Expression of the cell adhesion molecule E-cadherin by the human bone marrow stromal cells and its probable role in CD34+ stem cell adhesion

Bone marrow stroma is the physical basis of the haematopoietic microenvironment and regulates several key features of stem cell proliferation and differentiation. It plays a crucial role in maintaining haematopoietic homeostasis. Earlier studies have shown that this is achieved through interactions with the extracellular matrix and specific molecules called the cell adhesion molecules (CAMs). In this paper, we show that E-cadherin, a cell adhesion molecule which plays a crucial role in cell-cell aggregation during development, is also present in the bone marrow stroma. The expression of the CAM can also be demonstrated on a subset of CD34(+) stem cells. Stromal expression of E-cadherin is decreased when treated with lymphokine mixture, phytohaemagglutinin-treated-leukocyte-conditioned medium (PHA-LCM). This is the reverse of ICAM-I expression, which increases with PHA-LCM treatment. E-cadherin shows homotypic and homophilic interaction and its presence on a subset of CD34+ cells leads to speculation on whether this CAM has a role in adherence of primitive stem cells to the marrow stroma. (C) 1998 Academic Press.