MACF1通过Wnt/β-catenin信号通路参与模拟失重抑制成骨细胞分化的机制研究

Osteoblasts are responsible for bone formation. The decreased ability of osteoblast differentiation results in the reduction of bone formation, which is one main cause for weightlessness-induced bone loss. However, the mechanism of weightlessness inhibiting osteoblast differentiation is still unclear. MACF1 regulates the activation of Wnt/β-catenin signaling by translocating Axin complex from cytoplasm to cell membrane. The activation of Wnt/β-catenin signaling promotes osteoblast differentiation. Our recent advances showed that simulated weightlessness inhibited the differentiation and mineralization of osteoblasts and down-regulated the gene expression of MACF1. Besides, the mineralized nodules formation was significantly decreased in MACF1 gene knocking down preosteoblasts. Therefore, we propose that MACF1 may play a key role in simulated weightlessness inhibiting osteoblast differentiation through regulating Wnt/β-catenin signaling..Based on the previous research, this project will further investigate the following content: (1) The changes of MACF1 expression during simulated weightlessness inhibiting osteoblast differentiation; (2) The effects of simulated weightlessness or overexpression/low expression of MACF1 on osteoblast differentiation and Wnt/β-catenin signaling transduction; (3) The effects of simulated weightlessness or overexpression of MACF1 on bone formation in mice. The objective of this project is to provide some new experimental evidence for deeply understanding the mechanism of weightlessness-induced bone loss and also to provide some theoretical basis for the prevention and therapy of bone loss-related bone diseases.

成骨细胞是骨形成的主要功能细胞，其分化能力下降导致骨形成减少是引起失重性骨质流失的重要原因之一。然而，失重抑制成骨细胞分化的机制仍不清楚。MACF1通过介导Axin复合物转位，调节Wnt/β-catenin活化，而Wnt/β-catenin活化促进成骨细胞分化。申请者新近研究发现模拟失重抑制成骨细胞分化与矿化，下调细胞中MACF1的表达，且低表达MACF1的前成骨细胞矿化能力明显下降。因此提出：MACF1可能通过调节Wnt/β-catenin而在模拟失重抑制成骨细胞分化中起重要作用。.本项目拟研究：(1)模拟失重抑制成骨细胞分化过程中，MACF1表达的变化；(2)模拟失重或MACF1高/低表达对成骨细胞分化及Wnt/β-catenin信号转导的影响；(3)模拟失重或MACF1高表达对小鼠骨形成的影响。为深入理解失重性骨质流失的发生机制提供新的实验依据，并为骨质流失等疾病的防治提供理论基础。

本项目围绕“失重性骨质流失发生机制”这一空间生物学研究领域的重要科学问题，从“成骨细胞分化”角度出发，以调节成骨细胞分化的关键信号通路Wnt/β-catenin中组分“MACF1”为切入点，从分子、细胞、整体动物水平，深入研究MACF1在模拟失重条件抑制成骨细胞分化与骨形成中的作用及机制。本项目主要研究内容包括：(1)模拟失重抑制成骨细胞分化过程中，MACF1表达的变化；(2)模拟失重或MACF1高/低表达对成骨细胞分化及Wnt/β-catenin信号转导的影响；(3)模拟失重或MACF1高表达对小鼠骨形成的影响。通过构建MACF1高/低表达成骨细胞株与MACF1基因条件性敲除/敲入小鼠模型，结合模拟失重条件，获得主要结果如下：(1)模拟失重条件抑制成骨细胞分化与小鼠骨形成，MACF1参与成骨细胞响应模拟失重条件，其表达在模拟失重条件下明显下降；(2)MACF1缺失影响微丝、微管骨架分布，抑制成骨细胞增殖与细胞分化，且抑制β-catenin信号转导；(3)MACF1高表达促进成骨细胞分化，且起到对模拟失重条件抑制成骨细胞增殖的挽救作用；(4)MACF1缺失明显抑制骨形成，而MACF1高表达明显增加了小鼠股骨骨量与骨密度。相关研究结果发表在Journal of Cellular Physiology，Human Gene Therapy，BMB Reports，Cell Biology International等SCI期刊。本项目研究揭示了模拟失重抑制成骨细胞分化与骨形成的新机制，对深入理解失重性骨质流失发生的分子机制具有重要的科学意义，并且为骨质流失的防治研究提供了新靶点，具有防治航天员骨质流失与地面人群骨质疏松的潜在应用价值。