title: Human Induced Pluripotent Stem Cells Differentiate Into Functional Mesenchymal Stem Cells and Repair Bone Defects.
abstract: : Mesenchymal stem cells (MSCs) are currently the most established cells for skeletal tissue engineering and regeneration; however, their availability and capability of self-renewal are limited. Recent discoveries of somatic cell reprogramming may be used to overcome these challenges. We hypothesized that induced pluripotent stem cells (iPSCs) that were differentiated into MSCs could be used for bone regeneration. Short-term exposure of embryoid bodies to transforming growth factor-β was used to direct iPSCs toward MSC differentiation. During this process, two types of iPSC-derived MSCs (iMSCs) were identified: early (aiMSCs) and late (tiMSCs) outgrowing cells. The transition of iPSCs toward MSCs was documented using MSC marker flow cytometry. Both types of iMSCs differentiated in vitro in response to osteogenic or adipogenic supplements. The results of quantitative assays showed that both cell types retained their multidifferentiation potential, although aiMSCs demonstrated higher osteogenic potential than tiMSCs and bone marrow-derived MSCs (BM-MSCs). Ectopic injections of BMP6-overexpressing tiMSCs produced no or limited bone formation, whereas similar injections of BMP6-overexpressing aiMSCs resulted in substantial bone formation. Upon orthotopic injection into radial defects, all three cell types regenerated bone and contributed to defect repair. In conclusion, MSCs can be derived from iPSCs and exhibit self-renewal without tumorigenic ability. Compared with BM-MSCs, aiMSCs acquire more of a stem cell phenotype, whereas tiMSCs acquire more of a differentiated osteoblast phenotype, which aids bone regeneration but does not allow the cells to induce ectopic bone formation (even when triggered by bone morphogenetic proteins), unless in an orthotopic site of bone fracture.
  
  
  CONCLUSIONS
  Mesenchymal stem cells (MSCs) are currently the most established cells for skeletal tissue engineering and regeneration of various skeletal conditions; however, availability of autologous MSCs is very limited. This study demonstrates a new method to differentiate human fibroblast-derived induced pluripotent stem cells (iPSCs) to cells with MSC properties, which we comprehensively characterized including differentiation potential and transcriptomic analysis. We showed that these iPS-derived MSCs are able to regenerate nonunion bone defects in mice more efficiently than bone marrow-derived human MSCs when overexpressing BMP6 using a nonviral transfection method.
authors.affiliation: Department of Surgery, Cedars-Sinai Medical Center, Los Angeles, California, USA.|Board of Governors Regenerative Medicine Institute, Cedars-Sinai Medical Center, Los Angeles, California, USA.
authors.forename: Dmitriy
authors.initials: D
authors.lastname: Sheyn
authors.affiliation: Department of Surgery, Cedars-Sinai Medical Center, Los Angeles, California, USA.|Board of Governors Regenerative Medicine Institute, Cedars-Sinai Medical Center, Los Angeles, California, USA.
authors.forename: Shiran
authors.initials: S
authors.lastname: Ben-David
authors.affiliation: Skeletal Biotech Laboratory, Hebrew University of Jerusalem, Jerusalem, Israel.
authors.forename: Galina
authors.initials: G
authors.lastname: Shapiro
authors.affiliation: Department of Surgery, Cedars-Sinai Medical Center, Los Angeles, California, USA.|Board of Governors Regenerative Medicine Institute, Cedars-Sinai Medical Center, Los Angeles, California, USA.
authors.forename: Sandra
authors.initials: S
authors.lastname: De Mel
authors.affiliation: Department of Surgery, Cedars-Sinai Medical Center, Los Angeles, California, USA.|Board of Governors Regenerative Medicine Institute, Cedars-Sinai Medical Center, Los Angeles, California, USA.|Skeletal Biotech Laboratory, Hebrew University of Jerusalem, Jerusalem, Israel.
authors.forename: Maxim
authors.initials: M
authors.lastname: Bez
authors.affiliation: Board of Governors Regenerative Medicine Institute, Cedars-Sinai Medical Center, Los Angeles, California, USA.|iPSC Core Facility, The David and Janet Polak Stem Cell Laboratory, Cedars-Sinai Medical Center, Los Angeles, California, USA.
authors.forename: Loren
authors.initials: L
authors.lastname: Ornelas
authors.affiliation: Board of Governors Regenerative Medicine Institute, Cedars-Sinai Medical Center, Los Angeles, California, USA.|iPSC Core Facility, The David and Janet Polak Stem Cell Laboratory, Cedars-Sinai Medical Center, Los Angeles, California, USA.
authors.forename: Anais
authors.initials: A
authors.lastname: Sahabian
authors.affiliation: Skeletal Biotech Laboratory, Hebrew University of Jerusalem, Jerusalem, Israel.|iPSC Core Facility, The David and Janet Polak Stem Cell Laboratory, Cedars-Sinai Medical Center, Los Angeles, California, USA.|Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, California, USA.
authors.forename: Dhruv
authors.initials: D
authors.lastname: Sareen
authors.affiliation: Biomedical Imaging Research Institute, Cedars-Sinai Medical Center, Los Angeles, California, USA.
authors.forename: Xiaoyu
authors.initials: X
authors.lastname: Da
authors.affiliation: Department of Surgery, Cedars-Sinai Medical Center, Los Angeles, California, USA.|Board of Governors Regenerative Medicine Institute, Cedars-Sinai Medical Center, Los Angeles, California, USA.|Skeletal Biotech Laboratory, Hebrew University of Jerusalem, Jerusalem, Israel.
authors.forename: Gadi
authors.initials: G
authors.lastname: Pelled
authors.affiliation: Department of Surgery, Cedars-Sinai Medical Center, Los Angeles, California, USA.|Board of Governors Regenerative Medicine Institute, Cedars-Sinai Medical Center, Los Angeles, California, USA.|Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, California, USA.|Biomedical Imaging Research Institute, Cedars-Sinai Medical Center, Los Angeles, California, USA.
authors.forename: Wafa
authors.initials: W
authors.lastname: Tawackoli
authors.affiliation: Biostatistics and Bioinformatics Core, Samuel Oschin Comprehensive Cancer Institute, Cedars-Sinai Medical Center, Los Angeles, California, USA.
authors.forename: Zhenqiu
authors.initials: Z
authors.lastname: Liu
authors.affiliation: Department of Surgery, Cedars-Sinai Medical Center, Los Angeles, California, USA.|Board of Governors Regenerative Medicine Institute, Cedars-Sinai Medical Center, Los Angeles, California, USA.|Skeletal Biotech Laboratory, Hebrew University of Jerusalem, Jerusalem, Israel.|Biomedical Imaging Research Institute, Cedars-Sinai Medical Center, Los Angeles, California, USA.
authors.forename: Dan
authors.initials: D
authors.lastname: Gazit
authors.affiliation: Department of Surgery, Cedars-Sinai Medical Center, Los Angeles, California, USA zulma.gazit@csmc.edu.|Board of Governors Regenerative Medicine Institute, Cedars-Sinai Medical Center, Los Angeles, California, USA.|Skeletal Biotech Laboratory, Hebrew University of Jerusalem, Jerusalem, Israel.
authors.forename: Zulma
authors.initials: Z
authors.lastname: Gazit
keywords: Bone regeneration; Human induced pluripotent stem cells; Mesenchymal stem cells; Transforming growth factor-β