Department of Surgery, David Geffen School of Medicine at UCLA, University of California, Los Angeles, California 90095-1749, USA.
Connect Tissue Res. 2011 Apr;52(2):119-32. doi: 10.3109/03008207.2010.484515. Epub 2010 Aug 11.
Although recent studies have proposed that human adipose-derived stem cells (ASCs), together with BMP2, can heal critical-sized bony defects, a companion study in this issue suggests that ASCs may not respond to BMP2 in vivo. To examine why this may be occurring. ASCs were treated with BMP2 and the cells' in vitro osteogenic capacity assessed along with the canonical BMP2 signaling pathway. In vitro treatment of ASCs with BMP2 had no consistent and significant effect on matrix mineralization or their expression of several osteogenic markers. Consistent and significant changes to Smad1/5/8 phosphorylation levels were also not observed upon BMP2 induction. The removal of dexamethasone from the BMP2 induction conditions had no effect on the observed results nor did stimulating ASCs with BMP2 from an alternate source (INFUSE; Medtronic, Minneapolis, MN, USA). In addition, no BMP-induced nuclear translocation of Smad1/Smad4 complexes could be discerned, suggesting that the canonical BMP2 signaling pathway may not be functional in ASCs. Interestingly, three downstream BMP2 pathway genes, distal-less3 (dlx3), distal-less5 (dlx5), and osterix, were not expressed in BMP2-induced ASCs, calling the utility of BMP2 induced in ASCs into question. The results of this in vitro study were consistent with that of our companion in vivo study that suggests a lack of effect of BMP2 on the osteogenic capacity of ASCs. Taken together, the data from both studies suggest that ASC osteogenic differentiation may not be influenced by BMP2. Consequently, combining BMP2 treatment with adult stem cells, like ASCs, may not be a viable strategy for bony healing.
尽管最近的研究提出人类脂肪来源的干细胞 (ASCs) 与 BMP2 一起可以治愈临界大小的骨缺损,但本期的一项伴随研究表明,ASCs 可能不会在体内对 BMP2 产生反应。为了研究为什么会发生这种情况,研究人员用 BMP2 处理 ASCs,评估细胞的体外成骨能力以及经典的 BMP2 信号通路。体外用 BMP2 处理 ASCs 对基质矿化或几种成骨标志物的表达没有一致且显著的影响。在 BMP2 诱导下也没有观察到 Smad1/5/8 磷酸化水平的一致和显著变化。从 BMP2 诱导条件中去除地塞米松对观察结果没有影响,也没有用来自替代来源(INFUSE;Medtronic,明尼苏达州明尼阿波利斯,美国)的 BMP2 刺激 ASCs。此外,无法检测到 BMP 诱导的 Smad1/Smad4 复合物的核转位,表明经典的 BMP2 信号通路在 ASCs 中可能不起作用。有趣的是,BMP2 诱导的 ASCs 中没有表达三个下游 BMP2 途径基因,远侧 3 号(dlx3)、远侧 5 号(dlx5)和骨钙素,这使得 BMP2 诱导在 ASCs 中的效用受到质疑。这项体外研究的结果与我们的伴随体内研究一致,表明 BMP2 对 ASCs 的成骨能力没有影响。总之,这两项研究的数据表明,ASC 成骨分化可能不受 BMP2 影响。因此,将 BMP2 治疗与 ASC 等成年干细胞结合使用可能不是骨愈合的可行策略。