The origin, in vitro differentiation, and stemness specificity of progenitor cells.

Since the successful collection of the first progenitor stem cells (SCs), there has been an increased interest in these cells as a model for undiscovered and unlimited potential of differentiation and development. Additionally, it was shown that SC populations display an ability to form pluripotent and/or totipotent cell populations. It was found that human ovarian granulosa cells (GCs) maintain a large capacity for differentiation into several other cell lineages, such as chondrogenic, osteogenic, neurogenic, and adipogenic, particularly during long-term, in vitro culture. In these cases, the specific media supplements that promote various pathways of differentiation, such as leukemia-inhibiting factor (LIF) and/or FSH, are well recognized. However, these are only some examples of the differentiation possibilities of human SCs in vitro and other pathways still require further investigation. Many SC populations, which are directed to differentiate into specific cell types, are also successfully used in several human disease therapies, e.g. leukemia. Moreover, SCs are used for tissue scaffold construction in patients with respiratory and cardiovascular diseases. In this review, the most recent knowledge about the in vitro growth and differentiation capacity of SCs is presented. Furthermore, we discuss the possible worldwide application of SCs in advanced cell and tissue bioengineering. In conclusion, it is suggested that, in the future, SCs will be a basic strategy in human therapy, and their use will open new gates in regenerative and reconstructive medicine in the 21st century.