Mucin-Inspired Thermoresponsive Synthetic Hydrogels Induce Stasis in Human Pluripotent Stem Cells and Human Embryos

Abstract

Human pluripotent stem cells (hPSCs; both embryonic and induced pluripotent) rapidly proliferate in adherent culture to maintain their undifferentiated state. However, for mammals exhibiting delayed gestation (diapause), mucin-coated embryos can remain dormant for days or months in utero, with their constituent PSCs remaining pluripotent under these conditions. Here we report cellular stasis for both hPSC colonies and preimplantation embryos immersed in a wholly synthetic thermoresponsive gel comprising poly(glycerol monomethacrylate)-poly(2-hydroxypropyl methacrylate) [PGMA55-PHPMA135] diblock copolymer worms. This hydroxyl-rich mucin-mimicking nonadherent 3D gel maintained PSC viability and pluripotency in the quiescent G0 state without passaging for at least 14 days. Similarly, gel-coated human embryos remain in a state of suspended animation (diapause) for up to 8 days. The discovery of a cryptic cell arrest mechanism for both hPSCs and embryos suggests an important connection between the cellular mechanisms that evoke embryonic diapause and pluripotency. Moreover, such synthetic worm gels offer considerable utility for the short-term (weeks) storage of either pluripotent stem cells or human embryos without cryopreservation.

Bespoke cationic nano-objects via RAFT aqueous dispersion polymerisation

“…35,36,38 These worms are thermo-sensitive, with degelation occurring on cooling below the critical gelation temperature (CGT) as a result of a worm-to-sphere transition. 39,40 It is well-known that many cationic polymers exhibit anti-bacterial properties. This thermoreversible enables convenient sterilisation of the worm gels via cold ultrafiltration, 35 which suggests various biomedical applications.…”

“…22,23,[35][36][37][38] This prototypical aqueous PISA formulation allows the efficient formation of AB block copolymer nanoparticles with precise control over particle size and morphology by fixing the degree of polymerisation of the PGMA stabiliser block while systematically varying the degree of polymerisation of the core-forming PHPMA block. 35,36,38 Such thermo-responsive worm gels are readily sterilisable via cold ultrafiltration and have potential biomedical applications for the long-term storage and preservation of human stem cells 39 or red blood cells. 23 Furthermore, PGMA-PHPMA worms form free-standing soft hydrogels at 25°C due to multiple inter-worm contacts, with reversible degelation occurring on cooling to 4°C as a result of a wormto-sphere order-order transition.…”

A Critical Appraisal of RAFT-Mediated Polymerization-Induced Self-Assembly

“…Thus, these worm gels may offer a cost-effective alternative to cryo-preservation for global stem cell transportation. 182 Additionally, next-generation thiol-functional PGMA–PHPMA worm gels have been recently reported by Warren and co-workers. 183 These are currently being evaluated as potential muco-adhesive gels, while the gel reinforcement conferred by inter-worm disulfide cross-links 184 has just been demonstrated to be critical in the context of thermoreversible 3D hydrogels for “cells-in-gels-in-paper” applications.…”

Reactive and Functional Nanoobjects by Polymerization‐Induced Self‐Assembly

“…Since antimicrobial activity is a well‐known property of quaternary amine polymers, a pure worm phase was synthesized to form antimicrobial free‐standing gels at 20 wt% solids. Temperature‐dependent rheological studies proved the thermoresponsiveness of the system, which is, for instance, useful for purification by ultrafiltration . Subsequently, direct contact assays and incubation of Staphylococcus aureus S235 in the copolymer gel indicated a mild bactericidal effect for the cationic gels.…”