Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden.
Department of Evolutionary Morphology, Schmalhausen Institute of Zoology of NAS of Ukraine, Kiev, Ukraine.
Elife. 2020 Oct 16;9:e55212. doi: 10.7554/eLife.55212.
Growth plate and articular cartilage constitute a single anatomical entity early in development but later separate into two distinct structures by the secondary ossification center (SOC). The reason for such separation remains unknown. We found that evolutionarily SOC appears in animals conquering the land - amniotes. Analysis of the ossification pattern in mammals with specialized extremities (whales, bats, jerboa) revealed that SOC development correlates with the extent of mechanical loads. Mathematical modeling revealed that SOC reduces mechanical stress within the growth plate. Functional experiments revealed the high vulnerability of hypertrophic chondrocytes to mechanical stress and showed that SOC protects these cells from apoptosis caused by extensive loading. Atomic force microscopy showed that hypertrophic chondrocytes are the least mechanically stiff cells within the growth plate. Altogether, these findings suggest that SOC has evolved to protect the hypertrophic chondrocytes from the high mechanical stress encountered in the terrestrial environment.
生长板和关节软骨在发育早期构成一个单一的解剖实体，但后来通过次级骨化中心 (SOC) 分离成两个不同的结构。这种分离的原因尚不清楚。我们发现 SOC 出现在征服陆地的动物——羊膜动物中。对具有特殊四肢的哺乳动物（鲸鱼、蝙蝠、跳鼠）的骨化模式进行分析表明，SOC 的发展与机械负荷的程度有关。数学模型表明，SOC 降低了生长板内的机械应力。功能实验表明，肥大软骨细胞对机械应力非常敏感，并且 SOC 可以保护这些细胞免受过度负荷引起的细胞凋亡。原子力显微镜显示，肥大软骨细胞是生长板内机械硬度最低的细胞。总的来说，这些发现表明 SOC 的进化是为了保护肥大软骨细胞免受陆地环境中遇到的高机械应力的影响。
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