Quality Of Repair Tissue Research Articles

Use of Platelet-Rich Plasma Immediately After an Injury Did Not Improve Ligament Healing, and Increasing Platelet Concentrations Was Detrimental in an In Vivo Animal Model

Background: Limited information in basic science and clinical trials exists to determine if ligament healing may be accelerated with the use of biological adjuvants, such as platelet-rich plasma (PRP). However, there has been widespread acceptance of PRP for use in clinical practice, despite an inadequate understanding of its biological mechanism of action. Purpose: To determine whether a single dose of PRP could accelerate ligament healing and correspondingly improve histological characteristics and biomechanical properties when injected immediately postoperatively into the injured medial collateral ligament (MCL) of New Zealand White rabbits. Study Design: Controlled laboratory study. Methods: Eighty skeletally mature New Zealand White rabbits (160 knees) were used. The MCL was torn midbody to simulate a grade 3 tear. After an acute injury of the MCL, the administration of autologous PRP at 3 different platelet concentrations (0 million/uL, platelet-poor plasma [PPP]; 0.6 million/uL, 2 times the baseline [2× PRP]; and 1.2 million/uL, 4 times the baseline [4× PRP]) was performed and compared with a saline injection control in the contralateral knee. Histological analysis and a biomechanical endpoint characterization were utilized to assess ligamentous healing and compare it to a sham surgery group. Results: The PPP (P = .001) and 4× PRP (P = .002) groups had a significantly lower collagen subscore than the sham surgery group. No other differences were observed among the treatment groups, including the vascularity subscore and overall ligament tissue maturity index score. Compared with saline-injected contralateral knees, the maximum load for PPP and 2× PRP was not significantly different (P = .788 and .325, respectively). The maximum load and stiffness for knees treated with 4× PRP were significantly less than for the saline-treated contralateral knees (P = .006 and .001, respectively). Conclusion: One single dose of PPP or 2× PRP at the time of injury did not improve ligament healing. In addition, 4× PRP negatively affected ligament strength and histological characteristics at 6 weeks after the injury. Clinical Relevance: The current practice of treating knee ligament injuries with PRP may not improve healing at low doses of PRP. The decreased mechanical properties and histological appearance of the torn MCL suggest that high doses of PRP decrease the quality of repair tissue. Further in vivo studies are necessary to determine the dosing and timing of PRP administration after a ligament injury before the widespread use of PRP to treat ligament injuries is recommended.

Dynamic computational simulations for evaluating tissue loads applied by regulated negative pressure-assisted wound therapy (RNPT) system for treating large wounds

Regulated negative pressure-assisted wound therapy (RNPT) is one of the most important wound treatment technologies developed and applied over the last two decades. To-date RNPT has been proven to be clinically effective in treating chronic wounds, however, the effects of different specific pressure delivery protocols on the progress and quality of tissue repair are not adequately understood yet. Here, we suggest a viscoelastic, three-dimensional finite element modeling framework of RNPT, with several realistic features such as a non-symmetrically configured multi-layered tissue structure. The effects of the RNPT system on the wound-bed were simulated by applying time varying pressure boundary conditions. Three commonly-used operation modes were simulated: continuous, non-continuous intermittent and dynamic, and each mode was applied at four different pressure levels. Outcome measures of strain and stress magnitudes and distributions were acquired from the dermis and subcutaneous fat. Taken together, the strain and stress data from the different simulated RNPT modes and intensities demonstrated that tissue loads which are actually applied in and around the wound, and at the different tissue components of the wound, can differ substantially from the pressure levels that are set in the device during therapy sessions. This is critical information for understanding the potential effects of RNPT, for setting the device prior to therapy and for designing the next generation of these systems.

A Comparison of 2-Year Outcomes in Patients Undergoing Tibiofemoral or Patellofemoral Matrix-Induced Autologous Chondrocyte Implantation

Background: Matrix-induced autologous chondrocyte implantation (MACI) has demonstrated encouraging clinical results in the treatment of knee chondral defects. However, earlier studies suggested that chondrocyte implantation in the patellofemoral (PF) joint was less effective than in the tibiofemoral (TF) joint. Purpose: To compare the radiological and clinical outcomes of those undergoing MACI to either the femoral condyles or PF joint. Study Design: Cohort study; Level of evidence, 3. Methods: A total of 194 patients were included in this analysis, including 127 undergoing MACI to the medial (n = 94) and lateral (n = 33) femoral condyle, as well as 67 to the patella (n = 35) or trochlea (n = 32). All patients were evaluated clinically (Knee injury and Osteoarthritis Outcome Score [KOOS], visual analog scale, Short Form–36) before surgery and at 3, 12, and 24 months after surgery, while magnetic resonance imaging (MRI) was undertaken at 3, 12, and 24 months, with the MOCART (magnetic resonance observation of cartilage repair tissue) scoring system employed to evaluate the quality and quantity of repair tissue, as well as an MRI composite score. Patient satisfaction was evaluated. Results: No significant group differences (P > .05) were seen in demographics, defect size, prior injury, or surgical history, while the majority of clinical scores were similar preoperatively. All clinical scores significantly improved over time (P < .05), with a significant group effect observed for KOOS activities of daily living (P = .008), quality of life (P = .008), and sport (P = .017), reflecting better postoperative scores in the TF group. While the PF group had significantly lower values at baseline for the KOOS activities of daily living and quality of life subscales, it actually displayed a similar net improvement over time compared with the TF group. At 24 months, 93.7% (n = 119) and 91.0% (n = 61) of patients were satisfied with the ability of MACI to relieve their knee pain, 74.0% (n = 94) and 65.7% (n = 44) with their ability to participate in sport, and 90.5% (n = 115) and 83.6% (n = 56) satisfied overall, in the TF and PF groups, respectively. MRI evaluation via the MOCART score revealed a significant time effect (P < .05) for the MRI composite score and graft infill over the 24-month period. While subchondral lamina scored significantly better (P = .002) in the TF group, subchondral bone scored significantly worse (P < .001). At 24 months, the overall MRI composite score was classified as good/excellent in 98 TF patients (77%) and 54 PF patients (81%). Conclusion: MACI in the PF joint with concurrent correction of PF maltracking if required leads to similar clinical and radiological outcomes compared with MACI on the femoral condyles.

Featured Article: Invitro development of personalized cartilage microtissues uncovers an individualized differentiation capacity of human chondrocytes.

Personalized features in the treatment of knee injuries and articular replacement therapies play an important role in modern life with increasing demand. Therefore, cell-based therapeutic approaches for the regeneration of traumatic defects of cartilage tissue were developed. However, great variations in the quality of repair tissue or therapeutic outcome were observed. The aim of the study was to capture and visualize individual differentiation capacities of chondrocytes derived from different donors with regard to a possible personal regeneration capacity using a cell-based therapy. The redifferentiation potential of monolayer cultured cells was analyzed in a scaffold-free three-dimensional tissue model. Furthermore, stimulating options using cartilage maturation factors such as L-ascorbic acid and transforming growth factor beta 2 (TGF-β2) on this process were of special interest. Cells and tissues were analyzed via histological and immunohistochemical methods. Gene expression was measured by quantitative real-time polymerase chain reaction. In monolayer culture, cells from all donors showed an almost identical differentiation profile. In contrast, the differentiation state of cartilage-like three-dimensional microtissues revealed clear differences with respect to individual donors. Analyses at the protein and mRNA levels showed high variations regarding cartilage-typical matrix components (e.g. proteoglycans, collagen type II) and intracellular proteins (e.g. S100). Interestingly, only donor chondrocytes with a basic tendency to re-differentiate in a three-dimensional environment were able to increase this tissue-specific maturation when exposed to L-ascorbic acid and/or TGF-β2. Our approach revealed clear-cut possibilities for classification of individual donors into responders or non-responders. On the basis of these results an invitro platform could be designed to discriminate responders from non-responders. This invitro three-dimensional test system may be a suitable basis to establish a "personalized diagnostic tool" with the opportunity to assess the capacity of expanded chondrocytes to respond to an autologous cell-based therapy. Impact statement A challenge in cell-based cartilage regeneration therapies is the identification of a "personalized diagnostic tool" to predict the chondrogenic potency of cells from patients who are going to be treated with autologous cells. Comparing the phenotype of isolated chondrocytes from different donors invitro revealed an individual cartilage-specific differentiation capacity. These personalized features are not detectable invitro until the monolayer cells have the possibility to rearrange in 3D tissues. Cells from articular cartilage in monolayer culture may not be a suitable basis to discriminate responders from non-responders with respect to a personalized cell-based therapy to treat cartilage defects. A more physiological 3D (micro-)environment enable the cells to present their individual differentiation capacity. The here described microtissue model might be the basis for an invitro platform to predict the therapeutic outcome of autologous cell-based cartilage repair and/or a suitable tool to identify early biomarkers to classify the patients.

Sustained Release of Transforming Growth Factor-β1 from Platelet-Rich Chondroitin Sulfate Glycosaminoglycan Gels.

Activated platelet-rich plasma (PRP), also referred to as platelet-rich fibrin (PRF), has been used to augment numerous techniques of cartilage repair in the knee but does not always result in superior quality of repair tissue. One possible reason that PRF does not consistently result in excellent cartilage regeneration is the transiency of growth factor provision with PRF. The objective of this study was to compare the release of transforming growth factor (TGF)-β1 from PRF and from PRP combined with a novel chondroitin sulfate glycosaminoglycan (CS-GAG) gel. PRP was prepared from nine healthy dogs and split into two aliquots: one activated with bovine thrombin and calcium chloride (CaCl2) to form PRF and the other aliquot was used to rehydrate a lyophilized CS-GAG gel. Both PRF and the CS-GAG gels were incubated in media for 13 days and media were collected, stored, and replaced every 48 hours and the concentration of TGF-β1 quantified in the media using an enzyme-linked immunosorbent assay. Concentrations of TGF-β1 in the media were up to three times greater with the CS-GAG gels and were significantly (p < 0.05) greater than with PRF on days 3, 5, 7, 9, and 13. Furthermore, TGF-β1 elution was still substantial at day 13 with the use of the CS-GAG gels. Additional in vitro work is warranted to characterize TGF-β1 elution from this CS-GAG gel with human PRP and to determine whether the use of these CS-GAG gels can augment cartilage repair in vivo.

The comparison of the effects of a novel hydrogel compound and traditional hyaluronate following micro-fracture procedure in a rat full-thickness chondral defect model

PurposeThe aim of this experimental study was to investigate the impact of HA–CS–NAG compound (hyaluronate, sodium chondroitin sulfate, N-acetyl-d-glucosamine) on the quality of repair tissue after micro-fracture and to compare it with HA (hyaluronat), in a rat full-thickness chondral defect model. MethodsFull-thickness chondral defects were created in a non-weight bearing area by using a handle 2.7-mm drill bit, in the right knees of 33 Sprague–Dawley rats. Each specimen then underwent micro-fracture using a needle. Two weeks after surgery, 3 groups were randomly formed among the rats (n = 33). In Group 1, 0.2 mL of sterile saline solution (0.9%) was injected. In Group 2, 0.2 mL HA with a mean molecular weight of 1.2 Mda was injected. In Group 3, 0.2 mL of HA–CS–NAG compound (hyaluronate, sodium chondroitin sulfate, N-acetyl-d-glucosamine) was injected. The injections were applied on the 14th, the 21st and the 28th postoperative days. All rats were sacrificed on the 42nd postoperative day. Histological analysis of the repair tissue was performed for each specimen by two blinded observers using Wakitani scoring system. ResultsThere was significantly improved repair tissue in both Group 3 and Group 2 when compared with Group 1. Group 3 showed statistically significant improvement in terms of ‘cell morphology’ and ‘integration of donor with host’ when compared to Group 2 (p < 0.001). ConclusionIntra-articular injection of HA–CS–NAG compound after micro-fracture results in significantly improved repair tissue in rats' chondral defects when compared to HA regarding the donor integration and cell morphology.

Effect of Footprint Preparation on Tendon-to-Bone Healing: A Histologic and Biomechanical Study in a Rat Rotator Cuff Repair Model

To compare the histologic and biomechanical effects of 3 different footprint preparations for repair of tendon-to-bone insertions and to assess the behavior of bone marrow-derived cells in each method of insertion repair. We randomized 81 male Sprague-Dawley rats and green fluorescent protein-bone marrow chimeric rats into 3 groups. In group A, we performed rotator cuff repair after separating the supraspinatus tendon from the greater tuberosity and removing the residual tendon tissue. In group B, we also drilled 3 holes into the footprint. The native fibrocartilage was preserved in groups A and B. In group C, we excavated the footprint until the cancellous bone was exposed. Histologic repair of the tendon-to-bone insertion, behavior of the bone marrow-derived cells, and ultimate force to failure were examined postoperatively. The areas of metachromasia in groups A, B, and C were 0.033 ± 0.019, 0.089 ± 0.022, and 0.002 ± 0.001mm2/mm2, respectively, at 4weeks and 0.029 ± 0.022, 0.090 ± 0.039, and 0.003 ± 0.001mm2/mm2, respectively, at 8weeks. At 4 and 8weeks postoperatively, significantly higher cartilage matrix production was observed in group B than in group C (4weeks, P= .002; 8weeks, P < .001). In green fluorescent protein-bone marrow chimeric rats in group B, bone marrow-derived chondrogenic cells infiltrated the fibrocartilage layer. Ultimate force to failure was significantly higher in group B (19.7 ± 3.4N) than in group C (16.7 ± 2.0N) at 8weeks (P= .031). Drilling into the footprint and preserving the fibrocartilage improved the quality of repair tissue and biomechanical strength at the tendon-to-bone insertion after rotator cuff repair in an animal model. Drilling into the footprint and preserving the fibrocartilage can enhance repair of tendon-to-bone insertions. This method may be clinically useful in rotator cuff repair.

Co-culture of dedifferentiated and primary human chondrocytes obtained from cadaveric donor enhance the histological quality of repair tissue: an in-vivo animal study.

To compare the quality of the repair tissue in three-dimensional co-culture of human chondrocytes implanted in an in vivo model. Six cadaveric and five live human donors were included. Osteochondral biopsies from the donor knees were harvested for chondrocyte isolation. Fifty percent of cadaveric chondrocytes were expanded until passage-2 (P2) while the remaining cells were cryopreserved in passage-0 (P0). Fresh primary chondrocytes (P0f) obtained from live human donors were co-cultured. Three-dimensional constructs were prepared with a monolayer of passage-2 chondrocytes, collagen membrane (Geistlich Bio-Gide®), and pellet of non-co-cultured (P2) or co-cultured chondrocytes (P2+P0c, P2+P0f). Constructs were implanted in the subcutaneous tissue of athymic mice and left for 3months growth. Safranin-O and Alcian blue staining were used to glycosaminoglycan content assessment. Aggrecan and type-II collagen were evaluated by immunohistochemistry. New-formed tissue quality was evaluated with an adaptation of the modified O'Driscoll score. Histological quality of non-co-cultured group was 4.37 (SD ±4.71), while co-cultured groups had a mean score of 8.71 (SD ±3.98) for the fresh primary chondrocytes and 9.57 (SD ±1.27) in the cryopreserved chondrocytes. In immunohistochemistry, Co-culture groups were strongly stained for type-II and aggrecan not seen in the non-co-cultured group. It is possible to isolate viable chondrocytes from cadaveric human donors in samples processed in the first 48-h of dead. There is non-significant difference between the numbers of chondrocytes isolated from live or cadaveric donors. Cryopreservation of cadaveric primary chondrocytes does not alter the capability to form cartilage like tissue. Co-culture of primary and passaged chondrocytes enhances the histological quality of new-formed tissue compared to non-co-cultured cells.

Autologous Cartilage Chip Transplantation Improves Repair Tissue Composition Compared With Marrow Stimulation

Background: Repair of chondral injuries by use of cartilage chips has recently demonstrated clinical feasibility. Purpose: To investigate in vivo cartilage repair outcome of autologous cartilage chips compared with marrow stimulation in full-thickness cartilage defects in a minipig model. Study Design: Controlled laboratory study. Methods: Six Göttingen minipigs received two 6-mm chondral defects in the medial and lateral trochlea of each knee. The two treatment groups were (1) autologous cartilage chips embedded in fibrin glue (ACC) (n = 12) and (2) marrow stimulation (MST) (n = 12). The animals were euthanized after 6 months, and the composition of repair tissue was quantitatively determined using histomorphometry. Semiquantitative evaluation was performed by means of the International Cartilage Repair Society (ICRS) II score. Collagen type II staining was used to further evaluate the repair tissue composition. Results: Significantly more hyaline cartilage was found in the ACC (17.1%) compared with MST (2.9%) group (P < .01). Furthermore, the ACC group had significantly less fibrous tissue (23.8%) compared with the MST group (41.1%) (P < .01). No significant difference in fibrocartilage content was found (54.7% for ACC vs 50.8% for MST). The ACC group had significantly higher ICRS II scores for tissue morphological characteristics, matrix staining, cell morphological characteristics, surface assessment, mid/deep assessment, and overall assessment (P < .05). The ACC-treated defects had significantly more collagen type II staining (54.5%) compared with the MST-treated defects (28.1%) (P < .05). Conclusion: ACC transplant resulted in improved quality of cartilage repair tissue compared with MST at 6 months postoperatively. Clinical Relevance: Further studies are needed to investigate ACC as a possible alternative first-line treatment for focal cartilage injuries in the knee.

Cellular and Molecular Factors Influencing Tendon Repair.

Tendons are complex connective tissues that transmit tensile forces between muscles and tendons. Tendon injuries are among the most common orthopedic problems with long-term disability as a frequent consequence due to prolonged healing time. Furthermore, the repair tissue is of inferior quality, predisposing patients to high rates of recurrence following initial injury. Coordinated cellular processes and biological factors under the influence of mechanical loading are involved in tendon healing and our understanding of these events lags behind other musculoskeletal tissues. Tendons are relatively hypocellular and hypovascular, with little or no intrinsic regenerative capacity. Studies have documented fatty degeneration, chondrogenic dysplasia, and ectopic ossification within tendon repair tissue. The underlying pathogenesis for these metaplastic changes that compromise the quality of tendon repair tissue is poorly understood. The purpose of this review is to compile literature reporting molecular processes that regulate/control the phenotype of cells responsible for abnormal matrix deposition at repair site. In addition, recent studies reporting the interplay of mechanotransduction and cellular responses during tendon repair are summarized. Identifying the links between cellular, biological, and mechanical parameters involved in tendon repair is paramount to develop successful therapies for tendon healing.

Evidence Supporting Intralesional Stem Cell Therapy to Improve Equine Flexor Tendon Healing

&lt;p&gt;This Knowledge Summary addresses the published information supporting intralesional administration of cell-based therapies for the treatment of flexor tendinitis/tendinopathy in horses. The current body of evidence supports intralesional stem cell therapy to improve quality of repair tissue during equine SDFT healing, based on histological and histomorphometric analyses and, in some studies, tensile load testing. Accepting this, comparative analyses to determine relative efficacies of specific cell sources are inadequate to draw any firm conclusions on this issue and any informative meta-analysis of the existing studies is confounded by inconsistencies in cell sources, injury models and clinical case selections, times after injury when cells were injected, number of cells administered, delivery vehicles used, the outcomes used to assess utility and timing of outcomes after administration. Further, in none of the experimental studies were the horses subject to training and/or racing stresses, and it is still unclear how closely the existing experimental models reflect the clinical condition following repetitive strain injury. Further, single-cycle tensile testing does not necessarily model the high-frequency, recurrent, and (to be hoped) submaximal tensile loading that flexor tendons experience during high speed exercise.&lt;/p&gt;&lt;p&gt; &lt;/p&gt;&lt;img src="https://www.veterinaryevidence.org/rcvskmod/icons/oa-icon.jpg" alt="Open Access" /&gt; &lt;img src="https://www.veterinaryevidence.org/rcvskmod/icons/pr-icon.jpg" alt="Peer Reviewed" /&gt;

IGF-1 Gene Transfer to Human Synovial MSCs Promotes Their Chondrogenic Differentiation Potential without Induction of the Hypertrophic Phenotype.

Mesenchymal stem cell- (MSC-) based therapy is a promising treatment for cartilage. However, repair tissue in general fails to regenerate an original hyaline-like tissue. In this study, we focused on increasing the expression levels for insulin-like growth factor-1 (IGF-1) to improve repair tissue quality. The IGF-1 gene was introduced into human synovial MSCs with a lentiviral vector and examined the levels of gene expression and morphological status of MSCs under chondrogenic differentiation condition using pellet cultures. The size of the pellets derived from IGF-1-MSCs were significantly larger than those of the control group. The abundance of glycosaminoglycan (GAG) was also significantly higher in the IGF-1-MSC group. The histology of the IGF-1-induced pellets demonstrated similarities to hyaline cartilage without exhibiting features of a hypertrophic chondrocyte phenotype. Expression levels for the Col2A1 gene and protein were significantly higher in the IGF-1 pellets than in the control pellets, but expression levels for Col10, MMP-13, ALP, and Osterix were not higher. Thus, IGF-1 gene transfer to human synovial MSCs led to an improved chondrogenic differentiation capacity without the detectable induction of a hypertrophic or osteogenic phenotype.

Two-Year Outcomes of a Randomized Trial Investigating a 6-Week Return to Full Weightbearing After Matrix-Induced Autologous Chondrocyte Implantation

Background: Matrix-induced autologous chondrocyte implantation (MACI) has demonstrated encouraging outcomes in treating patients with knee cartilage defects. Postoperatively, the time required to attain full weightbearing (WB) remains conservative. Hypothesis: We hypothesized that patients would have no significant clinical or radiological differences or graft complications after an 8-week or 6-week return to full WB after MACI. Study Design: Randomized controlled trial; Level of evidence, 1. Methods: A total of 37 knees (n = 35 patients) were randomly allocated to either an 8-week return to full WB that we considered current best practice based on the existing literature (CR group; n = 19 knees) or an accelerated 6-week WB approach (AR group; n = 18 knees). Patients were evaluated preoperatively and at 1, 2, 3, 6, 12, and 24 months after surgery, using the Knee Injury and Osteoarthritis Outcome Score, 36-Item Short Form Health Survey, visual analog pain scale, 6-minute walk test, and active knee range of motion. Isokinetic dynamometry was used to assess peak knee extension and flexion strength and limb symmetry indices (LSIs) between the operated and nonoperated limbs. Magnetic resonance imaging (MRI) was undertaken to evaluate the quality and quantity of repair tissue as well as to calculate an MRI composite score. Results: Significant improvements (P < .05) were observed in all subjective scores, active knee flexion and extension, 6-minute capacity, peak knee extensor torque in the operated limb, and knee extensor LSI, although no group differences existed. Although knee flexor LSIs were above 100% for both groups at 12 and 24 months after surgery, LSIs for knee extensor torque at 24 months were 93.7% and 87.5% for the AR and CR groups, respectively. The MRI composite score and pertinent graft parameters significantly improved over time (P < .05), with some superior in the AR group at 24 months. All patients in the AR group (100%) demonstrated good to excellent infill at 24 months, compared with 83% of patients in the CR group. Two cases of graft failure were observed, both in the CR group. At 24 months, 83% of patients in the CR group and 88% in the AR group were satisfied with the results of their MACI surgery. Conclusion: Patients in the AR group who reduced the length of time spent ambulating on crutches produced comparable outcomes up to 24 months, without compromising graft integrity.

Beneficial clinical effects but limited tissue quality following osteochondral repair with a cell-free multilayered nano-composite scaffold in the talus

The treatment of larger osteochondral lesions of the talus remains an operative challenge. In addition to micro fracturing and osteochondral transplantation one promising strategy could be the operative repair with a cell-free multilayered nano-composite scaffold with the potential to regenerate bone and cartilage in one treatment. In this prospective case series four consecutive patients who suffered from a single osteochondral lesion (≥1.5cm2) on the medial talus were enrolled. The repair potential of the implant was assessed using MRI based biochemical, compositional MR sequences (T2 mapping) as well as semi-quantitative morphological analyses (MOCART score) at 18 months follow-up after the surgery. The clinical outcome was determined at 6-, 12-, 18-, and 24 months follow-up by using the Ankle Disability Index and the AOFAS score. At 18 months after the surgery, the clinical outcome was significantly improved compared to the preoperative baseline. Global T2 relaxation times of the repair tissue were significantly increased compared to the healthy control cartilage. Osteochondral repair with a cell-free, biomimetic scaffold provides good clinical, short-term results. However, biochemical MR imaging provides strong evidence for limited repair tissue quality at 18 months after the implantation. IV.

In Vivo Cellular Infiltration and Remodeling in a Decellularized Ovine Osteochondral Allograft.

Interest in decellularized tissues has steadily gained as potential solutions for degenerative diseases and traumatic events, replacing sites of missing tissue, and providing the relevant biochemistry and microstructure for tissue ingrowth and regeneration. Osteoarthritis, a progressive and debilitating disease, is often initiated with the formation of a focal defect in the otherwise smooth surface of articular cartilage. Decellularized cartilage tissue, which maintains the structural complexity of the native extracellular matrix, has the potential to provide a clinically relevant solution to focal defects or large tissue damage, possibly even circumventing or complementing current techniques such as microfracture and mosaicplasty. However, it is currently unclear whether implantation of decellularized cartilage in vivo may provide a mechanically and biochemically relevant platform to promote cell remodeling and repair. We examined whole decellularized osteochondral allografts implanted in the ovine trochlear groove to investigate cellular remodeling and repair tissue quality compared to empty defects and contralateral controls (healthy cartilage). At 3 months postsurgery, cells were observed in both the decellularized tissue and empty defects, although both at significantly lower levels than healthy cartilage. Qualitative and quantitative histological analysis demonstrated maintenance of cartilage features of the decellularized implant similar to healthy cartilage groups. Noninvasive analysis by quantitative magnetic resonance imaging showed no difference in T1ρ and T2* between all groups. Investigation of the mechanical properties of repair tissue showed significantly lower elasticity in decellularized implants and empty defects compared to healthy cartilage, but similar tribological quantities. Overall, this study suggests that decellularized cartilage implants are subject to cellular remodeling in an in vivo environment and may provide a potential tissue engineering solution to cartilage defect interventions.

Treatment of Articular Cartilage Defects of the Knee With Microfracture and Enhanced Microfracture Techniques.

Chondral injuries in the knee are a common source of pain and morbidity. Treatment of symptomatic chondral defects is challenging due to the limited healing capacity of articular cartilage. Microfracture is the most common surgical technique used to treat chondral defects in the knee and utilizes marrow stimulation to generate a fibrocartilage repair. Microfracture has demonstrated good short-term postoperative outcomes. Long-term outcomes following microfracture are variable, with loss of improvement attributed to the poor mechanical qualities of the fibrous repair tissue. Current research is focusing on ways to optimize the repair environment after microfracture using biological scaffolds (enhanced microfracture) to facilitate chondrogenic differentiation and proliferation to improve the quality of repair tissue.

Evaluation of a Hyaluronic Acid-Based Biomaterial to Enhance Wound Healing in the Equine Distal Limb

The objective of this study was to evaluate the ability of a cross-linked hyaluronic acid-based biomaterial (CMHA) to promote healing in an equine distal limb wound model. Three 6.25 cm2 full thickness skin wounds were surgically created on the dorsomedial metacarpus and metatarsus of each of four limbs of eight normal adult horses under general anesthesia. Three days after surgery, wounds were photographed and one of four treatments was applied to all three wounds on a single limb: control (no CMHA), single application of CMHA gel, multiple applications of CMHA gel, and multiple applications of CMHA film. Wounds were assessed for quality of repair tissue and photographed for image analysis at bandage changes every 4 days throughout the 47-day study. Exuberant granulation tissue was excised as needed and weighed. Size of granulating wounds was analyzed by repeated measures analysis of covariance and rate of wound healing assessed using a logistic decay model fitted to the data by nonlinear least-squares regression. Significance was set at P < .05. No adverse effects of CMHA were noted. There was a significant day by treatment interaction; however, overall, there were no significant differences among treatment groups (P = .09). Wounds treated with CMHA films decreased to half their original size significantly faster, were significantly smaller on day 31, and healed with higher quality, less fragile epithelium than wounds in other treatment groups. Treatment of distal limb wounds in horses may benefit from use of CMHA films to improve healing.

Osteochondral repair with synovial membrane‑derived mesenchymal stem cells.

The aim of the present study was to analyze cartilage repair tissue quality following synovial membrane-derived mesenchymal stem cell (SMSC) transplantation in a rabbit osteochondral defect. A total of 15 New Zealand white rabbits were randomly distributed into three groups (n=5 in each group). In group 1, an osteochondral defect model was established in the right knee trochlea, prior to transplantation with SMSCs (SMSC group). In group 2, an osteochondral defect model was established without further treatment (control group). Group 3 did not undergo osteochondral defect model establishment and served as the sham control (normal group). All animals were sacrificed 12 weeks following the surgical procedures for magnetic resonance imaging and histological examination. No significant differences were observed between the control and SMSC group in the macroscopic score (P>0.05), the 2D magnetic resonance observation of cartilage repair tissue score (P>0.05) or the modified O'Driscoll scale (P>0.05). Compared with the control group, a significant improvement in tissue quality was observed in the SMSCs group postoperatively. The repair tissue of the SMSCs group had a shorter T2, compared with that of the control group, although no significant difference was detected (P>0.05). Furthermore, the apparent diffusion coefficient in the repair tissue of the SMSC group had a significantly lower value, compared with that of the control group (P=0.016). The results of the present study demonstrated that osteochondral repair using SMSCs facilitated the repair of appropriate tissue texture.

Adipose-Derived Mesenchymal Stem Cells With Microfracture Versus Microfracture Alone: 2-Year Follow-up of a Prospective Randomized Trial

To compare the clinical and radiologic efficacy of adipose-derived stem cells (ADSCs) with fibrin glue and microfracture (MFX) versus MFX alone in patients with symptomatic knee cartilage defects. Patients who were aged 18 to 50 years and had a single International Cartilage Repair Society grade III/IV symptomatic cartilage defect (≥3 cm(2)) on the femoral condyle were randomized to receive ADSCs with fibrin glue and MFX treatment (group 1, n= 40) or MFX treatment alone (group 2, n= 40). There was a lack of blinding for patients because of the additional intervention method (liposuction). The cartilage defect was diagnosed using preoperative magnetic resonance imaging (MRI), and quantitative and qualitative assessments of the repair tissue were carried out at 24 months by using the Magnetic Resonance Observation of Cartilage Repair Tissue scoring system with follow-up MRI. Clinical results were evaluated using the Lysholm score, the Knee Injury and Osteoarthritis Outcome Score (KOOS), and a 10-point visual analog scale for pain (0 points, no pain; 10 points, worst possible pain) preoperatively and postoperatively at 3 months, 12 months, and the last follow-up visit. The 2 groups had similar baseline patient characteristics. Follow-up MRI was performed at 24 months (mean, 24.3 months; range, 24.0 to 25.1 months) after the operation. Group 1 included 26 patients (65%) who had complete cartilage coverage of the lesion at follow-up compared with 18 patients (45%) in group 2. Significantly better signal intensity was observed for the repair tissue in group 1, with 32 patients (80%) having normal or nearly normal signal intensity (i.e., complete cartilage coverage of the lesion) compared with 28 patients (72.5%) in group 2. The mean clinical follow-up period was 27.4 months (range, 26 to 30 months). The improvements in the mean KOOS pain and symptom subscores were significantly greater at follow-up in group 1 than in group 2 (pain, 36.6 ± 11.9 in group 1 and 30.1 ± 14.7 in group 2 [P= .034]; symptoms, 32.3 ± 7.2 in group 1 and 27.8 ± 6.8 in group 2 [P= .005]). However, the improvements in the other subscores were not significantly different between group 1 and group 2 (activities of daily living, 38.5 ± 12.8 and 37.6 ± 12.9, respectively [P= .767]; sports and recreation, 33.9 ± 10.3 and 31.6 ± 11.0, respectively [P= .338]; quality of life, 38.4 ± 13.1 and 37.8 ± 12.0, respectively [P= .650]). Among the 80 patients, second-look arthroscopies were performed in 57 knees (30 in group 1 and 27 in group 2), and biopsy procedures were performed during these arthroscopies for 18 patients in group 1 and 16 patients in group 2. The second-look arthroscopies showed good repair tissue quality, although no significant intergroup difference was observed. The mean total histologic score was 1,054 for group 1 compared with 967 for group 2 (P= .036). Age, lesion size, duration of symptoms before surgery, mechanism of injury, and combined procedures were not correlated with clinical results, Magnetic Resonance Observation of Cartilage Repair Tissue scores, and histologic outcomes at short-term follow-up. Compared with MFX alone, MFX and ADSCs with fibrin glue provided radiologic and KOOS pain and symptom subscore improvements, with no differences in activity, sports, or quality-of-life subscores, in symptomatic single cartilage defects of the knee that were 3 cm(2) or larger, with similar structural repair tissue. Level II, prospective comparative study.

Small-Diameter Awls Improve Articular Cartilage Repair After Microfracture Treatment in a Translational Animal Model

Background: Microfracture is the most commonly applied arthroscopic marrow stimulation procedure. Hypothesis: Articular cartilage repair is improved when the subchondral bone is perforated by small-diameter microfracture awls compared with larger awls. Study Design: Controlled laboratory study. Methods: Standardized rectangular (4 × 8 mm) full-thickness chondral defects (N = 24) were created in the medial femoral condyle of 16 adult sheep and debrided down to the subchondral bone plate. Three treatment groups (n = 8 defects each) were tested: 6 microfracture perforations using small-diameter awls (1.0 mm; group 1), large-diameter awls (1.2 mm; group 2), or without perforations (debridement control; group 3). Osteochondral repair was assessed at 6 months in vivo using established macroscopic, histological, immunohistochemical, biochemical, and micro–computed tomography analyses. Results: Compared with control defects, histological cartilage repair was always improved after both microfracture techniques (P < .023). Application of 1.0-mm microfracture awls led to a significantly improved histological overall repair tissue quality (7.02 ± 0.70 vs 9.03 ± 0.69; P = .008) and surface grading (1.05 ± 0.28 vs 2.10 ± 0.19; P = .001) compared with larger awls. The small-diameter awl decreased relative bone volume of the subarticular spongiosa (bone volume/tissue volume ratio: 23.81% ± 3.37% vs 30.58% ± 2.46%; P = .011). Subchondral bone cysts and intralesional osteophytes were frequently observed after either microfracture treatment. Macroscopic grading, DNA, proteoglycan, and type I and type II collagen contents as well as degenerative changes within the adjacent cartilage remained unaffected by the awl diameter. Conclusion: Small-diameter microfracture awls improve articular cartilage repair in the translational sheep model more effectively than do larger awls. Clinical Relevance: These data support the use of small microfracture instruments for the surgical treatment of cartilage defects and warrant prolonged clinical investigations.