TRPV4在扩展穿支皮瓣区血供中的作用及分子机制

The area of perforator flap has been research focus of plastic surgery for decades with its flexibility of surgical design and minimal trauma of donor site. However, one major drawback of this surgical technique is the blood supply of perforator flap is not always sufficient to meet the needs of massive trauma reconstruction. The existing concepts of perforator flap was established mainly upon the morphological studies of flaps conducted by Taylor and colleagues in the 1980's, through careful study he observed some delicate vessels which he then named "choke vessels". Choke vessels are reduced-caliber vessels connecting adjacent in physiological vascular conditions. This structure resembles the innate collateral vessel network of coronary artery. Recent studies in cardiovascular diseases demonstrated that under circumstance of acute coronary syndrome, pressure differences between different branches of coronary arteries create elevated fluid shear stress in the collateral vessel network, causing vasodilation of these vessels. Other data showed that TRPV4 plays a vital role in sensing shear stress variation as a mechanical receptor. The proposed research hypothesized that chemical activation of TRPV4 as a therapeutic target could promote the vasodilation of choke vessels in flaps and lead to larger cross-angiosome perforator flaps with single supply vessels. Methods of this research included the establishment of rat perforator flap model, the pharmacological intervention of TRPV4 agonist and antagonist in vivo, observation of the impact of TRPV4 activation and blockage to choke vessel dilation and flap survival. Along with that, in vitro research targeting HUVEC and VSMC was conduct to study the impact of TRPV4 activation and blockage to cell proliferation, cell migration and the cell factor secretion of downstream pathway. The results of in vivo and in vitro studies would be taken together to analyze the validity of the hypothesis mentioned above. Furthermore, the underlying mechanism of choke vessel dilation would be further discussed. Our research may also provide a theoretical basis for the establishment of cross-angiosome perforator flap blood supply and the possibility of design for larger flaps.

穿支皮瓣设计灵活、供区创伤小，是创伤修复外科研究热点。但是穿支供养范围有限，难以满足大面积创伤修复的需要。既往研究表明：心脑血管阻塞时，血管内压力差产生的剪切力变化能激活瞬时感受器离子通道（TRPV4），促使侧支循环开放，使缺血组织重获血供。而穿支皮瓣中相邻穿支间的阻塞性血管（choke vessels）与心脑血管侧支循环结构相似。我们前期研究提示：穿支皮瓣中，剪切力变化可以激活TRPV4，通过NF-kb通路从而使choke血管扩张，提高皮瓣存活。在此基础上，本项目提出"以TRPV4为靶点，化学激活该通道，促进choke血管开放，扩展穿支皮瓣范围"假说。拟通过体内应用TRPV4激活剂和抑制剂，观察其对choke血管开放、穿支皮瓣存活的影响；体外调控TRPV4，检测内皮细胞和平滑肌细胞增殖、迁移和下游因子分泌情况，探讨可能的治疗机制，为建立跨区穿支皮瓣提供理论基础。

穿支供养范围有限，难以满足大面积创伤修复的需要。相邻穿支间的阻塞性血管（choke vessels）是扩展穿支皮瓣血供的关键。前期研究提示：血管内压力差产生的剪切力变化能激活瞬时感受器离子通道（TRPV4），通过NF-kb 通路使choke vessels扩张，提高皮瓣存活。在此基础上，项目组提出“以TRPV4 为靶点，化学激活该通道，促进choke vessels开放，扩展穿支皮瓣范围”的假说。 .本项目体外实验发现，激活TRPV4可以提高脐静脉内皮细胞（HUVEC）和血管平滑肌细胞（VSMC）的增殖活力，并使HUVEC细胞迁移、成管能力提高；上皮间质转化（EMT）相关指标，NF-kB、MCP-1、ICAM-1、β-FGF、VEGF及G-CSF等细胞因子和炎症介质的基因表达提高。进一步在大鼠背部穿支皮瓣模型中，发现TRPV4受体的功能激活促进choke vessels扩张，改善皮瓣血流，提高组织代谢和血管化水平，扩大皮瓣的成活面积。同时，在大鼠腹部预构皮瓣模型中，发现激活TRPV4能够显著提高局部VEGF水平，提高毛细血管数量以及新生血管所占的面积比，增大预构皮瓣存活面积。以上研究明确了TRPV4在穿支皮瓣choke vessels扩张及预构组织血管化中的作用，为进一步的临床试验提供重要的临床前试验证据。进一步通过随机双盲临床试验，有望证实TRPV4受体调节剂的治疗效果，为临床提供便捷有效的促血管化治疗方案。.对穿支皮瓣血供扩展进行深入研究，在动物模型中证实了增压和血管预构技术均能有效扩张穿支皮瓣的血供范围。项目组将这一技术转化应用于大面积头颈软组织修复中，建立了一系列基于血管增压和皮瓣预构的面颈部缺损修复策略，提高了大面积穿支皮瓣的成活率和修复的效果。