Inhibition of gap-junctional communication induces the trans-differentiation of osteoblasts to an adipocytic phenotype in vitro
Inhibition of gap-junctional communication induces the trans-differentiation of osteoblasts to an adipocytic phenotype in vitro
复制标题
DOI：
10.1074/jbc.m011055200
复制
发表时间：
2001-04-27
影响因子：
4.8
通讯作者：
Howard, GA
中科院分区：
文献类型：
--
作者：
Schiller, PC;D'Ippolito, G;Howard, GA
成骨细胞和脂肪细胞被认为是从共同的基质祖细胞分化而来。这两种表型成熟的细胞类型显示出高度的可塑性，当细胞在特定的培养条件下生长时可以观察到这一点。间隙连接在体内和体外的成骨细胞中大量存在，而在脂肪形成过程中其表达下调。间隙连接通讯（GJC）调节与成熟成骨细胞表型相关的基因的表达。利用18-α-甘草次酸（AGRA）抑制GJC在体外阻断前成骨细胞的成熟。此外，在培养期结束时可检测到细胞质脂滴，表明GJC抑制可能有利于脂肪细胞表型。我们使用了几种人成骨细胞系，以及骨源性原代成骨细胞，显示在成骨条件下生长的人成骨细胞的汇合培养物在使用AGRA或油酰胺（两种不同的无毒可逆抑制剂）完全抑制GJC 3天后发展成脂肪细胞表型。通过甘油三酯液滴的积累和脂肪细胞标志物过氧化物酶体增殖物激活受体γ 2和脂蛋白脂肪酶、甘草酸（一种非抑制性AGRA类似物）或α-溴棕榈酸（一种不可降解脂肪酸）mRNA表达的增加证实了脂肪形成表型的形成。骨骼GJC的调节可能代表一种新的药理学靶点，通过这种靶点可以抑制骨髓脂肪生成，同时增强成骨细胞的生成，从而为治疗人类年龄相关性骨质减少疾病和绝经后骨质疏松症提供了一种新的治疗方法。
Osteoblasts and adipocytes are thought to differentiate from a common stromal progenitor cell. These two phenotypically mature cell types show a high degree of plasticity, which can be observed when cells are grown under specific culture conditions. Gap junctions are abundant among osteoblastic cells in vivo and in vitro, whereas they are down-regulated during adipogenesis, Gap junctional communication (GJC) modulates the expression of genes associated with the mature osteoblastic phenotype. Inhibition of GJC utilizing 18-alpha -glycyrrhetinic acid (AGRA) blocks the maturation of preosteoblastic cells in vitro, Moreover, cytoplasmic lipid droplets are detectable at the end of the culture period, suggesting that GJC inhibition may favor an adipocytic phenotype, We used several human osteoblastic cell lines, as well as bone-derived primary osteoblastic cells, to show that confluent cultures of human osteoblastic cells grown under osteogenic conditions developed an adipocytic phenotype after 3 days of complete inhibition of GJC using AGRA or oleamide, two dissimilar nontoxic reversible inhibitors. Development of an adipogenic phenotype was confirmed by the accumulation of triglyceride droplets and the increase in mRNA expression of the adipocytic markers peroxisome proliferator-activated receptor gamma2 and lipoprotein lipase, Glycyrrhizic acid, a noninhibitory AGRA analog, or alpha -bromopalmitate, a nondegradable fatty acid, had no effect. Modulation of skeletal GJC may represent a new pharmacological target by which inhibition of marrow adipogenesis can take place with the parallel enhancement of osteoblastogenesis, thus providing a novel therapeutic approach to the treatment of human age-related osteopenic diseases and postmenopausal osteoporosis.