Monocytes contribute to a pro-healing response in 40μm diameter uniform-pore, precision-templated scaffolds.

Abstract

Porous precision-templated scaffolds (PTS) with uniformly distributed 40μm spherical pores have shown a remarkable ability in immunomodulating resident cells for tissue regeneration. While the pore size mediated pro-healing response observed only in 40μm pore PTS has been attributed to selective macrophage polarization, monocyte recruitment and phenotype have largely been uncharacterized in regulating implant outcome. Here, we employ a double transgenic mouse model for myeloid characterization and a multifaceted phenotyping approach to quantify monocyte dynamics within subcutaneously implanted PTS. Within 40μm PTS, myeloid cells were found to preferentially infiltrate into the scaffold. Additionally, macrophage receptor with collagenous structure (MARCO), an innate activation marker, was significantly upregulated within 40μm PTS. When 40μm PTS were implanted in monocyte-depleted mice, the transcription of MARCO was significantly decreased and an increase in pro-inflammatory inducible nitric oxide synthase (iNOS) and tumor necrosis factor alpha (TNFα) were observed. Typical of a foreign body response (FBR), 100μm PTS significantly upregulated pro-inflammatory iNOS, secreted higher amounts of TNFα, and displayed a pore size dependent morphology compared to 40μm PTS. Overall, these results identify a pore size dependent modulation of circulating monocytes and implicates MARCO expression as a defining subset of monocytes that appears to be responsible for regulating a pro-healing host response.