The consequences of SARS-CoV-2 infection on the musculoskeletal system represents 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, 1x10 3 , 1x10 4 , and 1x10 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 1x10 5 PFU all experienced severe health declines that necessitated early euthanasia (6-7 dpi). For TG mice infected with 1x10 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 1x10 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.

Parkinson’s disease (PD) is a debilitating and common neurodegenerative disease. New insights implicating c-Abl activation as a driving force in PD have opened a new drug development avenue for PD treatment beyond the symptomatic relief by L-DOPA. BCR-Abl inhibitors, which include nilotinib and ponatinib, have been found to inhibit this process, and nilotinib has shown improvement in outcomes in a 12-patient, nonrandomized trial. However, nilotinib is a potent inhibitor of hERG, a cardiac K+ channel whose inhibition increases risk of sudden death. We used our machine learning approach to predict novel molecules that would inhibit c-Abl while also having minimal liability against hERG. Of our six novel compounds tested, we identified two that had c-Abl potencies comparable to nilotinib, but with significantly improved profiles regarding the hERG channel. Our best compound exhibited a hERG IC50 of 12.1 μM (compared to nilotinib with an IC50 of 0.45 μM and ponatinib with IC50 of 0.767 μM). This work is a step forward for a machine learning enabled, multiparameter optimization of a chemical space and represents a significant advance in the development of novel Parkinson’s therapies.

ObjectiveTo investigate the effects of vibration therapy on fracture healing in diabetic and non-diabetic rats.Methods148 rats underwent fracture surgery and were assigned to four groups: (1) SHAM: weight-matched non-diabetic rats, (2) SHAM+VT: non-diabetic rats treated with vibration therapy (VT), (3) DM: diabetic rats, and (4) DM+VT: diabetic rats treated with VT. Thirty days after diabetes induction with streptozotocin, animals underwent bone fracture, followed by surgical stabilization. Three days after bone fracture, rats began VT. Bone healing was assessed on days 14 and 28 post-fracture by serum bone marker analysis, and femurs collected for dual-energy X-ray absorptiometry, micro-computed tomography, histology, and gene expression.ResultsOur results are based on 88 animals. Diabetes led to a dramatic impairment of bone healing as demonstrated by a 17% reduction in bone mineral density and decreases in formation-related microstructural parameters compared to non-diabetic control rats (81% reduction in bone callus volume, 69% reduction in woven bone fraction, 39% reduction in trabecular thickness, and 45% in trabecular number). These changes were accompanied by a significant decrease in the expression of osteoblast-related genes (Runx2, Col1a1, Osx), as well as a 92% reduction in serum insulin-like growth factor I (IGF-1) levels. On the other hand, resorption-related parameters were increased in diabetic rats, including a 20% increase in the callus porosity, a 33% increase in trabecular separation, and a 318% increase in serum C terminal telopeptide of type 1 collagen levels. VT augmented osteogenic and chondrogenic cell proliferation at the fracture callus in diabetic rats; increased circulating IGF-1 by 668%, callus volume by 52%, callus bone mineral content by 90%, and callus area by 72%; and was associated with a 19% reduction in circulating receptor activator of nuclear factor kappa beta ligand (RANK-L).ConclusionsDiabetes had detrimental effects on bone healing. Vibration therapy was effective at counteracting the significant disruption in bone repair induced by diabetes, but did not improve fracture healing in non-diabetic control rats. The mechanical stimulus not only improved bone callus quality and quantity, but also partially restored the serum levels of IGF-1 and RANK-L, inducing bone formation and mineralization, thus creating conditions for adequate fracture repair in diabetic rats.

Megakaryocytes play a pivotal role in the bone fracture healing process through enhancing osteoblast proliferation, osteoclastogenesis, and angiogenesis. Current fracture repair therapies require direct implantation during surgery (BMP-2, grafts etc.), which has limitations. In order to address this, a novel drug, compound MAK122, was created with targeting technology that directs its actions to the fracture site without needing to be implanted during surgery, limiting undesirable offsite effects, increasing the quantity of drug at the fracture site, and allowing for non-invasive treatment following assessment of the natural healing process. Therefore, this study examined the ability of MAK122 to stimulate megakaryocytes and subsequent bone healing. To accomplish this, male mice on a C57BL/6 background underwent a surgically induced femoral fracture. Following surgery, the mice were injected daily for the first 7 days with either saline (vehicle) or MAK122. Mice were then euthanized 2, 3 and 4 weeks post-surgery.  Fracture healing was assessed by standard and novel methodologies. Biweekly X-rays were evaluated and bone union was scored showing that MAK122 accelerated bone healing compared to controls. Ex vivo µCT analysis demonstrated that MAK122 increased callus volume and the percentage of mineralized callus tissue compared to vehicle treatment. Biomechanical testing showed that MAK122 treatment resulted in stronger repairs as compared to vehicle treated controls with nearly a 2-fold increase in twist to failure and toughness parameters. Additionally, histological assessment demonstrated accelerated remodeling in MAK122 treated femurs compared to those treated with saline. Taken together, these pre-clinical data suggest that MAK122 is capable of promoting an environment in which megakaryocytes can favorably influence bone remodeling mechanisms, expediting fracture repair in murine models. Though further pharmacokinetic, pharmacodynamic, and toxicology studies are required, MAK122 displays potential to serve as a state-of-the-art therapy for improving fracture healing in humans.

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