iPS来源的胸腺上皮细胞用于异基因骨髓移植的研究

Our previous results and preliminary data have shown that allogeneic bone marrow transplantation (allo-BMT) combined with thymus transplantation efficiently enhanced the functions of T lymphocytes, facilitated stem cell engraftment and reduced the risk of infection and leukemia relapse. However, current application of thymus transplantation is restricted by its limited source. We propose a novel approach in which sufficient thymic epithelial cells are obtained by in vivo induction and differentiation of iPS cells. The protocol for generating thymic epithelial cells from iPS cells will be developed and optimized. In hoping to further reduce the likelihood of infection and leukemia relapse after BMT, as well as inhibit GVHD while preserving GVL, application of iPS-derived thymic epithelial cells will be combined with a new BMT technique-intrabone marrow BMT. Recovery of the functions of T lymphocytes from donor after allo-BMT will be examined. Our current proposal will likely enhance the success rate of both allo-BMT and organ transplantation by inducing immune tolerance, preventing GVHD, accelerating immune reconstitution, as well as reducing the likelihood of infection and tumor relapse. Therefore, our proposal provides a novel idea for treatment of malignant tumors.

我们的前期研究已表明，异基因骨髓移植联合胸腺移植能够有效提高T淋巴细胞功能，促进干细胞植入，减少移植后感染及白血病的复发。然而，胸腺来源困难制约了胸腺移植的应用。本课题拟探索诱导性多能干细胞（iPS）体内分化为胸腺上皮细胞的条件，在此基础上将iPS来源的胸腺上皮细胞用于异基因骨髓移植，联合应用骨髓内骨髓移植新技术，观察异基因骨髓移植后供者来源的T淋巴细胞功能的早期恢复，以期减少异基因骨髓移植后感染及白血病复发率，同时抑制移植物抗宿主病的发生，保留移植物抗白血病效应。本研究有望为异基因骨髓移植及实体器官移植中诱导免疫耐受、预防GvHD、促进免疫重建以降低机会性感染和肿瘤复发进而提高移植成功率提供实验基础，并为恶性肿瘤的治疗提供新的思路。

异基因骨髓移植(allo-BMT) 已成为治疗恶性血液系统疾病、先天性免疫缺陷病、某些自身免疫性疾病等的有效治疗手段，加快移植后T细胞免疫重建能够降低感染和肿瘤复发的几率。allo-BMT联合胸腺移植（TT）是促进T细胞重建和增强移植物抗肿瘤（GVT）效应的重要策略之一，且此方法不会引起明显的移植物抗宿主病（GVHD），然而，胸腺来源困难制约了这项研究的广泛开展。诱导性多能干细胞（iPS）技术的发展为这一难题的解决带来了希望。本项目研究了将iPS细胞体内诱导分化为iPS细胞嵌合体胸腺，并应用于allo-BMT。第一部分：鉴定iPS细胞嵌合体胸腺的功能，将iPS细胞嵌合率50%以上的胸腺移植到BALB/c裸鼠肾被膜下，4周后受体小鼠体内可检测到CD4+及CD8+T细胞，说明iPS嵌合体胸腺可以促进受体T淋巴细胞分化发育。第二部分：在骨髓内骨髓移植(IBM-BMT）同时联合iPS细胞嵌合体胸腺移植，4周后IBM-BMT+TT组的外周血CD4+ T和CD8+ T细胞比例均显著高于IBM-BMT+DLI（供体淋巴细胞输注）组及单纯IBM-BMT组，说明iPS细胞嵌合体的胸腺移植能促进T细胞数目的重建；对比IBM-BMT+DLI组，IBM-BMT+TT组及单纯IBM-BMT组的FOP3+占CD4+T细胞比例更高，且GVHD评分也更低，说明IBM-BMT+TT组GVHD反应轻。荷瘤小鼠IBM-BMT+TT组和IBM-BMT+DLI组肿瘤组织 CD8+T细胞浸润明显，因此IBM-BMT+TT组也具有较强的移植物抗肿瘤(GVT)效应。总之，骨髓内骨髓移植联合iPS细胞嵌合体胸腺移植，能够促进异基因骨髓移植后T细胞重建，减轻GVHD反应，并增强GVT效应，为将来人iPS来源胸腺联合移植提供了研究基础。