Effects of Aging on Macrophages and Bone Regeneration

描述（由申请人提供）：脆性骨折在我们的老年人群中继续导致显著的发病率和死亡率，特别是因为骨折愈合期间的延迟愈合和不愈合在老年人中更常见。骨折愈合的能力随着年龄的增长而下降，仍然需要有效的治疗方法来促进骨折愈合。衰老还导致免疫系统的显著变化，并且衰老免疫细胞在骨再生损伤中的作用尚未被研究。我们的建议将检验这一假设，即年龄相关的变化，骨髓细胞促进功能障碍的骨再生在骨折修复在老年人。我们提出，虽然巨噬细胞有利于年轻小鼠的骨修复，但在老年小鼠中，巨噬细胞表型和功能的变化导致巨噬细胞对骨再生的不利影响。我们的建议集中在确定如何在巨噬细胞的变化与老化影响其功能的相互作用与成骨细胞和间充质干细胞在骨再生。一个长期目标是开发针对巨噬细胞的治疗方法，以增强老年患者的骨折修复。我们的具体目标是：1）确定衰老对骨巨噬细胞在促进成骨细胞分化和功能方面的影响。2)通过年轻动物的骨髓移植，证明负责“拯救”老年动物骨折愈合的细胞类型。3)确定衰老对巨噬细胞和间充质干细胞（MSC）相互作用的影响，并确定巨噬细胞：MSC相互作用中对髓样细胞受体TREM2的需求

DESCRIPTION (provided by applicant): Fragility fractures continue to cause significant morbidity and mortality in our aging population particularly because delayed healing and non-union during fracture healing is more common in the elderly. The ability to heal fractures decreases with age and effective therapies to enhance fracture healing are still needed. Aging also leads to significant changes in the immune system and the role of aging immune cells in the impairment of bone regeneration has not been examined. Our proposal will examine the hypothesis that age-related changes in myeloid cells promote dysfunctional bone regeneration during fracture repair in the elderly. We propose that while macrophages are beneficial to bone repair in young mice, in aged mice, the changes in macrophage phenotype and function lead to a detrimental effect of macrophages on bone regeneration. Our proposal focuses on determining how changes in macrophages with aging affect their functional interactions with osteoblasts and mesenchymal stem cells in bone regeneration. A long-term goal is the development of therapeutics directed at macrophages that will enhance fracture repair in geriatric patients. Our specific aims are: 1) Determine the effect of aging on osteal macrophages in the promotion of osteoblast differentiation and function. 2) Demonstrate the cell type(s) responsible for the "rescue" of fracture healing in older animals by bone marrow transplant from young animals. 3) Determine the effect of aging on macrophage and mesenchymal stem cell (MSC) interactions and determine the requirement for the myeloid cell receptor TREM2 in macrophage: MSC interactions