PtgIr标记的内脏投射感觉神经元的发育及其在内脏痛形成中的作用研究

Persistent pain of visceral origin is a prominent symptom of many clinical conditions, whilst the management of visceral pain is frequently unsatisfactory. Currently, much of what we know about the mechanisms of pain derives from experimental studies of somatic nociception. However, significant differences between the nature of cutaneous and visceral pain suggest that the neural mechanisms involved in pain and hyperalgesia do not apply equally to superficial and to deep structures. The development of specific and efficient visceral pain therapies requires better understanding of the neuronal properties of visceral pain-mediating sensory neurons, and the regulatory mechanisms of their development and functions in normal and pathological conditions. Our unpublished data show that ectopic expression of Runt-related transcription factor 1 (Runx1) causes significant reduction or loss of the visceral innervation from DRG neurons, and hence visceral pain manifestation. Furthermore, genome-scale microarray analysis of Runx1 loss-of-function and gain-of-function DRG, together with retrograde tract tracing assay with cholera toxin subunit B (CTB), reveals Prostaglandin I Receptor (PtgIr) as a potential marker of bladder-innervated sensory neurons. In this project, a PtgIr-Cre mutant mice, in which the coding region of PtgIr gene is replaced by Cre recombinase, will be constructed. And the Cre activity in this line of mice will be analyzed. The successful construction of this PtgIr-Cre mice could lend great supports to analyzing the neuronal properties, the developmental mechanisms of visceral-innervated sensory neurons marked by PtgIr expression in vivo, and their role in visceral pain. These results will be of great significance in discovering the mechanisms of visceral pain, and will provide important basis and intriguing implications for the design of more effective visceral pain therapies.

内脏痛是最常见的临床症状之一，其临床治疗效果常不令人满意。此前痛觉形成机制的研究对象大多集中在体表，而内脏痛与皮肤痛的特性差异提示二者的形成和调控机制不同。目前对内脏投射感觉神经元的类型并不清楚。为了解内脏痛的形成机制，从而开发更专一有效的治疗方案，需要在分子和细胞水平上对介导内脏痛的感觉神经元的类型、发育途径及其功能的调控机理进行深入研究。前期研究结果表明转录因子Runx1对痛觉神经元形成正确的内脏投射起重要调控作用，其功能异常可导致内脏痛缺失。微阵列分析和逆向示踪实验显示前列腺素I受体（PtgIr）可作为膀胱投射感觉神经元的特异性标记。本课题拟构建PtgIr-Cre小鼠，使其基因组内的PtgIr基因表达框被替换为重组酶Cre的表达序列，从而在PtgIr基因启动子的调控下表达Cre，并对其Cre活性进行系统分析。该小鼠可作为工具用于阐明PtgIr+感觉神经元的特性、发育调控机理，及其在病理性膀胱痛形成中的作用。这些结果对了解内脏痛形成机制具有重要意义，并为开发更有效的内脏痛治疗方案提供科学依据。

内脏痛作为最常见的临床症状之一，其临床治疗效果常不令人满意。目前对内脏投射感觉神经元的类型并不清楚。前列腺素I受体（PtgIr）可能是一种内脏投射感觉神经元的特异性标记。本项目制备了PtgIr-Cre报告基因小鼠，其基因组的PtgIr启动子驱动重组酶Cre表达。该小鼠可作为工具，用于标记所有表达PtgIr基因的细胞，通过与其他报告基因小鼠品系结合使用，可以标记特定类型的PtgIr阳性细胞，如神经元。纯合型PtgIr-/-小鼠还可作为PtgIr基因敲除小鼠使用。此外，本项目初步检测了小鼠内脏和背根神经节中PtgIr基因的表达分布情况，证明PtgIr阳性感觉神经元主要是肽能神经元。