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

 描述（由申请人提供）：肺发育不全是早产的一种毁灭性并发症，占围产期死亡病例的70%以上。用参与生理过程并对局部信号线索做出反应的健康细胞替换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（ES）作为健康细胞的来源显示出巨大的前景。事实上，我们已经表明，小鼠ES细胞可以分化成专门的表面活性剂生产肺泡II型肺细胞，分布在肺实质植入早产小鼠。然而，免疫排斥的根本障碍排除了这些细胞的长期植入，并阻碍了转化为临床治疗。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种潜在的变革性治疗选择至关重要。我们对CD13有着长期的兴趣，CD13是一种多功能细胞表面肽酶，在许多细胞类型中表达，影响细胞粘附、迁移、抗原呈递和内吞作用。与此相关的是，CD13也存在于成体和胚胎干细胞中。在表征CD13 KO mES细胞的过程中，我们观察到，当作为畸胎瘤皮下注射到免疫受损小鼠中时，两种基因型的细胞生长同样良好，而CD13 KO ES在免疫活性动物中显示出显著增强的生长和分化。这些CD13 KO畸胎瘤含有较少的免疫细胞，这表明ES细胞上缺乏CD13使移植细胞逃避免疫检测。为了证实这一观点，我们在性别不匹配的WT和CD13 KO动物之间进行了皮肤移植。值得注意的是，CD13 KO移植物在WT和CD13 KO宿主中存活超过100天，而WT移植物容易被排斥，这支持了我们在畸胎瘤模型中的观察结果。此外，在移植后第7天，WT移植物中皮肤的结构明显被许多移植物浸润免疫细胞破坏，而CD13 KO移植物保留了更正常的结构，浸润细胞更少。虽然初始CD13 KO小鼠的造血特征是正常的，但与WT相比，性别不匹配的CD13 KO移植物中浸润T细胞、巨噬细胞群较少，脱颗粒肥大细胞数量显著减少，这与WT移植物引发更强的免疫应答一致。重要的是，与单独的媒介物相比，用阻断性抗CD13单克隆抗体治疗WT小鼠显著提高了不匹配的WT移植物的存活率，并且停药导致移植物排斥，这意味着CD13影响免疫检测而不是耐受诱导。综上所述，我们的研究将CD13确定为调节移植免疫的潜在靶点。我们假设供体细胞中缺乏CD13可以使它们逃避免疫检测和随后的排斥反应，从而延长存活时间。

 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.