Mesenchymal stem cells (MSCs) are multipotent stem cells that can differentiate into a variety of cell types, including osteoblasts (bone cells), chondrocytes (cartilage cells) and adipocytes (fat cells). They were originally found in mouse bone marrow, and successfully cultured by (Friedenstein, 1982), who also demonstrated that these MSCs could differentiate in vitro into bone and fat cells. Based on his work, a considerable number of studies have shown that this type of bone marrow-derived adherent cell has a large capacity for self-renewal while maintaining its multipotency (Chan et al., 2007; Kasper et al., 2007; Krause et al., 2007; Li et al., 2010; Naito et al., 2011; Tadokoro et al., 2011). More interesting is the fact that MSCs have low immunogenicity (Semenov et al., 2010) and can exert immune regulatory effects. MSCs cultured and amplified in vitro not only have immune regulatory effects on a variety of immune cells such as T lymphocytes, B lymphocytes, dendritic cells (DC) and natural killer cells (NK) (Aggarwal and Pittenger, 2005; Glennie et al., 2005; Jiang et al., 2005; Corcione et al., 2006; Sotiropoulou et al., 2006), but this inhibition is not major histocompatibility complex (MHC) restricted. bMSCs from the donor, recipient or a third party have similar immunosuppressive effects, and MSCs cultured in vitro can also play a role in immune regulation in vivo. For example, MSCs can extend the survival time of allogeneic skin grafts (Sundin et al., 2011) and promote the proliferation of allogeneic tumour cells (Deuse et al., 2011). The therapeutic effects of MSCs on graft-versus-host-disease (GVHD) have been proved not only in animal studies but also in clinical applications (Fang et al., 2006; Ringden et al., 2006; Cutler et al., 2010).
We have previously isolated an Flk1+ mesenchymal stem cell subset from adult bone marrow and found they had not only the three germ layers of cell differentiation potential (Fang et al., 2003, 2004, 2004; Guo et al., 2003), but significant immunomodulatory capacity (Deng et al., 2004, 2005; Zhang et al., 2004). We were able to isolate MSCs from discarded adipose tissue from patients undergoing liposuction and found they had morphology and phenotype similar to stem cells from bone marrow. Others have obtained similar results (Mizuno et al., 1999; De Ugarte et al., 2003; Cao et al., 2005; Johann et al., 2010; Weng et al., 2010; Wada et al., 2011), but it remains unknown whether aMSCs and bMSCs have similar immune functions.
Here we have isolated MSCs from bone marrow and adipose tissue and examined their effects on T-lymphocyte cell cycle, activation, inhibition and proliferation to compare their differences in immune regulation.