Abstract: Objectives To analyze serum amyloid protein A (SAA) subtype and amino acid mutation sequence of the renal biopsy specimens from patients with renal amyloidosis secondary to ankylosing spondylitis (AS) by laser microdissection combined with mass spectometry. Methods Kidney biopsy formalin-preserved paraffin-embedded (FFPE) specimen slices were stained by congo red, the positive areas of Congo red staining were selected by microdissection, after trypsin hydrolysis and filtration, peptide samples were subjected to liquid chromatography tandem mass spectrometry. Analysis softwares were used to evaluate the results, and the patient's amino acid sequence of SAA protein was compared to mutant amino acid sequence reported by literature or deduced from mutant SAA gene to determine whether there was a variation. Results SAA1 and SAA2 proteins with high abundance were identified by mass spectrometry, serum amyloid P and apolipoprotein E were also detected. No variation of SAA1 and SAA2 protein was detected. Conclusions The SAA1 and SAA2 proteins in AA amyloidosis secondary to AS were identified for the first time, which enriched the pathogenesis of amyloidosis secondary to AS and provided a new method for the accurate classification of AA amyloidosis.

Key words: Amyloidosis, Laser microdissection, Serum amyloid A prtotein (SAA), LC-MS/MS