Exploiting heparan sulfate proteoglycans-growth factor interactions to direct mesenchymal stem cell neurogenesis

Yu C, Okolicsanyi RK, Griffiths LR and Haupt LM

IHBI-QUT, Genomics Research Centre, School of Biomedical Sciences, 60 Musk Avenue, Kelvin Grove, Q 4059.

According to the World Health Organisation, neurological disorders, including trauma, affect 1 in 6 of the world population. With no current effective treatments, much current effort is focussed on the development and improvement of cellular replacement therapies. In particular, the propagation and direction of stem cells into specific neural lineages. Mesenchymal stem cells (MSCs) are capable of neurogenic differentiation but lack high frequency differentiation efficiency, particularly following transplantation. Heparan sulfate proteoglycans (HSPGs), including syndecans (SDCs) and glypicans (GPCs), are ubiquitous within the stem cell microenvironment and essential to numerous cellular activities, including self-renewal, proliferation and differentiation. In this study we examine the role of HSPGs in human MSC (hMSCs) neurogenesis and as potential biomarkers for therapeutic applications. Using two neural differentiation protocols: i.) direct terminal differentiation (TD), and ii.) terminal differentiation via hMSC-induced neurosphere formation (TD via hMSC-INs), hMSC populations (n=3) were directed towards neural lineages with growth factor supplementation for up to 14 days. Brain-derived neurotrophic factor (BDNF) and platelet-derived growth factor (PDGF) bind to HSPGs and have been implicated in neuronal and glial lineage differentiation, respectively. HSPG and neural lineage marker gene expression profiles (focussing on the core protein SDCs and GPCs) were examined under neural specific culture conditions by Q-PCR, WB and ICC. Gene expression analysis identified BDNF-treated cultures to express higher self-renewal (NANOG, POU5F1 and SOX2 (P<0.05)), and oligodendrocyte markers (Olig1 (P<0.05) and Olig2 (P<0.05)) when compared to PDGF-treated cultures. PDGF cultures maintained the highest cell numbers and expressed mature neuronal markers (MAP2 and TUBB3). Analysis of the culture HSPG profiles identified SDCs 1-4 and GPC1, -4, and -6 are likely involved in hMSC neural differentiation. Our data suggests HSPGs, in particular members of the SDC and GPC families, may play key roles during hMSC neurogenesis and are potentially central to controlling human neurogenesis.