Stem Cell Microarrays for Assessing Growth Factor Signaling in Engineered Glycan Microenvironments

Abstract

Extracellular glycans, such as glycosaminoglycans (GAGs), provide an essential regulatory component during the development and maintenance of tissues. GAGs, which harbor binding sites for a range of growth factors (GFs) and other morphogens, help establish gradients of these molecules in the extracellular matrix (ECM) and promote the formation of active signaling complexes when presented at the cell surface. As such, GAGs have been pursued as biologically active components for the development of biomaterials for cell-based regenerative therapies. However, their structural complexity and compositional heterogeneity make establishing structure-function relationships for this class of glycans difficult. Here, a stem cell array platform is described, in which chemically modified heparan sulfate (HS) GAG polysaccharides are conjugated to a gelatin matrix and introduced into a polyacrylamide hydrogel network. This array allowed for direct analysis of HS contributions to the signaling via the FGF2-dependent mitogen activated protein kinase (MAPK) pathway in mouse embryonic stem cells. With the recent emergence of powerful synthetic and recombinant technologies to produce well-defined GAG structures, a platform for analyzing both growth factor binding and signaling in response to the presence of these biomolecules will provide a powerful tool for integrating glycans into biomaterials to advance their biological properties and applications.

Synthetic Heparan Sulfate Hydrogels Regulate Neurotrophic Factor Signaling and Neuronal Network Activity

“…Diversely sulfated epitopes on HS chains regulate trophic factor binding and cellular signaling to promote angiogenesis as well as neurogenesis and plasticity. , HS interactions with the cell regulatory mitogen, fibroblast growth factor (FGF), and family of cognate FGF receptors (FGFRs) have been the subject of much investigation . However, most of these interactions have been elucidated using specific binding affinity assays, which are not designed to provide biological information regarding protein complexation and downstream signaling using hydrogel-based cellular bioassays …”