A Balance between Pro‐Inflammatory and Pro‐Reparative Macrophages is Observed in Regenerative D‐MAPS

Abstract

Microporous annealed particle scaffolds (MAPS) are a new class of granular materials generated through the interlinking of tunable microgels, which produce an interconnected network of void space. These microgel building blocks can be designed with different mechanical or bio‐active parameters to facilitate cell infiltration and modulate host response. Previously, changing the chirality of the microgel crosslinking peptides from L‐ to D‐amino acids led to significant tissue regeneration and functional recovery in D‐MAPS‐treated cutaneous wounds. In this study, the immunomodulatory effect of D‐MAPS in a subcutaneous implantation model is investigated. How macrophages are the key antigen‐presenting cells to uptake and present these biomaterials to the adaptive immune system is uncovered. A robust linker‐specific IgG2b/IgG1 response to D‐MAPS is detected as early as 14 days post‐implantation. The fine balance between pro‐regenerative and pro‐inflammatory macrophage phenotypes is observed in D‐MAPS as an indicator for regenerative scaffolds. The work offers valuable insights into the temporal cellular response to synthetic porous scaffolds and establishes a foundation for further optimization of immunomodulatory pro‐regenerative outcomes.

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

“…Each mouse received three injections of 50 μL hydrogel Implant Extraction and Flow Cytometry Study: At selected time points, the implants were extracted and cell extraction was performed as previously described. [20] An enzymatic digestion with the digestion solution (200 U mL −1 Collagenase IV and 125 U mL −1 DNase I) in RPMI media was used. Samples were stained and prepared following manufacturer instructions, and analyzed on the Cytek NL-3000 Flow Cytometer.…”

Spatial Confinement Modulates Macrophage Response in Microporous Annealed Particle (MAP) Scaffolds

“…This time point was chosen to explore the interface between the acute and late inflammatory phase of the foreign body response. [ 36 ] The total infiltrated live cell number and CD45+ cell number were similar among all MAP scaffolds groups (Figure 7c,d), which indicated that smaller pore size didn't pose a significant barrier to cell infiltration. We found that there was a size dependent increase in macrophage percentages, with 130 µm MAP scaffolds having the higher number of macrophages (Figure 7e), possibly due to the larger cell size of macrophages among all immune cells.…”

“…Only CD11c showed a high negative correlation with the size of the microgels. The uptake of MAP (labeled with AF647) by infiltrated cells was observed, [ 36 ] but there was no high correlation between phenotypical markers and AF647 level. Interestingly, both the pro‐inflammatory marker (iNOS) as well as pro‐regenerative marker (CD206) had a high positive correlation with the sphericity of cells/nucleus and a negative correlation with the area of a cell.…”

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

“…The total infiltrated live cell number and CD45+ cell number were similar among all MAP scaffolds groups (Figure 2b), which indicated that a smaller entry door size didn't pose a significant barrier to the cell infiltration. Macrophages and FcεRI+ cells (such as Langerhan cells, monocytes, mast cells, and other dendritic cells) dominated the immune cell infiltration 45 (Figure 2c). The immune cell recruitment followed a size-dependent manner.…”