The mesenchymal stromal cell (MSC) is of great interest for its immunomodulatory and regenerative properties. However, to research and use these MSCs it is essential to identify and characterize them as such. They need to fulfill the MSCs' minimal criteria which assess the differentiation potential, cell surface markers, and adherence. In this study, cells donated from human bone marrow were identified as MSC according to the minimal criteria. Methods used were flow cytometry, immunofluorescent staining, and ELISA. Furthermore, the population was cultured in three different media (DMEM-LG with either 10% FBS, 2% FBS, or 10% FBS supplemented with 10% conditioned media from human urinary bladder carcinoma cells (T24)) for 21 days whereupon tested for the mesenchymal characteristics, cells were counted and size measured at every passage. All cultures maintained their mesenchymal character, however, cells grown in 2% FBS became a considerably more heterogenous population regarding cell size and granularity, perhaps because of senescence. Additionally, these cells somewhat decreased in proliferation and resulted in 1 x 106 cells after 21 days, however, this was not a significant decrease when compared to the 10% FBS culture which had 2.16 x 106 cells after 21 days (p=0.061). On the contrary, the culture supplemented with T24 conditioned media resulted in a significantly higher cell count with 4.75 x 106 cells (p=0.008). Further studies could investigate which components in the conditioned media contributed to the proliferation. Moreover, the cell population in this study could not be characterized as MSC with certainty as additional cell surface markers should be tested.

Background: Mesenchymal stromal cells (MSCs) are multipotent cells that can differentiate into various cell types and possess immunomodulatory and anti-inflammatory effects, making them interesting candidates for therapeutic applications. MSCs are present in small quantities in tissues like bone marrow and therefore need to be expanded while preserving their essential characteristics. They should adhere to plastic, differentiate into osteocytes, adipocytes and chondrocytes and express specific cell surface markers. Currently, the “golden standard” culture media supplement is fetal bovine serum (FBS). However, there is a potential contamination risk of MSCs by xenogeneic and zoonotic infectious agents, which can trigger an immune response. As an alternative, xeno-free serum supplements derived from human sources, e.g., human serum (HS) can be used.  Aim: This study aimed to identify and characterize human bone marrow derived MSCs and examine the effects different supplements have on the cells.  Methods: MSCs were cultured in 10% FBS, 2% FBS and 10% HS for 20 -21 days. Differentiation was induced and the potential was detected with immunocytochemistry. Cell surface markers CD73, CD90, CD105 and CD45 were identified with flow cytometry.  Results and Conclusion: There was no significant difference in morphology, differential potential or immunophenotype between the different serum conditions. However, HS-supplemented culture media resulted in a significantly higher number of cells with 1 x 107 cells after 20 days without affecting their differentiation potential and immunophenotype in comparison to 10% FBS with 2.2 x 106 cells (p=0.0004). MSCs cultured in 2% FBS resulted in the least number of cells (9.9 x 105) after 21 days of expansion.