Formation of cartilage repair tissue in articular cartilage defects pretreated with microfracture and covered with cell‐free polymer‐based implants

The aim of our study was to evaluate the mid‐term outcome of a cell‐free polymer‐based cartilage repair approach in a sheep cartilage defect model in comparison to microfracture treatment. Cell‐free, freeze‐dried implants (chondrotissue®) made of a poly‐glycolic acid (PGA) scaffold and hyaluronan were immersed in autologous serum and used for covering microfractured full‐thickness articular cartilage defects of the sheep (n = 4). Defects treated with microfracture only served as controls (n = 4). Six months after implantation, cartilage implants and controls were analyzed by immunohistochemical staining of type II collagen, histological staining of proteoglycans, and histological scoring. Histological analysis showed the formation of a cartilaginous repair tissue rich in proteoglycans. Histological scoring documented significant improvement of repair tissue formation when the defects were covered with the cell‐free implant, compared to controls treated with microfracture. Immunohistochemistry showed that the cell‐free implant induced cartilaginous repair tissue and type II collagen. Controls treated with microfracture showed marginal formation of a mixed‐type repair tissue consisting of cartilaginous tissue and fibro‐cartilage. Covering of microfractured defects with the cell‐free polymer‐based cartilage implant is suggested to be a promising treatment option for cartilage defects and improves the regeneration of articular cartilage. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27:1353–1360, 2009     

Delivering rhFGF‐18 via a bilayer collagen membrane to enhance microfracture treatment of chondral defects in a large animal model

Augmented microfracture techniques use growth factors, cells, and/or scaffolds to enhance the healing of microfracture‐treated cartilage defects. This study investigates the effect of delivering recombinant human fibroblastic growth factor 18 (rhFHF18, Sprifermin) via a collagen membrane on the healing of a chondral defect treated with microfracture in an ovine model. Eight millimeter diameter chondral defects were created in the medial femoral condyle of 40 sheep (n = 5/treatment group). Defects were treated with microfracture alone, microfracture + intra‐articular rhFGF‐18 or microfracture + rhFGF‐18 delivered on a membrane. Outcome measures included mechanical testing, weight bearing, International Cartilage Repair Society repair score, modified O'Driscoll score, qualitative histology, and immunohistochemistry for types I and II collagen. In animals treated with 32 μg rhFGF‐18 + membrane and intra‐articularly, there was a statistically significant improvement in weight bearing at 2 and 4 weeks post surgery and in the modified O'Driscoll score compared to controls. In addition, repair tissue stained was more strongly stained for type II collagen than for type I collagen. rhFGF‐18 delivered via a collagen membrane at the point of surgery potentiates the healing of a microfracture treated cartilage defect. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:1120–1127, 2015.     

Extracellular matrix‐blood composite injection reduces post‐traumatic osteoarthritis after anterior cruciate ligament injury in the rat

The objective of this study was to determine if an injection of a novel extracellular matrix scaffold and blood composite (EMBC) after anterior cruciate ligament (ACL) injury would have a mitigating effect on post‐traumatic osteoarthritis (PTOA) development in rat knees. Lewis rats underwent unilateral ACL transection and were divided into three groups as follows: (1) no further treatment (ACLT; n = 10); (2) an intra‐articular injection of EMBC on day 0 (INJ0; n = 11); and (3) an intra‐articular injection of EMBC on day 14 (INJ14; n = 11). Ten additional animals received capsulotomy only (n = 10, SHAM group). The OARSI histology scoring of the tibial cartilage and micro‐CT of the tibial epiphysis were performed after 35 days. The ratio of intact/treated hind limb forces during gait was determined using a variable resistor walkway. The OARSI cartilage degradation sum score and total degeneration width were significantly greater in the ACLT group when compared to the INJ0 (p = 0.031, and p = 0.005) and INJ14 (p = 0.022 and p = 0.04) group. Weight bearing on the operated limb only decreased significantly in the ACLT group (p = 0.048). In the rat ACL transection model, early or delayed injection of EMBC ameliorated the significant decrease in weight bearing and cartilage degradation seen in knees subjected to ACL transection without injection. The results indicate that the injection of EMBC may slow the process of PTOA following ACL injury and may provide a promising treatment for PTOA. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:995–1003, 2016.     

Articular cartilage calcification of the humeral head is highly prevalent and associated with osteoarthritis in the general population

Articular cartilage calcification is considered a pathological albeit incompletely understood process which is known to be associated with osteoarthritis of the knee and hip. The goal of this study was to determine the prevalence of articular cartilage calcification of the shoulder as a non‐weight‐bearing joint and to analyze the interrelationship of calcification with age and histological severity of shoulder osteoarthritis in the general population. In a cross‐sectional study of 180 humeral heads from 90 donors (n = 49 male, n = 41 female; mean age 62.7 years [20–93]), cartilage calcification of the humeral head was quantified by digital contact radiography (DCR). Histological OA grade (OARSI) was determined and structural equation modeling (SEM) was used to analyze the interrelationship of cartilage calcification, OARSI and age. The prevalence of articular cartilage calcification was 98.9% (95%CI: [93.96%, 99.97%]) and was independent of gender (p = 0.55). Cartilage calcification of one shoulder correlated significantly with that of the contralateral side (r = 0.61, 95%CI: [0.46, 0.73], p < 0.001). SEM demonstrated significant associations between histological OA grade and cartilage calcification (r = 0.55, p = 0.039), between histological OA grade and age (β = 0.59, p < 0.001) but not between age and cartilage calcification (β = 0.24, p = 0.116). In conclusion, the prevalence of shoulder cartilage calcification in the general population is higher than anticipated. The high prevalence, its concomitant bilateral manifestation and the association between the amount of cartilage calcification and OA severity, but not age, suggest that cartilage calcification is a systemically driven process with early onset in life and may be a causative factor in the pathogenesis of OA. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1984–1990, 2016.     

A novel MSC‐seeded triphasic construct for the repair of osteochondral defects

Mesenchymal stem cells (MSC) are increasingly replacing chondrocytes in tissue engineering based research for treatment of osteochondral defects. The aim of this work was to determine whether repair of critical‐size chronic osteochondral defects in an ovine model using MSC‐seeded triphasic constructs would show results comparable to osteochondral autografting (OATS). Triphasic implants were engineered using a beta‐tricalcium phosphate osseous phase, an intermediate activated plasma phase, and a collagen I hydrogel chondral phase. Autologous MSCs were used to seed the implants, with chondrogenic predifferentiation of the cells used in the cartilage phase. Osteochondral defects of 4.0 mm diameter were created bilaterally in ovine knees (n = 10). Six weeks later, half of the lesions were treated with OATS and half with triphasic constructs. The knees were dissected at 6 or 12 months. With the chosen study design we were not able to demonstrate significant differences between the histological scores of both groups. Subcategory analysis of O'Driscoll scores showed superior cartilage bonding in the 6‐month triphasic group compared to the autograft group. The 12‐month autograft group showed superior cartilage matrix morphology compared to the 12‐month triphasic group. Macroscopic and biomechanical analysis showed no significant differences at 12 months. Autologous MSC‐seeded triphasic implants showed comparable repair quality to osteochondral autografts in terms of histology and biomechanical testing. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:1586–1599, 2010     

Possibility of quantitative T2‐mapping MRI of cartilage near metal in high tibial osteotomy: A human cadaver study

T2‐mapping is a widely used quantitative MRI technique in osteoarthritis research. An important challenge for its application in the context of high tibial osteotomy (HTO) is the presence of metallic fixation devices. In this study, we evaluated the possibility of performing T2‐mapping after a HTO, by assessing the extent of magnetic susceptibility artifacts and the influence on T2 relaxation times caused by two commonly used fixation devices. T2‐mapping with a 3D fast spin‐echo sequence at three Tesla was performed on 11 human cadaveric knee joints before and after implantation of a titanium plate and screws (n = 5) or cobalt chrome staples (n = 6). Mean T2 relaxation times were calculated in six cartilage regions, located in the distal and posterior cartilage of femoral condyles and the cartilage of tibial plateaus, both medially and laterally. T2 relaxation times before and after the implantation were compared with paired t‐tests and Wilcoxon rank tests. Due to the extent of the magnetic susceptibility artifact, it was not possible to segment the knee cartilage and thus calculate T2 relaxation times in the lateral weight‐bearing femoral and tibial cartilage regions only in the cobalt chrome group. In all cartilage regions of the titanium implanted knees and those unaffected by artifacts due to cobalt chrome implants, T2 relaxation times did not significantly differ between the two scans. Our results suggest that accurate T2‐mapping after a HTO procedure is possible in all areas after implantation of a titanium fixation device and in most areas after implantation of a cobalt chrome fixation device. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1206–1212, 2018.

     

Intra‐articular injection of rhFGF‐18 improves the healing in microfracture treated chondral defects in an ovine model

Microfracture is a common cartilage repair procedure. Strategies to improve healing post‐microfracture include the use of growth factors to enhance hyaline cartilage production. This study investigates the effect of intra‐articular recombinant human fibroblastic growth factor 18 (rhFHF18) on the healing of a chondral defect treated with microfracture in an ovine model. Chondral defects (8 mm diameter) were created in the medial femoral condyle of 80 sheep (n = 16/treatment group). Defects were treated with microfracture alone or microfracture + intra‐articular rhFGF‐18 (administered either as one or two cycles of 3× weekly injections). Outcome measures included mechanical testing, macroscopic International Cartilage Repair Society repair score, modified O'Driscoll histology score, qualitative histology, and immunohistochemistry for types I, II, and VI collagen. In treated animals, there was a statistically significant improvement in ICRS tissue repair score and tissue infill score, in the modified O'Driscoll score between control and 1 cycle of rhFGF‐18 at 6 m, and in the cartilage repair score and structural characteristic score between the control and both rhFGF‐18 groups at 6 m. There was no evidence of degeneration of adjacent cartilage in the rhFGF‐18 treated cartilage. The increase in hyaline cartilage‐like tissue formed in the microfracture + rhFGF‐18 treated groups indicates that rhFGF‐18 potentiates the formation of hyaline cartilage repair following microfracture. © 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 32:669–676, 2014.     

Organ‐level histological and biomechanical responses from localized osteoarticular injury in the rabbit knee

The processes of whole‐joint osteoarthritis development following localized joint injuries are not well understood. To demonstrate this local‐to‐global linkage, we hypothesized that a localized osteoarticular injury in the rabbit knee would not only cause biomechanical and histological abnormalities in the involved compartment but also concurrent histological changes in the noninvolved compartment. Twenty rabbits had an acute osteoarticular injury that involved localized joint incongruity (a 2‐mm osteochondral defect created in the weight‐bearing area of the medial femoral condyle), while another 20 received control sham surgery. At the time of euthanasia at 8 or 16 weeks post‐surgery, the experimental knees were subjected to sagittal‐plane laxity measurement, followed by cartilage histo‐morphological evaluation using the Mankin score. The immediate effects of defect creation on joint stability and contact mechanics were explored in concomitant rabbit cadaver experimentation. The injured animals had cartilage histological scores significantly higher than in the sham surgery group (p < 0.01) on the medial femoral, medial tibial, and lateral femoral surfaces (predominantly on the medial surfaces), accompanied by slight (mean 20%) increase of sagittal‐plane laxity. Immediate injury‐associated alterations in the medial compartment contact mechanics were also demonstrated. Localized osteoarticular injury in this survival animal model resulted in global joint histological changes. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 29:340–346, 2011     

Articular cartilage repair with recombinant human type II collagen/polylactide scaffold in a preliminary porcine study

The purpose of this study was to investigate the potential of a novel recombinant human type II collagen/polylactide scaffold (rhCo‐PLA) in the repair of full‐thickness cartilage lesions with autologous chondrocyte implantation technique (ACI). The forming repair tissue was compared to spontaneous healing (spontaneous) and repair with a commercial porcine type I/III collagen membrane (pCo). Domestic pigs (4‐month‐old, n = 20) were randomized into three study groups and a circular full‐thickness chondral lesion with a diameter of 8 mm was created in the right medial femoral condyle. After 3 weeks, the chondral lesions were repaired with either rhCo‐PLA or pCo together with autologous chondrocytes, or the lesion was only debrided and left untreated for spontaneous repair. The repair tissue was evaluated 4 months after the second operation. Hyaline cartilage formed most frequently in the rhCo‐PLA treatment group. Biomechanically, there was a trend that both treatment groups resulted in better repair tissue than spontaneous healing. Adverse subchondral bone reactions developed less frequently in the spontaneous group (40%) and the rhCo‐PLA treated group (50%) than in the pCo control group (100%). However, no statistically significant differences were found between the groups. The novel rhCo‐PLA biomaterial showed promising results in this proof‐of‐concept study, but further studies will be needed in order to determine its effectiveness in articular cartilage repair. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:745–753, 2016.     

A preliminary study comparing the use of allogenic chondrogenic pre‐differentiated and undifferentiated mesenchymal stem cells for the repair of full thickness articular cartilage defects in rabbits

Chondrogenic differentiated mesenchymal stem cells (CMSCs) have been shown to produce superior chondrogenic expression markers in vitro. However, the use of these cells in vivo has not been fully explored. In this study, in vivo assessment of cartilage repair potential between allogenic‐derived chondrogenic pre‐differentiated mesenchymal stem cells and undifferentiated MSCs (MSCs) were compared. Bilateral full thickness cartilage defects were created on the medial femoral condyles of 12 rabbits (n = 12). Rabbits were divided into two groups. In one group, the defects in the right knees were repaired using alginate encapsulated MSCs while in the second group, CMSCs were used. The animals were sacrificed and the repaired and control knees were assessed at 3 and 6 months after implantation. Quantitative analysis was performed by measuring the Glycosaminoglycans (GAGs)/total protein content. The mean Brittberg score was higher in the transplanted knees as compared to the untreated knee at 6 months (p < 0.05). Quantitative analysis of GAGs was consistent with these results. Histological and immunohistochemical analysis demonstrated hyaline‐like cartilage regeneration in the transplanted sites. Significant differences between the histological scores based on O'Driscoll histological grading were observed between contralateral knees at both 3 and 6 months (p < 0.05). No significant differences were observed between the Britberg, O'Driscoll scores, and GAGs/total protein content when comparing defect sites treated with MSC and CMSC (p > 0.05). This study demonstrates that the use of either MSC or CMSC produced superior healing when compared to cartilage defects that were untreated. However, both cells produced comparable treatment outcomes. © 2011 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 29: 1336–1342, 2011     

Bone marrow stimulation of the medial femoral condyle produces inferior cartilage and bone repair compared to the trochlea in a rabbit surgical model

The influence of the location of cartilage lesions on cartilage repair outcome is incompletely understood. This study compared cartilage and bone repair in medial femoral condylar (MFC) versus femoral trochlear (TR) defects 3 months after bone marrow stimulation in mature rabbits. Intact femurs from adult rabbits served as controls. Results from quantitative histomorphometry and histological scoring showed that bone marrow stimulation produced inferior soft tissue repair in MFC versus TR defects, as indicated by significantly lower % Fill (p = 0.03), a significant increase in collagen type I immunostaining (p < 0.00001) and lower O'Driscoll scores (p < 0.05). 3D micro‐CT analysis showed that repaired TR defects regained normal un‐operated values of bone volume fraction, trabecular thickness, and trabecular number, whereas in MFC defects the repaired bone architecture appeared immature and less dense compared to intact un‐operated MFC controls (p < 0.0001). Severe medial meniscal damage was found in 28% of operated animals and was strongly correlated with (i) low cartilage defect fill, (ii) incomplete bone repair in MFC, and (iii) with a more posterior defect placement in the weight‐bearing region. We conclude that the location of cartilage lesions influences cartilage repair, with better outcome in TR versus MFC defects in rabbits. Meniscal degeneration is associated with cartilage damage. © 2013 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 31:1757–1764, 2013     

Longitudinal evaluation of cartilage after osteochondral autogenous transfer with delayed gadolinium‐enhanced MRI of the cartilage (dGEMRIC)

The aim was to use repeat delayed gadolinium‐enhanced magnetic resonance imaging of cartilage (dGEMRIC) to estimate glycosaminoglycan (GAG) content in reparative cartilage after osteochondral autogenous transfer (OAT). The study group comprised 7 knees of 7 patients that were examined three times by dGEMRIC, at 3, 6, and 12 months using a 1.5 Tesla MRI system in both OAT operated and nonoperated condyles at 90 min after the injection. The gadolinium diethylene triamine pentaacetic acid (Gd‐DTPA)^2? containing contrast medium (0.2 mmols/kg) was injected intravenously. The mean T1 values of the plug cartilage at 3, 6, and 12 months after OAT was 230 ± 40, 213 ± 31, and 230 ± 23 ms (mean ± SD), respectively. There were differences between the plug and control cartilage at 3 (p < 0.01) and 12 (p < 0.05) months after OAT, but not at 6 months (p = 0.089). No T1 changes were detected between the plug cartilage at the different time points after OAT. The fact that the GAG content of the OAT plugs were maintained for 12‐month study period suggest that no major deterioration of load‐bearing properties occurs in the cartilage after the OAT. © 2011 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 30:221–225, 2012     

Repair of large full‐thickness articular cartilage defects by transplantation of autologous uncultured bone‐marrow‐derived mononuclear cells

The objective of this study was to investigate the feasibility of autologous uncultured bone marrow‐derived mononuclear cell transplantation in large full‐thickness cartilage regeneration. After fixing with a hinged external fixator, the entire surface of the left tibial plateau was resected and large full‐thickness cartilage defects were formed in 48 rabbits. Animals were divided into four groups: autologous uncultured bone marrow‐derived mononuclear cells with fibrin gel (BMC), autologous uncultured peripheral blood‐derived mononuclear cells with fibrin gel (PBC), fibrin gel alone (GEL), or nothing (CON) transplanted to the articular cavity 7 days after the operation. The rabbits were killed 8 or 12 weeks after the operation. The repair of defects was investigated histologically and scored using a histological and histochemical grading scale that was modified from the International Cartilage Repair Society Visual Histological Assessment Scale. To evaluate the regenerated cartilage, we also morphometrically measured the staining area positive for Safranin‐O or type II collagen and calculated the percentages of the positive staining areas with respect to the regenerated soft tissue area. Histological findings showed that the BMC group had superior cartilage repair compared with the other groups, and that the PBC and CON group showed better cartilage repair than did the GEL group. Histological scores and morphometrical measurements also showed the same results quantitively. The transplantation of autologous uncultured bone marrow‐derived mononuclear cells contributes to articular cartilage repair. The easy and safe method used in this study is potentially viable for clinical application. © 2007 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:18–26, 2008     

The effect of high‐energy extracorporeal shock waves on hyaline cartilage of adult rats in vivo

The aim of this study was to determine if extracorporeal shock wave therapy (ESWT) in vivo affects the structural integrity of articular cartilage. A single bout of ESWT (1500 shock waves of 0.5 mJ/mm²) was applied to femoral heads of 18 adult Sprague–Dawley rats. Two sham‐treated animals served as controls. Cartilage of each femoral head was harvested at 1, 4, or 10 weeks after ESWT (n = 6 per treatment group) and scored on safranin‐O‐stained sections. Expression of tenascin‐C and chitinase 3‐like protein 1 (Chi3L1) was analyzed by immunohistochemistry. Quantitative real‐time polymerase chain reaction (PCR) was used to examine collagen (II)α₁ (COL2A1) expression and chondrocyte morphology was investigated by transmission electron microscopy no changes in Mankin scores were observed after ESWT. Positive immunostaining for tenascin‐C and Chi3L1 was found up to 10 weeks after ESWT in experimental but not in control cartilage. COL2A1 mRNA was increased in samples 1 and 4 weeks after ESWT. Alterations found on the ultrastructural level showed expansion of the rough‐surfaced endoplasmatic reticulum, detachment of the cell membrane and necrotic chondrocytes. Extracorporeal shock waves caused alterations of hyaline cartilage on a molecular and ultrastructural level that were distinctly different from control. Similar changes were described before in the very early phase of osteoarthritis (OA). High‐energy ESWT might therefore cause degenerative changes in hyaline cartilage as they are found in initial OA. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:1050–1056, 2010     

Low‐intensity pulsed ultrasound (LIPUS) increases the articular cartilage type II collagen in a rat osteoarthritis model

In this study, the effect of low‐intensity pulsed ultrasound (LIPUS) on cartilage was evaluated in a rat osteoarthritis (OA) model using serum biomarkers such as CTX‐II (type II collagen degradation) and CPII (type II collagen synthesis) as well as histological criteria (Mankin score and immunohistochemical type II collagen staining). OA was surgically induced in the knee joint of rats by anterior cruciate/medial collateral ligament transection and medial meniscus resection (ACLT + MMx). Animals were divided into three groups: sham‐operated group (Sham), ACLT + MMx group without LIPUS (?LIPUS), and ACLT + MMx group with LIPUS (+LIPUS; 30 mW/cm², 20 min/day for 28 days). CTX‐II levels were elevated in both ?LIPUS and +LIPUS groups compared to that in the Sham group after the operation, but there was no significant difference between +LIPUS and ?LIPUS groups, suggesting that LIPUS does not affect the degradation of type II collagen in this model. In contrast, CPII was significantly increased in +LIPUS group compared to ?LIPUS and Sham. Moreover, histological damage on the cartilage (Mankin score) was ameliorated by LIPUS, and type II collagen was immunohistochemically increased by LIPUS in the cartilage of an OA model. Of interest, mRNA expression of type II collagen was enhanced by LIPUS in chondrocytes. Together these observations suggest that LIPUS is likely to increase the type II collagen synthesis in articular cartilage, possibly via the activation of chondrocytes and induction of type II collagen mRNA expression, thereby exhibiting chondroprotective action in a rat OA model. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:361–369, 2010     

Porous tantalum and poly‐ε‐caprolactone biocomposites for osteochondral defect repair: Preliminary studies in rabbits

Currently, various techniques are in use for the repair of osteochondral defects, none of them being truly satisfactory and they are often two step procedures. Comorbidity due to cancellous bone harvest from the iliac crest further complicates the procedure. Our previous in vitro studies suggest that porous tantalum (TM) or poly‐ε‐caprolactone scaffolds (PCL) in combination with periosteal grafts could be used for osteochondral defect repair. In this in vivo study, cylindrical osteochondral defects were created on the medial and lateral condyles of 10 rabbits and filled with TM/periosteum or PCL/periosteum biosynthetic composites (n = 8 each). The regenerated osteochondral tissue was then analyzed histologically, and evaluated in an independent and blinded manner by five different observers using a 30‐point histological score. The overall histological score for PCL/periosteum was significantly better than for TM/periosteum. However, most of the regenerates were well integrated with the surrounding bone (PCL/periosteum, n = 6.4; TM/periosteum, n = 7) along with partial restoration of the tidemark (PCL/periosteum, n = 4.4; TM/periosteum, n = 5.6). A cover of hyaline‐like morphology was found after PCL/periosteum treatment (n = 4.8), yet the cartilage yields were inconsistent. In conclusion, the applied TM and PCL scaffolds promoted excellent subchondral bone regeneration. Neo‐cartilage formation from periosteum supported by a scaffold was inconsistent. This is the first study to show in vivo results of both PCL and TM scaffolds for a novel approach to osteochondral defect repair. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:141–148, 2010     

Intraarticular injection of synovial stem cells promotes meniscal regeneration in a rabbit massive meniscal defect model

We investigated whether single intraarticular injection of synovial MSCs enhanced meniscal regeneration in a rabbit massive meniscal defect model. Synovium were harvested from the knee joint of rabbits, and the colony‐forming cells were collected. Two weeks after the anterior half of the medial menisci were excised in both knees, 1 × 10⁷ MSCs in 100 μl PBS were injected into the right knee. The MSC and control groups were compared macroscopically and histologically at 1, 3, 4, and 6 months (n = 4). Articular cartilage of the medial femoral condyle was also evaluated histologically at 6 months. Multipotentiality of the colony‐forming cells was confirmed. Injected MSCs labeled with DiI were detected and remained in the meniscal defect at 14 days. The size of meniscus in the MSC group was larger than that in the control group at 1 and 3 months. The difference of the size between the two groups was indistinct at 4 and 6 months. However, histological score was better in the MSC group than in the control group at 1, 3, 4, and 6 months. Macroscopically, the surface of the medial femoral condyle in the control group was fibrillated at 6 months, while looked close to intact in the MSC group. Histologically, defect or thinning of the articular cartilage with sclerosis of the subchondral bone was observed in the control group, contrarily articular cartilage and subchondral bone were better preserved in the MSC group. Synovial MSCs injected into the knee adhered around the meniscal defect, and promoted meniscal regeneration in rabbits. © 2013 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 31:1354–1359, 2013     

Effects of High‐Impact Training on Bone and Articular Cartilage: 12‐Month Randomized Controlled Quantitative MRI Study

Osteoarthritis and osteoporosis often coexist in postmenopausal women. The simultaneous effect of bone‐favorable high‐impact training on these diseases is not well understood and is a topic of controversy. We evaluated the effects of high‐impact exercise on bone mineral content (BMC) and the estimated biochemical composition of knee cartilage in postmenopausal women with mild knee osteoarthritis. Eighty women aged 50 to 66 years with mild knee osteoarthritis were randomly assigned to undergo supervised progressive exercise three times a week for 12 months (n = 40) or to a nonintervention control group (n = 40). BMC of the femoral neck, trochanter, and lumbar spine was measured by dual‐energy X‐ray absorptiometry (DXA). The biochemical composition of cartilage was estimated using delayed gadolinium‐enhanced magnetic resonance imaging (MRI) cartilage (dGEMRIC), sensitive to cartilage glycosaminoglycan content, and transverse relaxation time (T2) mapping that is sensitive to the properties of the collagen network. In addition, we evaluated clinically important symptoms and physical performance–related risk factors of falling: cardiorespiratory fitness, dynamic balance, maximal isometric knee extension and flexion forces, and leg power. Thirty‐six trainees and 40 controls completed the study. The mean gain in femoral neck BMC in the exercise group was 0.6% (95% CI, –0.2% to 1.4%) and the mean loss in the control group was –1.2% (95% CI, –2.1% to –0.4%). The change in baseline, body mass, and adjusted body mass change in BMC between the groups was significant (p = 0.005), whereas no changes occurred in the biochemical composition of the cartilage, as investigated by MRI. Balance, muscle force, and cardiorespiratory fitness improved significantly more (3% to 11%) in the exercise group than in the control group. Progressively implemented high‐impact training, which increased bone mass, did not affect the biochemical composition of cartilage and may be feasible in the prevention of osteoporosis and physical performance–related risk factors of falling in postmenopausal women. © 2014 American Society for Bone and Mineral Research.     

Development of a Tissue‐Engineered Artificial Ligament: Reconstruction of Injured Rabbit Medial Collateral Ligament With Elastin‐Collagen and Ligament Cell Composite Artificial Ligament

Ligament reconstruction using a tissue‐engineered artificial ligament (TEAL) requires regeneration of the ligament‐bone junction such that fixation devices such as screws and end buttons do not have to be used. The objective of this study was to develop a TEAL consisting of elastin‐coated polydioxanone (PDS) sutures covered with elastin and collagen fibers preseeded with ligament cells. In a pilot study, a ring‐type PDS suture with a 2.5 mm (width) bone insertion was constructed with/without elastin coating (Ela‐coat and Non‐coat) and implanted into two bone tunnels, diameter 2.4 mm, in the rabbit tibia (6 cases each) to access the effect of elastin on the bond strength. PDS specimens taken together with the tibia at 6 weeks after implantation indicated growth of bone‐like hard tissues around bone tunnels accompanied with narrowing of the tunnels in the Ela‐coat group and not in the Non‐coat group. The drawout load of the Ela‐coat group was significantly higher (28.0 ± 15.1 N, n = 4) than that of the Non‐coat group (7.6 ± 4.6 N, n = 5). These data can improve the mechanical bulk property of TEAL through extracellular matrix formation. To achieve this TEAL model, 4.5 × 10⁶ ligament cells were seeded on elastin and collagen fibers (2.5 cm × 2.5 cm × 80 µm) prior to coil formation around the elastin‐coated PDS core sutures having ball‐shape ends with a diameter of 2.5 mm. Cell‐seeded and cell‐free TEALs were implanted across the femur and the tibia through bone tunnels with a diameter of 2.4 mm (6 cases each). There was no incidence of TEAL being pulled in 6 weeks. Regardless of the remarkable degradation of PDS observed in the cell‐seeded group, both the elastic modulus and breaking load of the cell‐seeded group (n = 3) were comparable to those of the sham‐operation group (n = 8) (elastic modulus: 15.4 ± 1.3 MPa and 18.5 ± 5.7 MPa; breaking load: 73.0 ± 23.4 N and 104.8 ± 21.8 N, respectively) and higher than those of the cell‐free group (n = 5) (elastic modulus: 5.7 ± 3.6 MPa; breaking load: 48.1 ± 11.3 N) accompanied with narrowed bone tunnels and cartilage matrix formation. These data suggest that elastin increased the bond strength of TEAL and bone. Furthermore, our newly developed TEAL from elastin, collagen, and ligament cells maintained the strength of the TEAL even if PDS was degraded.     

CCL2 But Not CCR2 Is Required for Spontaneous Articular Cartilage Regeneration Post‐Injury

The role of the inflammatory response in articular cartilage degeneration and/or repair is often debated. Chemokine networks play a critical role in directing the recruitment of immune cells to sites of injury and have been shown to regulate cell behavior. In this study, we investigated the role of the CCL2/CCR2 signaling axis in cartilage regeneration and degeneration. CCL2^?/?, CCR2^?/?, CCL2^?/?CCR2^?/?, and control (C57) mice were subjected to full‐thickness cartilage defect (FTCD) injuries (n = 9/group) within the femoral groove. Cartilage regeneration at 4 and 12 weeks post‐FTCD was assessed using a 14‐point histological scoring scale. Mesenchymal stem cells (MSCs) (Sca‐1⁺, CD140a⁺), macrophages (M1:CD38⁺, M2:CD206⁺, and M0:F4/80⁺) and proliferating cells (Ki67⁺) were quantified within joints using immunofluorescence. The multi‐lineage differentiation capacity of Sca1⁺ MSCs was determined for all mouse strains. ACL transection (ACL‐x) was employed to determine if CCL2^?/?CCR2^?/? mice were protected against osteoarthritis (OA) (n = 6/group). Absence of CCR2, but not CCL2 nor both (CCL2 and CCR2), enhanced spontaneous articular cartilage regeneration by 4 weeks post‐FTCD. Furthermore, increased chondrogenesis was observed in MSCs derived from CCR2^?/? mice. CCL2 deficiency promoted MSC homing to the adjacent synovium and FTCD at both 4 and 12 weeks post‐injury; with no MSCs present at the surface of the FTCD in the remaining strains. Lower OA scores were observed in CCL2^?/?CCR2^?/? mice at 12 weeks post‐ACL‐x compared with C57 mice. Our findings demonstrate an inhibitory role for CCR2 in cartilage regeneration after injury, while CCL2 is required for regeneration, acting through a CCR2 independent mechanism. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:2561–2574, 2019