Expression of collagen types I, II and III in juvenile angiofibromas.

Extracellular matrix components have rarely been the focus of interest in juvenile angiofibroma (JA) studies. Although JAs are known to be collagen-rich tumours, single collagens have not been analysed so far. This investigation aimed to study the expression of the fibrillar collagen types I, II and III in JAs using quantitative RT-PCR (n = 15), Western blot analysis (n = 7) and immunohistochemical staining (n = 9). Nasal mucosa (NM) specimens were used as control tissues. ELISA investigation (n = 3) was performed to determine the concentration of C-terminal propeptide of type I collagen in blood serum before and after JA resection. Quantitative RT-PCR found significantly elevated Col1A1 (p < 0.001), Col1A2 (p < 0.001) and Col3A1 (p < 0.001) mRNA levels in JAs, compared with NM. Western blot analysis and immunohistochemical staining proved that there is a significant collagen type I and III protein expression in JAs. In none out of 3 patients, ELISA investigation found evidence for elevated concentrations of C-terminal propeptide of type I collagen before tumour resection, compared with postsurgical measurements. Results of the findings using quantitative RT-PCR, Western blot analysis and immunohistochemistry determined that type II collagen is practically absent in JAs. Based on these findings, type I and III collagen are confirmed as being major components of the extracellular matrix in JAs. However, our findings are not encouraging as regards the use of C-terminal Col I propeptide as a suitable serum tumour marker. Our findings confirming that collagen type II expression is practically absent in JAs refutes the theory that JAs originate in cartilage tissue.