The Sex-Specific Role of Prolactin in Apical Periodontitis Pain

摘要 仅在美国，每年就花费约80亿美元进行1500多万例根管手术，以 治疗和预防根尖周炎(AP)的发展。AP是一种痛苦的疾病，在这种疾病中，组织 由于牙髓感染或身体创伤，牙齿周围会发炎。这种炎症是 以机械性痛觉阈值降低或机械性痛觉异常为特征。在根管治疗的同时 缓解牙髓疼痛在大多数情况下，约7-12%的患者在6个月后会继续经历牙髓疼痛 这一过程中，女性经历术后慢性疼痛的可能性是男性的四倍。 目前的药物治疗方案带来了严重的风险，如成瘾、不良副作用和 服药过量。因此，尚不清楚的机制，使女性面临更大的疼痛风险，由于AP需要 被阐明，以允许潜在的新疗法，直接解决这一普遍的临床表现。 利用AP的临床前模型，我们发现催乳素在女性AP部位高表达 是老鼠，不是雄鼠。由于其新出现的性别特异性的伤害感受作用，催乳素信号可能是 是治疗女性AP患者的一个有希望的靶点。因此，我们假设催乳素水平升高 在女性中介导性二态AP介导的机械性痛觉异常与更大的痛觉异常相比 雄鼠。为了解决这一中心假设，目标1将测试细胞特异性催乳素和 在AP小鼠模型中，催乳素受体(PRLR)在雌性中的表达增加。在这里，我们将归纳AP 通过造成牙髓暴露并允许感染雄性和雌性小鼠的上颌第一磨牙。这个 感染将在3天、7天、14天和21天内出现，届时我们将确定 根尖周病变中催乳素及其受体表达细胞的百分比。在完成此操作后 目的：我们预计雌性小鼠将在根尖周围病变中表现出更高水平的催乳素并增加 PRLR在三叉神经传入神经和三叉神经节中的表达。此外，目标2将检验这一假设 催乳素以一种性二态的方式增加了根尖牙周炎引起的机械性异位痛症。之后 牙髓暴露、机械性痛觉过敏将使用振动垫上的von Frey细丝进行评估。我们会 使用全局的、伤害性感受器特异性的和免疫细胞特异性的PRLR基因敲除转基因小鼠来评估总体 催乳素在伤害性感受器敏化中的作用。此外，我们将量化免疫细胞种群在 使用RNAScope进一步了解催乳素在根尖周炎中的作用 伤害性感受器-敏化。随着这些实验的完成，我们将演示性别特定的角色 催乳素在AP诱导的机械痛觉异常中的作用。研究催乳素的作用提供了一个新的靶点 开发治疗方法以解决缺乏有效的AP治疗方法。了解催乳素是如何 性别特异性影响AP疼痛的调节以开发新的非阿片类药物治疗数百万 这个项目将加强我作为一名早期职业科学家的培训。

Abstract In the United States alone, ~$8 billion is spent each year to perform over 15 million root canal procedures to treat and prevent the development of apical periodontitis (AP). AP is a painful disease in which the tissues surrounding the tooth become inflamed due to dental pulp infection or physical trauma. This inflammation is characterized by decreased mechanical pain thresholds, or mechanical allodynia. While root canal treatments relieve AP pain in most cases, ~7-12% of patients will continue to experience endodontic pain >6 months after the procedure, with females being four times more likely than males to experience post-operative chronic pain. Current pharmacological treatment options pose serious risks such as addiction, unwanted side effects, and overdose. Therefore, the yet unknown mechanisms that put females at risk for greater pain due to AP need to be elucidated to allow for potential new therapies that directly address this prevalent clinical presentation. Using preclinical models of AP, we discovered that prolactin is highly expressed within the AP site in female mice, not male mice. Because of its emerging sex-specific pro-nociceptive effects, prolactin signaling could be a promising target for treating female AP patients. Thus, we hypothesize that increased prolactin levels mediate a sexually dimorphic AP-mediated mechanical allodynia with greater allodynia in female compared to male mice. To address this central hypothesis, Aim 1 will test the hypothesis that cell-specific prolactin and prolactin receptor (PRLR) expression is increased in females in a mouse model of AP. Here, we will induce AP by creating a pulp exposure and allow for infection in the maxillary first molar of male and female mice. The infection will manifest over the course of 3, 7, 14, and 21 days, at which point, we will determine the percentage of prolactin- and prolactin receptor-expression cells in the periapical lesion. Upon completion of this aim, we expect that female mice will exhibit greater levels of prolactin in the periapical lesion and increased PRLR expression on trigeminal afferents and in the trigeminal ganglia. Moreover, Aim 2 will test the hypothesis that prolactin increases apical periodontitis-induced mechanical allodynia in a sexually dimorphic manner. After pulp exposure, mechanical allodynia will be assessed using von Frey filaments on the vibrissal pad. We will use global; nociceptor-specific; and immune cell specific PRLR knockout transgenic mice to assess the overall contribution of prolactin to nociceptor-sensitization. Additionally, we will quantify immune cell populations within the lesion using RNAscope to further understand the role of prolactin in periapical inflammation contributing to nociceptor-sensitization. With the completion of these experiments, we will demonstrate the sex-specific role of prolactin in AP-induced mechanical allodynia. Examining the role of prolactin provides a new target for developing therapeutics to address the lack of effective AP treatments. It is crucial to understand how prolactin sex-specifically impacts regulation of AP pain to develop new non-opioid approaches to treat the millions of patients suffering from AP, and this project will serve to enhance my training as an early career scientist.