Maternal obesity increases the risk of neonatal adiposity and future risk of obesity. Previously, we reported greater adipogenesis in mesenchymal stem cells (MSCs) cultured from umbilical cords of human infants of mothers with obesity (Ob-MSCs) compared to those of normal weight mothers (NW-MSCs), which positively correlated with neonatal adiposity. However, it is unclear if greater adipogenesis is due to increased adipocyte number (hyperplasia) or size (hypertrophy), the latter of which is linked to proinflammatory markers and insulin resistance in adults with obesity.
Here, we compared 20 NW-MSCs with 17 Ob-MSCs. The Ob group had a significantly higher pre-pregnancy BMI (NW = 21.7 ± 0.1;Ob = 33.8 ± 0.8 kg/m2), along with higher fasting maternal insulin (NW = 7.3 ± 0.4;Ob = 13.1 ± 2.1 μU/mL) at mid-gestation (15-23 wks), but no difference in glucose. Women with gestational diabetes were excluded. Infants were born ≥ 37 wks and had similar gestational age and rates of cesarean delivery. To test the hypothesis that Ob-MSCs are larger and store more lipid than NW-MSCs, we induced adipogenesis for 14 days in 3-dimensional hydrogels for better quantification of adipocyte hypertrophy than traditional cell culture. We fixed and stained the hydrogels for BODIPY (neutral lipids), Wheat Germ Agglutinin (cell membrane), and DAPI (nucleus), and imaged them with confocal microscopy. We used Fiji to quantify fluorescence intensity by double-measuring 200 image Z-stacks (step size 1 µm) of > 100 cells/subject (avg repeatability > 0.88).
We used T-tests to determine whether differences in cell size and lipid content between the two groups were statistically significant. Ob-MSCs stored 77% more lipid (p = 0.014) and were 76% larger (p = 0.021) than NW-MSCs, indicating hypertrophy.
Greater adipocyte hypertrophy in infant MSCs may explain, in part, how infants of obese mothers have a heightened risk for obesity and insulin resistance later in life.