Mesenchymal stromal cell response to intervertebral disc-like pH is tissue source dependent.

Intervertebral disc (IVD) degeneration (IVDD) has become increasingly prevalent and is a common contributing factor to low back pain. Current treatment options are limited to either symptom management or surgery. A promising treatment option being explored is intradiscal administration of mesenchymal stromal cells (MSCs). However, there remains a gap in knowledge as to whether MSCs from different tissue sources have similar responses to the low pH microenvironment of the IVD and the possible mechanisms governing these responses. To study this, MSCs from three different tissue sources: adipose (adipose-derived mesenchymal stem cell), bone marrow (bone marrow mesenchymal stem cells), and amnion (amniotic membrane mesenchymal stem cell) were cultured at low pHs representative of IVDD. MSCs were assessed for survival, senescence, apoptosis, metabolic activity, and cytokine release profile. Additionally, western blot was utilized to assess acid sensing ion channel 1 and 3 expression. The results of this study indicated that MSC viability, cell proliferation, senescence, and metabolic activity is negatively affected by low pH and alters MSC cytokine production. This study also demonstrated that MSCs behavior is dependent on tissue source. Understanding how MSC behavior is altered by pH will allow further research aimed at increasing the efficacy of MSC therapy to promote in situ IVD tissue regeneration to combat IVDD.

Angle-ply scaffold supports annulus fibrosus matrix expression and remodeling by mesenchymal stromal and annulus fibrosus cells.

The angle-ply multilaminate structure of the annulus fibrosus is not reestablished following discectomy which leads to reherniation of the intervertebral disc (IVD). Biomimetic scaffolds developed to repair these defects should be evaluated for their ability to support tissue regeneration by endogenous and exogenous cells. Herein a collagen-based, angle-ply multilaminate patch designed to repair the outer annulus fibrosus was assessed for its ability to support mesenchymal stromal and annulus fibrosus cell viability, elongation, alignment, extracellular matrix gene expression, and scaffold remodeling. Results demonstrated that the cells remained viable, elongated, and aligned along the collagen fiber preferred direction of the scaffold, upregulated genes associated with annulus fibrosus matrix and produced collagen on the scaffold yielding biaxial mechanical properties that resembled native annulus fibrosus tissue. In conclusion, these scaffolds have demonstrated their potential to promote a living repair of defects in the annulus fibrosus and thus may be used to prevent recurrent IVD herniations.

Characterization of chondroitinase-induced lumbar intervertebral disc degeneration in a sheep model intended for assessing biomaterials.

Intervertebral disc (IVD) degeneration (IVDD) leads to structural and functional changes. Biomaterials for restoring IVD function and promoting regeneration are currently being investigated; however, such approaches require validation using animal models that recapitulate clinical, biochemical, and biomechanical hallmarks of the human pathology. Herein, we comprehensively characterized a sheep model of chondroitinase-ABC (ChABC) induced IVDD. Briefly, ChABC (1 U) was injected into the L1/2 , L2/3 , and L3/4 IVDs. Degeneration was assessed via longitudinal magnetic resonance (MR) and radiographic imaging. Additionally, kinematic, biochemical, and histological analyses were performed on explanted functional spinal units (FSUs). At 17-weeks, ChABC treated IVDs demonstrated significant reductions in MR index (p = 0.030) and disc height (p = 0.009) compared with pre-operative values. Additionally, ChABC treated IVDs exhibited significantly increased creep displacement (p = 0.004) and axial range of motion (p = 0.007) concomitant with significant decreases in tensile (p = 0.034) and torsional (p = 0.021) stiffnesses and long-term viscoelastic properties (p = 0.016). ChABC treated IVDs also exhibited a significant decrease in NP glycosaminoglycan: hydroxyproline ratio (p = 0.002) and changes in microarchitecture, particularly in the NP and endplates, compared with uninjured IVDs. Taken together, this study demonstrated that intradiscal injection of ChABC induces significant degeneration in sheep lumbar IVDs and the potential for using this model in evaluating biomaterials for IVD repair, regeneration, or fusion.

Multi-laminate annulus fibrosus repair scaffold with an interlamellar matrix enhances impact resistance, prevents herniation and assists in restoring spinal kinematics.

Focal defects in the annulus fibrosus (AF) of the intervertebral disc (IVD) arising from herniation have detrimental impacts on the IVD's mechanical function. Thus, biomimetic-based repair strategies must restore the mechanical integrity of the AF to help support and restore native spinal loading and motion. Accordingly, an annulus fibrosus repair patch (AFRP); a collagen-based multi-laminate scaffold with an angle-ply architecture has been previously developed, which demonstrates similar mechanical properties to native outer AF (oAF). To further enhance the mimetic nature of the AFRP, interlamellar (ILM) glycosaminoglycan (GAG) was incorporated into the scaffolds. The ability of the scaffolds to withstand simulated impact loading and resist herniation of native IVD tissue while contributing to the restoration of spinal kinematics were assessed separately. The results demonstrate that incorporation of a GAG-based ILM significantly increased (p < 0.001) the impact strength of the AFRP (2.57 ±â€¯0.04 MPa) compared to scaffolds without (1.51 ±â€¯0.13 MPa). Additionally, repair of injured functional spinal units (FSUs) with an AFRP in combination with sequestering native NP tissue and a full-thickness AF tissue plug enabled the restoration of creep displacement (p = 0.134), short-term viscous damping coefficient (p = 0.538), the long-term viscous (p = 0.058) and elastic (p = 0.751) damping coefficients, axial neutral zone (p = 0.908), and axial range of motion (p = 0.476) to an intact state. Lastly, the AFRP scaffolds were able to prevent native IVD tissue herniation upon application of supraphysiologic loads (5.28 ±â€¯1.24 MPa). Together, these results suggest that the AFRP has the strength to sequester native NP and AF tissue and/or implants, and thus, can be used in a composite repair strategy for IVDs with focal annular defects thereby assisting in the restoration of spinal kinematics.

Ethanol-mediated compaction and cross-linking enhance mechanical properties and degradation resistance while maintaining cytocompatibility of a nucleus pulposus scaffold.

Intervertebral disc degeneration is a complex, cell-mediated process originating in the nucleus pulposus (NP) and is associated with extracellular matrix catabolism leading to disc height loss and impaired spine kinematics. Previously, we developed an acellular bovine NP (ABNP) for NP replacement that emulated human NP matrix composition and supported cell seeding; however, its mechanical properties were lower than those reported for human NP. To address this, we investigated ethanol-mediated compaction and cross-linking to enhance the ABNP's dynamic mechanical properties and degradation resistance while maintaining its cytocompatibility. First, volumetric and mechanical effects of compaction only were confirmed by evaluating scaffolds after various immersion times in buffered 28% ethanol. It was found that compaction reached equilibrium at ~30% compaction after 45 min, and dynamic mechanical properties significantly increased 2-6× after 120 min of submersion. This was incorporated into a cross-linking treatment, through which scaffolds were subjected to 120 min precompaction in buffered 28% ethanol prior to carbodiimide cross-linking. Their dynamic mechanical properties were evaluated before and after accelerated degradation by ADAMTS-5 or MMP-13. Cytocompatibility was determined by seeding stem cells onto scaffolds and evaluating viability through metabolic activity and fluorescent staining. Compacted and cross-linked scaffolds showed significant increases in DMA properties without detrimentally altering their cytocompatibility, and these mechanical gains were maintained following enzymatic exposure. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B:2488-2499, 2019.

Differential Effector Response of Amnion- and Adipose-Derived Mesenchymal Stem Cells to Inflammation; Implications for Intradiscal Therapy.

Intervertebral disc degeneration (IVDD) is a progressive condition marked by tissue destruction and inflammation. The therapeutic effector functions of mesenchymal stem cells (MSCs) makes them an attractive therapy for patients with IVDD. While several sources of MSCs exist, the optimal choice for use in the inflamed IVD remains a significant question. Adipose (AD)- and amnion (AM)-derived MSCs have several advantages compared with other sources, however, no study has directly compared the impact of IVDD inflammation on their effector functions. Human MSCs were cultured in media with or without supplementation of interleukin-1ß (IL-1ß) and tumor necrosis factor-α at concentrations reportedly produced by IVDD cells. MSC proliferation and production of pro- and anti-inflammatory cytokines were quantified following 24 and 48 h of culture. Additionally, the osteogenic and chondrogenic potential of AD- and AM-MSCs was characterized via histology and biochemical analysis following 28 days of culture. In inflammatory culture, AM-MSCs produced significantly more anti-inflammatory IL-10 (14.47 ± 2.39 pg/ml; p = 0.004) and larger chondrogenic pellets (5.67 ± 0.26 mm2 ; p = 0.04) with greater percent area staining positively for glycosaminoglycan (82.03 ± 3.26%; p < 0.001) compared with AD-MSCs (0.00 ± 0.00 pg/ml; 2.76 ± 0.18 mm2 ; 34.75 ± 2.49%; respectively). Conversely, AD-MSCs proliferated more resulting in higher cell numbers (221,000 ± 8,021 cells; p = 0.048) and produced higher concentrations of pro-inflammatory cytokines prostaglandin E2 (1,118.30 ± 115.56 pg/ml; p = 0.030) and IL-1ß (185.40 ± 7.63 pg/ml; p = 0.010) compared with AM-MSCs (109,667 ± 5,696 cells; 1,291.40 ± 78.47 pg/ml; 144.10 ± 4.57 pg/ml; respectively). AD-MSCs produced more mineralized extracellular matrix (3.34 ± 0.05 relative absorbance units [RAU]; p < 0.001) compared with AM-MSCs (1.08 ± 0.06 RAU). Under identical inflammatory conditions, a different effector response was observed with AM-MSCs producing more anti-inflammatories and demonstrating enhanced chondrogenesis compared with AD-MSCs, which produced more pro-inflammatory cytokines and demonstrated enhanced osteogenesis. These findings may begin to help inform researchers which MSC source may be optimal for IVD regeneration. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:2445-2456, 2019.

Decellularization and characterization of a whole intervertebral disk xenograft scaffold.

Intervertebral disk (IVD) degeneration is a multifactor process that results in the physical destruction of the nucleus pulposus (NP) and annulus fibrosus (AF). This compromises IVD function and causes significant disability and economic burden. Strategies to replace the entire composite structure of the IVD are limited and most approaches do not recapitulate the heterogenous biochemical composition, microarchitecture or mechanical properties of the native tissue. Our central hypothesis was that donor IVDs which resemble the size and biochemistry of human lumbar IVDs could be successfully decellularized while retaining the tissue's structure and function with the long-term goal of creating a composite scaffold for tissue engineering the human IVD. Accordingly, we optimized a procedure to decellularize bovine tail IVDs using a combination of detergents, ultrasonication, freeze-thaw cycles, and nucleases. The resultant decellularized whole IVD xenografts retained distinct AF and NP regions which contained no visible intact cell nuclei and minimal residual bovine deoxyribose nucleic acid (DNA; 65.98 ± 4.07 and 47.12 ± 13.22 ng/mg, respectively). Moreover, the NP region of decellularized IVDs contained 313.40 ± 50.67 µg/mg glycosaminoglycan. The presence of collagen type II was confirmed via immunohistochemistry. Additionally, histological analysis of the AF region of decellularized IVDs demonstrated retention of the native angle-ply collagen microarchitecture. Unconfined compression testing demonstrated no significant differences in swelling pressure and toe-region modulus between fresh and decellularized IVDs. However, linear region moduli, peak stress and equilibrium moduli were all significantly reduced. Together, this research demonstrates a successful initial step in developing a biomimetic acellular whole IVD xenograft scaffold for use in IVD tissue engineering. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A:2412-2423, 2018.

Angle-ply biomaterial scaffold for annulus fibrosus repair replicates native tissue mechanical properties, restores spinal kinematics, and supports cell viability.

Annulus fibrosus (AF) damage commonly occurs due to intervertebral disc (IVD) degeneration/herniation. The dynamic mechanical role of the AF is essential for proper IVD function and thus it is imperative that biomaterials developed to repair the AF withstand the mechanical rigors of the native tissue. Furthermore, these biomaterials must resist accelerated degradation within the proteolytic environment of degenerate IVDs while supporting integration with host tissue. We have previously reported a novel approach for developing collagen-based, multi-laminate AF repair patches (AFRPs) that mimic the angle-ply architecture and basic tensile properties of the human AF. Herein, we further evaluate AFRPs for their: tensile fatigue and impact burst strength, IVD attachment strength, and contribution to functional spinal unit (FSU) kinematics following IVD repair. Additionally, AFRP resistance to collagenase degradation and cytocompatibility were assessed following chemical crosslinking. In summary, AFRPs demonstrated enhanced durability at high applied stress amplitudes compared to human AF and withstood radially-directed biaxial stresses commonly borne by the native tissue prior to failure/detachment from IVDs. Moreover, FSUs repaired with AFRPs and nucleus pulposus (NP) surrogates had their axial kinematic parameters restored to intact levels. Finally, carbodiimide crosslinked AFRPs resisted accelerated collagenase digestion without detrimentally effecting AFRP tensile properties or cytocompatibility. Taken together, AFRPs demonstrate the mechanical robustness and enzymatic stability required for implantation into the damaged/degenerate IVD while supporting AF cell infiltration and viability. STATEMENT OF SIGNIFICANCE: The quality of life for millions of individuals globally is detrimentally impacted by IVD degeneration and herniation. These pathologies often result in the structural demise of IVD tissue, particularly the annulus fibrosus (AF). Biomaterials developed for AF repair have yet to demonstrate the mechanical strength and durability required for utilization in the spine. Herein, we demonstrate the development of an angle-ply AF repair patch (AFRP) that can resist the application of physiologically relevant stresses without failure and which contributes to the restoration of functional spinal unit axial kinematics following repair. Furthermore, we show that this biomaterial can resist accelerated degradation in a simulated degenerate environment and supports AF cell viability.

Biomimetic nucleus pulposus scaffold created from bovine caudal intervertebral disc tissue utilizing an optimal decellularization procedure.

Intervertebral disc (IVD) degeneration (IDD) and herniation (IDH) can result in low back pain and impart significant socioeconomic burden. These pathologies involve detrimental alteration to the nucleus pulposus (NP) either via biochemical degradation or extrusion from the IVD, respectively. Thus, engineering living NP tissue utilizing biomaterial scaffolds that recapitulate native NP microarchitecture, biochemistry, mechanical properties, and which support cell viability represents an approach to aiding patients with IDD and IDH. To date, an ideal biomaterial to support NP regeneration has yet to be developed; however, one promising approach to generating biomimetic materials is to employ the decellularization (decell) of xenogeneic NP tissue to remove host DNA while maintaining critical native extracellular matrix (ECM) components. Herein, 13 different procedures were evaluated in an attempt to decell bovine caudal IVD NP tissue. An optimal method was identified which was confirmed to effectively remove bovine DNA, while maintaining physiologically relevant amounts of glycosaminoglycan (GAG) and type II collagen. Unconfined static and dynamic compressive mechanical properties of scaffolds approached values reported for human NP and viability of human amniotic stem cells (hAMSCs) was maintained on noncrosslinked and EDC/NHS treated scaffolds for up to 14 days in culture. Taken together, NP tissue obtained from bovine caudal IVDs can be successfully decelled in order to generate a biomimetic scaffold for NP tissue regeneration. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 3093-3106, 2016.

Reducing joint destruction due to septic arthrosis using an adenosine2A receptor agonist.

We assessed the efficacy of a new adenosine A2A agonist ATL146e, a potent inhibitor of white blood cell chemotaxis, to reduce cartilage damage in the treatment of septic arthrosis. A live septic arthrosis model was created using Staphylococcus aureus in rabbit knees. Animals were divided into five treatment groups: (1) untreated infected control, (2) antibiotics control, and antibiotics plus ATL146e for (3) 24, (4) 48, or (5) 72 h and assessed at 1, 4, and 7 days. Knees in all ATL146e treated animals exhibited no detectable effusion, and histologic examination revealed near normal cartilage and diminished synovial inflammatory response. Synovial WBC counts decreased with the addition of ATL146e when compared to infected and antibiotic controls. Histologic grading of osteochondral specimens demonstrated improved scores for animals treated with ATL146e compared to infected (p<0.00004) and antibiotics controls (p<0.05). Analysis of glycosaminoglycan content revealed significantly decreased loss of articular cartilage following infection in the ATL146e groups when compared to infected (p<0.03) and antibiotics controls (p<0.05). Addition of an adenosine A2A agonist to antibiotic therapy decreases joint inflammation and articular cartilage destruction without compromising bacterial clearance in rabbit knees following intraarticular bacterial infection. The use of adenosine agonists selective to the A2A receptor to augment conventional treatment of joint sepsis may be chondroprotective and ultimately help prevent arthrosis.

Fluoroscopically guided low-volume peritendinous corticosteroid injection for Achilles tendinopathy. A safety study.

BACKGROUND: The safety and efficacy of corticosteroid injection for the treatment of Achilles tendinopathy is not known, with some reports indicating the hazard of tendon rupture and others extolling the efficacy of such injections. This study was undertaken to assess the safety of fluoroscopically guided corticosteroid injections into the peritendinous space for the treatment of Achilles tendinopathy. METHODS: A series of patients was treated with fluoroscopically guided corticosteroid injections into the space surrounding the Achilles tendon. Major and minor complications were recorded, as were the number of repeat injections, the duration of symptomatic relief attained with the injection, and a subjective rating of symptoms related to the Achilles tendon. RESULTS: Of eighty-three patients who had been treated, seventy-eight were available for follow-up and forty-three met our requirement for a minimum two-year follow-up (average duration of follow-up, 37.4 months). No major complications and one minor complication occurred in the forty-three patients. Seventeen (40%) of the patients reported improvement after the procedure, twenty-three (53%) thought that their condition was unchanged, and three (7%) felt that their condition was worse than it had been prior to the injection. CONCLUSIONS: This retrospective cohort study establishes the safety of low-volume injections of corticosteroids for the treatment of Achilles tendinopathy when the needle is carefully inserted into the peritendinous space under direct fluoroscopic visualization.

Semitendinosus regrowth: biochemical, ultrastructural, and physiological characterization of the regenerate tendon.

BACKGROUND: Previous studies have suggested that hamstring tendons can regenerate following harvesting for anterior cruciate ligament reconstruction. HYPOTHESIS: This "neo-tendon" is a true, functional tendon, not scar tissue. STUDY DESIGN: Controlled laboratory study. METHODS: Semitendinosus tendons were harvested from 35 New Zealand white rabbits using a standard tendon stripper. The rabbits were sacrificed 9 to 12 months following the index procedure and thoroughly evaluated. RESULTS: Thirty-one rabbits were available at the time of sacrifice. The neo-tendon was present in 26 rabbits but was highly variable in size and location of its tibial insertion. Histologic and immunohistochemical staining confirmed that the regenerate tissue was indeed tendon with normal cellularity, organization, and immunolocalization of type I collagen. Electron microscopy showed regeneration of organized collagen tissue that simulated native tendon but with a smaller cross-sectional diameter. Functionally, the neo-tendon was able to transmit force across the musculotendinous junction but at a significantly slower rate than the opposite, control leg. Biomechanical properties of the neo-tendon were significantly less than the control side. Biochemical analysis revealed that the neo-tendons contained glycosaminoglycans and collagen, but levels were significantly lower than normal tendons. CONCLUSIONS: Semitendinosus tendons regenerate with biologically reactive tendinous tissues in an animal model. This tissue has many of the characteristics of a normal tendon but appears to be inferior to the original musculotendinous unit at 9- to 12-month evaluation. Further characterization of the "lizard tail phenomenon" is still needed. CLINICAL RELEVANCE: Hamstring tendon regrowth may have a dramatic impact on postoperative function of patients who undergo anterior cruciate ligament reconstruction with these tendons. Further modulation of this regeneration may further reduce graft harvesting morbidity.

Outcomes after meniscal repair using the meniscus arrow in knees undergoing concurrent anterior cruciate ligament reconstruction.

PURPOSE: To determine the healing rate of meniscal repair using the Meniscus Arrow (Bionx, Blue Bell, PA) in patients undergoing concurrent anterior cruciate ligament (ACL) reconstruction and to evaluate patient outcomes with the International Knee Documentation Committee (IKDC) form and a visual analog scale (VAS). TYPE OF STUDY: Case series with outcomes analysis. METHODS: We retrospectively analyzed 38 consecutive patients with 39 meniscal tears in knees undergoing concurrent endoscopic ACL reconstruction whose menisci were repaired with the Meniscus Arrow system. All meniscal tears were deemed amenable to repair according to length, stability, morphology, and zone of tear. There were 31 medial and 8 lateral meniscal tears, with an average tear length of 2.1 cm. An average of 2.5 arrows were used to repair each tear. All 39 tears were located in the posterior horn of the meniscus or extending into the body of the meniscus from the posterior horn. Follow-up was assessed by clinical examination, the knee disorders subjective history, VAS, and the IKDC evaluation form. Reconstructed ACL laxity was assessed by KT-2000 arthrometry and clinical evaluation. RESULTS: At an average follow-up of 2.3 years (range, 18-39 months), 32 patients have been surveyed to date. The success rate was 90.6% (29 of 32 patients) with 3 patients going on to arthroscopic partial meniscectomy. KT-2000 arthrometry showed that sagittal knee laxity was less than 3 mm in all reconstructed knees. Clinical criteria for success in the rest of the repaired menisci included (1) the absence of locking, catching, or giving way; (2) no history of recurrent effusions; (3) no joint line tenderness; (4) a negative McMurray test; and (5) no subsequent surgical procedures on the repaired meniscus. Additionally, the VAS showed the ability of these patients to return to a high level of activity, including competitive sports, without symptoms suggestive of a meniscal tear. The IKDC showed normal or nearly normal function of all success knees. CONCLUSIONS: The study shows that a high rate of meniscus healing can be achieved by the all-inside, bioabsorbable Meniscus Arrow system in conjunction with ACL reconstruction. Also, patients have excellent function of their knee and are able to return to a high level of activity. Our healing rates are comparable to those previously reported with the inside-out suture techniques without the need for an additional posterior incision that would increase operative time and risk to neurovascular structures.

Development and initial characterization of a chemically stabilized elastin-glycosaminoglycan-collagen composite shape-memory hydrogel for nucleus pulposus regeneration.

Nucleus pulposus (NP) is a resilient and hydrophilic tissue which plays a significant role in the biomechanical function of the intervertebral disc (IVD). Destruction of the NP extracellular matrix (ECM) is observed during the early stages of IVD degeneration. Herein, we describe the development and initial characterization of a novel biomaterial which attempts to recreate the resilient and hydrophilic nature of the NP via the construction of a chemically stabilized elastin-glycosaminoglycan-collagen (EGC) composite hydrogel. Results demonstrated that a resilient, hydrophilic hydrogel which displays a unique "shape-memory" sponge characteristic could be formed from a blend of soluble elastin aggregates, chondroitin-6-sulfate, hyaluronic acid and collagen following freeze-drying, stabilization with a carbodiimide and penta-galloyl glucose-based fixative, and subsequent partial degradation with glycosaminoglycan degrading enzymes. The resultant material exhibited the ability to restore its original dimensions and water content following multi-cycle mechanical compression and illustrated resistance to accelerated enzymatic degradation. Preliminary in vitro studies utilizing human adipose derived stem cells (hADSCs) demonstrated that the material was cytocompatible and supported differentiation towards an NP cell-like phenotype. In vivo biocompatibility studies illustrated host cell infiltration and evidence of active remodeling following 4 weeks of implantation. Feasibility studies demonstrated that the EGC hydrogel could be delivered via minimally invasive methods.

Regenerative potential of decellularized porcine nucleus pulposus hydrogel scaffolds: stem cell differentiation, matrix remodeling, and biocompatibility studies.

Nucleus pulposus (NP) tissue regeneration has been proposed as an early stage interventional therapy to combat intervertebral disc degeneration. We have previously reported on the development and characterization of a novel biomimetic acellular porcine NP (APNP) hydrogel. Herein, we aimed to evaluate this material for use as a suitable scaffold for NP tissue regeneration. Human-adipose-derived stem cells (hADSCs) were cultured for 14 days on APNP hydrogels in chemically defined differentiation media and were analyzed for an NP-cell-like mRNA expression profile, evidence of hydrogel remodeling including hydrogel contraction measurements, extracellular matrix production, and compressive dynamic mechanical properties. The innate capacity of the hydrogel itself to induce stem cell differentiation was also examined via culture in media lacking soluble differentiation factors. Additionally, the in vivo biocompatibility of non-crosslinked and ethyldimethylaminopropyl carbodiimide/N-hydroxysuccinimide and pentagalloyl glucose crosslinked hydrogels was evaluated in a rat subdermal model. Results indicated that hADSCs expressed putative NP-cell-positive gene transcript markers when cultured on APNP hydrogels. Additionally, glycosaminoglycan and collagen content of hADSC-seeded hydrogels was significantly greater than nonseeded controls and cell-seeded hydrogels exhibited evidence of contraction and tissue inhibitors of metalloproteinase-1 production. The dynamic mechanical properties of the hADSC-seeded hydrogels increased with time in culture in comparison to noncell-seeded controls and approached values reported for native NP tissue. Immunohistochemical analysis of explants illustrated the presence of mononuclear cells, including macrophages and fibroblasts, as well as blood vessel infiltration and collagen deposition within the implant interstices after 4 weeks of implantation. Taken together, these results suggest that APNP hydrogels, in concert with autologous ADSCs, may serve as a suitable scaffold for NP tissue regeneration.

Novel tissue-derived biomimetic scaffold for regenerating the human nucleus pulposus.

Numerous scaffold formulations have been investigated to support the regeneration of nucleus pulposus (NP) tissue for use as an early-stage therapy for intervertebral disc degeneration. Particular attention has focused on recreating the biochemical and mechanical properties of the native NP via the incorporation of exogenous extracellular matrix (ECM) components or synthetic surrogates. In the present study, we describe a novel approach to develop a tissue engineering (TE) scaffold comprised acellular porcine NP ECM. Complete decellularization of porcine NP was successfully achieved using a combination of chemical detergents, ultrasonication, and treatment with nucleases. Resulting NP scaffolds were devoid of host-cell remnants and the porcine antigen alpha-Gal. Native NP ECM components including aggrecan/chondroitin-6-sulfate and collagens types II, IX, and XI were found in physiologically relevant ratios within the NP scaffold. NP scaffold swelling capacity and unconfined mechanical properties were not significantly different from porcine NP tissue. Furthermore, NP scaffolds were conducive to repopulation with human adipose-derived stem cells as cell viability and proliferative capacity were maintained. These results demonstrate the successful decellularization of porcine NP and the resultant formation of a biomimetic scaffold exhibiting potential utility for TE the human NP.

The epidemiology of catastrophic spine injuries in high school and college football.

Athletic events have long been identified as a source of catastrophic spinal injuries. One of the most notorious sports has been American football. At both the amateur and professional level, this collision sport is associated with the highest number of direct catastrophic injuries including cervical spine trauma and quadriplegia. Although modifications in the rules of play and education of players and coaches have significantly diminished the rate of quadriplegia, there remains a need to decrease the number of catastrophic spine injuries in football. Further research related to the prevention and management of athletic cervical spine trauma is necessary.

Use of recombinant human bone morphogenetic protein-2 as an adjunct in posterolateral lumbar spine fusion: a prospective CT-scan analysis at one and two years.

INTRODUCTION: This study determines whether recombinant human bone morphogenetic protein-2 (rhBMP-2) (12 mg at the rate of 1.5 mg/mL) delivered on an absorbable collagen sponge with an added bulking agent can increase posterolateral lumbar spine fusion success rates and decrease time for fusion with autogenous bone grafts. METHOD: A prospective, single institution, clinical case-matched, radiographic, cohort study was undertaken. A total of 52 patients underwent posterolateral lumbar arthrodesis with pedicle screw instrumentation. The experimental group (n=41) underwent placement of Iliac crest bone graft (ICBG) with InFUSE (12 mg/level at the rate of 1.5 mg/mL). The control group (n=11) consisted of sex-matched patients, consecutively collected over the same time period with an instrumented posterolateral arthrodesis and ICBG placed in the intertransverse space. OUTCOME MEASURES: Thin-cut (2 mm) axial, coronal, and sagittal reconstructions were blindly evaluated for evidence of bridging bone and cortication of the fusion mass by 3 separate reviewers. Fusions were graded and an overall score was given to the quality of the fusion mass. RESULTS: Fifty patients (ICBG alone n=11; ICBG/rhBMP-2 n=39) were available for CT evaluation at 2-year follow-up. An overall 97% (68/70 levels; Definite+Probably Fused) fusion rate in the rhBMP-2 group was achieved as compared to the 77% fusion rate (17/22 levels) in the ICBG alone group (P<0.05). In the rhBMP-2 group, 92% of the patients (36/39 patients) received an overall excellent subjective fusion rating as compared to 27% (3/11) in the control group (P<0.05). There was no computed tomographic evidence of soft-tissue ossification, dural ossification, or laminar bone regrowth in any patient. CONCLUSIONS: The adjunctive use of rhBMP-2 and ICBG seems to be safe and results in significantly larger and more consistent posterolateral fusion masses.