The Sex-Specific Role of Prolactin in Apical Periodontitis Pain

摘要 仅在美国，每年花费约80亿美元进行超过1500万次根管治疗， 治疗和预防根尖周炎（AP）的发展。AP是一种疼痛性疾病， 由于牙髓感染或物理创伤，牙齿周围发炎。这种炎症是 其特征在于降低的机械性疼痛阈值或机械性异常性疼痛。什么是根管治疗？ 缓解AP疼痛在大多数情况下，约7-12%的患者将继续经历牙髓疼痛>6个月后， 女性比男性更有可能经历手术后的慢性疼痛。 目前的药理学治疗方案造成严重的风险，如成瘾，不必要的副作用， 服药过量因此，由于AP而使女性处于更大疼痛风险的未知机制需要 阐明，以允许潜在的新疗法，直接解决这种普遍的临床表现。 利用AP的临床前模型，我们发现催乳素在女性AP部位高度表达， 老鼠，不是雄性老鼠。由于其新兴的性别特异性促伤害性效应，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的增加 介导性二态AP介导的机械性异常性疼痛，女性的异常性疼痛更大， 雄性老鼠为了解决这一中心假设，目标1将检验细胞特异性催乳素和 在AP的小鼠模型中，雌性动物的催乳素受体（PRLR）表达增加。在这里，我们将诱导AP 通过造成牙髓暴露并允许雄性和雌性小鼠的上颌第一磨牙感染。的 感染将在3、7、14和21天内出现，届时，我们将确定 根尖周病变中催乳素和催乳素受体表达细胞的百分比。在完成此 目的，我们预期雌性小鼠在根尖周病变中表现出更高水平的催乳素， 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将检验假设 催乳素增加根尖牙周炎引起的机械异常性疼痛的性别二态性的方式。后 牙髓暴露、机械性异常性疼痛将使用vonFrey细丝在触须垫上进行评估。我们将 使用整体的、伤害感受器特异性的和免疫细胞特异性的PRLR敲除转基因小鼠来评估总体的 催乳素对伤害感受器敏感性的贡献。此外，我们将量化免疫细胞群， 使用RNAscope进一步了解催乳素在根尖周炎症中的作用， 伤害感受器敏化。随着这些实验的完成，我们将证明 催乳素在AP诱导的机械性异常性疼痛中的作用研究催乳素的作用为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治疗的问题。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方法来治疗数百万 患者患有AP，这个项目将有助于加强我作为一个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.