The effect of n-cadherin expressed in stromal cell derived osteoblast on hematopoietic stem cell properties

Abstract

Ex vivo expansion of Hematopoietic stem cells (HSCs) has been suggested as a way to overcome the limitation of hematopoietic cell number for clinical transplantation. However, there is no culture system that could promote both HSCs proliferation and maintenance. Here, we generate the ex vivo culture system using mouse marrow stromal cell-derived osteoblasts (MOBs) combine with noggin (BMP antagonist) overexpressed stromal cells (3T3 noggin), so called M3B feeder. This feeder system shows their ability to promote hematopoietic cell proliferation by increasing CD45+ cell more than 20 fold compared with MOBs alone. Moreover, we found that the LTC-IC number of cells derived from cell cultured on M3B feeder was comparable to MOBs. Interestingly, type of CFC of LTC-IC was changed from CFUM (colony forming unit macrophage) to CFU-GEMM (colony forming unit granulocyte, erythrocyte, macrophage and megakaryocyte) when cultured LSK cells on M3B feeder. This study proposes that combination of two cell types could generate proper microenvironments which both promote HSC maintenance and proliferation. We also used this new culture system to investigate the role of Ncadherin in osteoblastic niche. We found that overexpression of N-cadherin in osteoblasts limits number of CD45+ produced from M3B feeder and increases the number of CFC at week 2 of culture. This finding supports the important role of Ncadherin in HSC maintenance.