The changes of Proteome in MG-63 cells after induced by calcitonin gene-related peptide

Consequences of Aging on Bone

With the aging of the global population, the incidence of musculoskeletal diseases has been increasing, seriously affecting people's health. As people age, the microenvironment within skeleton favors bone resorption and inhibits bone formation, accompanied by bone marrow fat accumulation and multiple cellular senescence. Specifically, skeletal stem/stromal cells (SSCs) during aging tend to undergo adipogenesis rather than osteogenesis. Meanwhile, osteoblasts, as well as osteocytes, showed increased apoptosis, decreased quantity, and multiple functional limitations including impaired mechanical sensing, intercellular modulation, and exosome secretion. Also, the bone resorption function of macrophage-lineage cells (including osteoclasts and preosteoclasts) was significantly enhanced, as well as impaired vascularization and innervation. In this study, we systematically reviewed the effect of aging on bone and the within microenvironment (including skeletal cells as well as their intracellular structure variations, vascular structures, innervation, marrow fat distribution, and lymphatic system) caused by aging, and mechanisms of osteoimmune regulation of the bone environment in the aging state, and the causal relationship with multiple musculoskeletal diseases in addition with their potential therapeutic strategy.

[Protective effect of calcitonin gene-related peptide against oxidative damage in MC3T3-E1 osteoblasts]

OBJECTIVE

This study aimed to observe the protective effect of calcitonin gene-related peptide (CGRP), as well as its potential mechanism, against oxidative damage in MC3T3-E1 osteoblasts.

METHODS

1) MC3T3-E1 osteoblasts were treated with different hydrogen peroxide (H₂O₂) concentrations (10⁻¹, 10⁻², 10⁻³, 10⁻⁴, and 10⁻⁵ mol·L⁻¹) for 12, 24, 36, and 48 h to build an oxidative damage model, to determine cell proliferation activity in each group by using CCK-8 assay, and to determine the optimal modeling concentration. MC3T3-E1 osteoblasts were pretreated for 1 h with different CGRP concentrations (10⁻⁶, 10⁻⁷, 10⁻⁸, 10⁻⁹, and 10⁻¹⁰ mol·L⁻¹) followed by treatment with H₂O₂ (10⁻⁴ mol·L⁻¹). After 12, 24, 36, and 48 h, the CGRP expression and activity of osteoblasts were detected using the CCK-8 method to determine the optimal CGRP concentration that provides the best protective effect against oxidative damage. 2) Superoxide dismutase (SOD) activity, reactive oxygen species (ROS) content, and the levels of the inflammatory cytokines tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6 of the groups treated with CGRP, H₂O₂, CGRP+H₂O₂ were determined.

RESULTS

1) Compared with the control group, treatment with 10⁻⁴ mol·L⁻¹ H₂O₂ significantly started to inhibite the proliferation of osteoblasts (P<0.01) in a dose- and time-dependent manner. Compared with 10⁻⁴ mol·L⁻¹ H₂O₂ group, pretreatment with 10⁻⁸ mol·L⁻¹ CGRP significantly increased the proliferation of osteoblasts (P<0.01). 2) Compared with H₂O₂ group, CGRP+H₂O₂ group significantly increased the SOD activity (P<0.01), ROS content significantly decreased (P<0.01), TNF-α, IL-1β, and IL-6 secretion significantly decreased (P<0.05).

CONCLUSIONS

H₂O₂ can cause oxidative damage to MC3T3-E1 osteoblasts, whereas CGRP exerts protective effect against oxidative damage in MC3T3-E1 osteoblasts.

Age-dependent impact of inferior alveolar nerve transection on mandibular bone metabolism and the underlying mechanisms

Aging is associated with peripheral nerve degradation and bone destruction. The aim of the study is to elucidate the influence of sensory denervation on bone metabolism in different age groups by establishing a modified unilateral inferior alveolar nerve transection (IANT) model. The rats, divided into young, middle-aged and aged group, were sacrificed at 1, 2, 4 and 8 weeks after right IANT. The histological changes of mandibles were analyzed by fluorescent double labeling, micro-CT, HE, TRAP and anti-CGRP immunohistochemical staining. Molecular mechanisms underlying the changes were analyzed by qPCR and western blot. Differences between the test and control side were evaluated by paired-samples t test. The Friedman test and separate Wilcoxon signed-rank tests were applied to analyze age-dependent difference. The impact of IANT was the most intensive in developing bone, the most persistent in full grown bone and the faintest in the aged bone. The role of IAN in keeping homeostasis was closely related to the anabolic effect of CGRP, which suppressed the number of osteoclasts through OPG/RANKL ratio and controlled growth factors expression like BMP2. This study contributes to a better understanding of the molecular mechanisms of CGRP in vivo and the relationship among sensory nerve, bone metabolism and aging.