RESUMEN
The immunogenicity of transplanted allogeneic cells and tissues is a major hurdle to the advancement of cell therapies. Here we show that the overexpression of eight immunomodulatory transgenes (Pdl1, Cd200, Cd47, H2-M3, Fasl, Serpinb9, Ccl21 and Mfge8) in mouse embryonic stem cells (mESCs) is sufficient to immunologically 'cloak' the cells as well as tissues derived from them, allowing their survival for months in outbred and allogeneic inbred recipients. Overexpression of the human orthologues of these genes in human ESCs abolished the activation of allogeneic human peripheral blood mononuclear cells and their inflammatory responses. Moreover, by using the previously reported FailSafe transgene system, which transcriptionally links a gene essential for cell division with an inducible and cell-proliferation-dependent kill switch, we generated cloaked tissues from mESCs that served as immune-privileged subcutaneous sites that protected uncloaked allogeneic and xenogeneic cells from rejection in immune-competent hosts. The combination of cloaking and FailSafe technologies may allow for the generation of safe and allogeneically accepted cell lines and off-the-shelf cell products.
RESUMEN
Current in vivo models for investigating human primary bone tumors and cancer metastasis to the bone rely on the injection of human cancer cells into the mouse skeleton. This approach does not mimic species-specific mechanisms occurring in human diseases and may preclude successful clinical translation. We have developed a protocol to engineer humanized bone within immunodeficient hosts, which can be adapted to study the interactions between human cancer cells and a humanized bone microenvironment in vivo. A researcher trained in the principles of tissue engineering will be able to execute the protocol and yield study results within 4-6 months. Additive biomanufactured scaffolds seeded and cultured with human bone-forming cells are implanted ectopically in combination with osteogenic factors into mice to generate a physiological bone 'organ', which is partially humanized. The model comprises human bone cells and secreted extracellular matrix (ECM); however, other components of the engineered tissue, such as the vasculature, are of murine origin. The model can be further humanized through the engraftment of human hematopoietic stem cells (HSCs) that can lead to human hematopoiesis within the murine host. The humanized organ bone model has been well characterized and validated and allows dissection of some of the mechanisms of the bone metastatic processes in prostate and breast cancer.
