Abstract
Mesenchymal stem cells (MSCs) are multipotent cells that can be differentiated into osteoblasts and provide an excellent cell source for bone regeneration and repair. Recently, the canonical Wnt/beta-catenin signaling pathway has been found to play a critical role in skeletal development and osteogenesis, implying that Wnts can be utilized to improve de novo bone formation mediated by MSCs. However, it is unknown whether noncanonical Wnt signaling regulates osteogenic differentiation. Here, we find that Wnt-4 enhanced in vitro osteogenic differentiation of MSCs isolated from human adult craniofacial tissues and promoted bone formation in vivo. Whereas Wnt-4 did not stabilize beta-catenin, it activated p38 MAPK in a novel noncanonical signaling pathway. The activation of p38 was dependent on Axin and was required for the enhancement of MSC differentiation by Wnt-4. Moreover, using two different models of craniofacial bone injury, we found that MSCs genetically engineered to express Wnt-4 enhanced osteogenesis and improved the repair of craniofacial defects in vivo. Taken together, our results reveal that noncanonical Wnt signaling could also play a role in osteogenic differentiation. Wnt-4 may have a potential use in improving bone regeneration and repair of craniofacial defects.
Highlights
Human adult mesenchymal stem cells (MSCs)2 are multipotent cells originally isolated from the bone marrow that are able to differentiate into several cell types, including osteoblasts, chondrocytes, adipocytes, and myocytes (1–5)
Osteogenic Differentiation of Mesenchymal Cells Enhanced by Wnt-4—C2C12 mouse mesenchymal cells are well characterized cells that can be induced to differentiate into osteoblastlike cells in vitro following bone morphogenetic protein (BMP) stimulation (38)
Since Wnt/catenin signaling has been found to play an essential role in osteoblast differentiation, we screened several Wnts to determine if they could enhance BMP-4-induced osteogenic differentiation of C2C12 cells
Summary
Cell Culture and Retroviral Infection—C2C12 cells were purchased from ATCC and maintained in Dulbecco’s modified Eagle’s medium (Invitrogen) supplemented with 15% fetal bovine serum. To engineer C2C12 cells or MSCs stably expressing Wnt-4, the retrovirus-mediated infection was performed as described previously (38). 4.0 ϫ 106 of the cells were mixed with 40 mg of hydroxyapatite/tricalcium phosphate ceramic particles (Zimmer Inc., Warsaw, IN) and transplanted subcutaneously into the dorsal surface of 10-week-old immunocompromised beige mice (bg-nu/nu-xid; Harlan Sprague-Dawley, Indianapolis, IN) as previously described (11). Polylactic co-glycolide polymer scaffolds (3 ϫ 2 ϫ 1 mm) were seeded overnight with 2.5 ϫ 105 MSC/V or MSC/Wnt-4 cells and placed within the respective defects, as previously described for other tissue engineering applications. For CT scanning, the specimens were fitted in a cylindrical sample holder, 15.4 mm in diameter, with the coronal aspect of the calvarial bone in a horizontal position. On three-dimensional images of the specimen, bone volume (mm3) and bone mineral density in the defect site were measured directly
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
