Presence and role of glycosaminoglycans in amyloidosis

Though the presence of glycosaminoglycans in amyloid deposits has been recognized for a long time their role in the pathogenesis of the disorder has remained elusive. As shown here, liver and spleen of human patients with secondary amyloidosis contain 5 to 10 times the amount of glycosaminoglycans as normal organs. Of the three major glycosaminoglycans measured, the heparan sulfate fraction showed the largest increase. In mice where amyloidosis was induced by the injection of casein and enhancing factor (accelerated model) 35SO4-labeled, or Alcian blue stained glycosaminoglycans appeared as early as and at the same location as proteins detected by Congo red staining which was about 2 days after initiation of the procedure. When glycosaminoglycan synthesis was followed in liver and spleen slices of control and experimental animals a significant increase in rate was found in the spleen of the experimental mice. Though there was an increase in heparan sulfate synthesis the major contribution to the overall increase was made by the chondroitin sulfates in the accelerated as well as in the standard induction model. In addition, unlike in the human disorder the chondroitin sulfates were the major glycosaminoglycans which had accumulated in the spleens of animals which had amyloidosis induced by the long term standard procedure (6 weeks) as measured by isolation and uronic acid analysis. The data presented here show that glycosaminoglycans appear to play an important and perhaps direct role in the process of amyloid deposition in the human disease as well as in the experimentally induced disorder in animals.