The Sources and Roles of Thrombopoietin in Haematopoietic Stem Cell Self-Renewal

 All mature blood cell lineages are derived from a pool of multi-potential haematopoietic stem cells (HSCs). HSCs have the ability to differentiate into committed progenitors whilst retaining the ability to self-renew and thus maintain the HSC pool. Thrombopoietin (TPO) is an indispensable cytokine for HSC self-renewal (as well as in megakarypoiesis). HSCs reside in discrete anatomical locations within the bone marrow, termed niches. There is evidence that local production of TPO from specialised cells within the HSC niche occurs, yet the exact cells responsible are largely unidentified. We aim to identify the TPO-producing cells within the HSC niche and to determine to what extent they are needed for HSC self-renewal.