Three-Dimensional Nanofibrillar Surfaces Promote Self-Renewal in Mouse Embryonic Stem Cells

Abstract

The regulation of mouse embryonic stem cell (mESC) fate is controlled by the interplay of signaling networks that either promote self-renewal or induce differentiation. Leukemia inhibitory factor (LIF) is a cytokine that is required for stem cell renewal in mouse but not in human embryonic stem cells. However, feeder layers of embryonic fibroblasts are capable of inducing stem cell renewal in both cell types, suggesting that the self-renewal signaling pathways may also be promoted by other triggers, such as alternative cytokines and/or chemical or physical properties of the extracellular matrix (ECM) secreted by feeder fibroblasts. We have recently used a synthetic polyamide matrix (Ultra-Web) whose three-dimensional (3D) nanofibrillar organization resembles the ECM/basement membrane. Growth of mESCs on this nanofibrillar surface greatly enhanced proliferation and self-renewal in comparison with growth on tissue culture surfaces without nanofibers, despite the presence of LIF in both systems. Enhanced proliferation and self-renewal of the stem cells on nanofibrillar surfaces were correlated with the activation of the small GTPase Rac, the activation of phosphoinositide 3-kinase (PI3K) pathway, and the enhanced expression of Nanog, a homeoprotein required for maintenance of pluripotency. Inhibitors of PI3K reduced the expression level of Nanog in mESCs cultured on 3D nanofibrillar surfaces. These results provide support for the view that the three-dimensionality of the culture surface may function as a cue for the activation of Rac and PI3K signaling pathways, resulting in stem cell proliferation and self-renewal. STEM CELLS 2006;24:426 -433

Engineering integrin signaling for promoting embryonic stem cell self-renewal in a precisely defined niche

“…We note that other approaches, both based on matrices [5,41] and molecular [36,38] approaches have been presented. The matrix approach described here is particularly flexible, and moreover may be useful in investigating Fig.…”

“…These biologically derived materials are also very complex and are not subject to control at the molecular level. Synthetic hydrogel and fibrillar matrices have been explored, in an attempt to replace such complicated biological materials with defined artificial materials for short-term ESC culture [4,5], yet these materials still do not present the fullness of the ECMs repertoire of molecular characteristics. Sophisticated photochemical degradation approaches have been developed to explore the dynamic nature of cell-material interactions in the niche in artificial systems, for example the factors controlling stem cell chondrogenic differentiation [6].…”

Toward xeno-free culture of human embryonic stem cells

“…Indeed, most studies with synthetic substrates and stem cells are largely concerned with their differentiation (reviewed in Lutolf & Hubbell, 2005). The first report of such a scaffold being used for undifferentiated culture of ESCs comes from Nur-E-Kamal, Ahmed, Kamal, Schindler, and Meiners (2005) who have recently used a commercially available synthetic polyamide matrix (UltraWeb) for the growth of mouse ESCs. The authors showed that proliferation and self-renewal, as well as Nanog expression, were enhanced relative to 2D surfaces and suggested that dimensionality may play a role in 'stemness' in mESCs.…”

Tissue engineering with nano-fibrous scaffolds

“…Several cells types, including osteoblasts 78,79 , fibroblasts 80,81 , rat kidney cells 80 , smooth muscle cells 82 , neural stem cells 83 and embryonic stem cells 84 , have shown increased attachment on various nano-fibers compared to their corresponding control materials. Additionally, a recent study found that branched nano-fibers improve fibroblast attachment over linear nano-fibers 85 .…”