استئوکلاست

Although exercise is known as an effective factor in maintaining and improving bone strength; it is not clear that its effects on bone-forming and bone-eating cells of different age groups are the same. Therefore, this study aimed to investigate the effect of resistance-endurance training on the number of osteocyte, osteoblast, and osteoclast cells in femur bone tissue in male rats of different ages.

In the present study, 30 male Wistar rats in three age groups of 2 weeks, 6 weeks, and 96 weeks were randomly divided into 2 groups of 5 each, training and control. Resistance-endurance exercises were performed for 6 training sessions per week for 6 weeks. Rats were sacrificed under carbon dioxide gas. H&E staining was used for tissue microscopic examination.

The results of one-way analysis of variance with Tukey's post hoc test showed that higher amounts of osteoblast and osteocyte cells and lower amounts of osteoclast cells in trained rats of all three age groups were significant compared to their control group. The comparison of exercise groups showed that the number of osteoblasts in the child and adult groups, the number of osteocytes in the adult group, and the number of osteoclasts in the adult and elderly groups were higher.

The results showed that resistance-endurance training led to an increase in bone-forming cells and a decrease in bone-eating cells. However, the effects of exercise on bone formation in younger age groups were more than in old age. Nevertheless, the prevention of exercise from the process of bone loss in older age, especially old age, was evident.

Spinal cord injury (SCI) causes devastating injuries in patients. The main mechanisms of the pathogenesis of secondary injury include nerve degeneration, gliosis, and inflammation. Spinal cord injury induces a disorder or failure in several organs due to the vital role of the spinal cord in regulating bodily functions. Osteoporosis is a consequence of spinal cord injury that occurs in the vast majority of patients with spinal cord injury.
Articles on the related topic were searched in the following databases: Science Direct, Scopus, Springer Science, PubMed and Google scholar to have been used in writing from this review article. A total of 120 related research papers, including quantitatve and qualitative researches in English, from the last 57 years papers (1962- 2019) were included in this study. The review article is written according to 120 articles and the keywords “Spinal cord injury, Osteoporosis, Inflammation, Osteoblast and Osteoclast”.

Although weight loss is an important factor in the development of osteoporosis following SCI, inflammation, nerve damage, and hormonal changes also contribute to this process. Hormonal changes mediated by SCI may contribute to postoperative osteoporosis with several mechanisms. These mechanisms included: increased renal excretion and decreased intestinal absorption of calcium, consequently, a negative balance of calcium ions; Vitamin D deficiency; impair the function of the gonads and inhibits the osteoanabolic (ossification) activity of sex steroids; elevated blood leptin; Pituitary suppression of parathyroid hormone, and bone loss following SCI may (at least in part) be caused directly by insulin resistance and insulin-like growth factor.

It has been shown that growth factors have a great role in improving wound healing processes. In addition, a relatively high proportion of endodontically treated teeth will require retrograde treatment in the future. Therefore, the aim of the present study was to evaluate the effect of platelet-rich plasma (PRP) on differentiation of osteoblasts and osteoclasts in the presence of a three-dimensional scaffold.

In this in vitro study, mesenchymal stem cells were isolated from the Wharton jelly of human fetal umbilical cord and assigned into osteoblasts and osteoclasts groups for the evaluation of differentiation. Each group was subdivided into two subgroups with and without PRP. All the samples were cultured on two PCL/HA (polycaprolacton/hydroxyapatite) polymer scaffold. To evaluate differentiation into osteoblasts, DMEM (Dulbecco’s Modified Eagle’s Medium) was used that contained 7‒10-mol dexamethasone, 10-mol glycerophosphate, and 50-mol ascorbic acid. In the osteoclast differentiation group, RANKL (receptor activator of nuclear factor Kappa-B ligand) and CSF (colony-stimulating factor) were used. In addition to differentiation agents, 10% PRP was added to the two subgroups containing PRP. After 10 days, differentiation into osteoblasts and osteoclasts was evaluated by assessing the expression of specific genes using real-time PCR. In the osteoblast differentiation group, expression of osteocalcin and osteotrix genes was evaluated and in the osteoclast differentiation group, expression of TRAP (tartrate-resistant acid phosphatase) was evaluated. Data were analyzed using one-way ANOVA, two-way ANOVA, and post hoc Tukey tests, using Graph Pad software program.

Evaluation of the expression of the TRAP gene did not reveal any significant differences between the study and control groups. There was a significant difference between the group with the osteoclastogenic factor alone and the group with osteoclastogenic factor and PRP (p=0.0324). There was a significant difference in osterix expression between the control group and the PRP-treated group (p=0.0050). There was a significant difference between the group with osteoblastogenic factor alone and the group with osteoblastogenic factor and PRP (p=0.00001). There was a significant difference in the expression of osteocalcin gene between the control and PRP-treated groups (p=0.0110); however, the differences between the osteoblastogenesis groups with and without PRP treatment were not significant (P=0.5191). The differences in the expression of TRAP, osterix, and osteocalcin genes between the control and PRP-treated groups were significant (p=0.006 and p=0.0001, respectively).

The results of the present study showed that PRP resulted in an increase in osteoblastic differentiation, with no significant increase in osteoclastic differentiation.