Megakaryocytes are large cells that are vital for haemostasis through the production of platelets, which are critical for clotting. Despite their importance, in vitro production of megakaryocytes and platelets for human use is inefficient, and the main supply of platelets still relies on human plasma donations.
Single cell sequencing of megakaryocytes has revealed cellular heterogeneity within the bone marrow. This finding suggests the possibility that in vitro culture of megakaryocytes might not produce optimal platelet producing megakarycoyte.
In the mouse bone marrow, megakaryocytes mature from haematopoietic stem cells (HSCs). The most important cytokine in this process is thrombopoietin. HSCs stimulated with thrombopoietin can follow three known developmental pathways: canonical, steady-state, and megakaryocyte-biased. Different lineage fate decisions select which pathway is followed and intermediate cell types developed. Ultimately, these cells mature into megakaryocyte progenitors which undergo terminal maturation and polyploidization to form mature megakaryocytes.
We performed indexed FACS sorted single cell sequencing on a time course of mouse haematopoetic stem and progenitor cells cultures from which mature megakaryocytes were developed after thrombopoietin stimulation. This multiomic approach linked antibody profiles with their transcriptional identity allowing us to see if cellular identity correlates with canonical flow cytometry profiles as these cells matured. Comparison with a single cell sequencing in vivo dataset containing all known megakaryocyte precursor cells revealed which cell type intermediates were most common, indicating which of the three pathways were most predominant and whether cells transcriptionally matched their in vivo counterpart as defined by surface markers or formed unique clusters. So far, two distinct in vitro derived megakaryocytes were identified, one matching a group found in the bone marrow and one unique to this system. Further analysis will reveal how in vitro megakaryocyte production compares to their in vivo development and improve megakaryocyte - and ultimately platelet - production.