Department of Orthopaedic Trauma Surgery, University Hospital Erlangen, Krankenhausstr. 12, 91054 Erlangen, Germany.
Calcif Tissue Int. 2009 Nov;85(5):421-33. doi: 10.1007/s00223-009-9288-9. Epub 2009 Sep 10.
The aim of this study was to investigate the effect of transplanted chondrocytes on endochondral bone formation in cartilage repair tissue. In the knee joint of miniature pigs, cartilage lesions were treated by microfracturing and were then either left empty, covered with a collagen membrane, or treated by matrix-associated autologous chondrocyte transplantation. In control lesions, the subchondral bone plate was left intact (partial-thickness lesion). The repair tissues were analyzed after 12 weeks by histological methods focusing on bone formation and vascularization. The effect of chondrocytes on angiogenesis was assessed by in vitro assays. The presence of antiangiogenic proteins in cartilage repair tissue, including thrombospondin-1 (TSP-1) and chondromodulin-I (ChM-I), was detected immunohistochemically and their expression in chondrocytes and bone marrow stromal cells was measured by quantitative RT-PCR. Significant outgrowths of subchondral bone and excessive endochondral ossification within the repair tissue were regularly observed in lesions with an exposed or microfractured subchondral bone plate. In contrast, such excessive bone formation was significantly inhibited by the additional transplantation of chondrocytes. Cartilaginous repair tissue that resisted ossification was strongly positive for the antiangiogenic proteins, TSP-1 and ChM-I, which were, however, not detectable in vascularized osseous outgrowths. Chondrocytes were identified to be the major source of TSP-1- and ChM-I expression and were shown to counteract the angiogenic activity of endothelial cells. These data suggest that the resistance of cartilaginous repair tissue against endochondral ossification following the transplantation of chondrocytes is associated with the presence of antiangiogenic proteins whose individual relevance has yet to be further explored.
本研究旨在探讨移植软骨细胞对软骨修复组织中软骨下骨形成的影响。在小型猪膝关节中，通过微骨折处理软骨病变，然后将病变部位空置、用胶原膜覆盖或进行基质相关的自体软骨细胞移植。在对照病变中，软骨下骨板保持完整（部分厚度病变）。12 周后，通过组织学方法分析修复组织，重点关注骨形成和血管生成。通过体外实验评估软骨细胞对血管生成的影响。通过免疫组织化学检测软骨修复组织中存在的抗血管生成蛋白，包括血小板反应蛋白-1（TSP-1）和软骨调节素-I（ChM-I），并通过定量 RT-PCR 测量软骨细胞和骨髓基质细胞中的表达。在暴露或微骨折的软骨下骨板的病变中，通常会观察到软骨下骨的明显生长和修复组织内的过度软骨内骨化。相比之下，通过额外移植软骨细胞可显著抑制这种过度骨形成。抵抗骨化的软骨修复组织强烈表达抗血管生成蛋白 TSP-1 和 ChM-I，但在血管化的骨性生长中检测不到。软骨细胞被鉴定为 TSP-1 和 ChM-I 表达的主要来源，并显示出对内皮细胞血管生成活性的拮抗作用。这些数据表明，软骨细胞移植后软骨修复组织对软骨下骨化的抵抗与抗血管生成蛋白的存在有关，其各自的相关性有待进一步探讨。
