dlk1/FA1 Regulates the Function of Human Bone Marrow Mesenchymal Stem Cells by Modulating Gene Expression of Pro-inflammatory Cytokines and Immune Response-related Factors

Abstract

dlk1/FA1 (delta-like 1/fetal antigen-1) is a member of the epidermal growth factor-like homeotic protein family whose expression is known to modulate the differentiation signals of mesenchymal and hematopoietic stem cells in bone marrow. We have demonstrated previously that Dlk1 can maintain the human bone marrow mesenchymal stem cells (hMSC) in an undifferentiated state. To identify the molecular mechanisms underlying these effects, we compared the basal gene expression pattern in Dlk1-overexpressing hMSC cells (hMSC-dlk1) versus control hMSC (negative for Dlk1 expression) by using Affymetrix HG-U133A microarrays. In response to Dlk1 expression, 128 genes were significantly up-regulated (with >2-fold; p < 0.001), and 24% of these genes were annotated as immune response-related factors, including pro-inflammatory cytokines, in addition to factors involved in the complement system, apoptosis, and cell adhesion. Also, addition of purified FA1 to hMSC up-regulated the same factors in a dose-dependent manner. As biological consequences of up-regulating these immune response-related factors, we showed that the inhibitory effects of dlk1 on osteoblast and adipocyte differentiation of hMSC are associated with Dlk1-induced cytokine expression. Furthermore, Dlk1 promoted B cell proliferation, synergized the immune response effects of the bacterial endotoxin lipopolysaccharide on hMSC, and led to marked transactivation of the NF-B. Our data suggest a new role for Dlk1 in regulating the multiple biological functions of hMSC by influencing the composition of their microenvironment "niche." Our findings also demonstrate a role for Dlk1 in mediating the immune response.

Enhanced differentiation of human embryonic stem cells to mesenchymal progenitors by inhibition of TGF-β/activin/nodal signaling using SB-431542

“…(61) As shown in Fig. 5A, the cells were able to differentiate to the osteoblastic lineage, as assessed by increasing ALP activity and the formation of mineralized matrix (Fig.…”

Central (ICV) leptin injection increases bone formation, bone mineral density, muscle mass, serum IGF-1, and the expression of osteogenic genes in leptin-deficient ob/ob mice

“…(12,(42)(43)(44) The AEBP1 protein plays an important role in adipogenesis by modulating the differentiation of preadipocytes, and Aepb1 gene expression is increased in proliferating preadipocytes. (42,43) DLK1 is a regulator of mesenchymal cell differentiation.…”

“…(42,43) DLK1 is a regulator of mesenchymal cell differentiation. (44) The decreased expression of Dlk1 in bone marrow of mice treated ICV with the high dose of leptin may have been associated with increased differentiation of mesenchymal stem cells to osteoblasts. The decreased expression of Gata3 and Retn in bone marrow of mice treated ICV with the high dose of leptin likely reflects the reduced population of adipocytes in bone marrow of these mice.…”

Human serum levels of fetal antigen 1 (FA1/Dlk1) increase with obesity, are negatively associated with insulin sensitivity and modulate inflammation in vitro

“…12 We tested 1, 3 and 5 mg ml À1 of FA1 for 8 h on a THP-1 human monocytic cell line. As shown in Figure 3a, FA1 induced gene and protein expression of cytokines MCP-1, TNF-a (tumor necrosis factor-a) and IL-6 (interleukin-6).…”

“…Biological functions that differ from the above-mentioned developmental effect have been recently studied on bone marrow mesenchymal stem cells where FA1 was found to play a role in regulating cytokine gene expression. 12 Additionally, systemic effects of FA1 on bone and fat metabolism were also determined by generating adult mice, by hydrodynamic gene transfer procedure, which overexpressed FA1. In this model, high levels of FA1 reduced both bone and fat mass in a dose-dependent manner.…”