Variation in amount of wild-type transthyretin in different fibril and tissue types in ATTR amyloidosis

Abstract

Familial transthyretin (TTR) amyloidosis is caused by a mutation in the TTR gene, although wild-type (wt) TTR is also incorporated into the amyloid fibrils. Liver transplantation (LT) is the prevailing treatment of the disease and is performed in order to eliminate the mutant TTR from plasma. The outcome of the procedure is varied; especially problematic is a progressive cardiomyopathy seen in some patients, presumably caused by continued incorporation of wtTTR. What determines the discrepancy in outcome is not clear. We have previously shown that two structurally distinct amyloid fibrils (with or without fragmented ATTR) are found among ATTRV30M patients. In this study, we investigated the proportion of wtATTR in cardiac and adipose amyloid from patients having either fibril type. It was found that cardiac amyloid more easily incorporates wtTTR than adipose amyloid, offering a potential explanation for the vulnerability of cardiac tissue for continued amyloidosis after LT. In cardiac tissue, fibrils with fragmented ATTR contained a higher wt proportion than fibrils without, suggesting that continued incorporation of wtTTR after LT, perhaps, can take place more easily in these patients. In adipose tissue, a rapid increase in wt proportion after LT indicates that a rather fast turnover of the deposits must occur. A difference in wt proportion between the fibril types was seen post-LT but not pre-LT, possibly caused by differences in turnover rate. Conclusively, this study further establishes the basic dissimilarities between the two fibril types and demonstrates that their role in LT outcome needs to be further investigated.

In Vivo Visualization of Amyloid Deposits in the Heart with 11C-PIB and PET

“…Although previous studies have shown a good correlation between MBF based on 11 C-acetate and MBF as measured by 13 N-ammonia (20) and 15 O-water (19), both in healthy controls and patients with hypertrophic cardiomyopathy, the use of 11 C-acetate for MBF measurements in amyloidosis patients has not been validated. A possible explanation for the low apparent MBF in the patient group could be partial-volume effect.…”

“…They are not scarred tissue but nonfunctional, probably nonperfusable, myocardium with a mechanical restriction, resulting in a reduced apparent transmural MBF as measured by 11 C-acetate, because the kinetic model measures the mean perfusion in both perfusable and nonperfusable tissue. It may well be the case that MBF is normal in remaining perfusable tissue, and future studies will include MBF measurements with 15 O-water, with which MBF measurements solely in perfusable tissue can be obtained as well (27).…”

“…For immunohistochemistry, endomyocardial biopsy samples were incubated with the polyclonal rabbit antiserum 1898 against recombinant TTR50-127 developed in-house (15), the monoclonal antibody pwlam against AL l (16), and the monoclonal antibody Sne5 against protein serum amyloid A (unpublished data, Nyström and Westermark). Western blot analyses were performed on extracts from subcutaneous adipose tissue biopsies using antibodies as previously described (17).…”

Amyloid deposits derived from transthyretin in the ligamentum flavum as related to lumbar spinal canal stenosis

“…Biochemical analysis revealed that amyloid deposits in the ligamentum flavum of lumbar spinal canal stenosis patients consisted of C-terminal transthyretin fragments, which constantly occur in amyloid deposits in senile systemic amyloidosis, in addition to full-length transthyretin. 21,23 Although the roles of transthyretin fragmentation in amyloid formation remain to be clarified, there may be a common pathologic process for transthyretin amyloid formation in the ligamentum flavum of lumbar spinal canal stenosis patients and that in senile systemic amyloidosis. The small spotty transthyretin-negative amyloid deposits were more frequently seen in younger patients, but precursor proteins of those amyloid deposits remain to be determined.…”

“…A polyclonal antiserum against truncated transthyretin 50-127 (transthyretin 50-127), produced in rabbits, was diluted 1:2000 and used as the primary antibody. 21 A goat anti-rabbit antibody conjugated with horseradish peroxidase (Dako), diluted 1:5000, was used as the secondary antibody. The reaction was visualized by using an enhanced chemiluminescence system (GE Healthcare, Buckinghamshire, UK).…”