M1 Polarized Macrophages Persist in Skin of Post-Bariatric Patients after 2 Years

Background Obesity is considered a condition of systemic chronic inflammation. Under this condition, adipose tissue macrophages switch from an M2 (anti-inflammatory) activation pattern to an M1 (proinflammatory) activation pattern. Objective The study aimed to verify the profile of skin macrophage activation after bariatric surgery as well as the role of MMP-1 in extracellular tissue remodeling. Methods This is a prospective, controlled and comparative study with 20 individuals split into two groups according to their skin condition: post-bariatric and eutrophic patients. Histological and morphometric analyses based on hematoxylin-eosin, picrosirius red (collagen), orcein (elastic fiber systems), and alcian blue (mast cells)-stained sections and immunohistochemical analysis (CD68, iNOS, and mannose receptor) for macrophages and metalloproteinase-1 were performed. Results Post-bariatric skin showed an increase in inflammation, angiogenesis, CD68, M1 macrophages (P < 0.001), and mast cells (P < 0.01); a decrease in M2 macrophages (P < 0.01); and a significant decrease in the collagen fiber network (P < 0.001). MMP-1 was increased in the papillary dermis of post-bariatric skin and decreased in the epidermis compared to eutrophic skin (P < 0.05). Conclusion This study shows that post-bariatric skin maintains inflammatory characteristics for two years. Mast cells and M1 macrophages maintain and enhance the remodeling of the dermal extracellular matrix initiated during obesity in part due to the presence of MMP-1 in the papillary dermis. EBM Level IV This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors

Automated summary

The study confirmed that post-bariatric skin retains inflammatory characteristics for two years. Mast cells and M1 macrophages play a role in enhancing dermal extracellular matrix remodeling initiated during obesity, partially due to the presence of MMP-1 in the papillary dermis.