Abstract：
Approximately 5%-10% of fractures go on to delayed healing and nonunion, posing significant clinical, economic, and social challenges. Current treatment methods involving open bone harvesting and grafting are associated with considerable pain and potential morbidity at the donor site. Hence, there is growing interest in minimally invasive approaches such as bone marrow aspirate concentrate (BMAC), which contains mesenchymal stromal cells (MSCs), macrophages (Mφ), and T cells. However, the use of cultured or activated cells for treatment is not yet FDA-approved in the United States, necessitating further exploration of optimal cell types and proportions for effective bone formation. As our understanding of osteoimmunology advances, it has become apparent that factors from anti-inflammatory Mφ (M2) promote bone formation by MSCs. Additionally, M2 Mφ promote T helper 2 (Th2) cells and Treg cells, both of which enhance bone formation. In this study, we investigated the interactions among MSCs, Mφ, and T cells in bone formation and explored the potential of subsets of BMAC. Coculture experiments were conducted using primary MSCs, Mφ, and CD4+ T cells at specific ratios. Our results indicate that nonactivated T cells had no direct influence on osteogenesis by MSCs, while coculturing MSCs with Mφ and T cells at a ratio of 1:5:10 positively impacted bone formation. Furthermore, higher numbers of T cells led to increased M2 polarization and a higher proportion of Th2 cells in the early stages of coculture. These findings suggest the potential for enhancing bone formation by adjusting immune and mesenchymal cell ratios in BMAC. By understanding the interactions and effects of immune cells on bone formation, we can develop more effective strategies and protocols for treating bone defects and nonunions. Further studies are needed to investigate these interactions in vivo and explore additional factors influencing MSC-based therapies.
摘要：
大约5%-10%的骨折继续延迟愈合和骨不连，构成显著的临床，经济,和社会挑战。涉及开放式骨收获和移植的当前治疗方法与供体部位的相当大的疼痛和潜在的发病率相关。因此，越来越多的人对微创方法感兴趣，如骨髓穿刺液浓缩物(BMAC)，其中包含间充质基质细胞（MSC），巨噬细胞（Mφ），和T细胞。然而,在美国，使用培养或活化的细胞进行治疗尚未获得FDA批准，需要进一步探索有效骨形成的最佳细胞类型和比例。随着我们对骨免疫学的理解的进步，显然,来自抗炎Mφ(M2)的因子通过MSCs促进骨形成。此外,M2Mφ促进T辅助细胞2（Th2）和Treg细胞，两者都能促进骨骼形成。在这项研究中,我们调查了MSCs之间的相互作用，Mφ,和T细胞在骨形成中的作用，并探索了BMAC亚群的潜力。使用原代MSCs进行共培养实验，Mφ,和特定比例的CD4+T细胞。我们的结果表明，未活化的T细胞对MSCs的成骨没有直接影响，同时以1：5：10的比例将MSC与Mφ和T细胞共培养，对骨形成产生积极影响。此外，在共培养的早期，T细胞数量增加导致M2极化增加和Th2细胞比例增加。这些发现表明通过调节BMAC中的免疫和间充质细胞比率来增强骨形成的潜力。通过了解免疫细胞对骨形成的相互作用和影响，我们可以制定更有效的治疗骨缺损和骨不愈合的策略和方案.需要进一步的研究来研究这些体内相互作用，并探索影响基于MSC的治疗的其他因素。
