Reprogramming of human fibroblasts into multipotent cells with a single ECM proteoglycan, fibromodulin

Pluripotent and/or multipotent stem cell-based therapeutics are a vital component of tissue engineering and regenerative medicine. The generation or isolation of safer and readily available stem cell sources will significantly aid clinical applications. We report here a technique using a single molecule, recombinant human fibromodulin protein (FMOD), to reprogram human fibroblasts into multipotent cells. Like virally-induced pluripotent stem (iPS) cells, FMOD reprogrammed (FReP) cells express pluripotency markers, form embryoid bodies (EBs), and differentiate into ectoderm, mesoderm, and endoderm derivatives in vitro. Notably, FReP cells regenerate muscle and bone tissues but do not generate teratomas in vivo. Unlike iPS cells, undifferentiated FReP cells proliferate slowly and express low proto-oncogene c-MYC and unexpectedly high levels of cyclin-dependent kinase inhibitors p15(Ink4B) and p21(WAF1/Cip1). Remarkably, in a fashion reminiscent of quiescent stem cells, the slow replicative phenotype of undifferentiated FReP cells reverses after differentiation induction, with differentiating FReP cells proliferating faster and expressing less p15(Ink4B) and p21(WAF1/Cip1) than differentiating iPS cells. Overall, single protein, FMOD-based, cell reprograming bypasses the risks of mutation, gene instability, and malignancy associated with genetically-modified iPS cells, and provides an alternative strategy for engineering patient-specific multipotent cells for basic research and therapeutic application.