Interpenetrating Polymer Network Hydrogel Composition Alters Encapsulated MSC Spreading and In Vivo Degradation Behavior.

An interpenetrating polymer network (IPN) hydrogel was developed for the three-dimensional (3D) culture of multipotent mesenchymal stromal cells (MSCs) with the aim of independently controlling cell spreading and material modulus. Based on our previous studies, we formulated a semisynthetic material composed of two networks: a covalent network of poly(ethylene glycol) (PEG)-fibrinogen (PF) and a second guest-host (GH) network of hyaluronic acid (HA) coupled to β-cyclodextrin (CD) and adamantane (Ad). The PF network provided cell attachment, precise control over modulus through the incorporation of additional PEG-diacrylate (PEG-DA) cross-linking, and proteolytic degradability. The GH-HA network contributed to the hydrogel's dynamic properties through enhanced viscoelasticity. This dynamic versatility enabled MSCs to better spread and grow in the IPN, even within highly cross-linked formulations. We also observed that the IPN facilitated significantly faster cell spreading kinetics, independent of the material modulus, when compared to single-network PF hydrogels. Hydrogel biodegradation was also characterized after subcutaneous implantation for up to 8 weeks by using MRI analysis. Increasing the PEG-DA cross-linking of the IPN significantly accelerated the in vivo bioresorption, whereas the biodegradation in single-network PF hydrogels was significantly delayed by the additional PEG-DA. We conclude that the covalent cross-links maintain the bulk structural integrity of the hydrogel, whereas the reversible GH interactions provide more localized adaptability for cell-mediated proteolysis and matrix remodeling, possibly through increased network heterogeneity. This design effectively mimics the ECM by providing a more supportive environment for encapsulated cells that allows them to adhere, spread, and proliferate, which may be useful in various MSC-based tissue engineering and regenerative medicine applications.