StemBond hydrogels control the mechanical microenvironment for pluripotent stem cells

Abstract

Studies of mechanical signalling are typically performed by comparing cells cultured on soft and stiff hydrogel-based substrates. However, it is challenging to independently and robustly control both substrate stiffness and extracellular matrix tethering to substrates, making matrix tethering a potentially confounding variable in mechanical signalling investigations. Moreover, unstable matrix tethering can lead to poor cell attachment and weak engagement of cell adhesions. To address this, we developed StemBond hydrogels, a hydrogel in which matrix tethering is robust and can be varied independently of stiffness. We validate StemBond hydrogels by showing that they provide an optimal system for culturing mouse and human pluripotent stem cells. We further show how soft StemBond hydrogels modulate stem cell function, partly through stiffness-sensitive ERK signalling. Our findings underline how substrate mechanics impact mechanosensitive signalling pathways regulating self-renewal and differentiation, indicating that optimising the complete mechanical microenvironment will offer greater control over stem cell fate specification.

Plakoglobin is a mechanoresponsive regulator of naïve pluripotency

“…Here we used a microgel system to encapsulate embryonic stem cells into spherical 3D agarose scaffolds. Consistent with previous studies, we found the soft, non-degradable 3D matrix to be beneficial for pluripotency 21, 25, 50, 51 . The interpretation of RNA-seq data on microgel-encapsulated cells revealed Plakoglobin, a vertebrate homologue of β-catenin and a crucial factor for embryonic development, as one of the most differentially upregulated genes 52, 53 .…”

“…Any two of the three 2i/LIF components (PD, CHIR and LIF) are sufficient to maintain naïve pluripotency 20 . In addition to chemical and cytokine-mediated signals, biomechanical cues are emerging key players in the regulation of embryonic [21][22][23][24][25] and adult stem cells 4,[26][27][28] . However, the identity of mechanoresponsive genes in ESCs and the mechanisms transforming physical responses into transcriptional programs remain poorly understood.…”

A Review on the Design of Hydrogels With Different Stiffness and Their Effects on Tissue Repair

“…In the process of the above hydrogel stiffness affecting cell behavior, it may regulate cell expression by affecting the expression of related genes and proteins ( Labouesse et al, 2021 ). In human adipose-derived stem cells (hADSCs) encapsulated by methacrylated hyaluronan (MeHA) hydrogel, the contents of two cartilage-related gene aggrecans and type II collagen increased significantly with the increase of hydrogel stiffness.…”

Regulation of stem cell fate and function by using bioactive materials with nanoarchitectonics for regenerative medicine

“…Integrins form clusters, cause the conformation changes of mechanosensitive proteins like talin and vinculin, activate the mechanosensitive ion channels, and then activate the downstream transcription factor activity [ 120 ]. To construct an optimal mechanical microenvironment for culturing pluripotent stem cells, Chalut’s group modified PAAm hydrogel protocol by addition of 6-acrylamidohexanoic acid (AHA) as co-factor [ 121 ]. The carboxyl terminal groups of the AHA are covalently linked to extracellular matrix (ECM) protein through a carbodiimide reaction, and thus form stable ECM–substrate attachment.…”