , Actinas/metabolismo , Animales , Coartación Aórtica/cirugía , Presión Sanguínea/fisiología , Fibronectinas/metabolismo , Masculino , Modelos Animales , Cadenas Pesadas de Miosina/metabolismo , Conejos , Resistencia al Corte/fisiología , Estrés Mecánico , Talina/metabolismoRESUMEN
Insufficient sleep over long durations of the lifespan is believed to adversely affect proper development and healthful aging, although how this might become manifested is unknown. In the present study, rats were repeatedly sleep-restricted during 72 days to permit maladaptations to evolve, thereby permitting study. Densitometric and histomorphometric analyses were performed on harvested bone. In sleep-restricted rats, bone lined by osteoid was reduced 45-fold and osteoid thickness was decreased, compared with controls. This corresponded to a decrease in osteoblast number and activity. The percentage of bone lined by osteoclasts did not differ from that of controls. Plasma concentrations of an osteoclast marker (TRACP 5b) were increased in sleep-restricted rats, indicating increased bone resorption. The low amount of new bone formation without a reduction in bone resorption is diagnostic of osteopenia. Bone mineral density was decreased in femurs from sleep-restricted rats compared with controls, indicating osteoporosis. Red marrow in sleep-restricted rats contained only 37% of the fat and more than twice the number of megakaryocytes compared with that of the control rats. These findings in marrow suggest changed plasticity and increased hematopoiesis. Plasma concentrations of insulin-like growth factor-1, a known, major mediator of osteoblast differentiation and the proliferation of progenitor cells, was decreased by 30% in sleep-restricted rats. Taken together, these findings suggest that chronically inadequate sleep affects bone metabolism and bone marrow composition in ways that have implications for development, aging, bone healing and repair, and blood cell differentiation.
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Densidad Ósea , Desarrollo Óseo , Huesos/patología , Privación de Sueño , Fosfatasa Ácida/sangre , Animales , Enfermedades Óseas Metabólicas/patología , Enfermedades Óseas Metabólicas/fisiopatología , Médula Ósea/química , Células de la Médula Ósea , Resorción Ósea , Proliferación Celular , Hematopoyesis , Factor I del Crecimiento Similar a la Insulina/análisis , Isoenzimas/sangre , Megacariocitos , Osteoblastos/citología , Osteoclastos/citología , Osteoporosis/patología , Osteoporosis/fisiopatología , Ratas , Ratas Sprague-Dawley , Fosfatasa Ácida TartratorresistenteRESUMEN
Knowledge regarding the in vivo performance and periposthetic tissue response of cervical and lumbar total disc replacements (TDRs) continues to expand. This review addresses the following four main questions: 1) What are the latest lessons learned from polyethylene in large joints and how are they relevant to current TDRs? 2) What are the latest lessons learned regarding adverse local tissue reactions from metal-on-metal, CoCr bearings in large joints and how are they relevant to current TDRs? 3) What advancements have been made in understanding the in vivo performance of alternative biomaterials, such as stainless steel and polycarbonate urethane, for TDRs in the past five years? 4) How has retrieval analysis of all these various artificial disc bearing technologies advanced the state of the art in preclinical testing of TDRs? The study of explanted artificial discs and their associated tissues can help inform bearing selection as well as the design of future generations of disc arthroplasty. Analyzing retrieved artificial discs is also essential for validating preclinical test methods.
RESUMEN
INTRODUCTION: Coarctation of the aorta (CoA) is associated with morbidity despite treatment. Although mechanisms remain elusive, abnormal hemodynamics and vascular biomechanics are implicated. We present a novel approach that facilitates quantification of coarctation-induced mechanical alterations and their impact on vascular structure and function, without genetic or confounding factors. METHODS: Rabbits underwent thoracic CoA at 10weeks of age (~9 human years) to induce a 20mmHg blood pressure (BP) gradient using permanent or dissolvable suture thereby replicating untreated and corrected CoA. Computational fluid dynamics (CFD) was performed using imaging and BP data at 32weeks to quantify velocity, strain and wall shear stress (WSS) for comparison to vascular structure and function as revealed by histology and myograph results. RESULTS: Systolic and mean BP was elevated in CoA compared to corrected and control rabbits leading to vascular thickening, disorganization and endothelial dysfunction proximally and distally. Corrected rabbits had less severe medial thickening, endothelial dysfunction, and stiffening limited to the proximal region despite 12weeks of normal BP (~4 human years) after the suture dissolved. WSS was elevated distally for CoA rabbits, but reduced for corrected rabbits. DISCUSSION: These findings are consistent with alterations in humans. We are now poised to investigate mechanical contributions to mechanisms of morbidity in CoA using these methods.