Laser capture as a tool for analysis of gene expression in inflamed synovium

Most current approaches used to analyze gene expression in tissue samples are based on RNA isolated either from cultured synovial cells or from synovial biopsies. However, this strategy does not distinguish between specific gene expression profiles of cells originating from discrete tissue areas. Therefore, we established the combination of laser-mediated microdissection and RNA arbitrarily primed polymerase chain reaction (RAP-PCR) for differential display to analyze profiles of gene expression in histologically defined areas of arthritic tissue. Cryosections derived from synovial tissue were used to obtain cell samples from different tissue areas of both rheumatoid arthritis (RA) and osteoarthritis (OA) patients using a microbeam laser microscope. RNA was isolated and analyzed using nested RNA arbitrarily primed PCR to generate a fingerprint of the expressed gene sequences. Differentially expressed bands were isolated, cloned, and sequenced. Differential expression of identified sequences was confirmed by in situ hybridization and immunohistochemistry.