Activation of Astrocytes <i>in Vitro</i> by Macrophages Polarized with Keratin Biomaterial Treatment

Abstract

Reactive astrocytes contribute to glial scarring by rapid proliferation and up-regulation of glial fibrillary acidic protein (GFAP) expression and production of chondroitin sulfate proteoglycans (CSPGs). CSPGs play a crucial role in formation of the glial scar, which takes over the lesion site following spinal cord injury (SCI). This process corresponds to the inflammatory response of macrophages, which polarize toward a dominant pro-inflammatory M1 phenotype following SCI. The M1 phenotype is known to release various cytotoxic compounds that exacerbate the glial scar, which in turn impedes tissue regeneration. Recent studies have shown that anti-inflammatory M2 macrophages play a role in allowing neurite extensions to occur, even across inhibitory substrates, and can lessen the degree of secondary damage. Based on earlier results demonstrating that keratin biomaterials may polarize macrophages toward an anti-inflammatory M2 phenotype, we test the hypothesis that these polarized macrophages will have the potential to indirectly effect astrogliosis. Using an in vitro model of reactive astrogliosis, macrophage-conditioned media from cells that have been cultured with soluble keratin for 24 hours or 7 days appears to decrease reactivity and associates CSPG production. These results are statistically similar to the control M2 macrophage conditioned media. A comparable collagen-conditioned macrophage media does not resolve astrocyte reactivity, while control M1 macrophage conditioned media results in an increase in GFAP expression. These data suggest keratin-derived macrophages are more functionally similar to M2 macrophages and that keratin treatment may aid in limiting secondary inflammatorymediated damage.

Sophorolipid Butyl Ester Diacetate Does Not Affect Macrophage Polarization but Enhances Astrocytic Glial Fibrillary Acidic Protein Expression at Micromolar Concentrations in Vitro

“…As SL decreased macrophage nitric oxide production in a sepsis model, we hypothesized that SLBEDA would shift M1 macrophages to an anti-inflammatory phenotype. Additionally, due to the crosstalk between macrophages and astrocytes, − we hypothesized that astrocytes would shift to a less reactive phenotype. We studied peritoneal macrophage (PMAC) and spinal cord astrocyte viability as well as PMAC polarization and astrocytic GFAP expression in response to varying concentrations of SLBEDA in vitro.…”

The Hair Follicle: An Underutilized Source of Cells and Materials for Regenerative Medicine

“…However, in the case of macrophages, keratose coatings can promote monocyte differentiation toward anti-inflammatory "M2-type" macrophages over pro-inflammatory "M1-type" macrophages. 142 This is in contrast to collagen coatings, which promote equal monocyte differentiation into both M2 and M1 macrophages.…”

“…Inflammatory cytokines released by ‘M1-type’ macrophages can lead to excessive CSPG production by reactive astrocytes, hampering effective recovery. In an in vitro model for astrogliosis, media from monocytes grown on keratin films inhibited the process of astrogliosis 142. Thus, it opens up the possibility of controlling glial scarring by targeting and enhancing M2 macrophages, rather than astrocytes.…”

“…In an in vitro model for astrogliosis, media from monocytes grown on keratin films inhibited the process of astrogliosis. 142 This opens up the possibility of controlling glial scarring by targeting and enhancing M2 macrophages rather than astrocytes. The idea of exploiting biased induction of differentiation is not new, and other studies have used biomaterials to create pro-regenerative microenvironments by biasing the recruitment of alternatively activated macrophages.…”

A comparative study of materials assembled from recombinant K31 and K81 and extracted human hair keratins

“…Fibroblasts serve as a connective tissue cell model and attach to the ECM, a non-cellular structure that contains fibrous proteins [79]. Focal adhesions create transmembrane communication channels that can activate cell proliferation [80,81], phenotypic changes [82,83], and cell signaling cascades [84]. Actin fibers are an indication of focal adhesion formation [81].…”