Elena R Andreeva^1,, Irina V Andrianova¹, Polina I Bobyleva¹, Ludmila B Buravkova¹

In adults, low differentiated stromal cells like fibroblasts, multipotent mesenchymal stromal cells, reticular cells etc. are important integrative components of tissue homeostasis and regeneration. The purpose of this study was to compare immunomodulatory activity and hematopoiesis-supportive capacity of two human stromal cell types: fetal fibroblasts (fFBs) and multipotent mesenchymal stromal cells (MMSCs) under different oxygen tension (20% vs. 5%). Surface immunophenotyping by flow cytometry revealed that MMSCs and fFBs were СD90, СD105, HLA-ABC positive and СD34, СD45, HLA-DR negative regardless of the О₂ concentration. The percentage of T-cells was relatively unchanged after 72 hours co-culture with stromal cells; the proportion of B- and NK-cells was increased, but the share of CD3⁺/HLA-DR⁺ cells was decreased when co-culturing with both MMSCs and fFBs. This reduction was statistically significant at 5% O₂ in comparison with 20% O₂ (p < 0.05). CD3⁺/CD25⁺ cells decreased after co-culture with both stromal cells in 20% O₂. This effect was revealed only for MMSC at 5% O₂. After 72 hours in co-culture with MMSCs, mononuclear cells from umbilical cord blood (CBMCs) maintained the same number of colony forming units (CFU) as compared with the initial CBMC suspension. The number of CFU was 30% higher at 5% O₂ than in 20% O₂ (p < 0.05). The CFU number in CBMCs after co-culture with fFBs decreased and a stimulatory effect of low oxygen was not observed. CBMCs that were adhered to MMSCs formed colonies of undifferentiated progenitors after 2 weeks of co-culture both at 20% and 5% O₂. Colonies were not found on fFBs. The immunomodulatory potency and the hematopoiesis-supportive capacity of stromal cells can vary depending on their tissue origin and may be modified by the partial pressure of oxygen.

human multipotent mesenchymal stromal cells from adipose tissue, human fetal fibroblasts, peripheral blood mononuclear cells, mononuclear cells from umbilical cord blood, coculture, immunosuppression, hematopoiesis, low oxygen tension