Abstract
The consequences of SARS-CoV-2 infection on the musculoskeletal system represent a dangerous knowledge gap. Aging patients are at added risk for SARS-CoV-2 infection; therefore, a greater understanding of the resulting musculoskeletal sequelae of SARS-CoV-2 infection may help guide clinical strategies. This study examined fundamental bone parameters among mice treated with escalating viral loads. Male C57BL/6J (WT, n = 17) and B6.Cg-Tg(K18-ACE2)2Prlmn/J mice (K18-hACE2 transgenic mice, n = 21) expressing human ACE2 (TG) were divided into eight groups (n = 4-6/group) and subjected to intranasal dosing of 0, 1 × 10 3 , 1 × 10 4 , and 1 × 10 5 PFU (plaque forming units) of human SARS-CoV-2. Animal health was assessed daily by veterinary staff using established and validated scoring criteria (activity, posture, body condition scores and body weight). We report here that mock and WT infected mice were healthy and completed the study, surviving until 12-14 days post infection (dpi). In contrast, the TG mice infected with 1 × 10 5 PFU all experienced severe health declines that necessitated early euthanasia (6-7 dpi). For TG mice infected with 1 × 10 4 PFU, 2 mice were also euthanized after 7 dpi, while 3 mice showed signs of moderate disease at day 6 dpi, but recovered fully by day 11 dpi. Four of the 5 TG mice that were infected with 1 × 10 3 PFU remained healthy throughout the study. This suggests that our study mimics what is seen during human disease, where some patients develop severe disease resulting in death, while others have moderate to severe disease but recover, and others are asymptomatic. At necropsy, femurs were extracted and analyzed by μCT. No difference was found in μCT determined bone parameters among the WT groups. There was, however, a significant 24.4% decrease in trabecular bone volume fraction (p = 0.0009), 19.0% decrease in trabecular number (p = 0.004), 6.2% decrease in trabecular thickness (p = 0.04), and a 9.8% increase in trabecular separation (p = 0.04) among surviving TG mice receiving any viral load compared to non-infected controls. No differences in cortical bone parameters were detected. TRAP staining revealed surviving infected mice had a significant 64% increase in osteoclast number, a 27% increase in osteoclast surface, and a 38% increase in osteoclasts per bone surface. While more studies are needed to investigate the long-term consequences of SARS-CoV-2 infection on skeletal health, this study demonstrates a significant reduction in several bone parameters and corresponding robust increases in osteoclast number observed within 2 weeks post-infection in surviving asymptomatic and moderately affected mice.
Keywords: Bone mass; COVID-19; Infection; Musculoskeletal health; Osteoclasts; SARS-CoV-2.
【저자키워드】 COVID-19, Infection, SARS-CoV-2., Bone mass, Musculoskeletal health, Osteoclasts, 【초록키워드】 SARS-CoV-2, aging, knowledge, SARS-COV-2 infection, body weight, risk, hACE2, human ACE2, Health, Asymptomatic, Viral load, mice, animal, Patient, death, group, moderate, intranasal, K18-hACE2, K18-hACE2 transgenic mice, bone, severe disease, Decline, Bone mass, Musculoskeletal health, criteria, moderate to severe, volume fraction, musculoskeletal system, skeletal, Volume, Post-infection, Musculoskeletal, cortical bone, human disease, moderate disease, no difference, viral loads, no differences, help, fraction, staining, human SARS-CoV-2, TRAP, while, parameter, posture, controls, plaque forming units, consequence, decrease, non-infected, robust, K18-ACE2, greater, resulting, analyzed, affected, were infected, develop, examined, healthy, remained, eight, receiving, treated, added, increase in, groups, expressing, reduction in, days post infection, increases in, cortical, euthanized,