Sensory denervation increases potential of bisphosphonates to induce osteonecrosis via disproportionate expression of calcitonin gene–related peptide and substance P

Abstract

Bisphosphonate‐related osteonecrosis of the jaw (BRONJ) is a serious side effect of systematic administration of bisphosphonates (BPs). Sensory innervation is crucial for bone healing. We established inferior alveolar nerve injury (IANI) and inferior alveolar nerve transection (IANT) models characterized by disorganized periosteum, increased osteoclasts, and unbalanced neuropeptide expression. Zoledronate injection disrupted neuropeptide expression in the IANI and IANT models by decreasing calcitonin gene–related peptide (CGRP) and increasing substance P (SP); associated with this, BRONJ prevalence was significantly higher in the IANT model, followed by the IANI model and the sham control. CGRP treatment significantly reduced BRONJ occurrence, whereas SP administration had the opposite effect. In vitro, RAW 264.7 cells were treated with BPs and then CGRP and/or SP to study changes in zoledronate toxicity; combined application of CGRP and SP decreased zoledronate toxicity, whereas CGRP or SP applied alone showed no effects. These results demonstrate that sensory denervation facilitates the occurrence of BRONJ and that CGRP used therapeutically may prevent BRONJ progression, provided that SP is also present. Further studies are necessary to determine the optimal ratio of CGRP to SP for promoting bone healing and to uncover the mechanism by which CGRP and SP cooperate.

Establishment and assessment of rodent models of medication-related osteonecrosis of the jaw (MRONJ)

“…Thus, the MRONJ-like lesions should exist for at least one week in rodents before verifying the successful establishment of the MRONJ model. The total duration ranges from 2 weeks 68 to 17 weeks 56 , 58 , although it exceeds eight weeks in most studies 31 , 44 , 45 , 69 – 72 , indicating a relatively long induction period.…”

“…Regarding species selection, approximately 60% of relevant studies chose rats rather than mice for research, usually 8–12 weeks old and female 44 – 48 . Rats were selected due to their low cost, rapid and easy reproduction, and simple maintenance conditions 49 .…”

“… Empty bone lacunae 30 , 45 , 95 , 96 , 98 The proportion or the number of empty bone lacunae in a certain area indicates the degree of osteocyte loss, which present the bone necrosis. TRAP + osteoclast 44 , 49 , 57 , 58 , 64 , 67 , 69 , 72 , 93 , 95 – 101 The TRAP + osteoclasts present the bone resorption, commonly used indicators including numbers of osteoclast per area or per bone line. Osteoblast 30 , 44 , 49 , 64 , 67 , 93 , 97 Generally identified by hematoxylin-eosin staining or marked by alkaline phosphatase (ALP), bone morphogenetic protein-2 (BMP-2), or receptor activators of NF-κB ligand (RANKL), commonly used indicators including numbers of osteoclast per area or per bone line.…”

“… TRAP + osteoclast 44 , 49 , 57 , 58 , 64 , 67 , 69 , 72 , 93 , 95 – 101 The TRAP + osteoclasts present the bone resorption, commonly used indicators including numbers of osteoclast per area or per bone line. Osteoblast 30 , 44 , 49 , 64 , 67 , 93 , 97 Generally identified by hematoxylin-eosin staining or marked by alkaline phosphatase (ALP), bone morphogenetic protein-2 (BMP-2), or receptor activators of NF-κB ligand (RANKL), commonly used indicators including numbers of osteoclast per area or per bone line. Blood vessels 65 , 67 , 69 The extent of angiogenic inhibition is assessed by the density of blood vessels generally marked by CD31.…”

“…Mucosal healing and bone exposure are two important indexes in gross observation. Most studies mainly describe the gross MRONJ as “incomplete and delayed mucosal healing and bone exposure” 30 , 44 , 45 , 47 , 62 , 64 , 67 , 72 , 93 – 96 . However, in infection-induced MRONJ rodent models, the gross observation may only present mild to moderate inflammation with soft tissue swelling and erythema without exposure to bone tissue on probing 45 , 85 .…”