Division of Plastic and Reconstructive Surgery, UCLA David Geffen School of Medicine, Los Angeles, California.
Research Service, Greater Los Angeles VA Healthcare System, Los Angeles, California.
J Tissue Eng Regen Med. 2019 May;13(5):823-834. doi: 10.1002/term.2834. Epub 2019 Apr 15.
The ability of the extracellular matrix (ECM) to direct cell fate has generated the potential for developing a materials-only strategy for tissue regeneration. Previously, we described a nanoparticulate mineralized collagen glycosaminoglycan (MC-GAG) material that efficiently induced osteogenic differentiation of human mesenchymal stem cells (hMSCs) and calvarial bone healing without exogenous growth factors or progenitor cell expansion. In this work, we evaluated the interactions between MC-GAG and primary human osteoclasts (hOCs). In the absence of hMSCs, mineralized Col-GAG materials directly inhibited hOC viability, proliferation, and resorption in contrast to nonmineralized Col-GAG, which demonstrated a modest inhibition of resorptive activity only. Cocultures containing differentiating hMSCs with hOCs demonstrated increased hOC-mediated resorption only on Col-GAG while MC-GAG cocultures continued to inhibit resorption. Unlike Col-GAG, hMSCs on MC-GAG expressed increased amounts of osteoprotegerin (OPG) protein, the major endogenous osteoclast inhibitor. Interestingly, OPG expression was found to be antagonized by small mothers against decapentaplegic1/5 (Smad1/5) phosphorylation, an obligate pathway for osteogenic differentiation of hMSCs on MC-GAG, and potentiated by extracellular signal-regulated kinase (ERK1/2) phosphorylation. Collectively, these results suggested that the MC-GAG material both directly inhibited the osteoclast viability, proliferation, and resorptive activity as well as induced hMSCs to secrete osteoprotegerin, an antiosteoclastogenic factor, via a signalling pathway distinct from osteogenic differentiation.
细胞外基质（ECM）引导细胞命运的能力为开发仅用材料的组织再生策略提供了潜力。此前，我们描述了一种纳米颗粒矿化胶原糖胺聚糖（MC-GAG）材料，它可以有效地诱导人间充质干细胞（hMSCs）的成骨分化，并在没有外源性生长因子或祖细胞扩增的情况下促进颅骨骨愈合。在这项工作中，我们评估了 MC-GAG 与原代人破骨细胞（hOCs）之间的相互作用。在没有 hMSCs 的情况下，矿化的 Col-GAG 材料直接抑制 hOC 的活力、增殖和吸收，而非矿化的 Col-GAG 仅对吸收活性表现出适度的抑制作用。含有分化的 hMSCs 和 hOCs 的共培养物仅在 Col-GAG 上显示出增加的 hOC 介导的吸收，而 MC-GAG 共培养物继续抑制吸收。与 Col-GAG 不同，在 MC-GAG 上的 hMSCs 表达了更多的骨保护素（OPG）蛋白，这是内源性破骨细胞抑制剂的主要成分。有趣的是，发现 OPG 表达被小 mothers against decapentaplegic1/5（Smad1/5）磷酸化拮抗，这是 hMSCs 在 MC-GAG 上进行成骨分化的必需途径，并且被细胞外信号调节激酶（ERK1/2）磷酸化增强。总之，这些结果表明，MC-GAG 材料不仅直接抑制破骨细胞的活力、增殖和吸收活性，还通过不同于成骨分化的信号通路诱导 hMSCs 分泌骨保护素，这是一种抗破骨细胞生成因子。
