Cellular mechanism in support of allogenic human amnion epithelial cell transplantation without immunosuppression

Background & AimPlacenta is a non-controversial and readily available source of stem cells for regenerative medicine. We previously reported that human amnion epithelial cells (hAEC) from term placenta are not tumorigenic, have immunomodulatory and anti-inflammatory properties and once transplanted differentiate into functional hepatocyte-like cells. In preclinical studies with immune-competent mice, hAEC engrafted and survived without administration of immunosuppressive drugs, resulting in correction of metabolic liver diseases or the reversal of acute liver failure. In clinical settings allogenic hAEC have been transplanted without immunosuppression. However, little or null is known about immunomodulatory cells, as hAEC. During the past years we studied and identified molecular pathways this novel stem cells has, driving immunoregulatory capacity.Methods, Results & ConclusionWe performed a complete surface screening of hAEC, profiling all the molecules commonly described on other stem as well as somatic cells. Amnion characteristically lacks HLA class 2 expression and expresses both class 1a and non-polymorphic class 1b (responsible for maternal immune-toleration of the fetus). We quantified the level of expression of HLA-G and HLA-E molecules both as membrane-bound and soluble forms. Recently, purinergic mediators, hydrolyzed by plasma membrane nucleotidases, have also been identified to regulate immune cell response, thus we quantified the level of expression of all ecto-enzymes in hAEC preparations. Surprisingly, hAEC constitutively express all known ecto-enzymes. In addition, we proved constitutive expression of of CD47 (‘don't-eat-me’ signal) and complement system (CD55/CD59). Immunogenicity of the hAEC was confirmed on purified immune effector cells (T-, B- and NK-cells).ConclusionsHigh level expression of ecto-enzymatic axis and non-canonical HLA molecules likely play a key role in immunological tolerance and long-term acceptance of the human xeno-cell graft in immunocompetent mice. The ability to treat the most common (liver) diseases with one stem cell therapy without the administration of immunosuppressive drugs could be a “game changer” and will greatly expand the number of patients who could receive cellular therapy. Based on their safety and the successful preclinical studies, approval was granted to begin banking of hAEC under cGMP condition at Karolinska Institutet, and to perform hAEC transplants on 10 patients with liver disease without