Insulin-like growth factor 2 (IGF-2) potentiates BMP-9-induced osteogenic differentiation and bone formation

Abstract

Efficient osteogenic differentiation and bone formation from mesenchymal stem cells (MSCs) should have clinical applications in treating nonunion fracture healing. MSCs are adherent bone marrow stromal cells that can self-renew and differentiate into osteogenic, chondrogenic, adipogenic, and myogenic lineages. We have identified bone morphogenetic protein 9 (BMP-9) as one of the most osteogenic BMPs. Here we investigate the effect of insulin-like growth factor 2 (IGF-2) on BMP-9-induced bone formation. We have found that endogenous IGF-2 expression is low in MSCs. Expression of IGF-2 can potentiate BMP-9-induced early osteogenic marker alkaline phosphatase (ALP) activity and the expression of later markers. IGF-2 has been shown to augment BMP-9-induced ectopic bone formation in the stem cell implantation assay. In perinatal limb explant culture assay, IGF-2 enhances BMP-9-induced endochondral ossification, whereas IGF-2 itself can promote the expansion of the hypertropic chondrocyte zone of the cultured limb explants. Expression of the IGF antagonists IGFBP3 and IGFBP4 leads to inhibition of the IGF-2 effect on BMP-9-induced ALP activity and matrix mineralization. Mechanistically, IGF-2 is further shown to enhance the BMP-9-induced BMPR-Smad reporter activity and Smad1/5/8 nuclear translocation. PI3-kinase (PI3K) inhibitor LY294002 abolishes the IGF-2 potentiation effect on BMP-9-mediated osteogenic signaling and can directly inhibit BMP-9 activity. These results demonstrate that BMP-9 crosstalks with IGF-2 through PI3K/AKT signaling pathway during osteogenic differentiation of MSCs. Taken together, our findings suggest that a combination of BMP-9 and IGF-2 may be explored as an effective bone-regeneration agent to treat large segmental bony defects, nonunion fracture, and/or osteoporotic fracture. © 2010 American Society for Bone and Mineral Research.

Age-Related Insulin-Like Growth Factor Binding Protein-4 Overexpression Inhibits Osteogenic Differentiation of Rat Mesenchymal Stem Cells

“…Mechanistically, IGF-2 is further shown to enhance the BMP-9-induced BMPR-Smad reporter activity and Smad1/5/8 nuclear translocation. PI3-kinase (PI3K) inhibitor LY294002 abolishes the IGF-2 potentiation effect on BMP-9-mediated osteogenic signaling and can directly inhibit BMP-9 activity [16]. Consistent with these results, we observed that p-Erk1/2 and p-Smad1/5/8 levels were significantly decreased in IGFBP4-overexpressed MSCs and increased in IGFBP4 knockdown cells in the presence of BMP2.…”

“…Serum levels of IGFBP4 showed negative correlation with calcaneal bone mineral density among post-menopausal SouthIndian women [15]. Importantly, expression of IGFBP4 inhibits BMP-9-induced ALP activity and matrix mineralization in MSCs [16], suggesting that IGFBP4 is involved in the osteogenic potency of MSCs.…”

“…Overexpression of GATA-4 significantly increases MSC differentiation into a myocardial phenotype, which was associated with the upregulation of IGFBP4 [31]. In the osteogenic differentiation of MSCs, IGFBP4 may compete for the binding of IGFs to their receptors, thus inhibiting IGF-II induced osteogenic potential [16]. IGFBP4 plays a key role in MSC senescence.…”

Biphasic effects of TGFβ1 on BMP9-induced osteogenic differentiation of mesenchymal stem cells

“…Matrix mineralization nodules usually emerge at 10 days and reach peaks at 17-20 days after induction (19). TGFβ1 alone had no difference with AdGFP control that corresponded with ALP activity, indicating that TGFβ1 itself is unable to induce osteogenesis in MSCs (20), while small mineralized nodules were visible in the group treated with AdBMP9 in combination with 5 ng/ml or 10 ng/ml TGFβ1 at day 5 whereas AdBMP9 alone exhibited apparent nodules at day 13 ( Fig.…”

Skeletal and Adipose Tissue Engineering with Adipose-Derived Stromal Cells

“…There are two types, IGF-1 and IGF-2, which play a wide variety of cellular roles from the regulation of proliferation to apoptosis. Both IGF-1 and IGF-2 have been shown to be associated with increase in bone formation and density (Adami et al 2010, Chen et al, 2010 while their reduction has been shown to be associated with decreased bone density (Bennett, 1984). In order to specifically identify genes upregulated during osteogenesis, our group isolated RNA from human adipose-derived stromal cells during in-vitro osteogenesis and performed a microarray analysis (Lee, Longaker, 2010).…”