Effect of pregnancy on the proliferation of rat adipose-derived stem cells

Stem cell therapy faces many problems including poor survival rates and low viability. Enhancing the biological functions of stem cells improves efficacy of therapies. Estrogen, whose levels are elevated during pregnancy, affects the properties of bone marrow mesenchymal stem cells. Evidence suggests that adipose-derived stem cells (ADSCs), which are a type of adult mesenchymal stem cells, can be used in regenerative medicine. In fact, ADSCs from pregnant animals have been used in clinical therapies. However, the effect of the donor's reproductive status on proliferation of ADSCs is unknown. We investigated the effect of 17β-estradiol (E2) and progesterone (P) on the in vitro proliferation of ADSCs from laboratory rats. ADSCs were obtained from five different groups of 15 rats each - non-pregnant, pregnant, in perinatal period, non-pregnant and treated with E2, and non-pregnant and treated with P. Adhesion and viability of ADSCs were determined by MTT assay, and cell cycle was followed by flow cytometry. The proliferation rate of ADSCs from pregnant rats was significantly higher than those from the non-pregnant rats (P < 0.05); however, there was no statistically significant difference in proliferation rates during different phases of pregnancy (P > 0.05). Additionally, ADSCs from pregnant rats possess higher adhesion property in early stage (P1 passage) and higher proliferation rate than ADSCs from non-pregnant rats. Interestingly, ADSCs from non-pregnant rats that were treated with E2, but not those treated with P, showed higher proliferation rates than those from their untreated counterparts. These results suggest that the proliferative capacity and residence time in different cell cycle phases of ADSCs can be regulated by extrinsic factors such as estrogen concentration.