The Role of Bone Grafts in Preventing Medication-Related Osteonecrosis of the Jaw: Histomorphometric, Immunohistochemical, and Clinical Evaluation in Animal Model

Highlights on the Effects of Non-Coding RNAs in the Osteonecrosis of the Jaw

Osteonecrosis of the jaw is the progressive loss and destruction of bone affecting the maxilla or mandible in patients treated with antiresorptive and antiangiogenic agents without receiving prior radiation therapy. The pathogenesis involves the inflammatory pathway of receptor activator of nuclear factor NF-kB ligand and the macrophage colony-stimulating factor, essential for osteoclast precursors survival and proliferation and acting through its receptor c-Fms. Evidence has shown the role of non-coding RNAs in the pathogenesis of osteonecrosis of the jaw and this finding might be useful in diagnosis since these small RNAs could be considered as biomarkers of apoptotic activity in bone. Interestingly, it has been proved that miR-29 and miR-31-5p, acting on specific targets such as CALCR and RhoA, promote programmed-cell death and consequently the necrosis of bone tissue. Specific long non-coding RNAs, instead, have been detected both at reduced levels in patients with multiple myeloma and osteonecrosis, and associated with suppression of osteoblast differentiation, with consequences in the progression of mandible lesions. Among non-coding genic material, circular RNAs have the capability to modify the expression of specific mRNAs responsible for the inhibition of bisphosphonates activity on osteoclastogenesis.

Impact of beta-tricalcium phosphate on preventing tooth extraction-triggered bisphosphonate-related osteonecrosis of the jaw in rats

Antiresorptive or antiangiogenic drugs can cause medication-related osteonecrosis of the jaw that is refractory. Bisphosphonate-related osteonecrosis of the jaw (BRONJ) may be caused by procedures such as tooth extraction damage the alveolar bone, release bisphosphonates (BPs) and impede healing. This study investigated strategies for BRONJ prevention and molecular mechanisms of its onset. We assessed the effectiveness of filling extraction sockets with beta-tricalcium phosphate (β-TCP). Rats were administered zoledronic acid (ZA) 1.2 mg/kg once per week for 2 weeks, and a molar was extracted. They were randomly assigned to the β-TCP group (bone defects filled with 0.01 g of β-TCP) or control group. Tissue content measurements indicated 2.2 ng of ZA per socket in the β-TCP group and 4.9 ng in the control group, confirming BP distribution and BP adsorption by β-TCP in vivo. At 4 weeks after extraction, the β-TCP group had normal mucosal coverage without inflammation. Moreover, at 8 weeks after extraction, enhanced bone healing, socket coverage, and new bone formation were observed in the β-TCP group. Connective tissue in the extraction sockets suggested that local increases in BP concentrations may suppress the local autophagy mechanisms involved in BRONJ. Filling extraction sockets with β-TCP may prevent BRONJ.