IGFBP-2 and -3 co-ordinately regulate IGF1 induced matrix mineralisation of differentiating human dental pulp cells

Hanaa Alkharobi,Aishah Alhodhodi,Yousef Hawsawi,Hasanain Alkafaji,Deirdre Devine,Reem El-Gendy,James Beattie

doi:10.1016/j.scr.2016.09.026

Abstract

Human dental pulp cells (DPCs), which are known to contain a subset of stem cells capable of reforming a dentin and pulp-like complex upon in vivo transplantation, were isolated from third molars of three healthy donors and differentiated to a matrix mineralisation phenotype using by culture in dexamethasone and l-ascorbic acid. qRT-PCR analysis of insulin-like growth factor ( IGF) axis gene expression indicated that all genes, except insulin-like growth factor 1 (IGF1) and insulin-like growth factor binding protein-1 ( IGFBP-1), were expressed in DPCs. During differentiation upregulation of insulin-like growth factor binding protein-2 (IGFBP-2) and downregulation of insulin-like growth factor binding protein-3 (IGFBP-3) expression was observed. Changes in IGFBP-2 and IGFBP-3 mRNA expression were confirmed at the protein level by ELISA of DPC conditioned medium functional analysis indicated that IGF1 stimulated the differentiation of DPCs and that the activity of the growth factor was enhanced by pre-complexation with IGFBP-2 but inhibited by pre-complexation with IGFBP-3. Therefore changes in IGFBP-2 and -3 expression during differentiation form part of a co-ordinated functional response to enhance the pro-differentiative action of IGF1 and represent a novel mechanism for the regulation of DPC differentiation.

Highlights

The increasing demand for alternatives to bone grafting as a method of treating critical bone defects has led to a growing interest in cell based regenerative therapies and selection of appropriate cell sources for bone tissue engineering is a key research area
We have demonstrated reciprocal changes in insulin-like growth factor binding protein-2 (IGFBP-2) and insulin-like growth factor binding protein-3 (IGFBP-3) mRNA and protein expression in dental pulp stromal cells during differentiation to a mineralising phenotype and show that these changes are co-ordinated with the functions of both IGFBPs to enhance (IGFBP-2) or inhibit (IGFBP-3) the mineralising activity of insulin-like growth factor 1 (IGF1) in these cells
IGF1 has been reported previously to promote the differentiation of human dental pulp stem cells via mTor (Feng et al, 2014) and MAPK/Stat-3 (Vandomme et al, 2014) signalling pathways there is only a limited literature describing IGFBP-2 and/or IGFBP-3 expression and activity during osteogenic differentiation

Summary

Introduction

The increasing demand for alternatives to bone grafting as a method of treating critical bone defects has led to a growing interest in cell based regenerative therapies and selection of appropriate cell sources for bone tissue engineering is a key research area. Cells derived from human dental pulp (DPCs) have been characterised as an accessible source of multipotent stem cells which can be differentiated to a matrix mineralised phenotype. Undifferentiated cells display a fibroblast-like morphology with associated high efficiency for adherent colony formation and high proliferative potential (Kerkis & Caplan, 2011). All of these factors suggest that adult dental tissues may provide a source of material (often discarded in the clinic) to provide multipotent cells for subsequent tissue engineering studies

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