ENGINEERING A HUMAN BONE-MARROW MODEL - A CASE-STUDY ON EX-VIVO ERYTHROPOIESIS

Bone marrow, with its intricate, three-dimensional tissue structure fa cilitating cell-cell interactions, provides a microenvironment Support ing the production of hundreds of billions of multilineal blood cells everyday. We have developed a three-dimensional bone marrow culture sy stem in which marrow cells are cultured in a reactor packed with porou s microspheres. The culture supports a three-dimensional growth config uration and multilineal hemopoiesis mimicking the bone marrow in vivo. We studied ex vivo human erythropoiesis using the three-dimensional c ulture system. The system sustained extensive erythropoiesis at low er ythropoietin concentrations (0.2 U/mL), plus stem cell factor, interle ukin-3, granulocyte-macrophage colony-stimulating factor, and insulin- like growth factor-I. Erythroid cell production lasted for more than 5 weeks, and the percentage of erythroid cells in the nonadherent cell population was approximately 60%. Flow cytometric analysis using cell surface markers specific for erythroid cells (CD71 and glycophorin-A) indicated that the culture produced early, intermediate, and late eryt hroid cells. As the culture progressed, the erythroid cell population shifted gradually toward mature cell types. When compared to the three -dimensional culture, the traditional flask cultures failed to support extensive erythropoiesis under the same conditions. This indicates th at the three-dimensional bone marrow culture system provides a microen vironment conducive to erythropoiesis under more physiological conditi ons and is a better bone marrow model.