Immunohistochemical study of alpha-smooth muscle actin in odontogenic cysts and tumors

Context: Myofibroblasts (MFs) are fibroblasts with smooth muscle-like features characterized by the presence of a contractile apparatus. Alpha-smooth muscle actin (α-SMA) is the actin isoform that predominates within vascular smooth muscle cells and plays an important role in fibrogenesis. MFs are metabolically and morphologically distinctive fibroblasts expressing α-SMA, and their activation plays a key role in development of the fibrotic response. Aims and Objectives: The aim of this study is to demonstrate the frequency, distribution and expression of α-SMA-positive MFs in odontogenic keratocyst (OKC), dentigerous cyst (DC) and ameloblastoma and correlate it to their aggressive biological behavior. Settings and Design: A retrospective study of 45 diagnosed cases, which includes 15 cases of OKC, 15 cases of DC and 15 cases of ameloblastoma, was undertaken to demonstrate expression of α-SMA retrieved from archives of our department. Materials and Methods: α-SMA mouse anti-human antibody and horseradish peroxidase detection system were used in this study. Statistical Analysis: Descriptive statistical analysis and ANOVA test were used for statistical analysis. Results: The difference in mean α-SMA count was found to be statistically significant between ameloblastoma and DC group (P < 0.001) as well as OKC and DC group (P < 0.001). No significant difference is observed between ameloblastoma and OKC group (P > 0.05). Results showed that mean number of stromal MFs in OKC and ameloblastoma were significantly higher than DC. Conclusion: The present study has shown that the mean number of MFs was higher in OKC and ameloblastoma, while the mean number of MFs in DC was quite low and significantly different from that of ameloblastoma and OKC.