| In vivo, stem cells reside in specialized microenvironments called 'niches' that consist of soluble cytokines, cell-cell interactions, and cell-extra-cellular matrix (ECM) interactions. These niches enable cell survival and guide self-renewal or differentiation. Human embryonic stem cells (hESCs) are an ideal source for cells in regenerative medicine for their remarkable ability to self-renew as well as to differentiate into mature cell types. However, before hESCs can be exploited greater control over cell fate must be achieved. Here, we investigated the mechanisms by which micro-patterning technologies can be used to establish homogeneous artificial niches to more precisely regulate hESC fate. In our initial study, we demonstrated that the activation of the bone morphogenetic protein (BMP)/growth differentiation factor (GDF3) pathway within the hESC niche was a balance of two factors: niche-composition and niche-size. By restricting hESC colony diameter to 200-800μm, spatial control over self-renewal and differentiation was achieved. In a second study, we demonstrated that hESC differentiation into ExE (small colonies) or neural pre-cursors (large colonies) was highly efficient (>80%) within micro-fabricated niches, exceeding efficiencies obtained by current differentiation protocols. In a third study, a mathematical model was developed to provide mechanistic insight into how niche-size regulates endogenous signaling by estimating how the trapping of soluble ligands changes with alterations to the spatial arrangement of cell cultures. This model was validated by predicting and measuring endogenous signalling activity of the gp130-Janus kinase—signal transducer and activator of transcription (gp130-Jak-STAT) pathway in mouse embryonic stem cells (mESCs) in non-patterned and micro-patterned cultures. Overall, these studies highlight the opportunity of using micro-patterning to create homogenous niches capable of regulating endogenous signalling and hESC fate. This approach provides a novel method to regulate hESC differentiation into clinically revelant cell types that can be used in future regenerative medicine applications. |
