Fabian Junker

Excessive protease activity and impaired tissue regeneration are hallmarks of many disease states. Elevated matrix metalloproteinase-9 (MMP-9) plays a key role in adverse tissue remodeling by excessively degrading extracellular matrix (ECM) components and growth factors. Tissue inhibitor of metalloproteinase-3 (TIMP-3) regulates ECM turnover, and its bioavailability is influenced by glycosaminoglycans (GAGs). This study aimed to develop a methacrylated gelatin (GelMA)-based hydrogel functionalized with acrylated sulfated hyaluronan (sHA_c) as a TIMP-3 delivery system to decrease ECM degradation under pathophysiological conditions. sHA_c incorporation enhanced hydrogel stiffness, reduced degradation rates and yielded sustained TIMP-3 release for up to 28 days. Molecular modeling and surface plasmon resonance demonstrated preferential binding of TIMP-3 to sHA_c over hyaluronan methacrylates, together providing a molecular rationale for the reduced and sustained release of TIMP-3 from sHA_c-containing hydrogels. Angiogenesis-related functional assays, supported by molecular modeling studies, indicate that sHA_c modulates the anti-angiogenic activity of TIMP-3 by altering vascular endothelial growth factor receptor-associated signaling, while preserving metalloproteinase inhibition. Released TIMP-3 from GelMA/sHA_c hydrogels retained bioactivity, effectively inhibiting MMP-9 activity and mitigating ECM degradation in-vitro and in human ex-vivo models. In a murine subcutaneous implantation model, sHA_c-functionalized TIMP-3-loaded hydrogels were associated with reduced inflammatory cell presence and altered vascular- and matrix-related tissue signatures compared with GelMA controls. These findings underscore the potential of sHA_c-functionalized GelMA hydrogels as biomaterials for therapeutics delivery, offering controlled TIMP-3 release and sustained bioactivity to promote ECM stability and on-demand MMP inhibition. This system represents a promising strategy for addressing the challenges of excessive MMP activity.

Glycosaminoglycans (GAGs) are essential regulators of numerous biological processes through their interactions with growth factors, chemokines, cytokines, and enzymes. Their structural diversity and heterogeneity, however, limit reproducibility and translational use, as native GAGs are typically obtained from animal-derived sources with notable batch-to-batch variability. To overcome these challenges, a wide range of GAG mimetics has been developed with the aim of replicating or modulating the biological functions of native GAGs while offering improved structural definition, accessibility, and therapeutic potential. Polysaccharide-based GAG mimetics, including derivatives of heparan sulfate, hyaluronan, dextran, and other natural glycans, represent one major strategy, whereas non-saccharide-based mimetics provide alternative scaffolds with enhanced stability and selectivity. Both approaches have yielded compounds that serve as valuable tools for dissecting GAG/protein interactions and as candidates for therapeutic development. Biomedical applications of GAG mimetics span diverse areas such as cancer, cardiovascular and inflammatory diseases, bone and cartilage regeneration, wound healing, and infectious diseases. This mini-review summarizes key developments in the design and synthesis of GAG mimetics, highlights their potential biomedical applications, and discusses current challenges and future perspectives in advancing them toward clinical translation.

Islet-resident macrophages contribute to hypoxia-induced islet cell death during pancreatic islet transplantation. However, their specific role during this process remains elusive. Here, we report that interleukin-1α (IL-1α) and IL-1β are released by islet-resident macrophages, resulting in the suppression of insulin secretion. This may be due to a decreased inflammation-driven expression of pancreatic and duodenal homeobox 1 (PDX-1) and MafA in β cells. Islet-resident macrophages release significantly less IL-1α when compared to IL-1β. However, both cytokines inhibit insulin expression and secretion to a comparable extent. We identified heparan sulfate on the islet surface, which acts as a “molecular glue” potentiating the inhibitory action of IL-1α on insulin expression via specific binding to IL-1 receptor (IL-1R). In vivo analyses revealed that the loss of IL-1 signaling in isolated islets accelerates their revascularization and, thus, enhances their endocrine function. These findings indicate that heparan sulfate fine-tuned IL-1 signaling crucially determines the outcome of islet transplantation.