Eur J Haematol. 2017 Feb 3. doi: 10.1111/ejh.12865. [Epub ahead of print]

Impact of osteoblast maturation on their paracrine growth enhancing activity on cord blood progenitors.

Alsheikh M^1,2, Abu-Khader A¹, Michalicka M^1,2, Pasha R¹, Pineault N^1,2.

Abstract

BACKGROUND:

Osteoblasts possess strong growth modulatory activity on hematopoietic stem cells and progenitors. We sought to characterise the growth and differentiation modulatory activities of human osteoblasts at distinct stages of maturation on cord blood (CB) progenitors in the context of osteoblast conditioned medium (OCM).

METHODS:

OCM was produced from MSC-derived osteoblasts (M-OST) at distinct stages of maturation. The growth modulatory activities of the OCM were tested on CB CD34⁺ cells using different functional assays.

RESULTS:

OCMs raised the growth of CB cells and expansion of CD34⁺ cells independently of the maturation status of M-OST. However, productions of immature CB cells including committed and multipotent progenitors were superior with OCM produced with immature osteoblasts. Osteogenic differentiation was accompanied by the upregulation of IGFBP-2, several members of the Angpt-L family of growth factor and by the Notch ligands Dll-1 and Dll-4. However, the growth activity of OCM and the in vivo engraftment properties of OCM-expanded CB cells were retained after IGFBP-2 neutralization. Similarly, OCM-mediated expansion of CB myeloid progenitors was largely independent of Notch signaling.

CONCLUSIONS:

These results demonstrate that immature osteoblasts possess greater regulatory activity over hematopoietic progenitors, and that this activity is not entirely dependent on Notch signaling. This article is protected by copyright. All rights reserved.