As shown above, addition of ERCs markedly reduced the number of CD11c+MHC-II+ DCs in co-culture, which, however, was reversed by neutralization with anti-PD-L1 mAb in vitro. vivo and in vitro, as well as with elevated levels of anti-inflammatory cytokines and regulatory immune cells, including CD4+CD25+Foxp3+ Tregs and F4/80+CD206+ macrophages. These findings exhibited that ERCs-based treatment promotes immune tolerance in mouse colitis, in association with PD-L1, thus indicating that PD-L1 modulates immunosuppression by ERCs. strong class=”kwd-title” Keywords: Colitis, endometrial regenerative cells, immunosuppression, mice, PD-L1 Introduction Ulcerative colitis (UC) is usually a major type of inflammatory bowel disease (IBD) featuring chronic, relapsing, nonspecific inflammatory reactions in the colorectal area [1]. Rabbit Polyclonal to CK-1alpha (phospho-Tyr294) UC prevalence and incidence are currently elevated in developed nations, and have been quickly increasing in other countries, especially in China, in past decades [2]. Although a clear-cut etiology has not been proposed for UC, it is generally admitted that this ailment is usually associated with genetic susceptibility, environmental factors, Sennidin B changes in the gut microbiota and dysregulation of immune response [3]. UC is usually routinely treated with anti-inflammatory medicines and immunosuppressors, and even surgical removal of the colon [1]. However, satisfactory results are rarely obtained. In recent years, there has been increasing evidence that shows mesenchymal stromal cells (MSCs) therapy to be effective in the treatment of UC [4]. MSCs are multipotent stromal cells with self-renewal potential. They promote tissue repair and wound healing, and show immunomodulatory and anti-inflammatory features in UC [5]. Endometrial regenerative cells (ERCs), isolated from menstrual blood as a novel group of MSCs, also display tissue repair and immunomodulatory functions. Compared with MSCs from many conventional sources, ERCs present further advantages, including rich source, noninvasive Sennidin B method for harvesting, high abundance, easy purification, rapid proliferation, relatively unlimited expandability, and the potential to differentiate into more lineages [6]. Moreover, ERCs can produce matrix metalloprotease and a large number of growth factors to promote tissue repair [7]. In our previous study, ERCs were selected for the treatment of UC, and the results showed that systemic infusion of ERCs attenuates experimental colitis in mice with significantly reduced disease activity index (DAI). The intra-colon levels of proinflammatory cytokines were decreased while there was an increase in anti-inflammatory cytokines. It was also found that immune reactive cells in the spleen decreased, while regulatory T cells increased [8]. However, the molecular mechanism underlying ERC-mediated immunosuppression in the colitis model remains largely unclear. MSCs modulate some immune cells, including DCs, macrophages and T and B cells via secretion of soluble factors [5,9,10]. In addition, MSCs exert immunosuppressive effects on immune cells by direct cell-to-cell interactions (e.g. PD-L1 interacts with PD-1) [11], and production of surface adhesion molecules [12] and human leukocyte antigen-G [13]. MSC-expressed PD-L1 plays a significant role in MSC-mediated immune suppression [14]. Our previous research indicated that MSCs require PD-L1 for the induction of immune tolerance in a cardiac allotransplantation model [15]. Moreover, Song et al found that PD-L1-Fc markedly alleviates DSS associated acute colitis as well as T-cell dependent chronic colitis, by inducing colonic CD4+ Sennidin B T cell and DC regulation [16]. We detected that ERCs as mesenchymal-like stem cells also express PD-L1. Thus, we speculate that PD-L1 also plays an important role in immunosuppressive effects during the ERCs treatment for colitis. Materials and methods Animals BALB/c mice (Male, 8 weeks, 18-22 g; Aoyide Co., Tianjin, China) were maintained routinely under a cycle of 12 h-12 h light-dark in the vivarium of the Sennidin B Tianjin General Surgery Institute, with standard rodent chow and drinking water ad libitum. The study was approved by the Institutional Ethics Committee, following the Chinese Council on Animal Care guidelines. Preparation of ERCs The menstrual blood was collected from a 30-year-old healthy woman upon informed consent. ERCs were isolated following the isolation method as described by Y Lv et al previously [8]. In brief, menstrual blood was obtained by the Diva cup method in a solution supplemented with antibiotics. Approximately 10 ml of menstrual blood samples were used for ERCs isolation each time. Then, the Ficoll method was employed for mononuclear cell separation. The cells were cultured in Dulbeccos modified Eagles medium (DMEM) high glucose made up of 10% fetal bovine serum (FBS) overnight, with marginal adherence to tissue culture flasks. After 2 weeks of culture (with 2 medium changes weekly), adherent cells with a fibroblast-like.