Xeno‐implantation of pig chondrocytes into rabbit to treat localized articular cartilage defects: an animal model

Abstract

Articular cartilage has only a limited ability to regenerate. The transplantation of autologous chondrocytes is currently used to treat focal defects in human articular cartilage, although use of organs, tissues, or cells from different species is being investigated as an alternative treatment. The object of this study was to use xeno-transplantation of cultured pig chondrocytes for the repair of rabbit chondral defects, and to analyze the significance of tissue rejection in this animal model. Partial chondral defects, including removal of cartilage tissue and a part of the subchondral bone, were created in the lateral femoral condyles of 30 adult New Zealand White rabbits. A periosteal flap was sutured to the native cartilage with the cambium layer facing the defect. As a control, culture medium was injected into the defect void of one group of rabbits while in a treatment group, chondrocytes, isolated from normal femoral pig cartilage, were injected into the defect void. All rabbits were killed by 24 weeks. Macroscopic changes of the cartilage were analyzed using Mankin's score. The distal femoral portion was studied histologically using hematoxylin and eosin, alcian blue, toluidine blue, and Mason's trichrome. Pig cells and pig genetic material were detected in the neo-synthesized tissue by immunohistochemical detection of SLA-II-DQ and polymerase chain reaction analysis of the gene SLA-II-DQB. The synovial membrane was studied histologically by hematoxylin and eosin staining. In the control group, on average, less than 25 percent of the chondral defect was filled. The repair tissue had an irregular surface with few cells similar to chondrocytes or fibroblasts and a minimal formation of extracellular matrix. In the treatment group, the chondral defect was approximately 90 percent filled with good integration between the neo-synthesized cartilage and the native cartilage. The repair tissue had a smooth surface with cells similar to chondrocytes and a hyaline-like extracellular matrix. The neo-synthesized cartilage was morphologically similar to hyaline cartilage. Importantly, there were no signs of graft-vs.-host rejections or infiltration by immune cells. In the neo-synthesized tissue, pig genetic material was detected in 27 +/- 5 percent of all cells. These cells containing pig genetic material were distributed throughout the neo-synthesized cartilage. We conclude that the xeno-transplantation of chondrocytes could be an alternative method for the repair of articular cartilage defects.

Immunogenicity of Bovine and Leporine Articular Chondrocytes and Meniscus Cells

“…Although allogeneic sources have been commonly used for in vivo studies of cartilaginous tissue replacement, the use of xenogeneic sources is less common, 24,[27][28][29][30][31] but the available data indicate that xenogeneic cell sources may be used in cartilage and meniscal tissue engineering because of the immunoprivileged nature of these cells. 24,[27][28][29][30][31] The benefits of using a xenogeneic cell source for cartilage engineering are significant. Concerns regarding donor-site morbidity and difficulties associated with obtaining a sufficient number of cells required for tissue engineering efforts such as highdensity scaffold-free cartilage formation can be mediated using a xenogeneic approach.…”

“…[24][25][26] Moreover, studies testing allogeneic (human and leporine) and xenogeneic (porcine to leporine and leporine to caprine) implantation of ACs support these in vitro experiments, reporting that they produce little to no immune response. [27][28][29][30][31] A comparison of the literature results suggests that the degree of immune reaction to implanted cartilage material is inversely related to the amount of ECM it contains, indicating that, along with lacking critical surface markers involved with the induction of an immune response, cartilage ECM may shield immunogenic markers on chondrocytes from host T-cells, enhancing the reparative capacity of these therapies. 31 Although little investigation has been made into the immunogenicity of meniscus cells (MCs), some evidence suggests that they may share an immunoprivileged profile similar to that of chondrocytes.…”

Cell Therapy and Tissular Engeenering to Regenerate Articular Cartilage

“…Even though isolated chondrocytes result in immunogenic reaction, alloimplantation of chondrocytes encapsulated in their ECM (Schreiber et al, 1999) or embedded in collagen gel (Wakitani et al, 1989) or agarose (Rahfoth et al, 1998) resulted in few or no rejection reactions. Notably, xenotransplantation in vivo of cultured pig chondrocytes into rabbit chondral defects closed with periosteal membrane no signs of infiltration by immune cells (Ramallal et al, 2004).…”

“…Other therapeutic alternatives are allotransplantation (Wakitani et al, 1989;Rahfoth et al, 1998;Schreiber et al, 1999) and xenotransplantation of chondrocytes , Ramallal et al, 2004, that elude the damage added to the joint during autotransplantation to obtain isolated chondrocytes. Allotransplantation is constrained by the necessity for compatible donors and limitations on storage of cartilage or chondrocytes because cryopreservation reduces survival and proliferation of chondrocytes (RendalVázquez et al, 2001).…”

Clinical and experimental approaches to knee cartilage lesion repair and mesenchymal stem cell chondrocyte differentiation

“…Furthermore, varying degrees of responses have been described in diff erent experimental settings when the grafts are implanted in vivo into joint defects, which was dependant on how the heterologous cells were implanted. For example, after rabbit articular cartilage defects were treated with pig chondrocytes and covered with a periosteal graft, signifi cant tissue repair was observed after 24 weeks, showing a 90% defect fi ll and a good histological score; furthermore, neocartilage showed chondrocyte like cells, a smooth hyaline morphology and no tissue rejection was reported (Ramallal et al, 2004). In another report, rabbit chondrocytes suspended in fibrin glue were transplanted into goat full-thickness articularcartilage defects.…”