Felisbino Sérgio L, Carvalho Hernandes F
Department of Morphology, UNESP, Botucatu, SP, Brazil.
Cell Tissue Res. 2002 Mar;307(3):357-65. doi: 10.1007/s00441-001-0508-5. Epub 2002 Feb 2.
Mineralization of the articular cartilage is a pathological condition associated with age and certain joint diseases in humans and other mammals. In this work, we describe a physiological process of articular cartilage mineralization in bullfrogs. Articular cartilage of the proximal and distal ends of the femur and of the proximal end of the tibia-fibula was studied in animals of different ages. Mineralization of the articular cartilage was detected in animals at 1 month post-transformation. This mineralization, which appeared before the hypertrophic cartilage showed any calcium deposition, began at a restricted site in the lateral expansion of the cartilage and then progressed to other areas of the epiphyseal cartilage. Mineralized structures were identified by von Kossa's staining and by in vivo incorporation of calcein green. Element analysis showed that calcium crystals consisted of poorly crystalline hydroxyapatite. Mineralized matrix was initially spherical structures that generally coalesced after a certain size to occupy larger areas of the cartilage. Alkaline phosphatase activity was detected at the plasma membrane of nearby chondrocytes and in extracellular matrix. Apoptosis was detected by the TUNEL (TDT-mediated dUTP-biotin nick end-labeling) reaction in some articular chondrocytes from mineralized areas. The area occupied by calcium crystals increased significantly in older animals, especially in areas under compression. Ultrastructural analyses showed clusters of needle-like crystals in the extracellular matrix around the chondrocytes and large blocks of mineralized matrix. In 4-year-old animals, some lamellar bone (containing bone marrow) occurred in the same area as articular cartilage mineralization. These results show that the articular cartilage of R. catesbeiana undergoes precocious and progressive mineralization that is apparently stimulated by compressive forces. We suggest that this mineralization is involved in the closure of bone extremities, since mineralization appears to precede the formation of a rudimentary secondary center of ossification in older animals.
关节软骨矿化是一种与人类和其他哺乳动物的年龄及某些关节疾病相关的病理状况。在本研究中，我们描述了牛蛙关节软骨矿化的生理过程。对不同年龄动物的股骨近端和远端以及胫腓骨近端的关节软骨进行了研究。在变态后1个月的动物中检测到关节软骨矿化。这种矿化在肥大软骨出现任何钙沉积之前就已出现，始于软骨外侧扩展的一个受限部位，然后发展到骨骺软骨的其他区域。通过冯·科萨染色和钙黄绿素的体内掺入鉴定矿化结构。元素分析表明钙晶体由结晶性差的羟基磷灰石组成。矿化基质最初是球形结构，通常在达到一定大小后合并以占据软骨的更大区域。在附近软骨细胞的质膜和细胞外基质中检测到碱性磷酸酶活性。通过TUNEL（末端脱氧核苷酸转移酶介导的dUTP生物素缺口末端标记）反应在矿化区域的一些关节软骨细胞中检测到凋亡。在老年动物中，钙晶体占据的面积显著增加，尤其是在受压区域。超微结构分析显示软骨细胞周围的细胞外基质中有针状晶体簇和大块矿化基质。在4岁的动物中，与关节软骨矿化相同的区域出现了一些板层骨（含骨髓）。这些结果表明牛蛙的关节软骨经历了早熟和渐进性矿化，这显然是由压力刺激的。我们认为这种矿化参与了骨末端的闭合，因为在老年动物中矿化似乎先于初级骨化中心雏形的形成。
