The Influence of PHEMA Hydrogel Compressive Modulus and Chemistry on Lens Epithelial and Neutrophil-Like Cell Behaviours Associated with Posterior Capsular Opacification

Abstract

During cataract surgery, the impaired lens is removed and replaced with an artificial intraocular lens (IOL). Patients can experience a complication called posterior capsular opacification (PCO) that is corrected through surgery which has increased costs and can damage the retina and the IOL. PCO develops when lens epithelial cells (LECs) proliferate, migrate and undergo epithelial to mesenchymal transition (EMT). Neutrophils involved in the immune response triggered during implantation impact LEC behaviour and produce damaging neutrophil extracellular traps (NETs). Previous studies with rigid, hydrophobic acrylic materials demonstrated that stiffness and surface chemistry influence cellular responses. This project investigated neutrophil and LEC responses, simultaneously, to the material properties of a foldable, hydrophilic IOL material, poly(2-hydroxyethyl methacrylate) (PHEMA). PHEMA-based disks were synthesized with varying amounts of comonomer (HEMA with 0, 2, and 12 mol% MMA) and functionalized with carboxyl and amine groups, yielding nine different hydrogels. Material and chemical properties of the disks were characterized, and neutrophil-like HL60 cells and B3 LECs were incubated with the disks. HL60 cell behaviour was assessed by evaluating viability and visualizing adhered and citrullinated histone H3 (cit-H3) positive cells, indicating NETosis. B3 LEC behaviour was assessed by evaluating viability and visualizing adhered cells and alpha-smooth muscle actin (alpha-SMA) expression, a marker of EMT. The influence of NETs on LECs was examined by culturing B3 LECs with disks pre-treated with NETs isolated from HL60 cells and evaluating behaviour using the previously described methods. HL60 cell behaviour was more strongly influenced by chemical functionalization than by mechanical properties. This was demonstrated by significant increases in adherence and in cit-H3 visualization with functionalized disks and through principal component analysis (PCA). Conversely, B3 LECs behaviour and viability were more strongly influenced by mechanical properties. This was demonstrated by increases in cell adhesion and alpha-SMA expression with increasing compressive moduli of the disks and through PCA. Moreover, B3 LECs demonstrated decreased viability and increased alpha-SMA expression when cultured with NET-pre-treated disks. The notable influence of NETs on B3 LEC behaviour suggests that, when both immune responses and LEC responses are considered, the PHEMA12-based hydrogels are the most promising for future PCO-prevention studies.