Unbiased Analysis of the Impact of Micropatterned Biomaterials on Macrophage Behavior Provides Insights beyond Predefined Polarization States

Abstract

ABSTRACT:Macrophages are master regulators of immune responses towards implanted biomaterials. The activation state adopted by macrophages in response to biomaterials determines their own phenotype and function as well as those of other resident and infiltrating immune and non-immune cells in the area. A wide spectrum of macrophage activation states exists, with M1 (pro-inflammatory) and M2 (anti-inflammatory) representing either ends of the spectrum. In biomaterials research, cellinstructive surfaces that favour or induce M2 macrophages have been considered as beneficial due to the anti-inflammatory and pro-regenerative properties of these cells. In this study, we used a gelatin methacryloyl (GelMA) hydrogel platform to determine whether micropatterned surfaces can modulate the phenotype and function of human macrophages. The effect of microgrooves/ridges and micropillars on macrophage phenotype, function, and gene expression profile were assessed using conventional methods (morphology, cytokine profile, surface marker expression, phagocytosis) and gene microarrays.Our results demonstrated that micropatterns did induce distinct gene expression profiles in human macrophages cultured on microgrooves/ridges and micropillars. Significant changes were observed in genes related to primary metabolic processes such as transcription, translation, protein trafficking, DNA repair and cell survival. However, interestingly conventional phenotyping methods, relying on surface marker expression and cytokine profile, were not able to distinguish between the different conditions, and indicated no clear shift in cell activation towards an M1 or M2 phenotypes. This highlights the limitations of studying the effect of different physicochemical conditions on macrophages by solely relying on conventional markers that are primarily developed to differentiate between cytokine polarised M1 and M2 macrophages. We therefore, propose the adoption of unbiased screening methods in determining macrophage responses to biomaterials. Our data clearly shows that the exclusive use of conventional markers and methods for determining macrophage activation status could lead to missed opportunities for understanding and exploiting macrophage responses to biomaterials.

A Foreign Body Response‐on‐a‐Chip Platform

“…In contrast to the THP‐1 cell line, differentiation of primary human monocytes into M1 and M2 phenotypes vary from one donor to other, thus indicating the importance of personalized FBROC system to study the inter‐patient difference in FBR. Once the FBR is screened on the FBROC platform, methods of immunomodulation may then be accordingly personalized to mitigate the negative immune responses of the host towards the foreign body. Thus, we believe that the FBROC system has a potential to expand the studies of personalized FBR on vast categories of subjects including but not limited to, implants reported in the current work as well as biologically active materials and engineered tissues.…”

The Topography of Silica Films Modulates Primary Macrophage Morphology and Function

“…[7] Macrophages with spindle-like morphology are more likely to have a pro-healing phenotype, which contributes to tissue repair and wound healing, whereas the rounded "fried-egg" morphology shows pro-inflammatory behavior. [9] Surface patterns such as microgrooves, [10][11][12][13] wrinkles, [14] and concave/convex microstructures [15] have been reported to alter inflammatory responses of macrophages. [9] Surface patterns such as microgrooves, [10][11][12][13] wrinkles, [14] and concave/convex microstructures [15] have been reported to alter inflammatory responses of macrophages.…”

Biophysical regulation of macrophages in health and disease

“…Micropatterned posts appear to induce a greater M2‐like polarization in macrophages than line patterns, but interestingly the spacing between the features had a more significant effect on macrophage behavior than the size of the features themselves . Another study also compared macrophages cultured on micropillars, microgrooves and unpatterned surfaces, and found distinct gene expression profiles, particularly programs involved in transcription, translation, protein trafficking, DNA repair, and cell survival . Topographical features that elicit cellular elongation appear to enhance macrophage wound healing responses.…”

“…56 Another study also compared macrophages cultured on micropillars, microgrooves and unpatterned surfaces, and found distinct gene expression profiles, particularly programs involved in transcription, translation, protein trafficking, DNA repair, and cell survival. 57 Topographical features that elicit cellular elongation appear to enhance macrophage wound healing responses. In work from our own laboratory, macrophages cultured on an array of microgrooves of varied dimensions tend to express more Arg1, an M2 marker, with increased degree of elongation.…”