Dynamics of Mechanosensitive Neural Stem Cell Differentiation

Abstract

Stem cell differentiation can be highly sensitive to mechanical inputs from the extracellular matrix (ECM)1–3. Identifying temporal windows during which lineage commitment responds to ECM stiffness, and the signals that mediate these decisions, would advance both mechanistic insights and translational efforts. To address these questions, we investigate adult neural stem cell (NSC) fate commitment using an oligonucleotide-crosslinked ECM platform that for the first time offers dynamic and reversible control of stiffness. “Stiffness pulse” studies in which the ECM was transiently or permanently softened or stiffened at specified initiation times and durations pinpoint a 24-hour window in which ECM stiffness maximally impacts neurogenic commitment. Overexpression of the transcriptional co-activator YAP within this window suppressed neurogenesis, and silencing YAP enhanced it. Moreover, ablating YAP-β-catenin interaction rescued neurogenesis. This work reveals that ECM stiffness dictates NSC lineage commitment by signaling via a YAP and β-catenin interaction during a defined temporal window.

Novel biomaterials to study neural stem cell mechanobiology and improve cell-replacement therapies

“…This approach elegantly illustrates that different mechanical stimuli can direct NSC differentiation in varied ways, potentially via different signaling cascades. This report also further supports other studies suggesting that the timing of mechanical stimuli is significantly important in stem cell fate commitment [41,20]. …”

“…Moreover, we have identified Rho GTPase-mediated cytoskeletal dynamics and the transcriptional co-activator Yes-Associated Protein (YAP) as key players in stiffness-instructed NSC differentiation [20], and other work in the field has demonstrated the importance of focal adhesion proteins such as vinculin [21,22]. Adding to those findings, novel approaches have further explored the extent of NSC sensitivity to various biophysical inputs and the mechanisms that actuate mechanosensitive NSC behavior.…”

“…That said, the development of materials capable of reversible stiffening or softening could open access to an entirely new set of questions, such as the importance of the onset timing and duration of exposure to a given stiffness in guiding fate determination. To address this need, our group adopted a DNA-crosslinking approach [50] to develop a hydrogel that can be reversibly softened and re-stiffened, or vice versa (Figure 1C), over an order of magnitude spanning a relevant stiffness range for NSCs (0.3 – 3 kPa) [20]. Using this system, we identified a “mechanosensitive time window” of 12–36 hours after initiation of hippocampal NSC differentiation, such that stiffness cues only within this time window instructed neuro/astrocytic fate commitment, analyzed after 6 days of differentiation (Figure 1D).…”

Matrix Mechanosensing: From Scaling Concepts in ’Omics Data to Mechanisms in the Nucleus, Regeneration, and Cancer

“…Compared with traditional neurogenic induction methods that use soluble factors, hPSCs more rapidly and efficiently differentiated into neurons on the compliant gels in the absence of neurogenic induction factors. Furthermore, dynamic changes in substrate stiffness have highlighted an important window of mechanosensitivity in stem cell neuronal differentiation (60). However, the results for hPSCs on the stiff gels indicate differences from MSCs, which highlights the cell type–specific nature of mechanoresponses.…”

Mechanosensing of matrix by stem cells: From matrix heterogeneity, contractility, and the nucleus in pore-migration to cardiogenesis and muscle stem cells in vivo

“…Compared with traditional neurogenic induction methods that rely solely on soluble factors, culturing hPSCs on soft gels in the absence of neurogenic factors resulted in more rapid and efficient differentiation into neurons. Furthermore, dynamic changes in substrate stiffness have highlighted an important window of mechanosensitivity in stem cell neuronal differentiation [21]. However, the results for hPSCs on the stiff gels indicate differences from MSCs, highlighting the cell type-specific nature of mechanoresponses.…”