The Quality Control of Mesenchymal Stromal Cells by in Vitro Testing of Their Immunomodulatory Effect on Allogeneic Lymphocytes

Mesenchymal stromal cells (MSC) represent a promising treatment of graft-versus-host disease (GVHD) in patients after allogeneic haematopoietic stem cell transplantation. We performed co-cul-tivation experiments with non-specifically stimulated lymphocytes to characterize the immunosuppressive activity of MSC. MSC influenced expression of some activation antigens. CD25 expression was lower with MSC and reached 55.2 % vs. 84.9 % (CD4(+), P = 0.0006) and 38.8 % vs. 86.6 % (CD8(+), P = 0.0003) on day +4. Conversely, CD69 antigen expression remained higher with MSC (73.3 % vs. 56.8 %, P = 0.0009; 59.5 % vs. 49.7 %, ns) and its down-regulation along with the culture time was less pronounced. MSC reduced proliferation of the stimulated lymphocytes. The cell percentages detected in daughter generations were decreased (32.82 % vs. 10.68 % in generation 4, P = 0.0004 and 29.85 % vs. 10.09 % in generation 5, P = 0.0008), resulting in a lower proliferation index with MSC (1.84 vs. 3.65, P < 0.0001). The addition of MSC affected expression of some cytokines. Production of pro-inflammatory cytokines was decreased: IL-6 (19.5 vs. 16.3 MFI; P < 0.0001 in CD3(+)/CD4(+) and 14.5 vs. 13.2 MFI; P = 0.0128 in CD3(+)/CD8(+)), IFN-gamma (13.5 vs. 12.0 MFI; P = 0.0096 in CD3(+)/CD4(+)). Expression of anti-inflammatory IL-10 was only slightly increased after the addition of MSC (ns). The analysis confirmed the immunomodulatory activity of MSC. The functional tests have proved to be an important part of the quality control of the advanced therapy cellular product intended for GVHD treatment. Future research should focus on the interaction between MSC and the patient immune environment more closely.