Human Platelet Lysates Promote the Differentiation Potential of Adipose-Derived Adult Stem Cell Cultures

Adipose tissue from liposuction is a rich source for human mesenchymal stem cells. This type of adult stem cell is ethically acceptable, that paved the way for research on their potential use in regenerative medicine. However, any clinical application of adult stem cells is impeded by the use of FBS as an animal-derived growth supplement. In addition, stem cell cultures gained importance as innovative human-based alternative to animal testing, in vitro toxicology, drug testing and safety assessment. Thus, animal-derived component-free culture protocols are mandatory for a successful application of human stem cell-based testing systems under humanized conditions.Recently, we succeeded in using human platelet lysates (PL) as a serum alternative in the cell culture of a number of human and animal cell lines, and human mesenchymal stem cells. PL were prepared as cell-free extracts from activated donor thrombocytes.The minimal criteria defining multipotent mesenchymal cells are (1) the capacity to adhere to plastic, (2) the expression of specific surface antigens (e.g. CD73, CD90, CD105) for undifferentiated state, and (3) the potential of the cells to differentiate into the adipogenic, chondrogenic and osteogenic lineage. In the present study, adipose-derived stem cells (ADSC) were used as cell model. ADSC were maintained under PL or FBS and then switched to the respective media to induce mesodermal differentiation. Differentiation endpoints were assessed by phase-contrast microscopy and by histochemical staining: (1) lipid droplets in adipocytes were stained by Oil red O, (2) proteoglycans in chondrogenic spheroids were detected by toluidineblue, and fine structure of spheroids was monitored by scanning electron microscopy, and (3) calcium deposits in differentiated osteoblasts were stained with silver nitrate (von Kossa staining). Adipogenic differentiation was further confirmed by quantitative real-time PCR of selected marker genes (PREF1 vs. FABP4). There were no differences between FBS- and PL-grown ADSC, indicative for retention of the differentiation potential of ADSC under animal-derived component-free culture conditions in PL-supplemented culture media. The degree of adipogenic and osteogenic differentiation was even more pronounced under PL compared to FBS