Bone Biology Group, Division of Developmental Biology, The Roslin Institute and Royal (Dick) School of Veterinary Studies, The University of Edinburgh, Roslin, Midlothian, UK.
J Bone Miner Res. 2012 May;27(5):1055-66. doi: 10.1002/jbmr.1544.
Suppressor of Cytokine Signaling-2 (SOCS2) is a negative regulator of growth hormone (GH) signaling and bone growth via inhibition of the Janus kinase/signal transducers and activators of transcription (JAK/STAT) pathway. This has been classically demonstrated by the overgrowth phenotype of SOCS2(-/-) mice, which has normal systemic insulin-like growth factor 1 (IGF-1) levels. The local effects of GH on bone growth are equivocal, and therefore this study aimed to understand better the SOCS2 signaling mechanisms mediating the local actions of GH on epiphyseal chondrocytes and bone growth. SOCS2, in contrast to SOCS1 and SOCS3 expression, was increased in cultured chondrocytes after GH challenge. Gain- and loss-of-function studies indicated that GH-stimulated chondrocyte STATs-1, -3, and -5 phosphorylation was increased in SOCS2(-/-) chondrocytes but not in cells overexpressing SOCS2. This increased chondrocyte STAT signaling in the absence of SOCS2 is likely to explain the observed GH stimulation of longitudinal growth of cultured SOCS2(-/-) embryonic metatarsals and the proliferation of chondrocytes within. Consistent with this metatarsal data, bone growth rates, growth plate widths, and chondrocyte proliferation were all increased in SOCS2(-/-) 6-week-old mice as was the number of phosphorylated STAT-5-positive hypertrophic chondrocytes. The SOCS2(-/-) mouse represents a valid model for studying the local effects of GH on bone growth.
细胞因子信号转导抑制因子 2(SOCS2)是生长激素(GH)信号和骨骼生长的负调节剂,通过抑制 Janus 激酶/信号转导和转录激活因子(JAK/STAT)途径来实现。SOCS2(-/-)小鼠的过度生长表型经典地证明了这一点,其全身性胰岛素样生长因子 1(IGF-1)水平正常。GH 对骨骼生长的局部作用是有争议的,因此本研究旨在更好地了解 SOCS2 信号通路介导 GH 对骺板软骨细胞和骨骼生长的局部作用的机制。与 SOCS1 和 SOCS3 表达相反,GH 刺激后培养的软骨细胞中 SOCS2 的表达增加。获得和丧失功能的研究表明,GH 刺激的软骨细胞 STATs-1、-3 和 -5 磷酸化在 SOCS2(-/-)软骨细胞中增加,但在过表达 SOCS2 的细胞中没有增加。在 SOCS2 缺失的情况下,这种增加的软骨细胞 STAT 信号可能解释了观察到的 GH 对培养的 SOCS2(-/-)胚胎跖骨纵向生长和其中软骨细胞增殖的刺激作用。与这些跖骨数据一致,SOCS2(-/-)6 周龄小鼠的骨生长速率、生长板宽度和软骨细胞增殖均增加,磷酸化 STAT-5 阳性肥大软骨细胞的数量也增加。SOCS2(-/-)小鼠是研究 GH 对骨骼生长局部作用的有效模型。