Regulation of Chronic Colitis by Mesenchymal Stem Cells

描述(申请人提供)：炎症性肠病(IBD；克罗恩病；溃疡性结肠炎)是一种慢性小肠和/或结肠炎症性疾病，在美国大约有150万人受到影响，每年的医疗费用和工作损失都计算出近40亿美元。目前，治疗这些令人衰弱的炎症性疾病的药物屈指可数，预计在不久的将来只有几种新的疗法可用。因此，显然需要 治疗IBD患者的额外治疗药物的开发。虽然克罗恩病和溃疡性结肠炎的病因尚未完全阐明，但越来越多的临床和实验证据表明，慢性肠炎是由于对共生肠道抗原的免疫反应失调所致。最近的研究表明，骨髓间充质干细胞(MSCs)在体外和体内都具有很强的免疫调节活性。此外，最近的研究表明，在不同的自身免疫模型中，MSCs的免疫抑制活性并不局限于主要组织相容性复合体，这表明MSCs具有免疫特免性。一些报告表明，过继转移异基因或异种(人)MSCs成功地植入了受体小鼠或大鼠体内，它们抑制了在自身免疫性脑脊髓炎、同种异体移植排斥反应、胶原性关节炎和移植物抗宿主病动物模型中观察到的炎症。最近的一项研究报道，小鼠或人类的骨髓间充质干细胞可以减轻口服或直肠给予有毒化学物质所引起的侵蚀性自限性结肠炎。尽管很有说服力，但还没有人或小鼠骨髓间充质干细胞在慢性肠炎动物模型中的治疗效果进行评估。 因此，我们将评估人或小鼠骨髓来源的MSCs在具有良好特征的慢性结肠炎小鼠模型中的治疗效果。由于MSCs可以在体外生长和扩增，并在体内跨越主要组织相容性复合体屏障发挥其免疫调节活性，因此我们处于独特的地位，可以在更接近于人类IBD的动物模型中评估人或小鼠MSCs的治疗效果。我们假设，体外产生的MSCs位于肠系膜淋巴结(MLN)和/或结肠固有层，在那里它们直接通过产生强大的调节细胞因子转化生长因子(TGF)和/或间接通过诱导产生IL-10的调节性T细胞(Treg)的扩张来预防/限制肠道炎症。为了验证这一假说，我们将：a)使用小鼠慢性肠炎模型，评估人或小鼠MSCs在存在或不存在MLN或其他次级淋巴组织的情况下抑制慢性肠炎诱导的能力；b)确定人或小鼠MSCs在存在或不存在MLN或其他次级淋巴组织的情况下逆转/减轻先前存在的疾病的治疗效果；以及c)确定MSCs用来抑制慢性肠炎的诱导和持久的免疫调节机制。除了更好地了解MSCs用来抑制肠道炎症的调节机制外，从拟议的研究中获得的数据可能会确定可以开发的新的治疗策略，以治疗IBD患者。

DESCRIPTION (provided by applicant): The inflammatory bowel diseases (IBD; Crohn's disease; ulcerative colitis) are chronic inflammatory disorders of the small bowel and/or colon that affect approximately 1.5 million people in the US with a calculated annual cost for both medical expenses and work loss of almost $4 billion dollars. Currently, there are only a handful of medical treatments available for treating these debilitating inflammatory disorders with only a few new therapies projected to be available in the near future. Thus, there is a clear need for the development of additional therapeutic agents to treat patients with IBD. Although the etiologies of Crohn's disease and ulcerative colitis have yet to be fully elucidated, there is growing clinica and experimental evidence to suggest that chronic gut inflammation results from a dysregulated immune response to commensal enteric antigens. Recent studies demonstrate that bone marrow-derived mesenchymal stem cells (MSCs) have potent immunoregulatory activity in vitro and in vivo. In addition, recent investigations show that the immunosuppressive activity of MSCs in different mouse models of autoimmunity is not restricted to the major histocompatibility complex suggesting that MSCs are "immune-privileged". Several reports demonstrate that adoptive transfer of allogeneic or xenogeneic (human) MSCs successfully engraft in recipient mice or rats where they suppress the inflammation observed in animal models of autoimmune encephalomyelitis, allograft rejection, collagen-induced arthritis and graft vs. host disease. A fe recent studies have reported that mouse or human MSCs attenuate the erosive, self-limiting colitis induced by the oral or rectal administration of toxic chemicals. Although compelling, no attempt has been made to evaluate the therapeutic efficacy of human or mouse MSCs in an animal model of chronic gut inflammation. Therefore, we will evaluate the therapeutic efficacy of human or mouse bone marrow-derived MSCs in a well-characterized, mouse model of chronic colitis. Because MSCs can be grown and expanded in vitro and exert their immunoregulatory activity across major histocompatibility complex barriers in vivo, we are in the unique position to evaluate the therapeutic efficacy of human or mouse MSCs in an animal model that more closely mimics human IBD. We hypothesize that ex vivo-generated MSCs home to the mesenteric lymph nodes (MLNs) and/or colonic lamina propria where they prevent/limit gut inflammation directly via their production of the potent regulatory cytokine TGF¿1 (TGF¿) and/or indirectly by inducing the expansion of IL-10-producing regulatory T-cells (Tregs). In order to test this hypothesis we will: a) Evaluate the ability of human or mouse MSCs to suppress the induction of chronic gut inflammation in the presence or absence of MLNs or other secondary lymphoid tissue using mouse models of chronic intestinal inflammation; b) Determine the therapeutic efficacy of human or mouse MSCs in reversing/attenuating preexisting disease in the presence or absence of MLNs or other secondary lymphoid tissue and c) Define the immunoregulatory mechanisms utilized by MSCs to attenuate the induction and perpetuation of chronic gut inflammation. In addition to better understanding the regulatory mechanisms used by MSCs to suppress intestinal inflammation, data obtained from the proposed studies may identify new therapeutic strategies that could be developed to treat patients with IBD.