Characterization of aged rat vocal fold fibroblasts

Objectives/Hypothesis To elucidate the aging physiology of the vocal folds, we examined the characters of aged vocal fold fibroblasts (VFFs) in various conditions. Study Design In vitro study. Methods VFFs from young (12-week-old) and aged (19-month-old) Sprague-Dawley rats were compared. Proliferative capacity, ratio of myofibroblast to fibroblast, myofibroblast function, and extracellular matrix production were examined in the following conditions: naive, basic fibroblast growth factor (bFGF) supplemented, and hepatocyte growth factor (HGF) supplemented. Results Aged VFFs demonstrated reduced proliferation by cell counting, though the ratio of Ki-67-positive cells showed no difference. Aged VFFs exhibited an increased expression of alpha-smooth muscle actin (alpha-SMA); however, they demonstrated no enhanced contractile ability in a gel contraction assay. Type I collagen protein was increased age dependently, accompanied with decreased Mmp1 and unchanged Col1a1 transcription. Type I collagen protein and alpha-SMA represented quite similar reduction patterns to bFGF or HGF administration. Conclusions The following possible characteristics of aged VFFs were implied: long duration of mitosis, increased myofibroblast population size with certain dysfunctions, reduced type I collagen turnover, and correlation between alpha-SMA expression and type I collagen metabolism. Further investigations of these features will help to clarify presbyphonia's pathology and establish treatment strategies.