Uniform 40-μm-pore diameter precision templated scaffolds promote a pro-healing host response by extracellular vesicle immune communication

Implanted porous precision templated scaffolds (PTS) with 40-mu m spherical pores reduce inflammation and foreign body reaction (FBR) while increasing vascular density upon implantation. Larger or smaller pores, however, promote chronic inflammation and FBR. While macrophage (Mo) recruitment and polarization participates in perpetuating this pore-size-mediated phenomenon, the driving mechanism of this unique pro-healing response is poorly characterized. We hypothesized that the primarily myeloid PTS resident cells release small extracellular vesicles (sEVs) that induce pore-size-dependent pro-healing effects in surrounding T cells. Upon profiling resident immune cells and their sEVs from explanted 40-mu m- (pro-healing) and 100-mu m-pore diameter (inflammatory) PTS, we found that PTS pore size did not affect PTS resident immune cell population ratios or the proportion of myeloid sEVs generated from explanted PTS. However, quantitative transcriptomic assessment indicated cell and sEV phenotype were pore size dependent. In vitro experiments demonstrated the ability of PTS cell-derived sEVs to stimulate T cells transcriptionally and proliferatively. Specifically, sEVs isolated from cells inhabiting explanted 100 mu m PTS significantly upregulated T-h1 inflammatory gene expression in immortalized T cells. sEVs isolated from cell inhabiting both 40- and 100-mu m PTS upregulated essential T-reg transcriptional markers in both primary and immortalized T cells. Finally, we investigated the effects of T-reg depletion on explanted PTS resident cells. FoxP3+ cell depletion suggests T-regs play a unique role in balancing T cell subset ratios, thus driving host response in 40-mu m PTS. These results indicate that predominantly 40-mu m PTS myeloid cell-derived sEVs affect T cells through a distinct, pore-size-mediated modality.

Automated summary

The study found that sEVs released by myeloid cells from 40-micron PTS affect T cells through a distinct, pore-size-mediated modality. Experiment results indicated that the pore size of the PTS influenced the phenotype of resident cells and sEVs, leading to different effects on T cell transcription and proliferation. The depletion of T-regs in 40-mu m PTS indicated their unique role in balancing T cell subset ratios and driving host response.