Clinical application of a 3D-printed scaffold in chronic wound treatment: a case series.

OBJECTIVE: This case series evaluates the safety and effectiveness of 3D-printed scaffold in chronic wounds. The scaffold is a composite of natural and synthetic materials, and can be prepared in the form of powder or membrane. METHOD: We recruited patients with pressure ulcera (PU) and/or a diabetic foot ulcers (DFU). We used two methods: 3D-printed scaffolds alone, or 3D-printing powder mixed with platelet-rich fibrinogen (PRF). Clinicians and patients were asked to rate the scaffold's ease of application and comfort during use. RESULTS: A total of five patients were recruited; four with a PU and one with a DFU. For the patient treated with the 3D-printed scaffold membrane (n=1), their PU healed in 28 days, and for patients treated with the 3D-printed scaffold powder (n=2), their PUs healed in 54 days. For the patients treated with the 3D-printing powder mixed with PRF (n=2), the patient with a PU healed in 11 days, and the patient with the DFU healed in 14 days. All clinicians rated the 3D-printed scaffold as 'easy' or 'very easy' to use, and patients rated their comfort during wear and at dressing change as 'good' or 'very good'. CONCLUSION: This study demonstrated that 3D-printed scaffold was convenient to use, have the potential to improve wound healing rates, and provided a safe and effective way for treating chronic wounds.

The intraoperative use of polydioxanone foil to reduce the risk of sino-orbital fistula formation in orbital exenteration.

BACKGROUND: Orbital exenteration is a radical surgical procedure resulting in deformity. It involves removal of the globe, optic nerve, extra-ocular muscles, orbital fat, lacrimal gland, and peri-osteum. Sino-orbital fistula (SOF) formation is a common documented post-operative complication, usually connecting the orbit and the ethmoid sinus. SOFs can cause leaks of serous fluid, and act as an entry site for pathogens into the orbit leading to socket infection and breakdown. METHODS: This retrospective study analyzed exenterations performed over a 22-year period (1993-2015) at the National Ocular Oncology Service Centre for Scotland. PDS is a crystalline, biodegradable polyether-ester that is strong with good shape-memory and flexibility. Orbital exenterations with and without the use of PDS foil were compared in terms of SOF formation. RESULTS: A total of 30 exenterations were performed during the study period. A total of 29 were analyzed. Choroidal malignant melanoma was the most common indication for performing orbital exenteration (n = 7, 24.14%). The most common post-operative complications seen were SOF (n = 8, 27.59%). A total of 8 out 21 (38.10%) cases not using PDS developed SOFs. By contrast, none of nine patients receiving PDS plates developed SOFs (p = 0.0332). CONCLUSIONS: This is the first study to compare SOF rate in patients undergoing exenteration with and without the use of PDS foil. PDS foil is a safe material, which has effectively reduced the incidence of SOF formation.

Clinical and imaging outcome of osteochondral lesions of the talus treated using autologous matrix-induced chondrogenesis technique with a biomimetic scaffold.

BACKGROUND: The purpose of our study was to assess the clinical and imaging outcome of autologous matrix-induced chondrogenesis (AMIC) technique consisting of microfractures followed by the filling of osteochondral lesions of the talus (OLTs) with a cell-free biphasic collagen-hydroxyapatite osteochondral scaffold (MaioRegen). METHODS: Sixteen patients (eight males, age: 42.6 ± 18.4, range 14-74) with OLT repaired using AMIC technique, with implantation of MaioRegen, were clinically evaluated through the American Orthopedic Foot and Ankle Society Score (AOFAS) and a 10-point Visual Analogue Scale (VAS) pain score after a mean follow-up of 30 ± 16.9 months. The MRI examinations were performed 12 and 24 months after surgery. A paired t-test was applied to compare pre- and post-operative clinical findings (VAS and AOFAS) and Magnetic resonance observation of cartilage repair tissue (MOCART) score changes in the follow-up. To assess the correlation between variation of AOFAS and MOCART scores, the Pearson's correlation coefficient was calculated. RESULTS: No complications after surgery were encountered. From pre-operative to post-operative values, there was a significant (P < 0.001) reduction of mean VAS pain score (6.3 ± 0.9,range: 4-8 and 2.9 ± 1.8,range: 0-6, respectively) and increase of AOFAS score (60.2 ± 7.8,range: 50-74 and 77.4 ± 16.2,range: 50-100, respectively). Among 16 patients, six (37%) were not satisfied at the end of follow-up, six (37%) were moderately satisfied and four (25%) were highly satisfied. The treatment was considered failed in five out of 16 patients (31%). Among them, four (25%) required re-interventions with implantation of ankle prostheses, whereas one patient was treated with a further AMIC technique combined with autologous bone graft and platelet-rich plasma. The mean MOCART score was 41.9 ± 14.6 (25-70) 12 months after surgery and 51.9 ± 11.6 (30-70) after 24 months, with a statistically significant increase (P = 0.012). However, no correlation was seen between AOFAS and MOCART changes (r = 0.215, p = 0.609). CONCLUSION: The high rates of treatment failure encountered in our study using MaioRegen need to be confirmed by larger studies and should induce the scientific community questioning the reliability of this biomimetic scaffold for the treatment of OLTs.

Microencapsulated VEGF gene-modified umbilical cord mesenchymal stromal cells promote the vascularization of tissue-engineered dermis: an experimental study.

BACKGROUND AIMS: Tissue-engineered dermis (TED) is thought to be the best treatment for skin defect wounds; however, lack of vascular structures in these products can cause slow vascularization or even transplant failure. We assessed the therapeutic potential of microencapsulated human umbilical cord mesenchymal stromal cells (hUCMSCs) expressing vascular endothelial growth factor (VEGF) in vascularization of TED. METHODS: hUCMSCs were isolated by means of enzymatic digestion and identified by means of testing biological characteristics. hUCMSCs were induced to differentiate into dermal fibroblasts in conditioned induction media. Collagen-chitosan laser drilling acellular dermal matrix (ADM) composite scaffold was prepared by means of the freeze dehydration and dehydrothermal cross-linking method. hUCMSC-derived fibroblasts were implanted on composite scaffolds to construct TED. TED with microencapsulated VEGF gene-modified hUCMSCs was then transplanted into skin defect wounds in pigs. The angiogenesis of TED at 1 week and status of wound healing at 3 weeks were observed. RESULTS: The collagen-chitosan laser ADM composite has a uniform microporous structure. This composite has been used to grow hUCMSC-derived fibroblasts in vitro and to successfully construct stem cell-derived TED. Microencapsulated VEGF gene-modified hUCMSCs were prepared with the use of a sodium alginate-barium chloride one-step encapsulation technology. Seven days after the transplantation of the stem cell-derived TED and microencapsulated VEGF gene-modified hUCMSCs into the skin defect wounds on the backs of miniature pigs, the VEGF expression increased and the TED had a higher degree of vascularization. Re-epithelialization of the wound was completed after 3 weeks. CONCLUSIONS: Microencapsulated VEGF gene-modified hUCMSCs can effectively improve the vascularization of TED and consequently the quality of wound healing.

Adipose-derived stem cells modified genetically in vivo promote reconstruction of bone defects.

AIMS: Bone defects induced by different causes are difficult to replace and repair. We sought to repair bone defects by transplantation of genetically modified adipose-derived stem cells (ADSC) and acellular bone matrix (ACBM). METHODS: We constructed the biologic material of ACBM and evaluated its mechanical properties, general biocompatibility and biosafety. ADSC isolated from minipigs were cultured in vitro and then transfected by recombinant human bone morphogenetic protein-2 (rhBMP-2) and recombinant human vascular endothelial growth factor (rhVEGF) plasmids, respectively. Subsequently, the compounds of ACBM/ADSC/rhBMP-2/rhVEGF were used to repair bone defects of the ulna in minipigs. X-ray examination, radionuclide bone imaging and single photon emission computerized tomography (SPECT) were employed to monitor the therapeutic effects 2, 4, 8 and 12 weeks after operation. Histologic experiments were carried out 12 weeks after operation. RESULTS: ACBM had no or weak antigenicity and the natural mechanical properties of ACBM were preserved. In vitro, ADSC transfected by rhBMP-2 and rhVEGF, respectively, could release rhBMP-2 or rhVEGF for at least 4 weeks. The X-ray, radionuclide bone imaging and SPECT examinations indicated that the compound of ACBM/ADSC/rhBMP-2/rhVEGF had better treatment effects on bone defects compared with the controls. CONCLUSIONS: Scaffolds, seed cells and bioactive factors are key points in tissue engineering. This research indicates that ACBM is a good biologic material for tissue repair, and ACBM/ADSC/rhBMP-2/rhVEGF can accelerate bone formation significantly.

Implantation of polymer scaffolds seeded with neural stem cells in a canine spinal cord injury model.

BACKGROUND AIMS: Combinatorial approaches employing diverse therapeutic modalities are required for clinically relevant repair of injured spinal cord in human patients. Before translation into the clinic, the feasibility and therapeutic potential of such combinatorial strategies in larger animal species need to be examined. METHODS: The present study tested the feasibility of implanting polymer scaffolds via neural stem cell (NSC) delivery in a canine spinal cord injury (SCI) model. The poly(lactic-co-glycolic acid) (PLGA) scaffolds seeded with human NSC were implanted into hemisected canine spinal cord. RESULTS: The PLGA scaffolds bridged tissue defects and were nicely integrated with residual canine spinal cord tissue. Grafted NSC survived the implantation procedure and showed migratory behavior to residual spinal cord tissue. Ectopic expression of a therapeutic neurotrophin-3 gene was also possible in NSC seeded within the PLGA scaffolds. CONCLUSIONS: Our description of a canine SCI model would be a valuable resource for pre-clinical trials of combinatorial strategies in larger animal models.

Cell therapy for spinal cord repair: optimization of biologic scaffolds for survival and neural differentiation of human bone marrow stromal cells.

BACKGROUND AIMS: The suppression of cell apoptosis using a biodegradable scaffold to replace the missing or altered extracellular matrix (ECM) could increase the survival of transplanted cells and thus increase the effectiveness of cell therapy. METHODS: We studied the best conditions for the proliferation and differentiation of human bone marrow stromal cells (hBMSC) when cultured on different biologic scaffolds derived from fibrin and blood plasma, and analyzed the best concentrations of fibrinogen, thrombin and calcium chloride for favoring cell survival. The induction of neural differentiation of hBMSC was done by adding to these scaffolds different growth factors, such as nerve growth factor (NGF), brain-derived-neurotrophic factor (BDNF) and retinoic acid (RA), at concentrations of 100 ng/mL (NGF and BDNF) and 1 micro/mL (RA), over 7 days. RESULTS: Although both types of scaffold allowed survival and neural differentiation of hBMSC, the results showed a clear superiority of platelet-rich plasma (PRP) scaffolds, mainly after BDNF administration, allowing most of the hBMSC to survive and differentiate into a neural phenotype. CONCLUSIONS: Given that clinical trials for spinal cord injury using hBMSC are starting, these findings may have important clinical applications.

Tissue engineering with meniscus cells derived from surgical debris.

OBJECTIVE: Injuries to the avascular regions of the meniscus fail to heal and so are treated by resection of the damaged tissue. This alleviates symptoms but fails to restore normal load transmission in the knee. Tissue engineering functional meniscus constructs for re-implantation may improve tissue repair. While numerous studies have developed scaffolds for meniscus repair, the most appropriate autologous cell source remains to be determined. In this study, we hypothesized that the debris generated from common meniscectomy procedures would possess cells with potential for forming replacement tissue. We also hypothesized that donor age and the disease status would influence the ability of derived cells to generate functional, fibrocartilaginous matrix. METHODS: Meniscus derived cells (MDCs) were isolated from waste tissue of 10 human donors (seven partial meniscectomies and three total knee arthroplasties) ranging in age from 18 to 84 years. MDCs were expanded in monolayer culture through passage 2 and seeded onto fiber-aligned biodegradable nanofibrous scaffolds and cultured in a chemically defined media. Mechanical properties, biochemical content, and histological features were evaluated over 10 weeks of culture. RESULTS: Results demonstrated that cells from every donor contributed to increasing biochemical content and mechanical properties of engineered constructs. Significant variability was observed in outcome parameters (cell infiltration, proteoglycan and collagen content, and mechanical properties) amongst donors, but these variations did not correlate with patient age or disease condition. Strong correlations were observed between the amount of collagen deposition within the construct and the tensile properties achieved. In scaffolds seeded with particularly robust cells, construct tensile moduli approached maxima of approximately 40 MPa over the 10-week culture period. CONCLUSIONS: This study demonstrates that cells derived from surgical debris are a potent cell source for engineered meniscus constructs. Results further show that robust growth is possible in MDCs from middle-aged and elderly patients, highlighting the potential for therapeutic intervention using autologous cells.

Long-term Evaluation of Meniscal Tissue Formation in 3-dimensional-Printed Scaffolds With Sequential Release of Connective Tissue Growth Factor and TGF-ß3 in an Ovine Model.

BACKGROUND: Artificial meniscal scaffolds are being developed to prevent development of osteoarthritis after meniscectomy. Previously, it was reported that 3-dimensional (3D) anatomic scaffolds loaded with connective tissue growth factor (CTGF) and transforming growth factor ß3 (TGF-ß3) achieved meniscal regeneration in an ovine model. This was a relatively short-term study (3 months postoperative), and outcome analyses did not include magnetic resonance imaging (MRI). PURPOSE: To evaluate long-term outcome of meniscal replacement with growth factor-laden poly-ε-caprolactone (PCL) scaffolds. STUDY DESIGN: Controlled laboratory study. METHODS: Anatomically shaped ovine meniscal scaffolds were fabricated from PCL with a 3D printer based on MRI data. Skeletally mature sheep (N = 34) were randomly allocated to 3 groups: scaffold without growth factor (0-µg group), scaffold with CTGF microspheres (µS) (5 µg) + TGF-ß3 µS (5 µg) (5-µg group), and scaffold with CTGF µS (10 µg) + TGF-ß3 µS (10 µg) (10-µg group). Unilateral medial meniscal replacement was performed. Animals were euthanized at 6 or 12 months. Regenerated meniscus, articular cartilage status, and synovial reaction were evaluated quantitatively with gross inspection, histology, and MRI. Kruskal-Wallis and Dunn tests were used to compare the 3 groups. RESULTS: Remnants of the PCL scaffold were evident in the 6-month specimens and were decreased but still present at 12 months in most animals. There were no significant differences among groups in gross inspection, histology, or MRI for either meniscal regeneration or articular cartilage protection. All experimental groups exhibited articular cartilage degeneration as compared with control (nonoperated). In terms of synovitis, there were no clear differences among groups, suggesting that growth factors did not increase inflammation and fibrosis. MRI revealed that meniscal extrusion was observed in most animals (82.7%). CONCLUSION: Previously, the combination of CTGF and TGF-ß3 was shown to stimulate mesenchymal stem cells into a fibrochondrocyte lineage. CTGF and TGF-ß3 did not aggravate synovitis, suggesting no adverse response to the combination of 3D-printed PCL scaffold combined with CTGF and TGF-ß3. Further work will be required to improve scaffold fixation to avoid meniscal extrusion. CLINICAL RELEVANCE: A significant advantage of this technique is the ability to print custom-fit scaffolds from MRI-generated templates. In addition, average-size menisci could be printed and available for off-the-shelf applications. Based on the 1-year duration of the study, the approach appears to be promising for meniscal regeneration in humans.

Uptake of Drug-Eluting Bioresorbable Vascular Scaffolds in Clinical Practice: An NCDR Registry to Practice Project.

Importance: Physicians have been criticized for having an overly enthusiastic response to new device approvals, especially for novel technologies. However, to our knowledge, the rates of new product adoption and patterns of new device usage in clinical practice have not been well described. Objective: To characterize the patterns of uptake of bioresorbable vascular scaffolds (BVS) within the United States following device approval and to describe changes in response to subsequent releases of data and US Food and Drug Administration (FDA) warnings. Design, Setting, and Participants: This analysis of the uptake of BVS between January 2016 and June 2017 used CathPCI Registry data; all percutaneous coronary intervention (PCI) procedures with an implant of either a BVS or conventional stent were included. Data analysis was performed in October 2017. Exposures: Implant of BVS. Main Outcomes and Measures: The primary outcome was monthly use of BVS in the United States. In addition, the characteristics of patients who received BVS and of hospitals that used BVS were assessed and comparisons of patient characteristics between BVS recipients and patients who were treated contemporaneously with metallic stents were made. Results: Of 682 951 procedures, 471 064 (69.0%) were done in men, 587 301 (86.0%) were among white people, and the mean (SD) age of those undergoing procedures with BVS vs conventional stents was 62.6 (11.4) years vs 65.7 (11.9) years. Of these, 4265 procedures (0.6%) used BVS overall (after FDA approval of BVS). Procedures with implants of BVS occurred among patients with fewer comorbidities and lower-acuity presentations compared with procedures with implants of conventional stents. The patient characteristics for BVS use were not dissimilar to the inclusion criteria of the ABSORB III FDA approval trial, with notable differences based on trial eligibility (eg, excluding patients with myocardial infarctions). The maximum monthly use of BVS was 1.25% of all PCI procedures that occurred 90 days after FDA approval, but with site-to-site variability. Declines in use were observed coincident with the scientific presentation of adverse event data as well as FDA warnings. Conclusions and Relevance: Most US physicians and hospitals were selective in their use of BVS, primarily using them in patients similar to those in the device's FDA approval trial. In addition, declines in use were evident in the subsequent month following the release of data that reported negative outcomes. These results illustrate an example of an appropriate physician response to adverse data updates and FDA warnings.

A novel exogenous concentration-gradient collagen scaffold augments full-thickness articular cartilage repair.

OBJECTIVES: A collagen scaffold has been long used in order to enhance the regeneration of articular cartilage. In the present study, we investigate the effectiveness of a concentration-gradient (CG) collagen that is designed to recruit efficiently the mesenchymal stem cells (MSCs) to the central region of the full-thickness cartilage defects via haptotaxis. METHODS: The present study used Cellmatrix (0.3% type I collagen; Nitta gelatin, Osaka, Japan) as the collagen material. We prepared 33%CG collagen gel and 50%CG collagen gel. No gradient collagen gel served as negative control. Full-thickness cartilage defects were created at the patella groove of the rabbit knee, to which the three different collagen gels were transplanted. Bromodeoxyuridine (BrdU) positive, proliferating cells were enumerated and localized, whereas the histological grading score for cartilage regeneration was counted. The expression of type I and type II collagens was evaluated by immunohistochemistry. We also confirmed that the MSCs migrate toward the collagen substrate of higher concentration in a stringently in vitro haptotactic manner. RESULTS: Enumeration of the BrdU-positive cells demonstrated that 33%CG collagen gel recruited a significantly larger number of proliferating cells to the central region of the cartilage defect. The histological grading score for the regenerated cartilage treated with 33%CG collagen gel was superior to the other groups. CONCLUSIONS: CG collagen scaffold recruits effectively the MSCs to the center of full-thickness cartilage defect and enhances regeneration of the full-thickness cartilage defect.

Regeneration of tracheal epithelium utilizing a novel bipotential collagen scaffold.

OBJECTIVES: The purpose of the present study was to evaluate the effectiveness of a novel bipotential collagen scaffold as a bioengineered trachea for the regeneration of the tracheal epithelium. METHODS: The bipotential collagen scaffold was developed by conjugating a collagen vitrigel membrane to a collagen sponge in order to promote both epithelial cell growth and mesenchymal cell infiltration. The bipotential collagen scaffold was transplanted into tracheal defects in rats, and a conventional collagen sponge was implanted as a control model. Histologic examinations were undertaken to evaluate the results. RESULTS: The bioengineered trachea was covered with epithelium in the vitrigel model, but not in the control model, at 7 days after implantation. At 14 days after implantation, the bioengineered trachea was covered with epithelium involving the basal cell layer in the vitrigel model. At 28 days after implantation, a columnar ciliated epithelium was observed only in the vitrigel model. CONCLUSIONS: Our technique for trachea reconstruction using a novel bipotential collagen scaffold affords a feasible approach for accelerating epithelial regeneration on the intraluminal surface of the host tracheal defect.

On the process capability of the solid free-form fabrication: a case study of scaffold moulds for tissue engineering.

This study applies the methodology and procedure of process capability to investigate a solid free-form fabrication technique as a manufacturing method to produce scaffold moulds for tissue engineering. The process capability Cpk and process performance Ppk of scaffold mould manufacture using a solid free-form fabrication technique has been analysed with respect to the dimension deviations. A solid free-form fabrication machine T66 was used to fabricate scaffold moulds in this study and is able to create features that ranged from 200 microm to 1000 microm. The analysis showed that the printing process under the normal cooling conditions of the printing chamber was in statistical control but gave low process capability indices, indicating that the process was 'inadequate' for production of 'dimension-consistent' scaffold moulds. The study demonstrates that, by lowering the temperature of the cooling conditions, the capability Cpk of the printing process can be improved (about threefold) sufficiently to ensure the consistent production of scaffold moulds with dimension characteristics within their specification limits.

Tissue-Engineered Total Meniscus Replacement With a Fiber-Reinforced Scaffold in a 2-Year Ovine Model.

BACKGROUND: Meniscus injuries and associated meniscectomies cause patients long-term pain and discomfort and can lead to joint deterioration. PURPOSE: To evaluate a collagen-hyaluronan sponge reinforced with synthetic resorbable polymer fiber for total meniscus reconstruction in a long-term ovine model. STUDY DESIGN: Controlled laboratory study. METHODS: Eleven skeletally mature sheep were implanted with the total meniscus scaffold. At 2 years, explants were evaluated biologically (radial/circumferential histology, immunofluorescence) and mechanically (compression, tension), and articular surfaces were examined for damage. RESULTS: The fiber-reinforced scaffold induced formation of functional neomeniscus tissue that was intact in 8 of 11 animals. The implant was remodeled into organized circumferentially aligned collagen bundles to resist meniscus hoop stresses. Moreover, type II collagen and proteoglycan deposition near the inner margin suggested a direct response to compressive stresses and confirmed fibrocartilage formation. Cartilage damage was observed, but end-stage (severe) joint deterioration associated with meniscectomy was avoided, even with limitations regarding the ovine surgical procedure and postoperative care. CONCLUSION: A fiber-reinforced total meniscus replacement device induces formation of functional neomeniscus tissue that has the potential to prevent catastrophic joint deterioration associated with meniscectomy. CLINICAL RELEVANCE: An off-the-shelf meniscus device that can be remodeled into functional tissue and thus prevent or delay the onset of osteoarthritis could address a widespread clinical need after meniscus injury.

Electrically Conductive Scaffold to Modulate and Deliver Stem Cells.

Stem cell therapy has emerged as an exciting stroke therapeutic, but the optimal delivery method remains unclear. While the technique of microinjection has been used for decades to deliver stem cells in stroke models, this technique is limited by the lack of ability to manipulate the stem cells prior to injection. This paper details a method of using an electrically conductive polymer scaffold for stem cell delivery. Electrical stimulation of stem cells using a conductive polymer scaffold alters the stem cell's genes involved in cell survival, inflammatory response, and synaptic remodeling. After electrical preconditioning, the stem cells on the scaffold are transplanted intracranially in a distal middle cerebral artery occlusion rat model. This protocol describes a powerful technique to manipulate stem cells via a conductive polymer scaffold and creates a new tool to further develop stem cell-based therapy.

Is There a Role for Internal Bracing and Repair of the Anterior Cruciate Ligament? A Systematic Literature Review.

BACKGROUND: Renewed interest has arisen in arthroscopic anterior cruciate ligament (ACL) repair techniques. HYPOTHESIS: ACL repair with or without some form of internal bracing could lead to good outcomes in a carefully selected subset of patients. STUDY DESIGN: Systematic review. METHODS: An electronic database search was performed to identify 89 papers describing preclinical and clinical studies on the outcome of ACL repair. RESULTS: Proximal ACL tear patterns showed a better healing potential with primary repair than distal or midsubstance tears. Some form of internal bracing increased the success rate of ACL repair. Improvement in the biological characteristics of the repair was obtained by bone marrow access by drilling tunnels or microfracture. Augmentation with platelet-rich plasma was beneficial only in combination with a structural scaffold. Skeletally immature patients had the best outcomes. Acute repair offered improved outcomes with regard to load, stiffness, laxity, and rerupture. CONCLUSION: ACL repair may be a viable option in young patients with acute, proximal ACL tears. The use of internal bracing, biological augmentation, and scaffold tissue may increase the success rate of repair.

Therapeutic Effects of the Addition of Platelet-Rich Plasma to Bioimplants and Early Rehabilitation Exercise on Articular Cartilage Repair.

BACKGROUND: Treating articular cartilage lesions is clinically challenging. However, whether the addition of autologous platelet-rich plasma (PRP) to bioimplants along with early rehabilitation exercise provides therapeutic effects and regenerates the osteochondral defect remains uninvestigated. HYPOTHESIS: The addition of PRP to a polylactic-co-glycolic acid (PLGA) scaffold along with continuous passive motion (CPM) in osteochondral defects may offer beneficial in situ microenvironment changes to facilitate hyaline cartilage and subchondral bone tissue repair. STUDY DESIGN: Controlled laboratory study. METHODS: In 26 rabbits, 52 critical osteochondral defects were created in bilateral femoral trochlear grooves. The rabbits were allocated to 1 of the following 3 groups: PRP gel (PG group), PRP + PLGA scaffold (PP group), and PRP + PLGA scaffold + CPM (PPC group). At 4 and 12 weeks after surgery, the specimens were assessed by a macroscopic examination, a histological evaluation with immunohistochemical staining, and micro-computed tomography. RESULTS: The PPC group exhibited the most favorable therapeutic outcomes in terms of hyaline cartilage regeneration. At week 4, the PPC group exhibited significantly higher levels of glycosaminoglycan (GAG) and collagen (COL) II and modest increases in COL I, matrix metalloproteinase-3 (MMP-3), and inflammatory cells with tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6). At week 12, the PPC group had significantly higher tissue repair scores, corresponding to a sound articular cartilage surface and chondrocyte and collagen arrangement. This group demonstrated restored hyaline cartilage and mineralized bone volume per tissue volume, which had an integrating structure in the repair site. However, the PG and PP groups exhibited mainly fibrous tissue and fibrocartilage, corresponding to higher expressions of COL I, TNF-α, IL-6, and MMP-3. CONCLUSION: PRP with a PLGA graft along with early CPM exercise is promising for the repair of osteochondral defects in rabbit knee joints. CLINICAL RELEVANCE: This study demonstrates the efficacy of a triad therapy involving the addition of PRP to bioimplants along with early CPM intervention for hyaline cartilage and subchondral regeneration. However, PRP alone (with or without PLGA implants) is limited to osteochondral defect repair without significant regeneration.

Relevant biological processes for tissue development with stem cells and their mechanistic modeling: A review.

A potential alternative for tissue transplants is tissue engineering, in which the interaction of cells and biomaterials can be optimized. Tissue development in vitro depends on the complex interaction of several biological processes such as extracellular matrix synthesis, vascularization and cell proliferation, adhesion, migration, death, and differentiation. The complexity of an individual phenomenon or of the combination of these processes can be studied with phenomenological modeling techniques. This work reviews the main biological phenomena in tissue development and their mathematical modeling, focusing on mesenchymal stem cell growth in three-dimensional scaffolds.

The mechanisms of late scaffold thrombosis.

Coronary scaffolds have been recently developed to address the long-term limitations of metallic drug eluting stents. Concerns have however been expressed on the safety of these devices, with evidence of both early and late scaffold thrombosis. While early thrombosis has been associated with incomplete scaffold expansion, leading to flow disturbances, blood recirculation, and platelet activation, the pathophysiology of late events remains less understood. Recent cases series have shown that malapposition and scaffold dismantling might play a role in this phenomenon, an observation that further confirms the importance of an accurate implantation. Further, the role of dual antiplatelet therapy, and whether prolonging it may reduce event rates, remains to be elucidated. As well, the role of inflammatory phenomena has been proposed but never demonstrated. This brief review summarizes the current evidence on these phenomena.