Schiltz P M, Mohan S, Baylink D J
Department of Orthopedic Surgery, Loma Linda University, California.
J Bone Miner Res. 1993 Apr;8(4):391-6. doi: 10.1002/jbmr.5650080402.
This laboratory has purified a unique insulin-like growth factor binding protein (IGFBP-4) that was previously demonstrated to be inhibitory to bone cell proliferation. In this study, the hypothesis that IGFBP-4 is inhibitory to insulin-like growth factor (IGF) actions on cartilage was tested using the pelvic cartilages of 10-day-old chick embryos as an in vitro model system. Pelvic leaflets were incubated in serum-free medium for 18 h with effectors (BSA, IGF-I, IGF-II, IGFBP-4, or a combination of IGF and IGFBP-4). After the first 8 h, 1.5 microCi [3H]thymidine per well was added. Cartilage growth was assayed by TCA-insoluble [3H]thymidine incorporation into DNA. Additional experiments were conducted under similar conditions to assess the actions of the effectors on cartilage dry weight over a 72 h time period. In separate experiments, serum-free medium conditioned by chick pelvic cartilages for 72 h was assayed for IGF-II by radioreceptorassay, IGF-I by radioimmunoassay, and IGFBP by western ligand analysis. Exogenous IGF addition increased [3H]thymidine incorporation and dry weight of cartilages compared to controls. IGFBP-4 decreased both parameters in basal cartilage growth and also inhibited IGF-mediated cartilage growth. Pelvic cartilages secreted in vitro both IGF-I and IGF-II and a 32-34 kD IGFBP. In conclusion, the IGFs are stimulatory to cartilage growth in vitro and embryonic chick cartilage in vitro produces both IGF-I and II as well as an IGFBP.(ABSTRACT TRUNCATED AT 250 WORDS)
本实验室已纯化出一种独特的胰岛素样生长因子结合蛋白（IGFBP - 4），先前已证明其对骨细胞增殖具有抑制作用。在本研究中，以10日龄鸡胚的盆腔软骨作为体外模型系统，对IGFBP - 4抑制胰岛素样生长因子（IGF）对软骨作用的假说进行了验证。将盆腔小叶在无血清培养基中与效应物（牛血清白蛋白、IGF - I、IGF - II、IGFBP - 4或IGF与IGFBP - 4的组合）一起孵育18小时。在最初的8小时后，每孔加入1.5微居里的[³H]胸腺嘧啶核苷。通过将TCA不溶性的[³H]胸腺嘧啶核苷掺入DNA来测定软骨生长。在类似条件下进行了额外的实验，以评估效应物在72小时时间段内对软骨干重的作用。在单独的实验中，通过放射受体测定法测定鸡盆腔软骨在无血清培养基中培养72小时后的IGF - II，通过放射免疫测定法测定IGF - I，并通过western配体分析法测定IGFBP。与对照组相比，添加外源性IGF可增加[³H]胸腺嘧啶核苷掺入量和软骨干重。IGFBP - 4降低了基础软骨生长中的这两个参数，并且还抑制了IGF介导的软骨生长。盆腔软骨在体外分泌IGF - I和IGF - II以及一种32 - 34 kD的IGFBP。总之，IGF在体外对软骨生长具有刺激作用，并且鸡胚软骨在体外可产生IGF - I和II以及一种IGFBP。（摘要截断于250字）
