WISP‐1/CCN4 regulates osteogenesis by enhancing BMP‐2 activity

M Ono, CA Inkson, TM Kilts… - Journal of Bone and …, 2011 - academic.oup.com
M Ono, CA Inkson, TM Kilts, MF Young
Journal of Bone and Mineral Research, 2011academic.oup.com
Wnt‐induced secreted protein 1 (WISP‐1/CCN4) is a member of the CCN family that is
highly expressed in skeletal tissue and in osteoprogenitor cells induced to differentiate in
vitro. To determine the function of WISP‐1 during osteogeneis, osteogenic bone marrow
stromal cells (BMSCs) were transduced with WISP‐1 adenovirus (adWISP‐1) in the
presence or absence of bone morphogenetic protein 2 (BMP‐2) adenovirus (adBMP‐2).
WISP‐1 overexpression enhanced the ability of BMP‐2 to direct BMSCs toward osteogenic …
Abstract
Wnt‐induced secreted protein 1 (WISP‐1/CCN4) is a member of the CCN family that is highly expressed in skeletal tissue and in osteoprogenitor cells induced to differentiate in vitro. To determine the function of WISP‐1 during osteogeneis, osteogenic bone marrow stromal cells (BMSCs) were transduced with WISP‐1 adenovirus (adWISP‐1) in the presence or absence of bone morphogenetic protein 2 (BMP‐2) adenovirus (adBMP‐2). WISP‐1 overexpression enhanced the ability of BMP‐2 to direct BMSCs toward osteogenic differentiation and appeared to work by stimulating Smad‐1/5/8 phosphorylation and activation. The ability of WISP‐1 to enhance BMP‐2 activity also was shown in vivo using an ectopic osteogenesis assay with BMSCs transduced with WISP‐1, BMP‐2, or both. When BMSCs were infected with lentivirus containing human WISP1 shRNA, they formed less bone in vivo and were less responsive to BMP‐2, confirming that WISP‐1 and BMP‐2 have a functional interaction. Immunoprecipitation (IP) and Western blot analysis showed that WISP‐1 bound directly to BMP‐2 and showed that WISP‐1 increased BMP‐2 binding to hBMSCs in a dose‐dependent fashion. To understand how WISP‐1 enhanced BMP‐2 signaling, the influence of WISP‐1 on integrin expression was analyzed. WISP‐1 induced the mRNA and protein levels of α5‐integrin and, further, was found to bind to it. Antibody‐blocking experiments showed that the BMP‐2 binding to BMSCs that was enhanced by WISP‐1 was completely neutralized by treatment with anti‐integrin α5β1 antibody. Pilot studies and the use of transgenic mice that overexpressed human WISP‐1 in preosteoblasts had increased bone mineral density (BMD), trabecular thickness, and bone volume (BV/TV) over wild‐type controls, supporting observations using human osteoprogenitors that WISP‐1 has a positive influence on osteogenesis in vivo. In conclusion, these studies show, for the first time, that WISP‐1 has a positive influence on bone cell differentiation and function and may work by enhancing the effects of BMP‐2 to increase osteogenesis through a mechanism potentially involving binding to integrin α5β1. © 2011 American Society for Bone and Mineral Research.
Oxford University Press