Reprogramming somatic cells into an embryonic stem (ES) cell-like state, or induced pluripotent stem (iPS) cells, has emerged as a promising new venue for customized cell therapies. In this study, we performed directed differentiation to assess the ability of murine iPS cells to differentiate into bone, cartilage and fat in vitro and to maintain an osteoblast phenotype on a scaffold in vitro and in vivo. Embryoid bodies derived from murine iPS cells were cultured in differentiation medium for eight to twelve weeks. Differentiation was assessed by lineage specific morphology, gene expression, histological stain and immunostaining to detect matrix deposition. After 12 weeks of expansion, iPS derived osteoblasts were seeded in a gelfoam matrix followed by subcutaneous implantation in syngenic ICR mice. Implants were harvested at 12 weeks, and histological analyses of cell, mineral and matrix content were performed. Differentiation of iPS cells into mesenchymal lineages of bone, cartilage and fat was confirmed by morphology, and expression of lineage specific genes. Isolated implants of iPS cell derived osteoblasts expressed matrices characteristic of bone, including osteocalcin and bone sialoprotein. Implants were also stained with alizarin red and von Kossa, demonstrating mineralization and persistence of an osteoblast phenotype. Recruitment of vasculature and microvascularization of the implant was also detected. Taken together, these data demonstrate functional osteoblast differentiation from iPS cells both in vitro and in vivo and reveal a source of cells which merit evaluation for their potential uses in orthopaedic medicine and understanding of molecular mechanisms of orthopaedic disease.

Induced pluripotent stem cells (iPSCs) hold great promise for regenerative medicine; however, their potential clinical application is hampered by the low efficiency of somatic cell reprogramming. Here, we show that the synergistic activity of synthetic modified mRNAs encoding reprogramming factors and miRNA-367/302s delivered as mature miRNA mimics greatly enhances the reprogramming of human primary fibroblasts into iPSCs. This synergistic activity is dependent upon an optimal RNA transfection regimen and culturing conditions tailored specifically to human primary fibroblasts. As a result, we can now generate up to 4,019 iPSC colonies from only 500 starting human primary neonatal fibroblasts and reprogram up to 90.7% of individually plated cells, producing multiple sister colonies. This methodology consistently generates clinically relevant, integration-free iPSCs from a variety of human patient’s fibroblasts under feeder-free conditions and can be applicable for the clinical translation of iPSCs and studying the biology of reprogramming.

Recent breakthroughs in the generation of induced pluripotent stem cells (iPSCs) have provided a novel renewable source of cells with embryonic stem cell-like properties, which may potentially be used for gene therapy and tissue engineering. Although iPSCs have been differentiated into various cell types, iPSC-derived keratinocytes have not yet been obtained. In this study, we report the in vitro differentiation of mouse iPSCs into a keratinocyte lineage through sequential applications of retinoic acid and bone-morphogenetic protein-4 and growth on collagen IV-coated plates. We show that iPSCs can be differentiated into functional keratinocytes capable of regenerating a fully differentiated epidermis, hair follicles, and sebaceous glands in an in vivo environment. Keratinocytes derived from iPSCs displayed characteristics similar to those of primary keratinocytes with respect to gene and protein expression, as well as their ability to differentiate in vitro and to reconstitute normal skin and its appendages in an in vivo assay. At present, no effective therapeutic treatments are available for many genetic skin diseases. The development of methods for the efficient differentiation of iPSCs into a keratinocyte lineage will enable us to determine whether genetically corrected autologous iPSCs can be used to generate a permanent corrective therapy for these diseases.