Blockade of miR-29b-1-5p promotes MSC-mediated bone regeneration during aging

描述（由申请人提供）：大量证据表明骨是一种动态组织，可以在损伤后自行愈合。然而，这种再生过程在老年人群中经常失败，导致肌肉骨骼系统普遍出现与衰老相关的损伤。microRNAs （miRNAs）对mRNA翻译的抑制已成为成骨信号通路的重要调节因子。因此，miRNA失调与骨质疏松症和骨关节炎的发生和发展有关。这些发现为开发以空间和时间控制的方式靶向特定mirna的新型骨生物工程疗法提供了合理的基础。在其成员中，miR-29b-1-3p被认为是促进人间充质干细胞（MSCs）成骨分化的成熟优势miRNA物种。相比之下，对miR-29b-1-5p知之甚少，miR-29b-1-5p是由相同前体表达的另一种成熟miRNA，直到最近才被认为是副产物。我们有初步证据表明，miR-29b-1-5p具有抗成骨作用，从老年患者分离的MSCs与成人MSCs相比，miR-29b-1-5p水平升高，而miR-29b-1-3p的表达不变。这些新发现表明miR-29b-1-5p在成骨和骨再生中与衰老相关的缺陷中具有致病作用。基于这些发现，我们假设miR-29b-1-5p/miR-29b-1-3p比值随着年龄的增长而增加，从而向抗成骨特征倾斜。我们进一步假设miR-29b-1-5p抑制剂（抗miRNA治疗）可以有效逆转抗成骨作用，并随着年龄的增长促进骨再生。在本研究中，我们旨在阐明miR-29b-1-5p抑制成骨基因靶点并随着衰老破坏MSCs成骨分化的分子基础，并利用新型聚合物水凝胶确定改变miR-29b-1-5p水平对msc介导的体内局部骨形成的影响。为了实现这些目标，我们将在采用已建立的原位骨损伤模型之前使用各种分子细胞生物学和功能分析。这些研究将为miR-29b-1-5p抑制剂促进骨再生的治疗潜力以及抗mirna治疗的有效和改进的递送系统提供临床前证据。

DESCRIPTION (provided by applicant): A large body of evidence suggests that bone is a dynamic tissue that can heal spontaneously following injury. However, this regenerative process often fails in the geriatric population contributing to widespread aging- related injuries to the musculoskeletal system. Inhibition of mRNA translation by microRNAs (miRNAs) has emerged as an important regulator of osteogenic signaling pathways. Accordingly, miRNA dysregulation has been implicated in the onset and progression of osteoporosis and osteoarthritis. These findings provide a rational basis for the development of novel bone bioengineering therapies that target specific miRNAs in a spatially and temporally controlled fashion. Among its members, miR-29b-1-3p is considered a mature dominant miRNA species that facilitates osteogenic differentiation of human mesenchymal stem/stromal cells (MSCs). In contrast, little is known about miR-29b-1-5p, the other mature miRNA expressed from the same precursor, which until recently was thought of as a byproduct. We have preliminary evidence that miR-29b-1- 5p is anti-osteogenic and that MSCs isolated from geriatric patients exhibit elevated levels of miR-29b-1-5p compared to adult MSCs, while the expression of miR-29b-1-3p is unchanged. These novel findings suggest a pathogenic role for miR-29b-1-5p in aging-related defects in osteogenesis and bone regeneration. Based on these findings, we hypothesize that the miR-29b-1-5p/miR-29b-1-3p ratio increases with age thereby tilting the scale towards anti-osteogenic characteristics. We further hypothesize that inhibitors of miR-29b-1-5p (anti- miRNA therapy) would be effective in reversing anti-osteogenic effects and promoting bone regeneration with progressing age. In this proposal, we aim to elucidate the molecular basis by which miR-29b-1-5p suppresses osteogenic gene targets and disrupts osteogenic differentiation of MSCs with aging, and to determine the effects of altering miR-29b-1-5p levels on MSC-mediated local bone formation in vivo using novel polymer hydrogels. To address these aims, we will use a variety of molecular cell biology and functional assays prior to employing an established orthotopic bone injury model. These studies will provide preclinical evidence for the therapeutic potential of miR-29b-1-5p inhibitors to promote bone regeneration and also for an effective and improved delivery system for anti-miRNA therapy.