Classification and culture of spiral ligament fibrocytes from mice

In this study, we established an immunocytochemical strategy to classify the fibrocytes of the murine spiral ligament (SL), and SL cultures were characterized. Similar to those in other mammals, three different types of fibrocytes were identified. Type I fibrocytes, which are found lateral to the stria vascularis, showed positive immunoreactivity for caldesmon and S-100 protein and were not stained for sodium-potassium-adenosinetriphosphatase (Na-K-ATPase). Type II fibrocytes are located lateral to the spiral prominence epithelium and suprastrial region, and they were distinguishable by their positive staining for Na-K-ATPase. Type III fibrocytes, which are found adjacent to bone in the inferior region of the SL, contained caldesmon but not S-100 or Na-K-ATPase. Secondary cultures from the SL were positive for caldesmon and S-100 and negative for Na-K-ATPase, suggesting that these cells were type I fibrocytes. The present immunocytochemical approach was useful for the classification of murine fibrocyte cultures, and these cultures may benefit future immunological studies of the inner ear because mice have been well characterized immunologically.