The Effect of Cyclosporin A on Alveolar Bone in Rats Subjected to Experimental Periodontal Disease

Myricitrin: A promising herbal therapy for periodontitis in immunosuppressed status

Background

Periodontitis is a complex chronic inflammatory disease aggravated in immunosuppressed patients. However, adjuvant therapies can alleviate severe inflammation and slow down disease progression.

Objective

To evaluate the efficacy of myricitrin, a herbal flavonoid glycoside, in reducing immunosuppression-associated periodontitis and compare its effects with that of alendronate on alveolar bone regeneration.

Methods

Fifty albino Wistar rats were randomly allocated to the control, periodontitis, immunosuppressant, myricitrin, and alendronate groups. Ligature-associated periodontitis was induced in all groups, except the control group. Cyclosporin A (CsA) was administered subcutaneously in the immunosuppressant group for immunosuppression. The myricitrin group received CsA and myricitrin, whereas the alendronate group received CsA and alendronate. The therapeutic efficacies of myricitrin and alendronate were compared histologically, morphometrically, and biochemically.

Results

Myricitrin reversed bone destruction in the periodontitis and immunosuppressant groups. Morphometrically, myricitrin showed comparable improvements to alendronate in terms of gaining more bone area to 49.4 ± 4.6 and 59.5 ± 2%, respectively (P < 0.001 in relation to the untreated periodontitis group). Concomitantly, myricitrin increased osteoblast count significantly to 28.4 ± 4.7 closer to the 34.5 ± 2.4 count in the alendronate group (P < 0.001 compared with 22.5 ± 2.6 count of the immunosuppressant group). Moreover, myricitrin restored the serum calcium to 9.4 ± 0.6 mg/dL and alkaline phosphatase up to 112.9 ± 2.9 IU/L, which were almost normal levels similar to the control cohort (P > 0.05).

Conclusion

Myricitrin showed beneficial effects in counteracting bone resorption in subjects with immunosuppression-associated periodontitis. Its efficacy in slowing down disease progression was comparable to that of alendronate.

The immunopathogenic and immunomodulatory effects of interleukin-12 in periodontal disease

Interleukin 12 (IL-12) is an inflammatory cytokine that promotes the response of the immune system. This cytokine has been implicated as a potent stimulator of several diseases characterized by inflammatory-induced bone destruction, such as rheumatoid arthritis and periodontitis. Yet, the exact role of IL-12 in the development and progress of periodontitis has not been clarified. Several studies have demonstrated a positive correlation between the level of IL-12 and the severity of periodontal destruction. Deletion of IL-12 in mice with periodontitis significantly suppressed the level of bone destruction. Interestingly, next to a role in modulating the pathogenesis, IL-12 also has immunological-regulatory properties. This cytokine induces expression of immunosuppressive molecules, such as indoleamine-pyrrole 2,3-dioxygenase (IDO). Thus, these findings suggest both negative and positive influences of IL-12 in periodontal disease. It is currently proposed that the diversity of action of cytokines is a molecular key which regulates biological development and homeostasis. Accordingly, the actions of IL-12 might be one of the mechanisms that regulate homeostasis of periodontal tissue during and following inflammation. Therefore, this article aims to review both destructive and protective functionalities of IL-12 with an emphasis on periodontal disease.

Cyclophilin A (CypA) Plays Dual Roles in Regulation of Bone Anabolism and Resorption

CypA (Cyclophilin A) is a peptidyl-prolyl isomerase previously shown to be required for chondrogenic differentiation and endochondral ossification. However, the effects of CypA on osteoclast activity and bone maintenance are entirely unknown. Here, we show that Ppia(-/-) mice demonstrate low bone mineral density, reduced osteoblast numbers, and increased osteoclast numbers. When isolated from the calvaria, Ppia(-/-) osteoblasts demonstrate decreased osteogenic differentiation, whereas Ppia(-/-) osteoclasts derived from the long bones showed increased osteoclastic activity. Overexpression and gene silencing of CypA verified osteogenic and anti-osteoclastic effects. In osteoblasts, CypA is necessary for BMP-2 (Bone Morphogenetic Protein-2)-induced Smad phosphorylation. In osteoclasts, loss of CypA activates BtK (Bruton's tyrosine kinase) and subsequently integrates with TRAF6 (TNF receptor-associated factor 6) and/or c-fos signaling to induce NFATc1 (nuclear factors of activated T cells, cytoplasmic 1). Collectively, CypA dually exerts pro-osteogenic and anti-osteoclastic effects. Thus, modulation of CypA may be useful in future efforts targeting osteoporosis.

Effect of cyclosporine-A on orthodontic tooth movement in rats

OBJECTIVE

The objective of this study is to examine the effect of cyclosporine-A (CsA) on the rate of orthodontic tooth movement in rats.

SETTING AND SAMPLE POPULATION

This is a randomized controlled trial with a split-mouth design in Sprague-Dawley rats.

MATERIAL AND METHODS

Eighteen rats, divided at random in two groups, were fed with 8 mg/kg CsA (experiment) or mineral oil (control) daily after initial healing of bilateral maxillary second molar removal. All rats received orthodontic coil springs (10 cN) secured to the maxillary incisors and first molars at the rights side, while no springs were placed at the left. Distances between first and third molars were measured on days 0, 3, 6, and 12. After sacrificing on day 12, the alveolar ridges of the maxillae were sectioned and blood samples were collected for serum tartrate-resistant acid phosphatase (TRAP)-5b level detection and for histology, respectively.

RESULTS

Significantly larger changes in intermolar distances were found after orthodontic force application in the CsA group at days 3 and 12 when compared with the control group. The inter-radicular dental alveolus of CSA-fed rats was osteopenic. Significantly increased TRAP-5b serum level was noted in the CsA group when compared with the control group.

CONCLUSIONS

We suggest that CsA enhanced the rate of orthodontic tooth movement. The osteopenia and the increased osteoclastic activity could be the underlying factors.

The Expression of Vascular Endothelial Growth Factor in a Rat Model at Destruction and Healing Stages of Periodontal Disease

BACKGROUND

The major role of vascular endothelial growth factor (VEGF), an angiogenic mediator, in promoting the progression or the healing of periodontal disease is still unclear. The aim of this study was to evaluate the VEGF expression in the destruction and healing stages of periodontal disease and to investigate the association between VEGF expression and vascularization with regard to the number and diameters of blood vessels.

METHODS

Thirty rats were distributed equally into two test groups and a control group. Experimental periodontal disease was induced in the test groups by silk ligatures, which were kept in position for 40 days. On the 40th day, ligatures were removed from the healing group, whereas ligatures were left in position in the destruction group. On the 60th day, rats were sacrificed; histomorphometric and biochemical analyses were carried out to determine the number and diameters of blood vessels and the assessment of VEGF concentration by enzyme-linked immunosorbent assay, respectively.

RESULTS

There was a statistically significant increase in the number of blood vessels in the healing group and in the diameters of blood vessels in the destruction group compared to the control group (P <0.001). In vivo VEGF expressions were highest in the healing group (P <0.001) and correlated significantly with the number of blood vessels (r(2) = 0.814; P = 0.001).

CONCLUSION

VEGF expression may be related more to the healing stage of periodontal disease than to the destruction stage of the lesion.