Natural Polysaccharide Scaffolds as Immunomodulatory Biomaterials for Tissue Regeneration.

Tissue repair and regeneration represent multifaceted processes involving a coordinated interplay of diverse cell types, growth factors, and cytokines. Following tissue injury, innate immune cells serve as the primary cellular responders that infiltrate the damaged microenvironment, clear cellular debris, and undergo phenotype transitions essential for establishing a proregenerative environment. To facilitate functional recovery, three-dimensional scaffolds are conventionally used to give physical signals and structural support. However, these constructs frequently encounter barriers in host-scaffold integration, potential material cytotoxicity, and the induction of adverse chronic foreign body responses (e.g., chronic inflammation), which continue to hinder their successful clinical translation. In this regard, natural polysaccharides, including hyaluronic acid, alginate, and mannans, represent promising biomaterials for multifunctional scaffold engineering due to their extracellular matrix (ECM)-mimetic properties, high biocompatibility, rapid degradation, and tunable physicochemical characteristics. Moreover, the unique sugar moieties inherent to these polysaccharides can function as pathogen-associated molecular patterns and directly interact with pattern recognition receptors expressed on host immune cells. These receptor-ligand interactions trigger intracellular signaling cascades, driving the secretion of downstream cytokines and chemokines, guiding immune cells toward proregenerative phenotypes, and remodeling the ECM to achieve functional tissue repair. In this review, the dual functionality of natural polysaccharides in tissue engineering is described, emphasizing their role as physical supports and active immunomodulatory platforms in regenerative medicine. We critically evaluate the immuno-active motifs within natural polysaccharides, reveal their receptor-mediated interactions with immune cell subsets, and highlight recently reported polysaccharide constructs across distinct tissue targets. We also outline engineering design principles to modulate the chemical, structural, and biophysical properties of immune-active scaffolds. Furthermore, we explore the clinical progress of these scaffolds, addressing current milestones alongside ongoing regulatory and manufacturing challenges. This review provides key design criteria to guide the rational development of next-generation, immuno-instructive polysaccharide constructs for immune-mediated tissue regeneration.