Defined Surface Physicochemical Cues Inhibit M1 Polarization of Human Macrophages Using Colloidal Self-Assembled Patterns.

Biophysical and biochemical cues modulate mammalian cell behavior and phenotype simultaneously. Macrophages, indispensable cells in the innate immune system, respond to external threats such as bacterial infections and implanted devices, undergoing the classical M1 polarization to become a pro-inflammatory phenotype. In the study, lipopolysaccharide (LPS)-induced M1 polarization was examined using RAW264.7, THP-1, and primary human PBMCs on a family of artificial extracellular matrix (ECM), named colloidal self-assembled patterns (cSAPs). The results showed that cSAPs were biocompatible, which cannot induce M1 or M2 polarization. Interestingly, specific cSAPs (e.g., cSAP3) suppress the level of M1 polarization (i.e., reduced nitric oxide production, down-regulated gene expression of iNOS, IL-6, TNF-α, IL-1ß, and TLR4, and reduced proportion of CD11b+CD86+ cells). Transcriptome analysis showed that cell adhesion and cell-ECM interaction participated in the M1 polarization, and the mechano-sensitive genes such as PIEZO1 were down-regulated on the cSAP3. More interestingly, these genes were also down-regulated under LPS stimulation, indicating that cells became insensitive to the LPS. The abovementioned results indicate that the defined physicochemical cues can govern macrophage polarization. This study illustrates a potential surface design at biointerface, which is critical in tissue engineering and materiobiology. The outcome is also inspiring in ECM-mediated immune responses.

Knockout of AMD-associated gene POLDIP2 reduces mitochondrial superoxide in human retinal pigment epithelial cells.

Genetic and epidemiologic studies have significantly advanced our understanding of the genetic factors contributing to age-related macular degeneration (AMD). In particular, recent expression quantitative trait loci (eQTL) studies have highlighted POLDIP2 as a significant gene that confers risk of developing AMD. However, the role of POLDIP2 in retinal cells such as retinal pigment epithelium (RPE) and how it contributes to AMD pathology are unknown. Here we report the generation of a stable human RPE cell line ARPE-19 with POLDIP2 knockout using CRISPR/Cas, providing an in vitro model to investigate the functions of POLDIP2. We conducted functional studies on the POLDIP2 knockout cell line and showed that it retained normal levels of cell proliferation, cell viability, phagocytosis and autophagy. Also, we performed RNA sequencing to profile the transcriptome of POLDIP2 knockout cells. Our results highlighted significant changes in genes involved in immune response, complement activation, oxidative damage and vascular development. We showed that loss of POLDIP2 caused a reduction in mitochondrial superoxide levels, which is consistent with the upregulation of the mitochondrial superoxide dismutase SOD2. In conclusion, this study demonstrates a novel link between POLDIP2 and SOD2 in ARPE-19, which supports a potential role of POLDIP2 in regulating oxidative stress in AMD pathology.