“Gene Expression in Intracranial Aneurysms – A Comparison Analysis of Aneurysmal Walls and Extracranial Arteries with Real Time Polymerase Chain Reaction and Immunohistochemistry”

Background This study was aimed at evaluating the gene expression levels of 4 genes in the intracranial aneurysm wall and comparing them with extracranial arteries. The analysis was done using real-time polymerase chain reaction (RT-PCR) and immunohistochemistry (IHC). Also, a correlation of the differential genetic expression was done with various patient clinical and radiologic factors. Methods The quantitative assessment of ribonucleic acid levels was done with RT-PCR and was validated with IHC. The genes studied were collagen 1A2 (COL1A2), tissue inhibitor of metalloproteinase 4 (TIMP4), cathepsin B (CTSB), and alpha-1 antitrypsin (α-1 AT). The analysis was done on 24 aneurysm sacs and superficial temporal/occipital artery samples from patients undergoing surgical clipping. Results The mean fold change of COL1A2 in the aneurysm sample was 8.89, that of TIMP4 was 10.16, that of CTSB was 1.02, and that of α-1 AT was 1.46 when compared with normal control vessel on PCR. On semiquantitative IHC, COL1A2 was 94.44%, α-1 AT was 77.8% overexpressed, CTSB was positive in 50%, and the expression of TIMP4 was 94.4% underexpressed in aneurysmal walls. There was no statistically significant correlation between patient profile and gene expression. Conclusions On RT-PCR and IHC analysis, COL1A2 and α-1 AT were overexpressed, CTSB was marginally overexpressed, and TIMP4 had equivocal expression in the aneurysmal sac when compared with the normal extracranial vessel. This is the first study of its kind in the Indian population with the largest sample size on live human patients.