Reprogramming of mouse amniotic fluid cells using a PiggyBac transposon system

Stem cells (SC) are present in all organisms and possess the ability of keeping the undi erentiated state along the life span of a living subject or undergoing di erentiation on more specialized cell types a er speci c stimuli. Fetal SC are generally de ned as broadly multipotent SC because they are more prone to turn into di erent cell types than their adult counterpart. Among those, cKit (CD117) positive cells selected from the amniotic uid (AF) and de ned as amniotic uid stem (AFS) cells may be relevant to therapeutic approaches because they are easy to access1,2. AFS cells possess enhanced attitude of growing in culture, along with di erentiation ability toward mes- oderm, ectoderm and endoderm lineages, and can be reprogrammed without viral transfection3. e self-renewal capacity and broad multipotency of AFS cells have been proved not only in vitro, but also in vivo; in particular it has been demonstrated the ability of AFS cells to replenish the hematopoietic system and the muscle SC niche also a er secondary transplantation4,5, and to participate in mammary gland regeneration6 highlighting in the AF the presence of cells with stemness characteristics. According to the studies that have located and characterized the SC niches in mammalian tissues using in situ labeling systems, concrete evidences proved that niches are fun- damental to maintain SC pool and functions7–9. Along the years it has been proved that distinct classes of niches harbor di erent SC such as the hematopoietic, the neural and the mesenchymal (epidermis, gut and skeletal muscle)8–12. Postnatal hematopoiesis occurs mainly in the bone marrow in the best characterized SC niche, where hematopoietic stem and progenitor cells reside13. e niche is responsible to de ne the microenvironment where quiescent SC are located before speci c signals accomplish the dormant state and activate di erentiation process. In particular, this dynamic compartment ful ls mainly three functions through secreted or cell surface molecules: it controls SC proliferation, determines the fate of SC daughters and protects SC from exhaustion or death.