Molecular signature and regulatory network of human umbilical cord mesenchymal stromal cells as a niche for hematopoietic stem cells and progenitors.

The fate of hematopoietic stem cells (HSCs) is determined by a complex regulatory network supporting self-renewal and quiescence within a niche. Umbilical cord mesenchymal stromal cells (UC-MSCs) are classified as an alternative niche for the expansion of hematopoietic stem and progenitor cells (HSPCs). The molecular mechanisms by which UC-MSCs regulate hematopoiesis are still not fully understood. In this study, the cocultures of UC-MSCs and umbilical cord blood CD34+ (UCB-CD34+) cells were established. Immunophenotype, cell proliferation, and hematopoietic function of UCB-CD34+ cells were evaluated on days 0 to 7. UC-MSCs promoted UCB-CD34+ cell proliferation but were less effective at preserving their stemness. Notably, UC-MSCs promoted the myeloid lineage commitment, significantly observed on day 3. Integrative transcriptomic analysis highlighted the molecular signature and regulatory networks of UC-MSCs. The long non-coding RNA (lncRNA)-RNA binding protein (RBP) interaction network and lncRNA cis- and trans-regulatory networks were evident. The significant 3-gene modules and a set of 10-hub genes were identified in the protein-protein interaction (PPI) network, including RPS16, CD74, RPL35, COX7C, RPL38, RPS28, RPS27, RPS10, TARDBP, and TOMM7. These findings exemplify the niche activity of UC-MSCs in regulating cell differentiation, genomic stability maintenance, and modulation of the hematopoietic supportive niche. The transcriptional landscape, together with the identified regulatory networks, gene modules, and key hub genes provide new insights into the molecular mechanisms of UC-MSCs and establish a basis for refining ex vivo culture systems for therapeutic HSC expansion.