Impacts of SARS-CoV-2 Infection and Age on Musculoskeletal Health

项目摘要/摘要 截至2021年6月14日，冠状病毒病2019年(新冠肺炎)大流行已累计17602万 全球共接种了380万例死亡病例和23.7亿剂疫苗。然而，许多人 在接种疫苗前遭受痛苦，并在没有接种疫苗的情况下存活或仍将遭受痛苦。因此， 确定感染后可能产生的长期健康影响，以及这些影响在当时是如何基于年龄变化的 感染的严重程度以及疾病严重程度是否对长期健康产生不同的影响是当务之急。有关的信息 新冠肺炎如何影响骨代谢和动态平衡是有限的。这一点非常令人担忧，因为 老龄化人群一般有更高的骨丢失，并处于发展为严重新冠肺炎的最高风险 感染。目前应用的目标是确定骨量的长期缺陷 都是在感染SARS-CoV-2后经历的。长期目标是开发潜在的治疗方法。 对抗新冠肺炎相关骨质流失的策略。初步研究表明，在K18-hACE2小鼠中 新冠肺炎模型，感染1x103或1x104 pfu的存活小鼠表现出高达24%的减少 骨小梁体积分数仅在感染后2周(p&lt；0.001)。受感染的小鼠在感染后 破骨细胞数量(P&lt；0.0002)和破骨细胞所占表面面积(P&lt；0.02)相比增加了30% 未感染的对照组。此外，感染任何剂量的SARS-CoV-2的小鼠在 大鼠股骨骨髓中巨核细胞与模拟感染对照组的比较 (宝洁0.008)。此外，先前进行的研究表明，MKs调节骨量和破骨细胞(OC)。 形成(衰老的MKs增加OCS并增加RANKL的表达)。此外，患有重症的患者 各种形式的新冠肺炎上调了许多细胞因子和生长因子的表达，被称为 一场炎症性细胞因子风暴。已知许多这些细胞因子，包括IL-6和肿瘤坏死因子-α，可以调节 OCS和/或MKs，并可能是初步研究中观察到的骨丢失的原因。基于 这些观察结果假设：1)SARS-CoV-2感染会导致长期的健康并发症 肌肉骨骼系统，以及II)SARS-CoV-2感染和相关的细胞因子风暴增加MK- 刺激OC的形成。为了验证这一假设，将追求两个具体目标：1-确定 在感染SARS-CoV-2之后，观察到的骨丢失随着时间的推移而保持不变，以及 感染影响SARS-CoV-2感染引起的骨丢失的严重程度，和：2-调查 SARS-CoV-2导致骨质形成和骨吸收增加的机制 感染和年龄，包括感染小鼠的MK诱导OC形成和骨形成的程度 再吸收。这些研究的成功完成将加深对健康影响的理解 感染SARS-COV-2后，将展示疾病严重程度、年龄和MK如何影响骨骼 动态平衡以及OC的形成和吸收。

PROJECT SUMMARY/ABSTRACT The Coronavirus Disease 2019 (COVID-19) pandemic as of June 14, 2021, has totaled 176.02 million cases, 3.80 million deaths, and 2.37 billion vaccine doses have been administered globally. However, many have suffered prior to the vaccine and have survived or will still suffer without the vaccine. Therefore, determining the possible long-term health ramifications post-infection, how they vary based on age at the time of infection, and whether disease severity differentially impacts long-term health is imperative. Information on how COVID-19 affects bone metabolism and homeostasis is limited. This is of crucial concern because the aging population generally has higher bone loss and are at the highest risk of developing severe COVID-19 infection. The objective of the current application is to determine whether long-term deficits in bone mass are experienced following SARS-CoV-2 infection. The long-term goal is to develop potential treatment strategies to combat COVID-19 related bone loss. Preliminary studies showed that in a K18-hACE2 mouse model of COVID-19, surviving mice infected with 1x103 or 1x104 PFU exhibited up to a 24% reduction in trabecular bone volume fraction just 2 weeks post infection (p<0.001). Infected mice had a 63% increase in osteoclast numbers (p<0.0002) and a 30% increase in surface occupied by osteoclasts (p<0.02) compared to non-infected controls. Additionally, mice infected with any dose of SARS-CoV-2 had a 40% increase in megakaryocytes (MKs) within their femoral bone marrow compared to that observed in mock-infected controls (p<0.008). Further, previously conducted studies showed that MKs regulate bone mass and osteoclast (OC) formation (aged MKs increase OCs and have increased RANKL expression). Moreover, patients with severe forms of COVID-19 have upregulated expression of numerous cytokines and growth factors which is known as an inflammatory cytokine storm. Many of these cytokines, including IL-6 and TNF-α, are known to regulate OCs and/or MKs and may be responsible for the bone loss observed in the preliminary studies. Based on these observations it is hypothesized that i) SARS-CoV-2 infection results in long-term health complications in the musculoskeletal system, and ii) SARS-CoV-2 infection and the associated cytokine storm increases MK- stimulated OC formation. To test this hypothesis, two specific aims will be pursued: 1- determine whether following SARS-CoV-2 infection the bone loss observed remains over time and whether age at the time of infection impacts the severity of bone loss induced by SARS-CoV-2 infection, and: 2- investigate the mechanisms by which OC formation and bone resorption are increased as a consequence of SARS-CoV-2 infection and age, including the extent to which MKs from infected mice induce OC formation and bone resorption. The successful completion of these studies will deepen the understanding of the health implications post-infection with SARS-COV-2 and will demonstrate how disease severity, age, and MKs influence skeletal homeostasis as well as OC formation and resorption.