Research Scientist Yale School of Medicine, Connecticut, United States
Disclosure(s):
Zuzana Tobiasova, PhD: No financial relationships to disclose
Introduction/Rationale: 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.
