The present invention provides a novel method for enhancing engraftment of haematopoetic stem cells by an ex-vivo pretreatment comprising the steps of obtaining a sample containing haematopoetic stem cells and admixing a prostacyclin analogue to obtain a mixture, incubating said mixture for a period of time sufficient to stimulate G alphas-signalling in said cells and optionally and isolating said stimulated cells. Further, a composition comprising a prostacyclin analogue for use in the treatment of individuals undergoing haematopoetic stem cell transplantation is provided.
