Past matrix stiffness primes epithelial cells and regulates their future collective migration through a mechanical memory

Abstract

During morphogenesis and cancer metastasis, grouped cells migrate through tissues of dissimilar stiffness. Although the influence of matrix stiffness on cellular mechanosensitivity and motility are well-recognized, it remains unknown whether these matrix-dependent cellular features persist after cells move to a new microenvironment. Here, we interrogate whether priming of epithelial cells by a given matrix stiffness influences their future collective migration on a different matrix – a property we refer to as the ‘mechanical memory’ of migratory cells. To prime cells on a defined matrix and track their collective migration onto an adjoining secondary matrix of dissimilar stiffness, we develop a modular polyacrylamide substrate through step-by-step polymerization of different PA compositions. We report that epithelial cells primed on a stiff matrix migrate faster, display higher actomyosin expression, form larger focal adhesions, and retain nuclear YAP even after arriving onto a soft secondary matrix, as compared to their control behavior on a homogeneously soft matrix. Priming on a soft ECM causes a reverse effect. The depletion of YAP dramatically reduces this memory-dependent migration. Our results present a previously unidentified regulation of mechanosensitive collective cell migration by past matrix stiffness, in which mechanical memory depends on YAP activity.

Mechanical memory in cells emerges from mechanotransduction with transcriptional feedback and epigenetic plasticity

“…Additionally, microRNA-21 has been shown to enhance levels of αSMA and fibrotic mechanical memory of stem cells (22). Our previous work showed that nuclear YAP localization due to stiff-priming of epithelial cells enhances their pMLC levels and migration speed in future soft ECMs (24). Based on these established connections between mechanosensitive transcription, nuclear-cytoskeleton factor production, and overall cellular response, we assume that cellular mechanoactivation ( ) leads to mechano-sensitive transcriptional activity, which leads to production of mechanosensitive mRNA (normalized levels are denoted by ).…”

“…Separately, miRNA-21 transcription and downstream MRTF signaling have been implicated in long-term memory in stem cells over several weeks (22). In the context of cell migration, we have recently shown that epithelial cell sheets primed on a stiff matrix for 3 days store mechanical memory through nuclear YAP localization, which continues to enhance cell migration through enhanced pMLC expression and focal adhesion formation on soft matrix for 2-3 days (24). Priming less than 3 days substantially reduces memory, which suggests that memory processes operate progressively over time.…”

“…However, it is not clear why the cells do not commence new transcription and protein signaling as soon as they move to the soft matrix. Additionally, the reservoir model does not capture how the production and degradation kinetics of memory regulators, such as YAP, MRTF, and miR21, is coupled with the matrix-sensing cytoskeletal processes that ultimately govern cellular outcomes of memory-dependent migration or differentiation (22)(23)(24).…”

The desmosomal cadherin Desmoglein-3 regulates YAP and phospho-YAP in keratinocyte responses to mechanical forces

“…Such a delayed response could well reflect a sustained effect after the abrogation of stretch, or as a result of "repairing" the monolayer after cyclic strain. Alternatively, this could be due to the mechanical memory of keratinocytes as reported recently [36,59]. Distinct behaviors and cellular properties between oral and skin keratinocytes have been appreciated and these include aspects of wound healing and angiogenesis [9,50,56].…”

Breast tumor stiffness instructs bone metastasis via mechanical memory

“…Consistent with mechanical memory, upon removal from stiffness, RUNX2 target transactivation was only gradually lost, concomitant with a gradual increase in PLIN1, an adipogenic biomarker (Fig.3g). YAP target expression did not persist similarly to RUNX2 targets (Extended Data Fig.9k), which was surprising since YAP has been linked to mechanical memory in epithelial cells 26 . However, despite being a wellestablished transducer of mechanical cues, YAP has no known gene bookmarking function 19,27 .…”