Application of conditioned medium from mesenchymal stromal cells in the protocol for ex vivo production of megakaryocytes and platelets

Abstract

Introduction. Of interest is the use of a conditioned medium from mesenchymal stromal cells in order to increase the expansion of CD34+  hematopoietic stem cells (HSCs).Aim — to analyze the effi cacy of two methods of ex vivo production of human megakaryocytes and platelets from CD34+ cord blood HSC using conditioned media from mesenchymal stromal cells and IMDM. Methods. Two cultivation methods that differ from each other by medium composition were compared. As a control of antigen expression of the donor, venous blood platelets were used. CD34+ HSCs were isolated from mononuclear fraction of cord blood using the immunomagnetic selection technique. The resulting cells were introduced at a concentration of 1 × 104  cells/mL into 24-well plates and cultured at 39 °C and 10 % CO2  for the first 7 days, after which the conditions were changed to 37 °C and 5 % CO2  and cultured for 14 days. In Group 1, up to day 7, the culture was performed using conditioned medium from mesenchymal stromal cell containing TPO (30 ng/mL), SCF (2 ng/mL), IL-6 (7.5 ng/mL), IL-9 (13.5 ng/mL), and in Group 2 a IMDM medium with the same cytokine cocktail was used. The cells were calculated using haemocytometer. CD34, CD41a, CD42b expression was evaluated using fl ow cytometry. Statistic data was processed with using R-language. The differences were evaluated as statistically signifi cant at signifi cance level p < 0.05.Results. Megakaryocyte production was observed starting from day 7 of culture. The expression level using conditioned medium from mesenchymal stromal cells (Group 1) according to CD41a was 5.84 ± 0.33 % versus 10.43 ± 1.08 % using IMDM medium (Group 2). On day 13 the ratio increased up to 42.05 ± 1.71 % in Group 1 and 61.78 ± 1.71 % in Group 2. CD41a+ megakaryocytes of Group 1 expressed the CD42b marker at the level of 96.85 ± 1.06 % versus 88.7 ± 0.56 % in Group 2. With the application of MSC conditioned medium the average number of nucleated cells was signifi cantly higher on the day 11 and it was equal 326.016 ± 1.86 × 104  cells/mL vs 197.26 ± 10.55 × 104  cells/mL in IMDM medium. Proplatelet formation was observed with microscopy staring from the day 12. The ratio of CD41a+ /CD42b+  platelets was 59.5 ± 3.85 % in conditioned medium, 65.9 ± 8.72 % in IMDM, and 96.11 ± 0.89 % in control platelets derived from venous blood.Conclusion. It was demonstrated that the use of MSC conditioned medium leads to an increase in the expansion of nucleated cells, however it decreases the rate of differentiation in megakaryocytes.