Reichenberger E, Aigner T, von der Mark K, Stöss H, Bertling W
Max Planck Society, Clinical Research Unit for Rheumatology, Medical Clinic III, Federal Republic of Germany.
Dev Biol. 1991 Dec;148(2):562-72. doi: 10.1016/0012-1606(91)90274-7.
Type X collagen is a short, non-fibril-forming collagen restricted to the hypertrophic, calcifying zone of growth plate cartilage. It is developmentally regulated and found exclusively in hypertrophic cartilage. Here we report on the structure and distribution of human type X collagen based on the cloning of a PCR fragment covering 292 bp of the carboxy-terminal, non-triple-helical domain. Seventy-five percent of the sequence are identical to that of chicken type X collagen at nucleic acid level and 84% at amino acid level. This probe was used for in situ hybridization analyses of type X collagen expression in a human growth plate. Human fetal cartilage, which is different from the avian cartilage-bone transition zone, showed strong type X collagen expression confined to the lower hypertrophic zone of the growth plate. The upper zone of hypertrophic chondrocytes did not contain alpha 1(X) transcripts, indicating that type X collagen expression follows cellular hypertrophy. The distribution of type X collagen mRNA has been previously unreported in chondrocytes from zones of secondary ossification and in chondrocytes associated with endochondral bone trabecules containing calcified cartilage. In situ hybridization analyses with probes for type I and II collagen on consecutive sections indicated a spatial gradient in chondrocyte differentiation in the human epiphysis. Chondrocytes of low type II collagen expression in the resting zone are followed by proliferating columnar chondrocytes with strong type II collagen expression and a zone of hypertrophic chondrocytes synthesizing type X and type II collagen. In contrast to findings in avian growth cartilage in some of our samples of human epiphyseal cartilage hypertrophic chondrocytes continued to strongly express type II collagen down to the chondro-osseous junction. Transcripts of the alpha 2(I) collagen gene, however, were detected only in perichondrium, vascular cavities, and bone, but not in hypertrophic or any other chondrocytes. The above observations demonstrate that the isolation of the human type X collagen DNA will contribute to studies of pathways of chondrocyte differentiation in the mammalian growth plate.
X型胶原蛋白是一种短小的、不形成纤维的胶原蛋白，仅存在于生长板软骨的肥大、钙化区域。它受发育调控，仅在肥大软骨中发现。在此，我们基于克隆覆盖羧基末端非三螺旋结构域292 bp的PCR片段，报告了人X型胶原蛋白的结构和分布。该序列75%在核酸水平上与鸡X型胶原蛋白相同，84%在氨基酸水平上相同。此探针用于人生长板中X型胶原蛋白表达的原位杂交分析。与禽类软骨 - 骨过渡区不同，人胎儿软骨中X型胶原蛋白表达强烈，局限于生长板的下部肥大区域。肥大软骨细胞的上部区域不含α1(X)转录本，表明X型胶原蛋白的表达随细胞肥大而发生。X型胶原蛋白mRNA在继发骨化区的软骨细胞以及与含有钙化软骨的软骨内骨小梁相关的软骨细胞中的分布此前尚未见报道。对连续切片用I型和II型胶原蛋白探针进行原位杂交分析表明，人骨骺中软骨细胞分化存在空间梯度。静止区II型胶原蛋白表达低的软骨细胞之后是增殖的柱状软骨细胞，其II型胶原蛋白表达强烈，还有一个肥大软骨细胞区，合成X型和II型胶原蛋白。与禽类生长软骨中的发现不同，在我们的一些人骨骺软骨样本中，肥大软骨细胞在软骨 - 骨交界处仍强烈表达II型胶原蛋白。然而，α2(I)胶原蛋白基因的转录本仅在软骨膜、血管腔和骨中检测到，而在肥大软骨细胞或任何其他软骨细胞中未检测到。上述观察结果表明，人X型胶原蛋白DNA的分离将有助于研究哺乳动物生长板中软骨细胞分化的途径。
