Endothelial Cell MHC Molecules are Necessary and Sufficient to Reject 3D Printed Human Skin Grafts in an Advanced Human Immune System Mouse 2259219

Abstract

Abstract Introduction Allogeneic skin is among the tissues most prone to rejection. This need has driven development of synthetic skin substitutes. There are a number of different approved synthetic skin substitutes but none of them are completely satisfactory. Here we aimed to develop a humanized mouse model to study the process of skin graft rejection using bilayered 3D-printed skin grafts implanted on MISTRG6 immunodeficient mice. Methods Vascularized skins were 3D-printed using single donor human fibroblasts, pericytes, keratinocytes and endothelial cells (ECs), the latter either unmodified (WT-ECs) or deleted of MHC molecules (KO-ECs). Adult MISTRG6 immunodeficient mice neonatally inoculated with adult human hematopoietic stem cells (HSCs) received 3D-printed skin graft allogeneic to the HSCs and were boosted 3 weeks post-grafting with human PBMCs autologous to the HSCs. Results HSC inoculation alone produced low levels of circulating human myeloid and lymphoid cells without affecting grafts; PBMC boosting increased circulating human CD4+ T cells and dramatically boosted Granzyme B-producing CD8+ T cells only in mice with WT-EC grafts. These grafts became infiltrated by human macrophages, dendritic cells, CD4+ and CD8+ T cells, and showed evidence of rejection. Shared T cell clones were present in skin and spleen indicative of systemic alloresponse. KO-EC grafts had minimal infiltration of graft or spleen without signs of rejection despite MHC molecule expression on other graft cell types. Conclusion In our model we generated a rejection response against 3D-printed skin grafts involving human myeloid cells and lymphocytes and showed that ECs are necessary and sufficient to trigger graft rejection of bioengineered tissue lacking passenger leukocytes. Funding Source NIH 1R01HL169238 Topic Categories Transplantation Immunology (TRAN)