Immune Evasion in Embryonic Stem Cell-based Tissue Repair and Transplantation.

 描述(由申请人提供)：肺发育不良是早产的一种破坏性并发症，占围产儿死亡的70%以上。用参与生理过程并对局部信号信号做出反应的健康细胞取代受损细胞是一种治疗理想，可以使用基于干细胞的治疗来实现。胚胎干细胞作为健康细胞的来源显示出巨大的潜力。事实上，我们已经证明，小鼠ES细胞可以分化为专门的产生表面活性物质的肺泡II型肺泡细胞，当移植到早产小鼠体内时，这些细胞分布在肺实质中。然而，免疫排斥的根本障碍阻碍了这些细胞的长期植入，并阻碍了将其转化为临床治疗。显然，改变宿主对移植物的检测或诱导移植物耐受的新方法对于推进这一潜在的变革性治疗方案至关重要。长期以来，我们一直对CD13感兴趣，这是一种表达在多种细胞类型上的多功能细胞表面肽酶，它影响细胞的黏附、迁移、抗原递呈和内吞作用。与这一提议相关的是，在成人和胚胎干细胞上也发现了CD13。在鉴定CD13KO MES细胞的过程中，我们观察到，当两种基因的细胞作为畸胎瘤注射到免疫受损的小鼠皮下时，CD13KO ES在免疫功能正常的动物中表现出显著的生长和分化促进作用。这些CD13KO畸胎瘤含有较少的免疫细胞，这表明ES细胞上CD13的缺失使得移植的细胞能够逃避免疫检测。为了证实这一观点，我们在性别不匹配的WT和CD13KO动物之间进行了皮肤移植。值得注意的是，CD13KO移植物在WT和CD13KO宿主中存活超过100天，而WT移植物很容易被排斥，支持我们在畸胎瘤模型中的观察。此外，在移植后7d，WT移植物的皮肤结构明显被破坏，大量移植物免疫细胞渗入，而CD13KO移植物则保留了更正常的结构，浸润细胞较少。虽然幼稚CD13KO小鼠的造血谱是正常的，18与WT相比，性别不匹配的CD13KO移植物中渗入的T细胞和巨噬细胞数量更少，脱颗粒的肥大细胞数量显著减少，与触发更强免疫反应的WT移植物一致？重要的是，与单独使用载体相比，用封闭的抗CD13单抗治疗WT小鼠显著提高了不匹配的WT移植物的存活率，并且停止治疗导致了移植物排斥，这意味着CD13影响免疫检测而不是耐受诱导。综上所述，我们的研究确定CD13是调节移植免疫的潜在靶点。我们假设，供体细胞中CD13的缺失使其能够逃脱免疫检测和随后的排斥反应，从而延长生存时间。

 DESCRIPTION (provided by applicant): Pulmonary hypoplasia is a devastating complication of preterm delivery that is responsible for over 70% of the cases of perinatal mortality. Replacement of damaged cells with healthy cells that would participate in physiological processes and respond to local signaling cues is a therapeutic ideal that may be achievable using stem cell-based therapy. Embryonic stem (ES) cells show tremendous promise as a source of healthy cells. Indeed, we have shown that murine ES cells can be differentiated into specialized surfactant-producing alveolar type II pneumocytes that distribute in the lung parenchyma when implanted into preterm mice. However, the fundamental obstacle of immune rejection precludes long-term engraftment of these cells and impedes translation to clinical therapy. Clearly, new methods to alter the host's detection of the graft or induce graft tolerance are critical to advance of this potentially transformative therapeutic option. We have a longstanding interest in CD13, a multifunctional cell surface peptidase expressed on many cell types where it influences cell adhesion, migration, antigen presentation and endocytosis. Pertinent to this proposal, CD13 is also found on adult and embryonic stem cells. During the course of characterizing CD13KO mES cells, we observed that while cells of both genotypes grew equally well when subcutaneously injected as teratomas into immune-compromised mice, CD13KO ES showed markedly enhanced growth and differentiation in immune competent animals. These CD13KO teratomas contained fewer immune cells, suggesting that the absence of CD13 on the ES cells allowed the transplanted cells to evade immune detection. To confirm this notion, we performed skin transplants between gender-mismatched WT and CD13KO animals. Remarkably, the CD13KO grafts survived for greater than 100 days in both WT and CD13KO hosts while WT grafts were readily rejected, supporting our observations in the teratoma model. Furthermore, at 7d post-transplant the architecture of the skin in WT grafts was clearly disrupted with numerous graft-infiltrating immune cells, while the CD13KO grafts retained a more normal architecture with fewer infiltrating cells. While the hematopoietic profiles of naïv CD13KO mice are normal, 18 there are fewer infiltrating T cell, macrophage populations and significantly reduced numbers of degranulated mast cells in gender-mismatched CD13KO grafts when compared to WT, consistent with WT grafts triggering a stronger immune response? Importantly, treatment of WT mice with a blocking anti-CD13 monoclonal antibody significantly enhanced the survival of mismatched WT grafts when compared to vehicle alone and treatment withdrawal led to graft rejection, implying that CD13 influences immune detection rather than tolerance induction. Taken together, our studies identify CD13 as a potential target for modulation of transplant immunity. We hypothesize that the absence of CD13 in donor cells allows them to escape immune detection and subsequent rejection, thus prolonging survival.