Exploring the Role of Spatial Confinement in Immune Cell Recruitment and Regeneration of Skin Wounds

Microporous annealed particle (MAP) scaffolds are injectable granular materials comprised of micron sized hydrogel particles (microgels). The diameter of these microgels directly determines the size of the interconnected void space between particles where infiltrating or encapsulated cells reside. This tunable porosity allows us to use MAP scaffolds to study the impact of spatial confinement (SC) on both cellular behaviors and the host response to biomaterials. Despite previous studies showing that pore size and SC influence cellular phenotypes, including mitigating the macrophage inflammatory response, there is still a gap in knowledge regarding how SC within a biomaterial modulates immune cell recruitment in vivo in wounds and implants. Thus, we studied the immune cell profile within confined and unconfined biomaterials using small (40 μm), medium (70 μm), and large (130 μm) diameter spherical microgels, respectively. We discovered that MAP scaffolds imparted regenerative wound healing with an IgG1-biased Th2 response. MAP scaffolds generated from 130 μm diameter microgels have a median pore size that can accommodate ∼40 µm diameter spheres induced a more balanced pro-regenerative macrophage response and better wound healing outcomes with more mature collagen regeneration and reduced levels of inflammation.