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Expression of CD163+ cells and collagen deposition in subcutaneous and visceral adipose tissue of young male children

Introduction: Adipose tissue (AT) has the ability to adapt to a dynamically changing nutritional environment which is critical to maintain metabolic control. In response to changes in the nutritional status, the AT undergoes through dynamic remodeling, including quantitative and qualitative alternations in adipose tissue-resident cells that indicates that AT remodeling in obesity is closely associated with AT function. Little is known about extracellular matrix (ECM) remodeling and immune cells in AT in children, possibly due to the difficulties in obtaining AT samples. The ECM is essential for tissue architecture and has an important role in adipogenesis and thus AT growth. Adipose tissue macrophages (ATMs) are the dominant leukocyte population in AT in lean and obese state. Resident ATM population has properties that overlap with alternatively activated macrophages and is associated with suppression of the immune response and with ECM remodeling. An understanding of how AT remodeling differs between visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) may unlock the links between visceral adiposity and metabolic disease. The aim of this study was to examine if there are some differences between collagen deposition and number of CD163+ cells in SAT and VAT of healthy young male children depended on their age. Participants and Methods: The research is based on young male children, 30 subjects for this preliminary part of the research, who were hospitalized for elective abdominal surgery at the Department of Pediatric Surgery of the University Hospital Osijek. Prior to the beginning of the research every parent of the subject was given written explanation of the purpose of the research and signed an informed consent. Samples of SAT and VAT were gained during surgical procedure. Histological staining of extracellular components was performed with Masson’s trichrome stain and histomorphometric analysis of digital images of histological tissue sections was conducted using the free online image analysis program Fiji. Immunohistochemistry for CD163+ cells was also performed and number of positive cells was counted per mm2 of adipose tissue. Data analysis was performed using IBM SPSS Statistics software. Results: Tissue sections staining with Masson’s trichrome stain for ECM content showed increased collagen deposition in SAT in the group where subjects were =>5 years of age which was statistically significant compared to the group up to 5 years of age ; p=0, 031. There was no statistical significance among groups when comparing adipocyte surface area in SAT and VAT. In children =>5 years of age more CD163+ cells were counted in VAT compared with children up to 5 years of age ; p=0, 017 ; and also BMI was statistically higher compared to the group up to 5 years of age ; p=0, 036. Conclusion: In healthy, growing young male children, increased deposition of collagen content is age related. For more and detailed conclusions, further analytical methods need to be done such as RT- PCR and ELISA on a larger sample size.

adipose tissue, collagen, adipocytes, adipose tissue remodeling, extracellular matrix

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