Stem cell conditioned medium for cell-free therapies.

Stem cells become an effective tool for treatment of a variety of defects and diseases. Recently, it appears that the therapeutic effect of stem cells lies not only in their integration and differentiation into cells of the tissue, but especially in their paracrine activity, i.e. the ability to secrete trophic and growth factors, cytokines and chemokines that have regenerative and anti-inflammatory effects. Conditioned medium (CM) containing secretory products of stem cells can thus be used in cell-free therapy which represents an alternative to the cell-based therapy, with advantage of lower risks, the possibility of allogenic administration and mass production. Preclinical studies confirm that the therapeutic effect of CM is comparable to the effect of the application of stem cells. The aim of this paper is to summarize the results of studies using CM from different types of stem cells in regenerative medicine and simultaneously develop an overview of the factors that can modify cellular secretion and the composition of CM.