Hematopoietic stem cells ( KKM ) are able to renew the transplant patient's hematopoietic system . Renewal is preceded by their implantation ( called homing ) in the hematopoietic microenvironment of the bone marrow . Mechanisms regulating cell implantation in the bone marrow are therefore one of the issues on which they focus research hematologists clinical and experimental studies. Adhesion molecules are identified , proteolytic enzymes and chemotactic factors involved in cell engraftment after transplantation.