Diverse effects of anti‐CD44 antibodies on the stromal cell‐mediated support of normal but not leukaemic (CML) haemopoiesis in vitro

Abstract

Summary.We have identified three non-cross-reacting antihuman CD44 monoclonal antibodies that have significant positive or negative (or no) effects on normal human haemopoiesis in the long-term culture (LTC) system. These effects manifested as increases or decreases in the number of LTC-initiating cells (LTC-IC), and the number of colonyforming cells (CFC) recovered from cultures in which either unseparated or highly purified CD34 þ CD38 ¹ normal marrow cells were placed on pre-established normal marrow feeder layers in the presence or absence of each antibody. The effects seen were rapid and sustained, and dependent on the presence of a preformed feeder layer.Interestingly, the same anti-CD44 antibodies had no effect on the maintenance of leukaemic (Ph þ ) progenitors (from patients with chronic myeloid leukaemia) when these cells were cultured on preformed feeder layers established from normal marrow. CD44 appears to be part of a mechanism by which stromal elements can regulate primitive normal haemopoietic cells but not their leukaemic (Ph þ ) counterparts.

Expression of CD44 variant exons in acute myeloid leukemia is more common and more complex than that observed in normal blood, bone marrow or CD34+ cells

“…[3][4][5] Antibodies to CD44 can dysregulate the production of myeloid and lymphoid cells in long-term bone marrow cultures with some CD44 antibodies inhibiting hematopoietic cell output while others enhance it. 6 Taken together, these data indicate that CD44 is important for the interaction of hematopoietic cells with the bone marrow microenvironment and is involved in the regulation of hematopoietic cell production. [7][8][9] CD44 can occur in many isoforms derived from a single gene by alternative mRNA splicing.…”

Kinetics of in vivo homing and recruitment into cycle of hematopoietic cells are organ-specific but CD44-independent

“…These findings do not negate previous evidence of specific anti-CD44 antibody effects on hematopoietic cell homing, 18,21 stroma-dependent hematopoiesis in vitro 47 or leukemic hematopoiesis. 20,22 However, they do suggest that the latter are mediated either by antibody-stimulated activation of intracellular signalling pathways, opsonization, or the induction of other indirect effects on hematopoiesis which can be functionally replaced by other molecules.…”

“…19 On the other the hand, we and others have demonstrated that antibodies against CD44 can affect the growth, differentiation and adhesion of normal and leukemic hematopoietic progenitors in vitro in different ways, depending on the epitope specificity of the anti-CD44 antibodies tested. 6,16,[20][21][22] Thus, it was of interest to further examine the role of CD44 in the homing and engraftment of normal bone marrow cells in a syngeneic setting using other strategies. To address this question we compared various parameters of in vitro and in vivo hematopoietic stem cell activity and transplant engraftment in normal mice and mice deficient in CD44 expression (CD44 Ϫ/Ϫ mice).…”

A protocol for the isolation and cultivation of brown bear (Ursus arctos) adipocytes

“…Undifferentiated cells In order to better define the SVF-derived cell population, we performed RT-qPCR on undifferentiated cell cultures at or below passage 2 to test for the expression of the stem cell markers CD44 and CD90 (bears F, G, H) (Ghaffari et al 1997;Haynesworth et al 1992) as well as for peroxisome proliferator-activated receptor gamma (PPARc) (bears E, F, G, H), which stimulates lipogenesis and is critical for differentiation (Chawla et al 1994;Morrison and Farmer 2000). Undifferentiated passage 1 cells from 2 juvenile male bears (A and B) originating from the active season and hibernation were stained with alizarin red and alcian blue after reaching confluence to assess multipotency.…”