Hyaluronan and rat renal fibroblasts: In vitro studies

Hyaluronic acid (HA) is a ubiquitous component of extracellular matrix. Aft er tissue injury, HA appears in greater abundance during the inflammatory r esponse and the phase of clearance of cell and matrix debris, before collag en production and matrix degradation. The aim of this study was to examine whether normal rat renal fibroblasts were capable of HA synthesis and to de termine the effect of HA on in vitro collagen production in a series of nor mal rat cortical fibroblast cultures. Fibroblast cultures from both renal c ortex and medulla were established from adult Sprague-Dawley rats. HA synth esis was measured by radioimmunoassay, and incorporation of H-3-proline int o collagen was used to determine collagen synthesis. Fibroblasts were defin ed on the basis of morphology and alpha smooth muscle actin immunohistochem istry. HA synthesis was measured in both renal cortical and medullary fibro blasts at passage 3 for both 24 and 48 h in 5 animals and expressed as a fr action of protein content. HA was synthesized by both cortical and medullar y fibroblasts; however, cortical fibroblasts produced less HA than medullar y fibroblasts at both 24 h (p = 0.05) and 48 h (p = 0.02). In normal cortic al fibroblasts, exogenous HA suppressed overall total (cell and media) coll agen production after a 22-hour labelling period (p = 0.002 compared to con trols). Decreased collagen production was also found individually in cell ( p = 0.02) and media fractions (p = 0.01). Both cortical and medullary fibro blasts are capable of synthesizing HA in vitro. Furthermore, the findings i n this study suggest that HA may be an important mediator in reducing renal cortical fibroblast collagen production and may play an important role in limiting renal interstitial scarring. Copyright (C) 2001 S. Karger AG, Base l.