Extracellular matrix (ECM) remodeling is essential for adipose tissue growth and expansion in high fat-fed mice, and there is evidence of fibrosis in adipose tissue in human obesity.

The aim of the study was to explore the role of ECM remodeling in adipose tissue in healthy, growing children.

Abdominal sc adipose biopsies were obtained from 65 otherwise healthy children [57 boys; age, 5.3 ± 3.8 yr (mean ± sd)] having elective surgery (cross-sectional study). Twenty percent of the participants were classified as overweight/obese based on body mass index (BMI) z score.

We examined collagen (total and pericellular), HAM56+ macrophages, CD206+ M2 phenotype macrophages, and CD3+ T cells measured by immunohistochemistry and ECM gene expression markers.

Overweight children had significantly less total collagen compared to normal weight children (median, 3.4 vs. 9.1%; P = 0.001). However, collagen areas were not positive for COL6 and showed little evidence of collagen surrounding adipocytes. Fat cell size was negatively correlated with the percentage of total (r = −0.398; P = 0.003) and pericellular collagen (r = −0.462; P < 0.001) but positively correlated with HAM56+ macrophages (r = 0.541; P < 0.001). The percentage of total collagen was inversely associated with BMI z score (r = −0.345; P = 0.01) and age (r = −0.348; P = 0.005), with older (>11 yr old) children in the top BMI z tertile having less collagen (3.8%) than younger (2–5 yr old) children in the bottom BMI z tertile (12.6%). Adipose tissue in overweight children showed little evidence of crown-like structures or T cells.

In healthy, growing children, increased collagen in adipose tissue is associated with decreased fat cell size and BMI z score and increased M2+ phenotype macrophages, suggesting dynamic interaction between ECM remodeling and immune cells even at an early age.