The influence of extracellular matrix proteins and mesenchymal stem cells on erythropoietic cell maturation

Background and Objectives As part of the bone marrow niche, cellular and acellular components like mesenchymal stem cells (MSCs) and extracellular matrix (ECM) proteins influence human haematopoiesis. To identify factors able to improve the in vitro generation of red blood cells (RBCs), we investigated the effect of these factors on proliferation and differentiation of human haematopoietic stem cells (HSCs) into erythroid cells. Material and Methods Granulocyte colony-stimulating factor-mobilized CD34⁺ HSCs were cultured for 16days using an in vitro erythropoiesis assay as described previously (by our group). The HSCs were co-cultured with MSCs in either direct or indirect contact and with different ECM proteins (fibronectin, laminin, collagen and a mixture of ECM proteins, called ECM gel). Results Co-culturing of HSCs with ECM gel improved cell viability, and the presence of laminin slightly increased the maturation into enucleated RBCs. HSC expansion could not be improved by addition of any of the ECM proteins investigated. In contrast, fibronectin inhibited erythroid formation. Co-culturing of HSCs with MSCs generally stimulated cell viability and HSC proliferation, however, in favour of the myeloid lineage. In summary, of all investigated factors, only laminin and ECM gel had a supportive effect on RBC development under the described in vitro culture conditions.