Caldesmon Expression in Odontogenic Cysts
Caldesmon is an actin-myosin binding protein which regulates actin-myosin interactions. The heavy isoform (h-caldesmon) is specific to smooth muscle cells and the non-muscle type light isoform (l-caldesmon) is involved in maintaining cytoskeletal architecture and integrity. The role of caldesmon in the pathogenesis of odontogenic cysts is unknown. The aim of this study was to evaluate caldesmon expression in benign odontogenic cysts using immunohistochemistry (IHC). Caldesmon expression was compared with markers of myoid differentiation, alpha-smooth muscle actin (α-SMA) and calponin.
Methods: Eleven cases of formalin-fixed paraffin-embedded periapical granuloma (PAG), radicular cyst (RC), inflamed dentigerous cyst (IDC) and uninflamed dentigerous cyst (UDC) were selected. Histopathology was confirmed and tissue microarrays were constructed by coring three representative areas from each specimen. IHC was performed using antibodies against SMA, calponin and caldesmon. Microscopic analysis determined the percentage of positive cells in each core. Statistical analyses were performed using PRISM software and significance was denoted when p>0.05.
Results: More cells were caldesmon positive in IDC compared with UDC and similarly, more cells were caldesmon positive in PAG compared with RC (p=0.01). There was no significant difference when inflammatory lesions (PAG/RC) were compared with developmental lesions (UDC/IDC). More cells were caldesmon positive in all disease types compared with α-SMA and calponin, staining predominantly spindle/stellate-shaped cells (p<0.05). There was no significant difference between α-SMA and calponin expression in PAG and RC but α-SMA expression was significantly higher in IDC and UDC.
Conclusions: Cells histomorpholoigically consistent with fibroblasts were the predominant caldesmon positive cell type in odontogenic cysts. Caldesmon expression was significantly higher in all disease types when compared with other myoid markers implicating the role of l-caldesmon in the disease processes. This is likely to reflect the stromal tissue characteristics in odontogenic lesions studied, particularly increased cell motility and differentiation related to the degree of inflammation in the cyst walls.