Brain-Derived Acetylcholine Maintains Peak Bone Mass in Adult Female Mice

Risk of fracture in patients with myasthenia gravis: a nationwide cohort study in Korea

Myasthenia gravis (MG) is an autoimmune disorder that affects the neuromuscular junctions, resulting in muscle weakness and fatigue. Muscle weakness, restricted mobility, and frequent use of corticosteroids in patients with MG may predispose them to a higher risk of fractures. However, studies on the impact of MG on bone health and the associated fracture risk are scarce. Utilizing claim database of the Korean National Health Insurance Service collected between 2002 and 2020, we compared the risk of major osteoporotic fracture between 23 118 patients with MG and 115 590 individuals as an age- and sex-matched control group using multivariable Cox proportional hazard models. Over a median follow-up duration of 5.58 years, the MG group (mean age 53.7 years; 55% women) had higher risk of major osteoporotic fracture compared with controls (incidence rate 13.59 versus 9.74 per 10 000 person-years), which remained independent of age, sex, comorbidities, drug use including anti-osteoporotic agents, and previous fracture history (adjusted hazard ratio [aHR] 1.19, P < 0.001; subdistributed HR 1.14, P < 0.001 adjusted for mortality as competing risk). Subgroup analyses showed a greater association between MG and major osteoporotic fracture risk in younger (age 50 or younger) than older individuals (aHR 1.34 vs. 1.17) and in men compared with women (aHR 1.32 vs. 1.15; P for interaction < 0.05 for all). An imminent divergence of the fracture risk curve between MG and controls was observed for vertebral fracture, while there was time delay for non-vertebral sites, showing site-specific association. Factors associated with higher fracture risk in patients with MG were older age, female gender, high dose glucocorticoid use (>7.5 mg/day), immunosuppressant use, and previous history of fracture. In summary, patients with MG had higher risk of major osteoporotic fracture compared with controls, which calls further preventive actions in this patient group.

Bone-nerve crosstalk: a new state for neuralizing bone tissue engineering-A mini review

Neuro bone tissue engineering is a multidisciplinary field that combines both principles of neurobiology and bone tissue engineering to develop innovative strategies for repairing and regenerating injured bone tissues. Despite the fact that regeneration and development are considered two distinct biological processes, yet regeneration can be considered the reactivation of development in later life stages to restore missing tissues. It is noteworthy that the regeneration capabilities are distinct and vary from one organism to another (teleost fishes, hydra, humans), or even in the same organism can vary dependent on the injured tissue itself (Human central nervous system vs. peripheral nervous system). The skeletal tissue is highly innervated, peripheral nervous system plays a role in conveying the signals and connecting the central nervous system with the peripheral organs, moreover it has been shown that they play an important role in tissue regeneration. Their regeneration role is conveyed by the different cells' resident in it and in its endoneurium (fibroblasts, microphages, vasculature associated cells, and Schwann cells) these cells secrete various growth factors (NGF, BDNF, GDNF, NT-3, and bFGF) that contribute to the regenerative phenotype. The peripheral nervous system and central nervous system synchronize together in regulating bone homeostasis and regeneration through neurogenic factors and neural circuits. Receptors of important central nervous system peptides such as Serotonin, Leptin, Semaphorins, and BDNF are expressed in bone tissue playing a role in bone homeostasis, metabolism and regeneration. This review will highlight the crosstalk between peripheral nerves and bone in the developmental stages as well as in regeneration and different neuro-bone tissue engineering strategies for repairing severe bone injuries.

Effects of Donepezil on the Musculoskeletal System in Female Rats

The extension of human life makes it more and more important to prevent and treat diseases of the elderly, including Alzheimer's disease (AD) and osteoporosis. Little is known about the effects of drugs used in the treatment of AD on the musculoskeletal system. The aim of the present study was to investigate the effects of donepezil, an acetylcholinesterase inhibitor, on the musculoskeletal system in rats with normal and reduced estrogen levels. The study was carried out on four groups of mature female rats: non-ovariectomized (NOVX) control rats, NOVX rats treated with donepezil, ovariectomized (OVX) control rats and OVX rats treated with donepezil. Donepezil (1 mg/kg p.o.) was administered for four weeks, starting one week after the ovariectomy. The serum concentrations of CTX-I, osteocalcin and other biochemical parameters, bone mass, density, mineralization, histomorphometric parameters and mechanical properties, and skeletal muscle mass and strength were examined. Estrogen deficiency increased bone resorption and formation and worsened cancellous bone mechanical properties and histomorphometric parameters. In NOVX rats, donepezil decreased bone volume to tissue volume ratio in the distal femoral metaphysis, increased the serum phosphorus concentration and tended to decrease skeletal muscle strength. No significant bone effects of donepezil were observed in OVX rats. The results of the present study indicate slightly unfavorable effects of donepezil on the musculoskeletal system in rats with normal estrogen levels.

Alzheimer's Disease and Impaired Bone Microarchitecture, Regeneration and Potential Genetic Links

Alzheimer's Disease (AD) and osteoporosis are both age-related degenerative diseases. Many studies indicate that these two diseases share common pathogenesis mechanisms. In this review, the osteoporotic phenotype of AD mouse models was discussed, and shared mechanisms such as hormonal imbalance, genetic factors, similar signaling pathways and impaired neurotransmitters were identified. Moreover, the review provides recent data associated with these two diseases. Furthermore, potential therapeutic approaches targeting both diseases were discussed. Thus, we proposed that preventing bone loss should be one of the most important treatment goals in patients with AD; treatment targeting brain disorders is also beneficial for osteoporosis.

Interaction between the nervous and skeletal systems

The skeleton is one of the largest organ systems in the body and is richly innervated by the network of nerves. Peripheral nerves in the skeleton include sensory and sympathetic nerves. Crosstalk between bones and nerves is a hot topic of current research, yet it is not well understood. In this review, we will explore the role of nerves in bone repair and remodeling, as well as summarize the molecular mechanisms by which neurotransmitters regulate osteogenic differentiation. Furthermore, we discuss the skeleton’s role as an endocrine organ that regulates the innervation and function of nerves by secreting bone-derived factors. An understanding of the interactions between nerves and bone can help to prevent and treat bone diseases caused by abnormal innervation or nerve function, develop new strategies for clinical bone regeneration, and improve patient outcomes.

The use of oral glucocorticoids and the risk of major osteoporotic fracture in patients with myasthenia gravis

Oral glucocorticoids may increase major osteoporotic fracture risk (MOF) in myasthenia gravis patients. To assess this risk, we performed a case-control study including all Danish patients with a MOF between 1995 and 2011. We also pooled our data with data from another study. We found no increased risk. Osteoporosis prevention remains advisable.

PURPOSE/INTRODUCTION

The prolonged use of high doses of oral glucocorticoids (GCs), a common treatment in patients with myasthenia gravis (MG), may increase major osteoporotic fracture (MOF) risk. Previous epidemiological studies did not exclusively focus on patients with MG or had relatively few GC-exposed MG patients. Aims were to evaluate the risk of MOF in MG patients using oral GCs in a large study population and to perform a pooled analysis with data from previous work.

METHODS

A population-based case-control study (1995-2011) was conducted using the Danish National Health Service. Cases had sustained a MOF, and controls had not. All were aged ≥ 18 years. Multivariate conditional logistic regression estimated odds ratios (ORs) among MG patients using oral GCs versus non-users. Adjustments were made for comorbidities and comedications. In the pooled analysis, results were pooled by the use of generic inverse variance methods, assuming a random-effects model.

RESULTS

We identified 376,858 cases and 376,858 controls. MOF risk was not elevated in MG patients currently using oral GCs compared to MG patients not on oral GCs (OR_adj.: 1.26 (95% CI 0.68-2.33)). The use of the highest cumulative dose of oral GCs (≥ 7 g) did not show an increased risk of MOF among MG patients (OR_adj.: 2.00 (95% CI 0.90-4.44)). Our pooled analysis also showed no association between oral GC use and MOF risk.

CONCLUSION

This study showed that oral GC use in patients with MG was not associated with increased risk of MOF in our case-control study and pooled analysis. Osteoporosis prevention in MG patients based on clinical guidelines remains advisable.