Investigation of the effect of ghrelin on bone fracture healing in rats

Sinusoidal alternating electromagnetic field accelerates fracture healing in rats

OBJECTIVES

To investigate the effect of sinusoidal alternating electromagnetic field (SEMF) on fracture healing and its mechanism.

METHODS

Femoral fracture model was established using SPF male Wistar rats, 30 model rats were randomly divided into model control (MC) and SEMF groups with 15 rats in each group. The SEMF group was given 50 Hz 1.8 mT for 90 min every day, and the MC group was not treated. X-ray examinations were performed every two weeks to determine the formation of bone scabs in each group of rats. Three rats were sacrificed after 2 and 4 weeks of treatment in both groups. Protein was extracted from the fractured femurs, and the expression of type Ⅰ collagen (COL-1), Osterix (OSX), Runt-related transcription factor 2 (RUNX2), and vascular endothelial growth factor (VEGF) protein level was detected by immunoblotting. After 8 weeks, the femur on the operated side was taken for micro-CT scanning to observe fracture healing, angiography to observe blood vessel growth, and organs such as hearts, livers, spleens, lungs, and kidneys were taken for safety evaluation by hematoxylin-eosin staining (HE staining).

RESULTS

The bone scab scores of the SEMF group were significantly higher than those of the MC group after 2, 4, 6, and 8 weeks of treatment (all P<0.01); the fracture healing of the SEMF group was better than that of the MC group after 8 weeks, and the bone volume scores of the two groups were 0.243±0.012 and 0.186±0.008, respectively, with statistically significant differences (P<0.01); and the number of blood vessels in the SEMF group was also more than that of the MC group after 8 weeks. The results of protein blotting method showed that the protein expression of VEGF, COL-1, RUNX2, and OSX was higher in the SEMF group than in the MC group after 2 and 4 weeks of treatment (all P<0.05), and the HE staining showed that there was no abnormality in histopathological observation of examined organs in both groups.

CONCLUSIONS

SEMF can accelerate fracture healing by promoting the expression of osteogenic factors and vascular proliferation without significant adverse effects.

Cellular and Molecular Mechanisms Associating Obesity to Bone Loss

Obesity is an alarming disease that favors the upset of other illnesses and enhances mortality. It is spreading fast worldwide may affect more than 1 billion people by 2030. The imbalance between excessive food ingestion and less energy expenditure leads to pathological adipose tissue expansion, characterized by increased production of proinflammatory mediators with harmful interferences in the whole organism. Bone tissue is one of those target tissues in obesity. Bone is a mineralized connective tissue that is constantly renewed to maintain its mechanical properties. Osteoblasts are responsible for extracellular matrix synthesis, while osteoclasts resorb damaged bone, and the osteocytes have a regulatory role in this process, releasing growth factors and other proteins. A balanced activity among these actors is necessary for healthy bone remodeling. In obesity, several mechanisms may trigger incorrect remodeling, increasing bone resorption to the detriment of bone formation rates. Thus, excessive weight gain may represent higher bone fragility and fracture risk. This review highlights recent insights on the central mechanisms related to obesity-associated abnormal bone. Publications from the last ten years have shown that the main molecular mechanisms associated with obesity and bone loss involve: proinflammatory adipokines and osteokines production, oxidative stress, non-coding RNA interference, insulin resistance, and changes in gut microbiota. The data collection unveils new targets for prevention and putative therapeutic tools against unbalancing bone metabolism during obesity.

Circadian clock genes as promising therapeutic targets for bone loss

The circadian clock regulates many key physiological processes such as the sleep-wake cycle, hormone release, cardiovascular health, glucose metabolism and body temperature. Recent evidence has suggested a critical role of the circadian system in controlling bone metabolism. Here we review the connection between bone metabolism and the biological clock, and the roles of these mechanisms in bone loss. We also analyze the regulatory effects of clock-related genes on signaling pathways and transcription factors in osteoblasts and osteoclasts. Additionally, osteocytes and endothelial cells (ECs) regulated by the circadian clock are also discussed in our review. Furthermore, we also summarize the regulation of circadian clock genes by some novel modulators, which provides us with a new insight into a potential strategy to prevent and treat bone diseases such as osteoporosis by targeting circadian genes.