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Synergistic Effects of Nell‐1 and BMP‐2 on the Osteogenic Differentiation of Myoblasts
Author(s) -
Cowan Catherine M,
Jiang Xinquan,
Hsu Tiffany,
Soo Chia,
Zhang Beiji,
Wang Joyce Z,
Kuroda Shun'ichi,
Wu Benjamin,
Zhang Zhiyuan,
Zhang Xinli,
Ting Kang
Publication year - 2007
Publication title -
journal of bone and mineral research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.882
H-Index - 241
eISSN - 1523-4681
pISSN - 0884-0431
DOI - 10.1359/jbmr.070312
Subject(s) - osteopontin , runx2 , c2c12 , osteoblast , mesenchymal stem cell , microbiology and biotechnology , bone morphogenetic protein 2 , alkaline phosphatase , cellular differentiation , bone morphogenetic protein , growth differentiation factor , bone morphogenetic protein 7 , chemistry , mapk/erk pathway , chondrogenesis , growth factor , biology , myocyte , signal transduction , immunology , biochemistry , myogenesis , gene , in vitro , enzyme , receptor
Abstract Osteogenesis is synergistically enhanced by the combined effect of complimentary factors. This study showed that Nell‐1 and BMP‐2 synergistically enhanced osteogenic differentiation of myoblasts and phosphorylated the JNK MAPK pathway. The findings are important because of the osteochondral specificity of Nell‐1 signaling and the potential therapeutic effects of coordinated BMP‐2 and Nell‐1 delivery. Introduction: BMPs play an important role in the migration and proliferation of mesenchymal cells and have a unique ability to alter the differentiation of mesenchymal cells toward chondrogenic and osteogenic lineages. Signaling upstream of Cbfa1/Runx2, BMPs effects are not limited to cells of the osteoblast lineage. Thus, additional osteoblast‐specific factors that could synergize with BMP‐2 would be advantageous for bone regeneration procedures. NELL‐1 (NEL‐like molecule‐1; NEL [a protein strongly expressed in neural tissue encoding epidermal growth factor like domain]) is a novel growth factor believed to preferentially target cells committed to the osteochondral lineage. Materials and Methods: C2C12 myoblasts were transduced with AdLacZ, AdNell‐1, AdBMP‐2 , or AdNell ‐ 1+AdBMP‐2 overexpression viruses. Effects were studied by cell morphology, alkaline phosphatase activity, osteopontin production, and MAPK signaling. Additionally, in a nude mouse model, viruses were injected into leg muscles, and new bone formation was examined after 2 and 8 wk. Results: C2C12 myoblasts co‐transduced with AdNell ‐ 1 + AdBMP ‐ 2 showed a synergistic effect on osteogenic differentiation as detected by alkaline phosphatase activity and osteopontin production. Nell‐1 stimulation on AdNell ‐ 1 + AdBMP‐2 preconditioned C2C12 cells revealed significant activation of the non‐BMP‐2 associated c‐Jun N‐terminal kinase (JNK) MAPK signaling pathway, but not the p38 or extracellular signal‐regulated kinase (ERK1/2) MAPK pathways. Importantly Nell‐1 alone did not induce osteogenic differentiation of myoblasts. In a nude mouse model, injection of AdNell ‐ 1 alone stimulated no bone formation within muscle; however, injection of AdNell ‐ 1 + AdBMP ‐ 2 stimulated a synergistic increase in bone formation compared with AdBMP ‐ 2 alone. Conclusions: These findings are important because of the confirmed osteochondral specificity of Nell‐1 signaling and the potential therapeutic effects of enhanced BMP‐2 action with coordinated Nell‐1 delivery.