Hyaluronan and versican in the kidney in obesity

Abstract

Hyaluronan in the kidney is located in the outer and inner medulla with the majority found near the papilla tip. Hyaluronan accumulates in the inner medulla in obesity. However, the distribution of hyaluronan in the inner medulla is not known. Versican is a hyaluronan binding protein but the amount in the inner medulla in lean kidneys or in obesity is not known. Thus, the objective of this study was to determine the distribution of hyaluronan in the inner medulla from obese and lean dogs using confocal microscopy and to quantify versican by Western blot. The distribution of hyaluronan in kidneys from lean dogs was heterogeneous in the inner medulla with most of the hyaluronan found on the basal lateral side of the collecting ducts. In obese dog kidneys, the hyaluronan was more homogenous with increased amounts found throughout the interstitium. Versican increased 3-fold in obese dog kidney inner medulla compared to lean (p<0.05). The heterogeneous distribution of hyaluronan may indicate a compartmentalization of the bound water with most of the water being bound just outside the collecting duct. Another possible interpretation is that hyaluronan may provide support to the collecting ducts in the inner medulla. These results also suggest that hyaluronan is bound to a binding protein, namely versican. In conclusion, hyaluronan is not homogenously distributed in the inner medulla in normal lean kidney but is more evenly distributed in obesity. In addition, this hyaluronan is not free, as in skin, but appears to be bound to versican.