Injection of rats with kainic acid (KA), a non-N-methyl-D-aspartate (NMDA) type glutamate receptor agonist, induces recurrent (delayed) convulsive seizures and subsequently hippocampal neurodegeneration, which is reminiscent of human epilepsy. The protective effect of anti-epileptic drugs on seizure-induced neuronal injury is well known; however, molecular basis of this protective effect has not yet been elucidated. In this study, we investigated the effect and signaling mediators of voltage-gated Na+ channel blockers (Lamotrigine, Rufinamide, Oxcarbazepine, Valproic Acid, and Zonisamide) on KA-induced apoptosis in rat primary hippocampal neurons. Exposure of hippocampal neurons to 10 μM KA for 24 h caused significant increases in morphological and biochemical features of apoptosis, as determined by Wright staining and ApopTag assay, respectively. Analyses showed increases in expression and activity of cysteine proteases, production of reactive oxygen species (ROS), intracellular free [Ca2+], and Bax:Bcl-2 ratio during apoptosis. Cells exposed to KA for 15 min were then treated with Lamotrigine, Rufinamide, Oxcarbazepine, Valproic Acid, or Zonisamide. Post-treatment with one of these anti-epileptic drugs (500 nM) attenuated production of ROS and prevented apoptosis in hippocampal neurons. Lamotrigine, Rufinamide, and Oxcarbazepine appeared to be less protective when compared with Valproic Acid or Zonisamide. This difference may be due to blockade of T-type Ca2+ channels also by Valproic Acid and Zonisamide. Our findings thus suggest that the anti-epileptic drugs that block both Na+ channels and Ca2+ channels are significantly more effective than agents that block only Na+ channels for attenuating seizure-induced hippocampal neurodegeneration.

Extracellular matrix (ECM) remodeling is essential for the process of capillary morphogenesis. Here we employed synthetic poly(ethylene glycol) (PEG) hydrogels engineered with proteolytic specificity to either matrix metalloproteinases (MMPs), plasmin, or both to investigate the relative contributions of MMP‐ and plasmin‐mediated ECM remodeling to vessel formation in a 3D‐model of capillary self‐assembly analogous to vasculogenesis. We first demonstrated a role for both MMP‐ and plasmin‐mediated mechanisms of ECM remodeling in an endothelial‐fibroblast co‐culture model of vasculogenesis in fibrin hydrogels using inhibitors of MMPs and plasmin. When this co‐culture model was employed in engineered PEG hydrogels with selective protease sensitivity, we observed robust capillary morphogenesis only in MMP‐sensitive matrices. Fibroblast spreading in plasmin‐selective hydrogels confirmed this difference was due to protease preference by endothelial cells, not due to limitations of the matrix itself. In hydrogels engineered with crosslinks that were dually susceptible to MMPs and plasmin, capillary morphogenesis was unchanged. These findings highlight the critical importance of MMP‐mediated degradation during vasculogenesis and provide strong evidence to justify the preferential selection of MMP‐degradable peptide crosslinkers in synthetic hydrogels used to study vascular morphogenesis and promote vascularization. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B:2507–2516, 2019.

There is a critical need for biomaterials that support robust neovascularization for a wide-range of clinical applications. Here we report how cells alter tissue-level mechanical properties during capillary morphogenesis using a model of endothelial-stromal cell co-culture within poly(ethylene glycol) (PEG) based hydrogels. After a week of culture, we observed substantial stiffening in hydrogels with very soft initial properties. Endothelial cells or stromal cells alone, however, failed to induce hydrogel stiffening. This stiffening tightly correlated with degree of vessel formation but not with hydrogel compaction or cellular proliferation. Despite a lack of fibrillar architecture within the PEG hydrogels, cell-generated contractile forces were essential for hydrogel stiffening. Upregulation of alpha smooth muscle actin and collagen-1 was also correlated with enhanced vessel formation and hydrogel stiffening. Blocking cell-mediated hydrogel degradation abolished stiffening, demonstrating that matrix metalloproteinase (MMP)-mediated remodeling is required for stiffening to occur. These results highlight the dynamic reciprocity between cells and their mechanical microenvironment during capillary morphogenesis and provide important insights for the rational design of materials for vasculogenic applications.

Synthetic hydrogels represent an exciting avenue in the field of regenerative biomaterials given their injectability, orthogonally tunable mechanical properties, and potential for modular inclusion of cellular cues. Separately, recent advances in soluble factor release technology have facilitated control over the soluble milieu in cell microenvironments via tunable microparticles. A composite hydrogel incorporating both of these components can robustly mediate tendon healing following a single injection. Here, a synthetic hydrogel system with encapsulated electrospun fiber segments and a novel microgel‐based soluble factor delivery system achieves precise control over topographical and soluble features of an engineered microenvironment, respectively. It is demonstrated that three‐dimensional migration of tendon progenitor cells can be enhanced via combined mechanical, topographical, and microparticle‐delivered soluble cues in both a tendon progenitor cell spheroid model and an ex vivo murine Achilles tendon model. These results indicate that fiber reinforced hydrogels can drive the recruitment of endogenous progenitor cells relevant to the regeneration of tendon and, likely, a broad range of connective tissues.