Maxwell H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY, USA.
Department of Statistics, University of Kentucky, Lexington, KY, USA.
Cartilage. 2021 Dec;13(2_suppl):82S-94S. doi: 10.1177/1947603519841680. Epub 2019 Apr 25.
Articular cartilage in mammals has limited intrinsic capacity to repair structural defects, a fact that contributes to the chronic and progressive nature of osteoarthritis. In contrast, Mexican axolotl salamanders have demonstrated the remarkable ability to spontaneously and completely repair large joint cartilage lesions, a healing process that involves interzone cells in the intraarticular space. Furthermore, interzone tissue transplanted into skeletal defects in the axolotl salamander demonstrates a multi-differentiation potential. Cellular and molecular mechanisms of this repair process remain unclear. The objective of this study was to examine whether paracrine mitogenic signals are an important variable in the interaction between interzone cells and the skeletal microenvironment.
The paracrine regulation of the proliferation of equine interzone cells was evaluated in an co-culture system. Cell viability and proliferation were measured in equine fetal interzone cells after exposure to conditioned medium from skeletal and nonskeletal primary cell lines. Steady-state expression was determined for genes encoding 37 putative mitogens secreted by cells that generated the conditioned medium.
All experimental groups of conditioned media elicited a mitogenic response in interzone cells. Fetal anlage chondrocytes ( < 0.0001) and dermal fibroblasts ( < 0.0001) conditioned medium showed a significantly higher mitogenic potential compared with interzone cells. Conditioned medium from bone marrow-derived cells elicited a significantly higher proliferative response relative to that from young adult articular chondrocytes ( < 0.0001) or dermal fibroblasts ( < 0.0001). Sixteen genes had expression patterns consistent with the functional proliferation assays.
The results indicate a mitogenic effect of skeletal paracrine signals on interzone cells.
哺乳动物的关节软骨修复结构缺陷的内在能力有限，这一事实导致了骨关节炎的慢性和进行性特征。相比之下，墨西哥蝾螈具有显著的自发性和完全修复大关节软骨损伤的能力，这种愈合过程涉及关节内空间的间区细胞。此外，间区组织移植到蝾螈的骨骼缺陷中表现出多分化潜力。这种修复过程的细胞和分子机制尚不清楚。本研究的目的是研究旁分泌有丝分裂原信号是否是间区细胞与骨骼微环境相互作用的一个重要变量。
在共培养系统中评估了旁分泌对马间区细胞增殖的调节作用。在暴露于骨骼和非骨骼原代细胞系的条件培养基后，测量了马胎儿间区细胞的细胞活力和增殖。确定了产生条件培养基的细胞分泌的 37 种潜在有丝分裂原基因的稳定表达。
所有实验组的条件培养基均能刺激间区细胞产生有丝分裂反应。胚胎软骨细胞（<0.0001）和真皮成纤维细胞（<0.0001）的条件培养基显示出比间区细胞更高的有丝分裂潜力。骨髓来源细胞的条件培养基与年轻的成年关节软骨细胞（<0.0001）或真皮成纤维细胞（<0.0001）相比，具有更高的增殖反应。16 个基因的表达模式与功能增殖测定一致。
这些结果表明骨骼旁分泌信号对间区细胞有丝分裂作用。
