Effect Of Different Sera On The Senescence Process Of Mesenchymal Stem Cells

Mesenchymal stem cells (MSCs) hold great therapeutic potential in clinicaltreatment. However, MSCs undergo replication senescence due to multiple passagesduring the in vivo expansion process, and thus some biological characteristics arechanged, which affects the clinical application and research. Some studies haveproved that the microenvironment of cells are closely related to the stem cell aging,but the impact of different sera on cellular aging is still unclear. Currently fetal bovineserum (FBS) and calf serum (CS) are the most commonly supplements for the cultureof MSCs. Therefore, in this experiment, the effects of fetal bovine serum and calfserum on the senescence process of MSCs were compared.Mesenchymal stem cells from human umbilical cord were obtained by tissueadherent culture. The typical separate method was improved by a secondary adherentculture of tissues that was generally discarded after culture. Some fusiform cellscrawled out from umbilical cord tissues after cultivation for5days and some cellularcolonies were formed about at10days. Then the tissues were removed and furthercultured in fresh dishes.More cells appeared again on day2and cellular colonies wereformed on day5. The biological characteristics of the cells obtained were thenanalyzed. The isolated cells expressed CD90, CD105and were negative for themarkers of CD34, CD45, HLA-DR. The results demonstrated that the cells from thesecond tissue culture possessed the feature of MSCs and more primary umbilical cordMSCs were acquired through the improved method. Meanwhile, the biologicalcharacteristics of the mesenchymal stem cells derived from umblical cord andplacenta were compared and no significant differences were found.Cells were seeded in dishes at the identical density and were cultured in mediumsupplemented with FBS or CS. The population doublings and the cumulativepopulation doublings were calculated by cell count at the time of passage. Cells inthree phases with the identical cumulative population doublings were selected forbiological functional evaluation, including proliferation, differentiation, apoptosis andsenescence-related gene expression. The results showed that with passaging, MSCsdemonstrated alteration of cell morphology, decrease of cell proliferation anddifferentiation potential. Meanwhile, the activity of β-galactosidase and the ROSlevels, as well as the expression of senescence associated genes were increased.However, in the same culture span, MSCs cultured in medium supplemented with FBS shown more potential in proliferation and differentiation, but low ratio ofapoptotic cells and senescence related gene expression, compared with MSCs culturedin medium supplemented with CS. These data demonstrated that FBS provided anideal microenvironment for MSCs and preserved MSCs properties, while calf serumaccelerated the senescence pcocess of MSCs.