[The Maintenance Effects of Extracellular Vesicles Derived from Placental Tissue and Mesenchymal Stem Cells on Hematopoietic Stem and Progenitor Cells].

OBJECTIVE

To investigate the role of extracellular vesicles (EVs) derived from placental tissue and placental mesenchymal stem cells in supporting the growth and function of adult hematopoietic stem and progenitor cells (HSPCs), so as to optimize their culture system.

METHODS

EVs were isolated from mouse placental tissue (PL-EV) and placental mesenchymal stem cells (PL-MSC-EV). These EVs were co-cultured with 3 000 adult bone marrow LKS+ (lineage- c-Kit+ Sca-1+ ) cells for 72 hours at concentrations of 0, 1, 10, 50, 100, and 200 μg/ml. The proportion and absolute count of LKS+ cells after co-culture were analyzed by flow cytometry, while their self-renewal and multi-lineage differentiation potential were evaluated using colony-forming unit (CFU) assays.

RESULTS

Compared to the blank control group, the proportion of LKS+ cells were significantly increased in PL-EV groups at concentrations ≥10 μg/ml after 72 hours of co-culture. Notably, LKS+ cells co-cultured at the concentration of 10 μg/ml exhibited the highest absolute count (899±171) and the highest proportion of LT-HSCs (LKS+ CD135- CD34-) (0.67%±0.07%). In the PL-MSC-EV co-culture system, the absolute count of LKS+ cells peaked at the concentration of 1 μg/ml (1011±99 cells), though the proportion of LT-HSCs was relatively low (0.15%±0.05%). The comparison between these two culture systems revealed that PL-EV at 10 μg/ml and PL-MSC-EV at 1 μg/ml displayed the most pronounced effects on LKS+ cell proliferation, but with no significant difference between them. CFU assays showed that, in the PL-EV culture system, the number of LKS+ colony formed in 1 and 10 μg/ml groups was not significantly different compared with the blank control group. In contrast, in the PL-MSC-EV system, the highest LKS+ colony-forming capacity was observed when co-cultured with 1 μg/ml PL-MSC-EV, while a significant reduction was noted at concentrations above 10 μg/ml.

CONCLUSION

PL-EV and PL-MSC-EV effectively support the growth and function of HSPCs. And PL-MSC-EV exhibits a superior efficacy in preserving the stemness of LKS+ cells, thus suggesting its potential for optimizing culture systems of HSPCs.