Osteogenin and recombinant bone morphogenetic protein 2B are chemotactic for human monocytes and stimulate transforming growth factor beta 1 mRNA expression.

Abstract

Subcutaneous implantation of deminerli bone matrix initiates a sequence of developmental events, which nate in endochondial bone formation. During early stages of development of matrix-induced Impts, ED1, Tapositive monocytes-macrophages were observed, sgeting that in the initial phases of the endochondral bone formation de, the bone-inductive protein osteogenin and related bone morphogenetic proteins (BMPs) might serve as potent chemoattractants to recruit circulating monocytes. In this investigation, we demonstrate that at concentrations of 10-100 fg/ml (0.3-3 fM), native bovine osteogenin and recombinant human BMP-2B (rhBMP-2B) induce the directed migration of human blood monocytes in vitro. This chemotactic response was associated with expression ofBMP binding sites (receptors) on monocytes. About 750 receptors per cell were detected with an apparent dissocition constant of 200 pM. Both osteogenin and rhBMP-2B at higher concentrations (0.1-30 ng/ml) stimulated mRNA expression for an additional regulatory molecule, type hi transforming growth factor (TGF-l1) in human monocytes. TGF-p1, in turn, is known to induce a cascade of events leading to matrix generation. Monocytes stimulated by TGF-3 are known to secrete a number of chemotactic and mitogenic cytokines that recruit endothelial and mesenchymal cells and promote their synthesis of collagen and associated matrix constituents. TGF-fl1 in concert with these other cytokines and matrix components regulates chemotaxis, mesenchymal proliferation, differentiation, angiogenesis, and controlled synthesis of extracellular matrix. Our results demonstrate that osteogenin and related BMPs through their profound effects on monocyte recruitment and cytokine synthesis may promote additional successive steps in the endochondral bone formation cascade.Bone has considerable potential for repair and regeneration, and the stages of fracture repair recapitulate the sequential developmental stages of embryonic endochondral bone formation. A cellular cascade that mimics embryonic endochondral bone development can be induced locally by implantation of demineralized bone matrix in extraskeletal sites (1-3). The cellular and biochemical events of this matrix-induced endochondral bone-forming cascade have been well characterized (3). Upon implantation of demineralized bone matrix, there is a transient immigration of polymorphonuclear leukocytes on day 1. This is followed by migration and attachment of mesenchymal cells to the matrix by day 3. These mesenchymal progenitor cells proliferate and differentiate into chondroblasts and chondrocytes on days 6-7. Vascularization of the implant occurs concomitantly with calcification of the hypertrophic cartilage matrix on day 9, and the cartilage is resorbed and replaced by new bone on days 10-12. Bone remodeling (days 12-18) and differentiation of hematopoietic cells result in formation of an ossicle complete with all associated marrow elements by day 21.Although the precise molecular mechanisms involved in this biological cascade a...

Identification of Progenitor Cells That Contribute to Heterotopic Skeletogenesis

“…Cunningham et al 44 showed that BMPs have profound effects on the recruitment of monocytes, known precursors of tissue macrophages. Subsequent studies have shown that BMP receptors are robustly expressed on monocytes and tissue macrophages 45 .…”

Bone morphogenetic protein 2 stimulation of tumor growth involves the activation of Smad-1/5

“…During development, BMP-2/4 enhance cell proliferation, stimulate cell survival pathways, and induces self-renewal of stem cells (Ying et al, 2003). BMP-2/4 regulate postnatal tissues, which include the differentiation of ovarian granulosa cells (Souza et al, 2002) and the migration of smooth muscle and endothelial cells (Cunningham et al, 1992;Willette et al, 1999;Langenfeld and Langenfeld, 2004). BMPs mediate signaling by activating serine kinase receptors, which activate the Smad-1/5 transcription factor (Yamashita et al, 1996).…”

Bone morphogenetic protein 9 is a potent synergistic factor for murine hemopoietic progenitor cell generation and colony formation in serum-free cultures

“…This observation is reminiscent of the increased TGF-␤1 expression in a human osteoblast cell line by BMP-2 22 and in human monocytes by BMP-4. 23 Because we did not find increased TGF-␤1 mRNA levels in a series of stromal cells stimulated with BMP-9, our data suggest that BMP-9 does not act on bone marrow stroma. However, a more definitive conclusion requires the determination of TGF-␤1 mRNA levels in primary stromal cells exposed to BMP-9.…”