胸腺上皮细胞在小鼠后肢同种异体复合组织移植中的免疫调节作用及相关机制研究

针对传统外科手术不能修复的颜面、四肢和会阴部等处的人体复杂毁损伤，同种异体复合组织移植（VCA）是目前世界上最有效的外科重建手段。这种新型的外科治疗方式能够较好地同时恢复毁损器官的外观和功能。但随之而来的，是移植术后的免疫排斥难题。VCA免疫排斥问题远比实体器官移植（SOT）来的复杂。近几十年的科学研究也并没有使得免疫耐受在当前临床VCA转化中成为现实，这意味着在未来一定时期内，接受VCA治疗的患者仍然会持续受到因长期服用免疫抑制剂所带来的副作用，比如慢性免疫排斥反应、肝肾毒性、机会感染，甚至是器官衰竭导致的生命威胁。这些由免疫排斥所带来的诸多问题，将原来无性命之虞的患者不断推向面临死亡威胁的深渊，从根本上违背了VCA治疗的初衷，阻碍了VCA 的进一步发展。因此，建立VCA免疫耐受，戒断长期或终身免疫抑制剂的使用，是VCA发展的终极目标。细胞治疗是目前移植免疫耐受研究的最大热点之一。在众多前期研究中，课题负责人在小鼠的体内、外实验研究中发现：在一定条件下，胸腺上皮细胞（TECs）不仅可以被移植，还能存活并发挥原有的特性和功能。我们知道，胸腺上皮细胞占比虽不到胸腺组织的1%，却通过皮质胸腺上皮细胞和髓质胸腺上皮细胞，分别参与胸腺细胞的“阳性选择”和“阴性选择”过程，调控T淋巴细胞的自我识别和中枢性耐受，在免疫源头上主导着细胞免疫应答的方向。目前，尚未有相关研究报道VCA背景下胸腺上皮细胞移植对移植免疫调节的影响。因此，本着新颖和创新的研究宗旨，本课题拟构建小鼠后肢原位移植的同种异体复合组织移植动物模型，以胸腺上皮细胞作为主要研究对象，研究胸腺上皮细胞移植对构建功能性“杂合胸腺”、重构胸腺微环境、改造T细胞受体免疫属性和诱导免疫耐受的影响，并揭示供体和受体的胸腺上皮细胞、树突状细胞和胸腺细胞等在同种异体复合组织移植背景下参与移植免疫调节的分子作用机制。

To devastating composite tissue defects in the craniomaxillofacial regions, extremities and perineum that not amendable to conventional surgical approaches, vascularized composite allotransplantation (VCA) is currently the most promising reconstructive option. However, immune rejection has always been the bottle neck for graft survival and the host, indicating far more sophisticated than that in solid organ transplantation (SOT). Immune tolerance is the ultimate goal to achieve for a stable and successful VCA, but has remained impossible from bench to bed even after decades’ research. It means future chronic rejection episodes, hepatotoxicity, nephrotoxicity, opportunistic infection and even death caused by long-term administration of immunosuppressants, to the VCA patients for a long period to come. All of these adverse effects convert the non-life threatening disfigurements to a life-threatening VCA reconstruction, running counter to the original intention of VCA. Therefore, stable immune tolerance which will make withdrawal of administration of any immune reagents possible is the urge and necessity for VCA agenda. Cell-based therapies are the most promising strategies in VCA. Among the pilot and previous researches, the author revealed that not only can the thymic epithelial cells (TECs) be transplantable; they can also maintain survival and proliferation after transplantation both in vivo and in vitro in a specific condition. It is well known that the cortical thymic epithelial cells (cTECs) and medullary thymic epithelial cells (mTECs) are directly involved in the processes of “positive selection” and “negative selection” in the thymus. They fundamentally regulate the T cell central immune tolerance and dominate the cell-mediated immune response. Up to date, no study reports the immunomodulation of TECs transplantation in setting of VCA. In the light of novelty and innovation on scientific research, the present study aims to investigate the immunomodulatory effects of TECs in a mouse hindlimb orthotopic allotransplantation model, and reveals molecular mechanisms on their re-engineering of “hybrid thymus”, the reestablishment of the microenvironment of early thymic progenitors, the recombination of T cell receptor repertoire and the induction of immune tolerance in VCA transplantation, which expects to display cell interactions and potential molecular pathways in donor- and recipient-derived TECs, dentritic cells and immature T cells on immunoregulation of VCA.