Process and Separations Design
While neural progenitor cells (NPCs) and their progeny have significant therapeutic promise, the difficulty and cost of expanding a large number of NPCs remains a significant barrier to widespread clinical use. Recently, 3D hydrogels have been proposed as in vitro culture platforms for the expansion of stem cell populations to overcome the space limitations of 2D culture. However, very little is known about which 3D material properties are required to maintain NPCs in an undifferentiated state for expansion. It is well-established that matrix stiffness modulates stemness in strongly adherent stem cells, including mesenchymal stem cells and muscle satellite cells, but the impact of stiffness on stemness maintenance in less contractile stem cells such as NPCs is not well known. We present data demonstrating that 3D matrix stiffness does not correlate with the maintenance of NPC stemness over a broad range of matrix mechanical properties (E~0.5-50 kPa). In contrast, matrix degradability strongly correlated with the expression of NPC stem markers and NPC proliferation in two different biomaterial systems. Our results have identified matrix remodeling as a previously unknown requirement for maintenance of NPC stemness in 3D hydrogels and suggest that adaptable biomaterials will be useful for expansion of therapeutically relevant numbers of NPCs.