Relative quantification of collagen mRNA in fibroblasts by a radioactive polymerase chain reaction technique

A radioactive polymerase chain reaction (PCR) method has been developed for the relative quantification of the human alpha-2 chain of type I collagen [hu alpha-2(I)] in cells. cDNAs generated by reverse transcription from the total pool of cytoplasmic RNA serve as a template for polymerase chain reaction amplification of a hu alpha-2(I) cDNA primed by two sequence-specific synthetic oligonucleotides. The distinctive 390 bp hu alpha-2(I) cDNA and two Aval fragments of 220 and 170 bp are identified by agarose gel electrophoresis. alpha-32P-dCTP of defined specific activity is included in the PCR reaction and the 390 bp cDNA is excised from the electrophoresis gel to permit direct radioactive quantification of hu alpha-2(I) mRNA. The amount of hu alpha-2(I) mRNA expressed in as few as 111 fibroblasts was determined reliably. In contrast, the hu alpha-2(I) mRNA from at least 5 x 10(5) fibroblasts was required for detection by Northern blot analysis developed with the same cDNA probe radiolabelled with alpha-32P-dCTP by random priming. Human bronchoalveolar lavage (BAL) fluids of six patients with fibrosing lung diseases stimulated the level of expression of hu alpha-2(I) mRNA in cultured human fibroblasts as determined by this technique. The radioactive PCR method thus quantifies hu alpha-2(I) mRNA in fibroblasts with sufficient sensitivity to study fibroblast activation in vitro and detect fibroblast stimuli in human clinical samples.