Oral Mucosa in Bisphosphonate-associated Osteonecrosis of the Jaw

描述(由申请人提供)：双磷酸盐相关性颌骨坏死(ONJ)对生活质量产生不利影响，并在患者中产生显著的发病率。其特征是在口腔内发现裸露的牙槽骨。接受大剂量静脉注射双膦酸盐(帕米膦酸盐和唑伦膦酸)治疗的癌症患者发生骨坏死的风险比接受低剂量口服双膦酸盐治疗的骨质疏松症患者(0.00001%至0.0001%)更高，从1%到10%不等。据推测，ONJ的原发病变位于骨骼，与过度抑制骨转换有关。然而，目前尚不清楚为什么这些病变以下颌或上颌的口腔黏膜覆盖缺失为主要临床特征。这一症状的一个可能解释是，双膦酸盐在骨骼中积聚的浓度足以直接对口腔粘膜产生毒性，并导致软组织病变无法愈合，从而导致ONJ的发病。此外，拔牙是ONJ之前的主要事件，尽管其他原因，如牙周病、种植手术、外生骨病和不合适的义齿也是ONJ的先行因素。此外，最近报道了双膦酸类化合物的抗血管生成作用。由于充分的血管重建是伤口愈合的先决条件，抑制血管生成可能导致软组织病变愈合失败，从而导致ONJ的发病。尽管这些发现提示双膦酸类药物参与了NJ的发生和/或进展，但静脉注射双膦酸类药物对口腔黏膜的影响尚未在体内进行研究。我们的总体假设是静脉注射双膦酸盐可能抑制口腔粘膜的愈合，并有助于NJ的发生和/或进展。我们计划通过测试以下目的来阐明双磷酸盐与口腔粘膜的关系。目的1利用基础组织学和活/死细胞活力测定的方法，研究静脉注射双膦酸唑来膦酸在大鼠拔牙后伤口愈合过程中对口腔黏膜的细胞毒作用。目的：阐明唑来膦酸在拔牙后口腔黏膜愈合过程中的细胞毒作用。在目标2.1中，我们将使用免疫荧光方法，确定在拔牙后的愈合过程中，唑来膦酸是否会改变口腔粘膜中血管的重建。在目标2.2中，我们将进一步研究血管重建的改变是否是由于血管生成和缺氧相关基因的表达受到抑制。目的是在活体实验中证实唑来膦酸在拔牙后口腔黏膜愈合过程中的抗血管生成作用。如果成功，拟议的实验将推进研究，填补目前在静脉注射双膦酸盐对口腔软组织作用的分子机制表征方面的知识空白，这可能随后导致了解双膦酸盐相关ONJ的发生和/或进展的病理生理学。 公共卫生相关性：双磷酸盐相关性颌骨坏死(ONJ)的特征是口腔中发现暴露的牙槽骨，对患者的生活质量造成不利影响，并在患者中产生显著的发病率。ONJ的发病机制尚不清楚。拟议的实验将推进研究，填补目前在静脉注射双膦酸类药物对口腔软组织作用的分子机制表征方面的知识空白，从而有助于理解双膦酸类药物相关ONJ的发生和/或进展的病理生理学。

DESCRIPTION (provided by applicant): Bisphosphonate-associated osteonecrosis of the jaw (ONJ) adversely affects the quality of life and produces significant morbidity in afflicted patients. It is characterized by the finding of exposed alveolar bone in the oral cavity. The risk of ONJ in patients with cancer treated with high doses of intravenous bisphosphonates (Pamidronate and Zolendronic acid) is higher, ranging from 1 to 10 %, compared to patients with osteoporosis treated with low dose, oral bisphosphonates (0.00001 to 0.0001 %). It has been assumed that the primary lesion for ONJ lies in bone and is related to over-suppression of bone turnover. However, it is unclear why these lesions present with loss of the oral mucosal covering of the mandible or maxilla as the primary clinical feature. A possible explanation of this symptom is that bisphosphonates are accumulated in bone in concentrations sufficient to be directly toxic to the oral mucosa and result in the failure of healing of soft tissue lesions, leading to the pathogenesis of ONJ. In addition, tooth extraction is the dominating event preceding ONJ, although other causes such as periodontal disease, dental implant procedures, exostoses, and ill-fitting dentures are also preceding factors for ONJ. Moreover, an anti-angiogenic effect of bisphosphonates has been reported recently. Since sufficient reconstitution of vasculature is prerequisite for wound healing, suppression of angiogenesis may result in the failure of healing of soft tissue lesions leading to the pathogenesis of ONJ. Although, these findings suggest involvement of bisphosphonate on oral mucosa in the development and/or progression ONJ, the effect of intravenous bisphosphonates on oral mucosa has not been studied in vivo. Our overall hypothesis is that intravenous bisphosphonates may inhibit healing of oral mucosa and contribute to the development and/or progression ONJ. We plan to elucidate the relationship between bisphosponates and the oral mucosa by testing the following Aims. In Aim 1, we will determine the cytotoxic effect of intravenous bisphosphonate, zoledronic acid, on oral mucosa, in vivo, during the wound healing process after tooth extraction in a rat model, by utilizing basic histology and the live/dead cell vitality assay. The aim will demonstrate the cytotoxic effect of zoledronic acid during healing of oral mucosa after tooth extraction. In Aim 2.1, we will determine if reconstitution of the vasculature in the oral mucosa is altered by zoledronic acid during the healing process after a tooth extraction, using immunofluorescence method. In Aim 2.2 we will further investigate whether the alternation of vasculature reconstitution is due to suppression of angiogenic and hypoxia related gene expression. The aim will demonstrate the anti-angiogenic effect of zoledronic acid during healing of oral mucosa after tooth extraction, in vivo. If successful, the proposed experiments will advance research that will fill a current knowledge gap in characterization of molecular mechanisms of action of intravenous bisphosphonates on oral soft tissues that may subsequently lead to the understanding of pathophysiology of development and/or progression of bisphosphonate-associated ONJ. PUBLIC HEALTH RELEVANCE: Bisphosphonate-associated osteonecrosis of the jaw (ONJ) is characterized by the finding of exposed alveolar bone in the oral cavity and adversely affects the quality of life and produces significant morbidity in afflicted patients. The underlying pathogenesis of ONJ is yet to be clearly elucidated. The proposed experiments will advance research that will fill a current knowledge gap in characterization of molecular mechanisms of action of intravenous bisphosphonates on oral soft tissues that subsequently lead to the understanding of pathophysiology of development and/or progression of bisphosphonate-associated ONJ.