Role of oral mucosa in bisphosphonate related osteonecrosis of the jaw

描述(申请人提供)：双膦酸盐(BPS)是一种有效的抗吸收药物，广泛用于治疗骨质疏松症和转移性骨骼疾病。长期服用BPS的人患颌骨坏死(ONJ)的风险更高。双磷酸盐相关性颌骨坏死(BRONJ)的病因被认为是由于其对破骨细胞的抑制作用，破骨细胞是骨重建和愈合的重要骨吸收细胞。然而，单凭这一点不足以解释BRONJ的病理生理学，因为口腔环境中的伤口愈合是一个多因素的复杂过程，需要包括口腔粘膜细胞在内的不同细胞类型的协调努力。BRONJ通常发生在以前拔牙或其他手术的部位，临床定义为裸露的坏死骨，伴有未愈合和开放的口腔粘膜。然而，口腔粘膜在BRONJ病理生理学中的确切作用尚不完全清楚。为了更好地了解多糖硫酸酯对口腔黏膜细胞的影响，我们建立了口腔黏膜三维创面愈合模型，发现多糖硫酸酯能显著抑制角质形成细胞的增殖和迁移。与这一体外模型类似，我们的体外研究也表明，对原代正常口腔角质形成细胞(NHOK)具有显著的抑制增殖和迁移的BPS。我们最近开发的动物模型概括了BA-ONJ，也揭示了伤口闭合受损，下方有裸露和坏死骨。根据我们的初步数据，我们假设BP通过靶向甲羟戊酸途径直接损害口腔黏膜的再上皮化(例如，增殖和迁移)。为此，我们建议1)检测法尼基焦磷酸合成酶(FPPS)和RhoA在BP处理的NHOK中的作用；2)通过动物模型检测体内伤口愈合相关蛋白的空间表达模式。临床结果和益处大于使用BPS的负面影响。因此，BPS将继续用于治疗骨质疏松症和转移性骨疾病，正确治疗和预防BRONJ仍将是牙科和医疗实践中重要的相关临床问题。我们的建议将为BRONJ以口腔特有的方式发生提供可能的解释，并将为未来临床应用于BRONJ的管理和治疗奠定基础。当前项目的成功完成可能会导致R01赠款机制，重点是将研究结果应用于临床环境。 公共卫生相关性：由于双膦酸盐在多种临床环境中的有效性，随着其越来越多地使用，双膦酸盐相关性颌骨坏死(BRONJ)已成为一个重大的牙科和医学问题，因为目前还没有明确的预防和治疗方法。虽然BRONJ在临床上被定义为裸露的骨，覆盖着未愈合和开放的口腔粘膜，但口腔粘膜在BRONJ的病理生理学中的确切作用尚不完全清楚。在这项提案中，我们将调查双膦酸盐对口腔粘膜细胞的直接影响，我们的结果有望通过改进治疗和预防方式，为管理长期使用双膦酸盐的人做出重大贡献。

DESCRIPTION (provided by applicant): Bisphosphonate (BPs) are potent anti-resorptive agents that are widely used to treat osteoporosis and metastatic bone diseases. Long-term users of BPs are at the higher risk of developing osteonecrosis of the jaw (ONJ). The etiology of bisphosphonate-related osteonecrosis of the jaw (BRONJ) is thought to be due to its inhibitory effects on osteoclasts, bone resorbing cells important for bone remodeling and healing. However, this alone is insufficient to explain the pathophysiology of BRONJ because wound healing in oral environment is a multi-factorial and complex process that requires orchestrated efforts of different cell types including oral mucosal cells. BRONJ commonly occurs at the site of previous tooth extraction or other surgical interventions and is clinically defined as exposed necrotic bone with unhealed and open oral mucosa. Nonetheless, the exact role of oral mucosa in the pathophysiology of BRONJ is not fully understood. To better understand effects of BPs on oral mucosal cells, we established a 3 dimensional (3D) oral mucosal wound healing model and found that BPs drastically inhibit proliferation and migration of keratinocytes. Similar to this ex vivo model, our in vitro studies also showed the marked inhibition of proliferation and migration by BPs specific to primary normal human oral keratinocytes (NHOK). Our recently developed animal model which recapitulates BA-ONJ also revealed the impaired wound closure with underlying exposed and necrotic bone. Based on our preliminary data, we hypothesize that BP directly impairs reepithelialization (e.g., proliferation and migration) of oral mucosa by targeting the mevalonate pathway. To this end, we propose 1) to examine roles of farnesyl pyrophosphate synthase (FPPS) and RhoA in BP-treated NHOK in vitro and ex vivo, and 2) to examine spatial expression patterns of wound healing-associated proteins in vivo using animal model. The clinical outcomes and benefits outweigh the adverse effects of using BPs. Therefore, BPs will continually be used to manage osteoporosis and metastatic bone diseases, and proper treatment and prevention of BRONJ will remain important and relevant clinical issues in dental and medical practices. Our proposal will provide possible explanations as to why BRONJ occurs in oral-cavity specific manner, and will establish a basis for the future clinical applications in managing and treating BRONJ. Successful completions of the current project will likely lead to R01 grant mechanism focusing on the application of findings to the clinical settings. PUBLIC HEALTH RELEVANCE: With the increasing use of bisphosphonates due to its effectiveness in multiple clinical settings, bisphosphonate-related osteonecrosis of the jaw (BRONJ) has been surfaced as a significant dental and medical problem because no definitive prevention and treatment are currently available. Although BRONJ is clinically defined as exposed bone with unhealed and opened overlaying oral mucosa, the exact role of oral mucosa in the pathophysiology of BRONJ is not fully understood. In this proposal, we will investigate direct effects of bisphosphonates on the oral mucosal cells, and our results are expected to contribute significantly on managing long-term bisphosphonate users by improving treatment and prevention modalities.