Gelatin methacrylate (GelMA) is a photocrosslinkable biomaterial that has gained widespread use in tissue engineering due to its favorable biological attributes and customizable physical and mechanical traits. While GelMA is compatible with various cell types, distinct cellular responses are observed within GelMA hydrogels. As such, tailoring hydrogels for specific applications has become imperative. Thus, our objective was to develop GelMA hydrogels tailored to enhance cell viability specifically for TC28a2 chondrocytes in a three-dimensional (3D) cell culture setting. We investigated GelMA synthesis using PBS and 0.25M CB buffer, analyzed the mechanical and physical traits of GelMA hydrogels, and evaluated how varying GelMA crosslinking conditions (GelMA concentration, photoinitiator concentration, and UV exposure time) affected the viability of TC28a2 chondrocytes. The results revealed that GelMA synthesis using 0.25M CB buffer led to a greater degree of methacrylation compared to PBS buffer, and the LAP photoinitiator demonstrated superior efficacy for GelMA gelation compared to Irgacure 2959. Additionally, the stiffness, porosity, and swelling degree of GelMA hydrogels were predominantly affected by GelMA concentration, while cell viability was impacted by all crosslinking conditions, decreasing notably with increasing GelMA concentration, photoinitiator concentration, and UV exposure time. This study facilitated the optimization of crosslinking conditions to enhance cell viability within GelMA hydrogels, a critical aspect for diverse biomedical applications.

Osteoarthritis (OA) is a chronic joint disease characterized by irreversible cartilage degradation. Current clinical treatment options lack effective pharmaceutical interventions targeting the disease’s root causes. MMP (matrix metalloproteinase) inhibitors represent a new approach to slowing OA progression by addressing cartilage degradation mechanisms. However, very few drugs within this class are in preclinical or clinical trial phases. Hydrogel-based 3D in vitro models have shown promise as preclinical testing platforms due to their resemblance to native extracellular matrix (ECM), abundant availability, and ease of use. Metalloproteinase-13 (MMP-13) is thought to be a major contributor to the degradation of articular cartilage in OA by aggressively breaking down type II collagen. This study focused on testing MMP-13 inhibitors using a GelMA-alginate hydrogel-based OA model induced by cytokines interleukin-1 beta (IL-1β) and tumor necrosis factor alpha (TNF-α). The results demonstrate a significant inhibition of type II collagen breakdown by measuring C2C concentration using ELISA after treatment with MMP-13 inhibitors. However, inconsistencies in human cartilage explant samples led to inconclusive results. Nonetheless, the study highlights the GelMA-alginate hydrogel-based OA model as an alternative to human-sourced cartilage explants for in vitro drug screening.

Embryonic fishes provide valuable models for understanding the ontogeny of vertebrate cardiovascular regulation, yet the timing of autonomic control onset varies widely among species. In most teleosts, it is generally accepted that parasympathetic (vagal) influence over heart rate arises only near hatching, but historical observations suggest that killifishes deviate from this paradigm. Here, we characterized the development of vagal control in Gulf killifish (Fundulus grandis), a precocial species with an extended embryonic period. Using both direct mechanical and indirect vibrational startle stimuli, combined with atropine treatment, we identified two distinct cardiac response phenotypes: (1) a transient atrial and ventricular arrest evident by 70% of embryonic development, and (2) a later-developing transient bradycardia beginning at 80%. Both responses were abolished by atropine, confirming parasympathetic mediation, and neither habituated to repeated stimulation. These findings demonstrate that F. grandis embryos acquire functional vagal tone well before hatching, contrasting with the delayed autonomic development typical of most vertebrates. Here, we revisit and expand upon early observations from nearly a century–old study, establishing the Gulf killifish as a tractable model for investigating the developmental physiology of early autonomic control in vertebrates.

In adult zebrafish, morphological and functional changes in the ventricle phenotype are dependent on the timing of the hypoxic exposure. Exposure to hypoxia as an adult did not alter the ventricle phenotype, unlike the changes caused by continuous hypoxic exposure from the embryonic to adult phase. Thus, exposure to hypoxia before the adult phase life results in changes in the zebrafish ventricle. However, adults may lack the plasticity needed to respond to hypoxic environments.