Chondrocyte apoptosis in the regenerated articular cartilage after allogenic chondrocyte transplantation in the rabbit knee

We attempted to repair full-thickness defects in the articular cartilage of the trochlear groove of the femur in 30 rabbit knee joints using allogenic cultured chondrocytes embedded in a collagen gel. The repaired tissues were examined at 2, 4, 8, 12 and 24 weeks after operation using histological and histochemical methods. The articular defect filling index measurement was derived from safranin-O stained sections. Apoptotic cellular fractions were derived from analysis of apoptosis in situ using TUNEL staining, and was confirmed using caspase-3 staining along with quantification of the total cellularity. The mean articular defect filling index decreased with time. After 24 weeks it was 0.7 (SD 0.10), which was significantly lower than the measurements obtained earlier (p < 0.01). The highest mean percentage of apoptotic cells were observed at 12 weeks, although the total cellularity decreased with time. Because apoptotic cell death may play a role in delamination after chondrocyte transplantation, anti-apoptotic gene therapy may protect transplanted chondrocytes from apoptosis.     

Rabbit articular cartilage defects treated by allogenic chondrocyte transplantation

Articular cartilage defects have a poor capacity for repair. Most of the current treatment options result in the formation of fibro-cartilage, which is functionally inferior to normal hyaline articular cartilage. We studied the effectiveness of allogenic chondrocyte transplantation for focal articular cartilage defects in rabbits. Chondrocytes were cultured in vitro from cartilage harvested from the knee joints of a New Zealand White rabbit. A 3 mm defect was created in the articular cartilage of both knees in other rabbits. The cultured allogenic chondrocytes were transplanted into the defect in the right knees and closed with a periosteal flap, while the defects in the left knees served as controls and were closed with a periosteal flap alone, without chondrocytes. Healing of the defects was assessed at 12 weeks by histological studies. Allogenic chondrocyte transplantation significantly increased the amount of newly formed repair tissue (P=0.04) compared with that found in the control knees. The histological quality score of the repair tissue was significantly better (P=0.05), with more hyaline characteristics in the knees treated with allogenic chondrocytes than in the control knees. Articular cartilage defects treated with allogenic chondrocyte transplantation result in better repair tissue formation with hyaline characteristics than those in control knees.     

Use of a guanidine extract of demineralized bone in the treatment of osteochondral defects of articular cartilage

In order to evaluate the ability of a guanidine extract of demineralized bone to repair osteochondral defects in articular cartilage, plugs made of this extract were implanted into defects in rabbit knees. The repair tissue was examined macroscopically, histologically, and immunohistochemically at 4, 8, 12 and 30 weeks. Controls (defects that were left empty) showed no cartilage formation. Four weeks after implantation of a guanidine extract plug, histological examination showed a nonhomogeneous metachromatically stained region extending from the surface of the repair tissue down to cancellous bone. This region also was labeled by an anti-type-II collagen antibody, indicating that cartilage-like tissue had been induced. At 8 weeks, the newly formed cartilage in the subchondral and cancellous bone had been partially replaced by bone. At 12 weeks, the thickness of the newly formed cartilage layer had decreased, and most of the newly formed cartilage in the subchondral and cancellous bone had been replaced by bone. In addition, a tidemark was observed. At 30 weeks, the repair tissue was a mixture of cartilage and fibrocartilage, and there was severe degeneration of the cartilage surrounding the repaired defects. These findings indicate that osteochondral defects of articular cartilage can be partially repaired by the implantation of a guanidine extract and that the newly formed cartilage-like tissue is not permanent.     

Repair of rabbit articular surfaces with allografts of chondrocytes embedded in collagen gels

In an attempt to restore articular cartilage, allogeneic articular chondrocytes embedded in collagen gels were transplanted onto full-thickness defects in rabbit articular cartilage. Within 24 weeks after the transplantation, the defects were filled with hyaline cartilage, specifically synthesizing type II collagen. These chondrocytes were autoradiographically proven to be originated from the originally transplanted chondrocytes. As histologically assessed, success rate was about 80%, a marked improvement over the results (40% success rate) in previous studies reporting chondrocyte transplantation without collagen gels. On the other hand, the defects without chondrocyte transplantation healed with fibrocartilaginous tissue more than 24 weeks after treatment. Immunological enhancement induced by transplanted allogeneic chondrocytes or collagen was not significant for eight weeks after treatment, so far as shown by both direct and indirect blastformation reactions. Thus, allogeneic transplantation of isolated chondrocytes embedded in collagen gels appears to be one of the most promising methods for the restoration of articular cartilage.     

Repair of rabbit articular surfaces with allograft chondrocytes embedded in collagen gel

In an attempt to repair articular cartilage, allograft articular chondrocytes embedded in collagen gel, were transplanted into full-thickness defects in rabbit articular cartilage. Twenty-four weeks after the transplantation, the defects were filled with hyaline cartilage, specifically synthesising Type II collagen. These chondrocytes were autoradiographically proven to have originated from the transplanted grafts. Assessed histologically the success rate was about 80%, a marked improvement over the results reported in previous studies on chondrocyte transplantation without collagen gel. By contrast, the defects without chondrocyte transplantation healed with fibrocartilage. Immunological enhancement induced by transplanted allogenic chondrocytes or collagen was not significant at eight weeks after treatment, so far as shown by both direct and indirect blastformation reactions. Thus, allogenic transplantation of isolated chondrocytes embedded in collagen gel appears to be one of the most promising methods for the restoration of articular cartilage.     

Patient experiences with interventions to reduce surgery cancellations: a qualitative study

Chondral defects of the articular surface are a common condition that can lead to osteoarthritis if not treated. Therapy of this condition is a topic of constant debate and a variety of chondral repair strategies are currently used. One strategy involves implantation of a cell-free matrix of type I collagen (COL1), to provide a scaffold for chondrocyte migration and proliferation and extracellular matrix production. Although several studies have suggested that chondrocytes can move, to the best of our knowledge there is still no proof of chondrocyte occurrence in a former cell-free scaffold for articular cartilage repair in humans. An 18-year-old male patient underwent arthroscopic surgery of the knee for patellar instability and a chondral defect of the femoral condyle. Clinical outcome scores were recorded pre-operatively, after 6 weeks and after 6, 12, 24 and 36 months. MRI was recorded after 6 weeks and after 6, 12, 24 and 36 months postoperatively. At 42 months after implantation of a cell-free type I collagen matrix and reconstruction of the medial patellofemoral ligament, the patient was again treated arthroscopically for a tear of the medial meniscus of the same knee. A biopsy of the previous chondral defect was taken during arthroscopy for histological examination. In addition to good clinical and radiological results reported for cell-free scaffolds for cartilage repair in several other studies, transformation of the scaffold could be observed during re-arthroscopy for the meniscal tear. Histological examination of the specimen revealed articular cartilage with vital chondrocytes and a strong staining reaction for type II collagen (COL II), but no reaction for type I collagen staining. This might indicate a complete transformation of the scaffold and supports the theory that cell free scaffolds could support cell migration. Although the cell source remains unclear, migrating chondrocytes from the periphery remain a possibility.     

异体软骨细胞移植修复猪膝关节软骨缺损的免疫学观察

目的应用同种异体软骨细胞移植修复猪膝关节软骨缺损,评估术后免疫学表现及其修复效果。方法供体为1月龄上海白猪2头,取其膝关节全层软骨片,0.25%胰蛋白酶和0.2%型胶原酶消化,分离培养软骨细胞。受体为2月龄巴马猪8头,在两侧股骨髁关节负重面造成0.5cm×0.5cm软骨缺损,深及软骨下骨。于受体猪双侧膝关节软骨缺损处注入软骨细胞悬液0.2ml,含软骨细胞(1.0～2.0)×106个,密封入口。术前、术后3、5、7、12周分离受体外周血淋巴细胞,检测其与异体软骨细胞混合后的刺激指数(stimulationindex,SI);术后5、7、24周取修复区软骨及软骨下骨观察局部组织学反应。结果术后3、5、7、12周受体外周血淋巴细胞SI分别为1.457±0.062、1.739±0.142、1.548±0.047和1.216±0.028,较术前(1.102±0.034)增高,且差异均有统计学意义(P<0.05);SI术后3周开始升高,5周达高峰,7、12周后开始逐渐下降;3、7、12周SI与5周比较差异均有统计学意义(P<0.05)。组织学观察:术后5周,出现较多的炎性浸润,分散于软骨下骨、修复组织与正常软骨的整合部等;7周,炎性浸润开始减退,仅在软骨下骨可见;24周,缺损处修复软骨与周围软骨整合良好。结论异体软骨细胞移植后,免疫反应一般在移植早期开始出现,并逐渐达到高峰,但随着软骨基质的重新合成,免疫反应也逐渐下降,并最终修复全层关节软骨缺损。     

Minced cartilage without cell culture serves as an effective intraoperative cell source for cartilage repair.

Traumatic articular cartilage injuries heal poorly and may predispose patients to the early onset of osteoarthritis. One current treatment relies on surgical delivery of autologous chondrocytes that are prepared, prior to implantation, through ex vivo cell expansion of cartilage biopsy cells. The requirement for cell expansion, however, is both complex and expensive and has proven to be a major hurdle in achieving a widespread adoption of the treatment. This study presents evidence that autologous chondrocyte implantation can be delivered without requiring ex vivo cell expansion. The proposed improvement relies on mechanical fragmentation of cartilage tissue sufficient to mobilize embedded chondrocytes via increased tissue surface area. Our outgrowth study, which was used to demonstrate chondrocyte migration and growth, indicated that fragmented cartilage tissue is a rich source for chondrocyte redistribution. The chondrocytes outgrown into 3-D scaffolds also formed cartilage-like tissue when implanted in SCID mice. Direct treatment of full-thickness chondral defects in goats using cartilage fragments on a resorbable scaffold produced hyaline-like repair tissue at 6 months. Thus, delivery of chondrocytes in the form of cartilage tissue fragments in conjunction with appropriate polymeric scaffolds provides a novel intraoperative approach for cell-based cartilage repair.     

Repair of full-thickness articular cartilage defects using injectable type II collagen gel embedded with cultured chondrocytes in a rabbit model

BACKGROUND: Recently, tissue-engineered chondrocyte transplantation has been tried to treat full-thickness cartilage defects. We developed an injectable type II collagen gel scaffold by chemically reacting type II collagen with polyethylene glycol crosslinker. This type II collagen was prepared from the nasal septa of cattle. In the present study, chondrocytes embedded in type II collagen gel were injected into rabbit full-thickness cartilage defects without a periosteal graft, and the feasibility for clinical application of the gel was evaluated. METHODS: Chondrocytes were isolated from 1-kg New Zealand white rabbits. A full-thickness articular cartilage defect (5 mm diameter, 4 mm depth) was created on the patellar groove of the femur of 16 male 3-kg New Zealand white rabbits. A type II collagen solution of mixed chondrocytes at a density of 1 x 10(7) cells/ml was injected and transplanted into the defect in the right knee. The controls were the defect only in the left knee. At 4, 8, 12, and 24 weeks after operation, four cases from each group were evaluated macroscopically and histologically. RESULTS: After injection into the cartilage defect, the gel bonded to the adjacent cartilage and bone within several minutes. Macroscopic examination revealed that the surface of the transplanted area was smooth and exhibited similar coloration and good integration with the surrounding cartilage at 12 and 24 weeks after transplantation. Histological examination at 8 weeks revealed favorable hyaline cartilage regeneration with good chondrocyte morphology. At 12 and 24 weeks, reparative cartilage remained rich in type II collagen. According to O'Driscoll histological scores, significant differences between the transplanted and control groups were apparent at 12 and 24 weeks. Immunohistochemical staining indicated sufficient type II collagen synthesis in regenerated cartilage 8 weeks after transplantation, and it was maintained until 24 weeks. CONCLUSIONS: These results indicate that type II collagen gel is suitable for injection into cartilage defects without any covering of a graft and offers a useful scaffold during chondrocyte transplantation.     

Determination of characteristics of degenerative joint disease using optical coherence tomography and polarization sensitive optical coherence tomography

BACKGROUND AND OBJECTIVES: Previous studies have demonstrated that optical coherence tomography (OCT) could be used to delineate alterations in the microstructure of cartilage, and have suggested that changes in the polarization state of light as detected by OCT could provide information on the birefringence properties of articular cartilage as influenced by disease. In this study we have used both OCT and polarization sensitive optical coherence tomography (PS-OCT) technologies to evaluate normal and abnormal bovine articular cartilage according to established structural, organizational, and birefringent characteristics of degenerative joint disease (DJD) in order to determine if this technology can be used to differentiate various stages of DJD as a minimally invasive imaging tool. MATERIALS AND METHODS: Fresh bovine femoral-tibial joints were obtained from an abattoir, and 45 cartilage specimens were harvested from 8 tibial plateaus. Whole ex vivo specimens of normal and degenerative articular cartilage were imaged by both OCT and PS-OCT, then fixed and processed for histological evaluation. OCT/PS-OCT images and corresponding histology sections of each specimen were scored according to a modified Mankin structural grading scale and compared. RESULTS: OCT and PS-OCT imaging allowed structural evaluation of intact articular cartilage along a 6 mm surface length to a depth of 2 mm with a transverse resolution of 12 microm and an axial resolution of 10 microm. The OCT and PS-OCT images demonstrated characteristic alterations in the structure of articular cartilage with a high correlation to histological evaluation (kappa = 0.776). The OCT images were able to demonstrate early to advanced structural changes of articular cartilage while the optical phase retardation images obtained by PS-OCT imaging were able to discriminate areas where disorganization of the cartilage matrix was present, however, these characteristics are much different than those reported where OCT images alone were used to characterize tissue birefringence. No evidence of differences in OCT or PS-OCT images were detected between specimens of similar structural characteristics where proteoglycan was judged present or absent by safranin-O Fast Green staining. CONCLUSIONS: The combined use of OCT and PS-OCT technologies to obtain images from a single system is able to demonstrate and discriminate between characteristics of very early stages of surface irregularities not previously reported for OCT imaging, to deep clefts and collagen matrix disorganization for tissue at depths of up to 2 mm with good correlation to histology. PS-OCT and accumulated optical phase retardation images of articular cartilage as constructed from alterations in Stokes vector parameters appear to give a valuable but different assessment of alterations in tissue birefringence and organization than have been reported for OCT images obtained with the use of polarized or non-polarized light sources. This is the first time that alterations in the polarization state of light reflected from within the tissue have been demonstrated to be consistent with changes observed in the orientation and organization of the collagen matrix in advanced stages of DJD. The degree of phase transformation of light reflected from within the tissue as determined by PS-OCT imaging does not appear to be altered by the presence or absence of proteoglycan.     

Comparison of optical coherence tomography and histopathology in quantitative assessment of goat talus articular cartilage

Background and purpose — Optical coherence tomography (OCT) is a light-based imaging technique suitable for depiction of thin tissue layers such as articular cartilage. Quantification of results and direct comparison with a reference standard is needed to confirm the role of OCT in cartilage evaluation.

Materials and methods — Goat talus articular cartilage repair was assessed quantitatively with OCT and compared with histopathology using semi-automated analysis software. Osteochondral defects were created centrally in goat tali with subsequent healing over 24 weeks. After sacrifice, the tali were analyzed using OCT and processed into histopathology slides. Cartilage thickness, repair tissue area, and surface roughness were measured. Also, light attenuation coefficient measurements were performed to assess differences in the properties of healthy tissue and repair tissue.

Results — Intra-class correlation coefficients for resemblance between the 2 techniques were 0.95 (p < 0.001) for thickness, 0.73 (p = 0.002) for repair tissue area, and 0.63 (p = 0.015) for surface roughness. Light attenuation differed significantly between healthy cartilage (8.2 (SD 3.9) mm^-1) and repair tissue (2.8 (SD 1.5) mm^-1) (p < 0.001).

Interpretation — Compared to histopathology as the standard reference method, OCT is a reproducible technique in quantitative analysis of goat talus articular cartilage, especially when assessing cartilage thickness and to a lesser extent when measuring repair tissue area and surface roughness. Moreover, differences in local light attenuation suggest measurable variation in tissue structure, enhancing the clinical applicability of quantitative measurements from cartilage OCT images.     

Tissue engineering of trachea-like cartilage grafts by using chondrocyte macroaggregate: experimental study in rabbits

Abstract:  Treatment and management of tracheal defects remain challenges in head and neck surgery. The purposes of this study were to explore a novel strategy to fabricate tissue-engineered trachea by using chondrocyte macroaggregate, and evaluate the feasibility of creating tracheal cartilage equivalents grown in the shape of cylindrical structure without scaffold. Chondrocytes from rabbit cartilage were expanded and seeded into a culture dish at high density to form mechanically stable chondrocyte macroaggregate. Once the chondrocyte macroaggregate was harvested by scrapping technique, it was wrapped around a silicon tube and implanted subcutaneously into the cell donor rabbit. Eight weeks later, specimens were harvested and analyzed for gross appearance, and histological, biochemical, and biomechanical properties. These values were compared with native rabbit cartilage. It was found that expanded chondrocytes could be harvested as a coherent cellular macroaggregate and could be fabricated into a tubelike graft. After in vivo implantation, cartilage-like tissue with cylindrical structure was regenerated successfully. Histological analysis showed engineered trachea cartilage consisted of evenly spaced lacunae embedded in a matrix rich in proteoglycans; type II collagen was also highly expressed in this engineered trachea cartilage. In a conclusion, based on the chondrocyte macroaggregate strategy, tracheal cartilage equivalents with cylindrical shape could be successfully reconstructed. This construct has advantages of high cell-seeding efficiency, good nutritional perfusion, and minimal inflammatory reaction, which provided a highly effective cartilage graft substitute and could be useful in many situations of trachea–cartilage loss encountered in clinical practice.     

骨髓基质细胞修复兔关节软骨的实验研究

目的　研究骨髓基质细胞修复兔关节软骨的可行性。方法　取自体骨髓基质细胞体外培养扩增 ,聚乳酸吸附骨髓基质细胞植入兔膝关节软骨负重 (内髁 )和非负重区 (外髁 )缺损内 ,观察 4、 8、 12周后软骨缺损的修复情况 ,并对组织切片评分。结果　 8、 12周后 ,骨髓基质细胞在负重区缺损内可以形成透明软骨 ,组织评分接近正常软骨优于对照 ,非负重区内没有形成透明软骨。结论　骨髓基质细胞可以修复关节软骨缺损 ,摩擦和压应力是成软骨的重要条件。     

三维动态诱导对自体组织工程软骨远期退变抑制效应的实验研究

目的体外诱导自体骨髓间充质干细胞（aMSC）向软骨细胞分化,验证三维动态诱导培养的软骨分化效率和远期修复效应。方法分离培养多样本aMSC,分别行转壁生物反应器内三维动态诱导（三维动态诱导组）培养和常规二维平面诱导（二维平面诱导组）培养,比较各自的软骨分化效率;收获细胞与注射型蛋白胶混合,修复动物关节软骨缺损。8、12、24、48周后分别取材,观察大体形态和组织学形态,进行组织学评分,比较长期修复效果。结果二维平面诱导时仅出现局部蛋白多糖沉积,只少数细胞表达Ⅱ型胶原;三维动态诱导培养时蛋白多糖沉积明显并广泛表达Ⅱ型胶原,其胶原产量和蛋白多糖含量明显高于二维平面诱导组。在体内实验中,三维动态诱导组：8、12周后缺损完全修复,表面光滑,质地坚硬,与周围软骨紧密结合,组织学表现为类透明软骨结构,24、48周后修复组织与周围界限消失,仍保持类透明软骨的结构。二维平面诱导组：8周后软骨缺损即可被类透明软骨修复,但12周后即开始出现退变,24周后退化明显,软骨组织骨化变薄,48周后则大部分骨性退化,表层残留菲薄纤维组织。结论三维动态诱导培养可提高aMSC的软骨分化效率和远期修复效果,可为深化自体软骨组织工程研究提出新思路。     

Autologous chondrocyte implantation--technique and long-term follow-up

Cartilage has a limited capacity for self repair after injury. This biological deficiency has led to a variety of surgical attempts to improve the repair of injured articular cartilage surfaces over the past 50 years. The first example of clinical cartilage tissue engineering was performed in 1987 when a knee with an articular cartilage defect on the femoral condyle was treated by implanting the patient's own chondrocytes that had been expanded in vitro into the defect in combination with a covering mechanical membrane-the periosteum. This technology is either termed autologous chondrocyte transplantation (ACT) or autologous chondrocyte implantation (ACI). Today, many modifications of the technique exist, from the first generation to now second and third generations of chondrocyte implantation. This paper describes the basic techniques for the clinical use of chondrocyte implantation and gives an update on the clinical results.     

Human autologous culture expanded bone marrow mesenchymal cell transplantation for repair of cartilage defects in osteoarthritic knees

OBJECTIVE: There is no widely accepted method to repair articular cartilage defects. Bone marrow mesenchymal cells have the potential to differentiate into bone, cartilage, fat and muscle. Bone marrow mesenchymal cell transplantation is easy to use clinically because cells can be easily obtained and can be multiplied without losing their capacity of differentiation. The objective of this study was to apply these cell transplantations to repair human articular cartilage defects in osteoarthritic knee joints. DESIGN: Twenty-four knees of 24 patients with knee osteoarthritis (OA) who underwent a high tibial osteotomy comprised the study group. Adherent cells in bone marrow aspirates were culture expanded, embedded in collagen gel, transplanted into the articular cartilage defect in the medial femoral condyle and covered with autologous periosteum at the time of 12 high tibial osteotomies. The other 12 subjects served as cell-free controls. RESULTS: In the cell-transplanted group, as early as 6.3 weeks after transplantation the defects were covered with white to pink soft tissue, in which metachromasia was partially observed. Forty-two weeks after transplantation, the defects were covered with white soft tissue, in which metachromasia was observed in almost all areas of the sampled tissue and hyaline cartilage-like tissue was partially observed. Although the clinical improvement was not significantly different, the arthroscopic and histological grading score was better in the cell-transplanted group than in the cell-free control group. CONCLUSIONS: This procedure highlights the availability of autologous culture expanded bone marrow mesenchymal cell transplantation for the repair of articular cartilage defects in humans.     

Chondrocyte transplantation in PGLA/polydioxanone fleece

The transplantation of chondrogenic cells in a supportive carrier structure proved to be a promising alternative for the treatment of cartilage defects. In the study presented we focused on the transplantation of allogeneic chondrocytes in a biodegradable polymer scaffold (PGLA/Polydioxanon) in articular cartilage defects in a rabbit defect model. Isolated allogeneic chondrocytes embedded in a PGLA polymer scaffold were transplanted into osteochondrogenic defects of the patellar groove and compared with empty defects and transplants of polymer scaffolds without cells. The histological and histochemical analysis was performed after 4 and 12 weeks. The transplant integration and the architecture of the newly formed cartilage were evaluated with a semiquantitative score. After 4 weeks the development of a hyaline-like cartilage tissue of the cell-polymer-transplants was observed, after 12 weeks the defects were nearly completely filled with hyaline-like cartilage. The biodegradation of the polymer construct did not affect the histological structure of the transplant area. Defects of the groups with empty defect and polymer transplants without cells revealed no or insufficient healing indices. The study demonstrated that biodegradable polymers served as suitable carriers for the chondrocyte transplantation, which is due to the in-vitro establishment of a semi-solid cartilage transplant and the resulting effective transplant fixation into the defect. In-vivo the polymer cell transplants seem to provide a supportive microenvironment for the development of hyaline cartilage. The controlled release of morphogenic factors or bioactive molecules and the use of pluripotent mesenchymal progenitor cells opens new perspectives for the optimization of cartilage repair procedures.     

Immature porcine knee cartilage lesions show good healing with or without autologous chondrocyte transplantation

OBJECTIVE: The purpose of this study was to find out how deep chondral lesions heal in growing animals spontaneously and after autologous chondrocyte transplantation. METHODS: A 6mm deep chondral lesion was created in the knee joints of 57 immature pigs and repaired with autologous chondrocyte transplantation covered with periosteum or muscle fascia, with periosteum only, or left untreated. After 3 and 12 months, the repair tissue was evaluated with International Cartilage Repair Society (ICRS) macroscopic grading, modified O'Driscoll histological scoring, and staining for collagen type II and hyaluronan, and with toluidine blue and safranin-O staining for glycosaminoglycans. The repair tissue structure was also examined with quantitative polarized light microscopy and indentation analysis of the cartilage stiffness. RESULTS: The ICRS grading indicated nearly normal repair tissue in 65% (10/17) after the autologous chondrocyte transplantation and 86% (7/8) after no repair at 3 months. At 1 year, the repair tissue was nearly normal in all cases in the spontaneous repair group and in 38% (3/8) in the chondrocyte transplantation group. In most cases, the cartilage repair tissue stained intensely for glycosaminoglycans and collagen type II indicating repair tissue with true constituents of articular cartilage. There was a statistical difference in the total histological scores at 3 months (P=0.028) with the best repair in the spontaneous repair group. A marked subchondral bone reaction, staining with toluidine blue and collagen type II, was seen in 65% of all animals. CONCLUSIONS: The spontaneous repair ability of full thickness cartilage defects of immature pigs is significant and periosteum or autologous chondrocytes do not bring any additional benefits to the repair.     

Autologous chondrocyte implantation in a novel alginate-agarose hydrogel: outcome at two years

Autologous chondrocyte implantation is an established method of treatment for symptomatic articular defects of cartilage. CARTIPATCH is a monolayer-expanded cartilage cell product which is combined with a novel hydrogel to improve cell phenotypic stability and ease of surgical handling. Our aim in this prospective, multicentre study on 17 patients was to investigate the clinical, radiological, arthroscopic and histological outcome at a minimum follow-up of two years after the implantation of autologous chondrocytes embedded in a three-dimensional alginate-agarose hydrogel for the treatment of chondral and osteochondral defects. Clinically, all the patients improved significantly. Patients with lesions larger than 3 cm(2) improved significantly more than those with smaller lesions. There was no correlation between the clinical outcome and the body mass index, age, duration of symptoms and location of the defects. The mean arthroscopic International Cartilage Repair Society score was 10 (5 to 12) of a maximum of 12. Predominantly hyaline cartilage was seen in eight of the 13 patients (62%) who had follow-up biopsies. Our findings suggest that autologous chondrocyte implantation in combination with a novel hydrogel results in a significant clinical improvement at follow-up at two years, more so for larger and deeper lesions. The surgical procedure is uncomplicated, and predominantly hyaline cartilage-like repair tissue was observed in eight patients.     

Degree of differentiation of chondrocytes and their pretreatment with platelet-derived-growth factor. Regulating induction of cartilage formation in resorbable tissue carriers in vivo

Current methods for articular cartilage repair are unpredictable with respect to clinical success. In the present study, we investigated the ability of cells from articular cartilage, perichondrium, and costochondral resting zone to form new cartilage when loaded onto biodegradable scaffolds and implanted into calf muscle pouches of nu/nu mice. Prior in vitro studies showed that platelet derived growth factor-BB (PDGF-BB), but not transforming growth factor beta-1 (TGF-beta 1), basic fibroblast growth factor, or bone morphogenetic protein-2 promoted proliferation and extracellular matrix sulfation of resting zone chondrocytes without causing the cells to exhibit a hypertrophic chondrocyte phenotype. TGF-beta 1 has also been shown to stimulate chondrogenesis by multipotent chondroprogenitor cells like those in the perichondrium. In addition, PDGF-BB has been shown to modulate chondrogensis by resting zone cells implanted in poly(D,L-lactide-co-glycolide) (PLG) scaffolds. In the present study we examined whether the cartilage formation is dependent on state of chondrocyte maturation and whether the pretreatment of chondrocytes with growth factors has an influence on the cartilage formation. Scaffolds were manufactured from 80% PLG with a 75:25 lactide:glycolide ratio and 20% modified PLG with a 50:50 lactide:glycolide ratio (PLG-H scaffolds). For each experimental group, four nude mice received two identical implants, one in each calf muscle resulting in an N = 8 implants: PLG-H scaffolds alone; PLG-H scaffolds with cells derived from either the femoral articular cartilage, costochondral periochondrium, or costochondral resting zone cartilage of 125 g male Sprague-Dawley rats; PLG-H scaffolds with either articular chondrocytes or resting zone chondrocytes that were pretreated with 37.5 ng/ml rhPDGF-BB for 4 h or 24 h before implantation, or with perichondrial cells treated with PDGF-BB plus 0.22 ng/ml rhTGF beta-1 for 4 h and 24 h. At 4 or 8 weeks after implantation, samples were harvested and analyzed histomorphometrically for new cartilage formed, area of residual implant and area of fibrous connective tissue. Only resting zone cells showed the ability to form new cartilage at a heterotopic site in this study. There was no neocartilage found in nude mice with implants loaded with either articular chondrocytes or perichondrial cells. Pretreatment of resting zone chondrocytes for 4 h prior to implantation significantly increased the amount of newly formed cartilage after 8 weeks and suppressed chondrocyte hypertrophy. The amount of fibrous connective tissue around implants containing either articular chondrocytes or perichondrial cells decreased with time, whereas the amount of fibrous connective tissue around implants containing resting zone chondrocytes pretreated with PDGF-BB was increased. The results showed that resting zone cells can be successfully incorporated into biodegradable porous PLG scaffolds and can induce new cartilage formation in a nonweight-bearing site. Articular chondrocytes as well as perichondrial cells did not have the capacity for neochondrogenesis when implanted heterotopically in this model.