内皮祖细胞与间充质干细胞联合促进HSCT损伤骨髓血管niche修复的作用及机理研究

Engraftment failure and delayed hematopoiesis are severe complications after hematopoietic stem cell transplantation, affecting patients’ survival and life quality. Bone marrow vascular niche is the place where hematopoietic stem cells home to and regulates the proliferation and differentiation of hematopoietic stem cells. Vascular niche injury after transplantation is the major pathological basis for hematopoietic stem cells engraftment failure and delayed hematopoiesis..Endothelial progenitor cells (EPCs) are the precursor cells of endothelial cells. We have previously demonstrated that EPCs could promote the repair of damaged bone marrow vascular niche and early hematopoietic reconstitution. However, the longer effect is not satisfactory. Some studies showed that EPCs-mediated formation of effective vascular cavity requires the support of stromal cells. Bone marrow mesenchymal stem cells (MSCs) are not only important stromal cells of vascular niche, but also one of the effective strategies to treat severe graft-versus-host disease (GVHD). Therefore, based on previous works, using EPCs and MSCs as tools, this project aims to investigate their role in the repair of bone marrow vascular niche, promotion of hematopoietic reconstitution, as well as prevention of engraftment failure and delayed hematopoiesis after transplantation. In addition, this project further studies the mechanism of EPCs/MSc-mediated repair of damaged vascular niche. If succeed, it not only provide novel strategies for the prevention of hematopoietic stem cell transplantation-associated complications in clinic, but also provide theory for studies on the prevention of other vascular damage-associated diseases.

植入不良/造血延迟是造血干细胞移植后严重并发症，影响移植受者的生存率与生存质量。骨髓血管niche是造血干细胞归巢的门户，并调控造血干细胞增殖与分化，移植后血管niche损伤是造血干细胞植入失败或造血延迟的主要病理基础。. 内皮祖细胞（EPC）是内皮细胞的前体细胞。我们前期研究发现EPCs可促进骨髓损伤血管niche修复，促进早期造血重建，但远期疗效欠佳；有研究显示，EPCs形成有效血管腔需周细胞支持；骨髓中的MSCs是血管niche的重要周细胞，同时MSCs还是重度GVHD治疗的有效策略之一。为此，本研究则拟在前期工作基础上，以EPCs和MSCs为工具，探索骨髓血管niche修复，促进造血重建、防治移植后植入不良/造血延迟的作用，并进一步探索其修复损伤血管龛niche的机理。如获成功，不仅可为临床造血干细胞移植并发症的防治提供新策略，还可为其他血管损伤性疾病的防治研究提供新思路。

HSC植入失败/植入功能不良是异基因造血干细胞移植（HSCT）后重要并发症之一，不仅影响移植的成功率，也影响患者移植后的生活质量。HSCT中，受者血管龛严重受损，制约了HSC的归巢，是导致HSC植入失败/造血延迟的重要因素；为此，明确损伤血管niche修复机理、促进其修复是防治植入失败/造血延迟的潜在有效策略，深入探索具有重要的临床现实意义。为此，本研究着眼于并发症发生的病理基础--内皮系统损伤入手，在 EPCs 与 MSCs 存在天然的相互促进的基础上，采用造血干细胞移植联合输注 EPCs 与 MSCs，促进损伤骨髓血管内皮的修复，而从防治移植后植入不良/造血延迟的发生，提高生存率与生存质量。主要研究内容如下：①建立EPCs和MSCs的体外诱导培养体系和鉴定方案；②EPCs和MSCs骨髓植入功能验证；③探索了联合移植EPCs和MSCs在造血干细胞移植预处理损伤后对造血重建的影响；④开展MSCs联合输注EPCs对造血干细胞移植靶器官如肠道和肺损伤的影响研究，确认联合输注防治移植并发症的确定性并对相关机制进行探讨。结果：1.EPCs 和 MSCs联合输注能够修复血管损伤，促进造血重建；2.EPCs 和 MSCs联合输注能够升高亚致死照射损伤小鼠的生存率；3.联合输注MSCs+EPCs不仅能够促进异基因造血干细胞移植后血管内皮细胞修复，还能够促进肠道上皮细胞的修复，影响肠道菌群，减轻GVHD靶器官肠道和肺脏损伤；4.p38 MAPK信号通路可能参与损伤内皮的修复过程。研究结果为植入功能不良及内皮损伤修复的研究提供了新策略，也为后续EPCs 与 MSCs 联合促进造血重建策略在省内外移植单位推广提供了可靠的理论依据。

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