An In vitro Model of a Hemopoietic-Inductive Microenvironment Using Sintered Hydroxyapatite

We studied the role of Hydroxyapatite (HAP) in a hemopoietic-inductive microenvironment (HIM) by an in vitro, long-term, human marrow culture method. Human bone marrow mononuclear cells were cultured on a disc of HAP and a culture dish (control). The numbers of stromal cells at the time of confluence were almost the same between the HAP dish and the control dish. Strong adhesion of the stromal cells to HAP was observed. At the initial stage of a long-term culture, the number of the non-adherent cells was increased more in the control dish than in the HAP dish, but adherent cell numbers were increased more in the HAP dish by 3- to 14- fold. Progenitors in non-adherent cells were decreased after three weeks, while those in the adherent cells were maintained in the both dishes. In the first week, progenitors in non-adherent cells were increased more in HAP. Our results newly indicate that HAP contributes to the proliferation of progenitors and their fixation to stroma. This study obtained basic data on in vitro culturing of human bone marrow mononuclear cells with HAP. This research is the first trial to establish a more favorable in vitro model of HIM, and to prove that HAP is a component of HIM in humans.