Human embryonic stem cell-derived Sertoli cells as an immune modulator of cell transplantation therapy in a diabetic mice model

Abstract

Objective Sertoli cells (SCs) are somatic cells that are a part of the seminiferous tubules in the testes and support germ cell development and maturation. Additionally, SCs play another role in protecting male germ cells from immune destruction via the formation of the blood-testis barrier and the secretion of several immunoregulatory factors. Based on these characteristics, SCs have been suggested to create a tolerogenic environment to protect co-transplanted cells as immune modulators. Because mature SCs are quiescent somatic cells and show lower proliferation activity in vitro, it is difficult to obtain the number of human cells needed for clinical applications. Materials and methods We established a protocol for mass production of SCs from human ESCs (hESC-SCs) and their functional properties were analyzed in vitro and in diabetic-induced mice after their co-transplantation with human insulin-secreting cells. Results hESC-SCs were successfully produced via a stepwise differentiation protocol. In addition, a mass culture method was established to secure the number of hESC-SCs available for cell therapy. hESC-SCs obtained from in vitro derivation highly express marker genes of SCs, such as GATA4, SOX9, CLDN11, and AR, and have shown immune-modulation activity similar to that of human bone marrow-mesenchymal stem cells. In diabetic-induced mice subcutaneously co-transplanted with EndoC-βH1 cells (insulin-secreting cells) and hESC-SCs, lower blood glucose levels were maintained for 6 months than in those transplanted with EndoC-βH1 cells alone. Conclusions We believe that hESC-SCs could be useful tool for securing cell therapy to treat human diseases in the future.

1. Introduction

Transplantation of donated pancreatic islets or insulin-producing cells from pluripotent human embryonic stem cells (hESCs) is an effective cell therapy for patients with insulin dependent (type I) diabetes (T1DM) [1–3]. Although the supply of pancreatic cells from hESCs meets some clinical demands, another main obstacle caused by immune-rejection must be addressed before its broad application as a cell therapy for T1DM [4, 5]. In fact, to reduce the need for continuous immunosuppressive treatment to prevent graft rejection, encapsulation and immune isolation barriers to protect engrafted cells from the host immune system have been explored and shown to have increased efficacy. However, the recently introduced encapsulation systems still requires improvements in structural and cellular components to increase the survival of donor hESC-derived pancreatic cells, maintain their long-term function, and decrease the area of fibrosis after transplantation [6, 7].

Sertoli cells (SCs) lining the seminiferous tubules of the testis not only provide appropriate support for the development and maturation of male germ cells but also protect them from the autoimmune response. Meiotic and post-meiotic germ cells are auto-antigenic and targeted for immune destruction [8–10]. In fact, SCs protect the germ cells from immune destruction through a combination of a physical and immunological barriers [11]. In addition to the blood-testis barrier (BTB), which consists of tight junctions, SCs express several immunoregulatory factors, such as complement inhibitors, which inhibit B-cell proliferation, decrease the activity of natural killer (NK) cells, inhibit or modulate the adaptive immune response, inhibit FAS-FAS ligand-induced cell death, and induce tolerogenic dendritic cells and regulatory T-cells (Tregs) [11]. Therefore, researchers have suggested that SCs can be useful sources of immunological barriers and immunosuppressants when allogeneic- and xenogeneic islets are transplanted [12]. In many studies, co-encapsulation of SCs with xenogeneic islets prolonged graft survival.