Human Muscle-Derived Vascular Stem Cells Can Support Hematopoietic Stem/Progenitor Cells In Vitro

Background: The normal hematopoiesis of the body depends on the interaction between hematopoietic stem/progenitor cells (HSPCs) and mesenchymal stem cells (MSCs) that support the growth and development of hematopoietic cells. However, the separation of MSCs from bone marrow is somewhat limited, and the researchers have turned their attention to stromal cells outside the bone marrow. As the largest organ of human body, skeletal muscle tissue stores a variety of muscle-derived vascular stem/progenitor cells, including muscle-derived pericytes/perivascular cells (MD-PCs) and skeletal muscle derived myoendothelial cells (MECs). Studies have shown that MD-PCs and MECs are similar to bone morrow-derived MSCs (BM-MSCs), which express the surface markers of MSCs and have the potential of multidirectional differentiation. However, very few researches have been done on whether MD-PCs and MECs, like MSCs, can support HSPCs expansion/proliferation, differentiation and possible hematopoietic regulation mechanisms, so the hematopoietic support of these cells remains to be studied. Objective: To identify the biological characteristics of CD146⁺ PCs and MECs isolated from human skeletal muscle and to study their supporting effect on umbilical cord blood (UCB) CD34⁺ cells in vitro. Methods: Human skeletal muscle-derived CD146⁺ PCs and MECs were isolated and purified by multiparameter flow cytometry and their biological characteristics were identified. The coculture system for CD34⁺ cells with CD146⁺ PCs and MECs as trophoblastic layer, and BM-MSCs as positive control, was established in vitro, respectively. The main outcome measures, including the number and immunophenotype of the cells, the colony formation ability, the expression levels of cytokines were analyzed and compared at 1, 2, and 4 weeks after coculture. Results: CD146⁺ PCs and MECs were isolated by multiparameter flow cytometry and their purity of was 92.55% ± 0.55% and 96.60% ± 1.14% (n = 18), respectively. Both of the cells could be differentiated into osteoblasts, chondrocytes, adipocytes, and myocytes. Compared with the positive control group of BM-MSCs, the experimental group of CD146⁺ PCs and MECs showed no significant differences in cell number, colony formation ability and immunophenotype (CD45⁺, CD34⁺ CD33^-, CD14⁺, and CD10⁺/CD19⁺; p  > 0.05, n = 5), separately. The expression levels of cytokines in the culture supernatants of CD146⁺ PCs group, MECs group, and BM-MSCs group were measured by ELISA. The expression levels of TPO, IFN-γ, HGF, MCSF, and SCF cytokines were different among CD146⁺ PCs, MECs, and human BM-MSCs (p < 0.05, n = 3). Due to the no nourishing feeder layer in culture system, the number of CD34⁺ cells decreased significantly in the 1st week and no cells survived in the 2nd week. Therefore, the cell immunophenotype and colony analysis and the expression levels of cytokines could not be performed. Conclusion: In summary, CD146⁺ PCs and MECs from human skeletal muscle, like human BM-MSCs, have hematopoietic support capacity in vitro.