MMP-12, a novel matrix metalloproteinase associated with giant cell arteritis.

MMP-12, a novel matrix metalloproteinase associated with giant cell arteritis SIR, Identification of specific mediators of arterial damage in GCA is crucial to understand its pathogenesis, and may have important clinical implications both for diagnosis and treatment. Thirty-two non-consecutive patients who underwent a temporal artery biopsy for evaluation of GCA were included in this study. Nineteen of the 32 biopsies had histological evidence of GCA. Detailed pathological findings were recorded on every biopsy and assessed using semi-quantitative scales [1]. Patients' demographic and clinical information was collected. All subjects gave written informed consent. The study was approved by our institutional review board (Wills Eye Institute). In brief, total RNA was isolated from the temporal artery biopsies. The concentration and quality of RNA was determined using an Agilent 2100 Bioanalyzer (Agilent Technologies, Wilmington, DE, USA). DNA microarray analysis using Affymetrix U133 Plus 2.0 human genome arrays was performed in two temporal artery specimens with histologically proven GCA and two that were negative for GCA. We focused on identifying which of the 23 human MMPs were up-regulated in GCA. To confirm the expression levels of those genes up-regulated in the microarray analysis, relative quantification by real-time PCR was performed in all the 32 temporal artery biopsies, and gene expression between arteries with histological evidence of GCA and controls were compared. Single-strand cDNA was synthesized from total RNA. Real-time PCR SYBR Green assays with pre-designed primers for MMP-2,-9,-12 and GAPDH (SABioscience Corp., Frederick, USA) were run in a Stratagene Mx3000P thermal cycler. All the assays were run in triplicate by an investigator blinded to the pathological and clinical data. Demographic and clinical features of the patients are shown in Table 1. Those who had negative biopsy results were diagnosed with conditions different from GCA based on their clinical manifestations, the negative biopsy, their lack of response to steroid therapy and their clinical evolution. Seven biopsy-negative patients fulfilled the ACR classification criteria for GCA. In the GCA-negative arteries, >80% of the internal elastic lamina (IEL) was preserved, whereas IEL degradation was common in temporal arteries with histological evidence of GCA. Mild intimal hyperplasia was observed in some of the GCA-negative temporal arteries, but all the GCA-positive arteries showed a high level of intimal hyperplasia and in seven (36.8%) of these, the lumen was virtually occluded. A total of approximately 2000 genes showed a significant differential level of expression in our microarray analysis. Approximately half of …