Yohei Misumi

SELDI-TOF Mass Spectrometry Evaluation of Variant Transthyretins for Diagnosis and Pathogenesis of Familial Amyloidotic Polyneuropathy

BACKGROUND Mass spectrometric analyses are valuable for detection of transthyretin (TTR) variants, which cause familial amyloidotic polyneuropathy (FAP). However, those methods require an immunoprecipitation step with an anti-TTR antibody and are not suitable for quantitative detection. We investigated the usefulness of SELDI-TOF mass spectrometry (MS) without an immunoprecipitation step. METHODS We used ProteinChips with chromatographic capture formats to detect TTRs. We attempted to correlate the intensity of mixed samples of amyloidogenic TTR (ATTR) V30M to wild-type (WT) TTR. We analyzed the proportion of ATTR V30M in amyloid-laden cardiac tissues from FAP patients, and also evaluated samples from FAP patients with 16 other TTR mutations. RESULTS Detection of ATTR required only 3 h of SELDI-TOF MS analysis. We determined that SELDI-TOF MS was suitable for quantitative detection of ATTR V30M and demonstrated that the proportion of ATTR V30M to WT TTR was 46.6% in amyloid-laden cardiac tissue from an FAP patient who died 10 years after liver transplantation. With this method, we identified 12 of 17 TTR variants. Small mass shifts and low concentrations of variants prevented ATTR detection. By changing the analytical conditions, we achieved detection of low concentrations of ATTR Y114C in serum. CONCLUSIONS SELDI-TOF MS is a reliable tool for quantitative evaluation of TTR variants, in both tissue amyloid deposits and body fluids. This method is useful for the diagnosis and investigation of the pathogenesis of FAP.

Clinicopathological features of senile systemic amyloidosis: an ante- and post-mortem study

Senile systemic amyloidosis is a common age-related amyloidosis that involves accumulation of wild-type transthyretin, with cardiac dysfunction being a predominant result. The importance of obtaining an accurate diagnosis of senile systemic amyloidosis has been increasingly recognized, so that novel treatments are being developed. However, the clinicopathological features of senile systemic amyloidosis remain to be completely understood. Here, we evaluated cardiac specimens from 181 consecutive post-mortem cases older than 40 years, including 6 cases of senile systemic amyloidosis, and 5 cases of familial amyloidotic polyneuropathy, which is a hereditary systemic amyloidosis caused by mutant forms of transthyretin. Furthermore, we studied ante-mortem clinicopathological findings of 11 senile systemic amyloidosis cases, in which 9 cases underwent gastrointestinal tract biopsy and/or subcutaneous tissue biopsy, at Kumamoto University Hospital. Of the autopsied cases of elderly Japanese (older than 80 years), 12% had senile systemic amyloidosis, with the percentage increasing with age. The occurrence of senile systemic amyloidosis in elderly Japanese patients was lower than that in previous reports, which suggests that a genetic background and/or environmental factor(s) may have important roles in the occurrence of senile systemic amyloidosis. Transthyretin amyloid deposits in familial amyloidotic polyneuropathy cases developed mainly in the pericardium and the surrounding muscle fascicles, whereas in cases with senile systemic amyloidosis the transthyretin amyloid deposits had a patchy plaque-like shape and developed mainly inside the ventricular wall. Biopsies from senile systemic amyloidosis patients evidenced amyloid deposits in 44% (4/9) of gastrointestinal tract and subcutaneous tissue samples combined. As myocardial biopsy may be dangerous for elderly people, the use of a combination of gastrointestinal tract and subcutaneous tissue biopsies may make diagnosis of senile systemic amyloidosis easier.

Changes in pathological and biochemical findings of systemic tissue sites in familial amyloid polyneuropathy more than 10 years after liver transplantation

Objective To elucidate the long-term effects of liver transplantation (LT) on familial amyloid polyneuropathy (FAP). Methods We investigated clinicopathological and biochemical characteristics of systemic tissues in four autopsied cases of FAP patients surviving more than 10 years after LT and seven autopsied cases without LT. For analysing the truncated form of transthyretin (TTR) in amyloid, we also employed specimens from additional 18 FAP patients. Results Several tissue sites such as the heart, tongue and spinal cord had moderate-to-severe amyloid deposits but other tissues showed no or mild amyloid deposition. Those findings seemed similar to those observed in senile systemic amyloidosis (SSA), a sporadic amyloidosis caused by wild-type (WT) TTR. Also, amyloid deposits in systemic tissue sites except for the spinal cord in patients after LT derived mostly from WT TTR secreted from the normal liver grafts. In addition, in non-transplantation patients, proportions of WT TTR seemed to be relatively high in those tissue sites in which patients after LT had severe amyloid deposition, which suggests that WT TTR tends to form amyloid in those tissue sites. Finally, although the truncation of TTR in amyloid deposits did not depend on undergoing LT, we elucidated the truncation of TTR occurred predominantly in patients from non-endemic areas of Japan, where FAP amyloidogenic TTR V30M patients are late onset and low penetrance, compared with patients from an endemic area of Japan. Conclusions FAP may shift to systemic WT TTR amyloid formation after LT, which seems to be similar to the process in SSA. The truncation of TTR in amyloid deposits may depend on some genetic or environmental factors other than undergoing LT.

Chain reaction of amyloid fibril formation with induction of basement membrane in familial amyloidotic polyneuropathy

Familial amyloidotic polyneuropathy (FAP) is characterized by extracellular deposition of amyloid fibrils caused by a point mutation in the transthyretin (TTR) gene. Despite data from a number of in vitro studies of TTR amyloidogenesis, many questions, including where and how these fibrils form in vivo and what is the impact of amyloid deposition on tissues, remain unanswered. Here, we analysed the relationship between amyloid fibril formation and micro‐environmental changes by using autopsy cardiac tissues from 11 patients with FAP and a smooth muscle cell line. Ultrastructural studies of cardiomyocytes and vascular smooth muscle cells showed that amyloid fibrils formed first at the basement membrane and that amorphous non‐fibrillar TTR deposits and premature fibrils predominated during the early stage of amyloid deposition. Immunohistochemical analyses revealed that expression of major components of the basement membrane, such as collagen IV, laminin, and fibronectin, increased in parallel with the accumulation of TTR amyloid fibrils. In vitro studies with a vascular smooth muscle cell line revealed that synthetic TTR aggregates increased expression of these basement membrane components. Serum levels of collagen IV in FAP patients were significantly higher than those in healthy controls. Our data thus indicate that TTR amyloid fibrils formed first at the basement membrane and that expression of basement membrane components that was induced by amyloid deposition contributed to further amyloid deposition. This chain reaction may have important implications for FAP pathogenesis. Copyright

Transmission of circulating cell-free AA amyloid oligomers in exosomes vectors via a prion-like mechanism

Recent studies clearly demonstrated that several types of pathogenic amyloid proteins acted as agents that could transmit amyloidosis by means of a prion-like mechanism. Systemic AA amyloidosis is one of the most severe complications of chronic inflammatory disorders, particularly rheumatoid arthritis. It is well known that, similar to an infectious prion protein, amyloid-enhancing factor (AEF) acts as a transmissible agent in AA amyloidosis. However, how AEF transmits AA amyloidosis in vivo remained to be fully elucidated. In the present study, we focused on finding cell-free forms of AEF and its carriers in circulation by using the murine transfer model of AA amyloidosis. We first determined that circulating cell-free AEF existed in blood and plasma in mice with systemic AA amyloidosis. Second, we established that plasma exosomes containing AA amyloid oligomers derived from serum amyloid A had AEF activity and could transmit systemic AA amyloidosis via a prion-like mechanism. These novel findings should provide insights into the transmission mechanism of systemic amyloidoses.

Effect of liver transplantation on transthyretin Tyr114Cys-related cerebral amyloid angiopathy

Objective: Patients with amyloidogenic transthyretin (ATTR) Tyr114Cys develop amyloid deposits in cerebral blood vessels, cerebral hemorrhage, and rapidly progressive dementia that presents with hereditary cerebral amyloid angiopathy (CAA). However, no treatment has been identified for CAA. Although liver transplantation has become an acceptable treatment of TTR-related amyloidosis, liver transplantation may not successfully treat CNS manifestations of the disorder. In this study, we examined the effect of liver transplantation on these manifestations of TTR-related CAA. Methods: We compared clinical courses of three patients with CAA associated with ATTR Tyr114Cys who underwent liver transplantation with those of five patients with the disorder who did not undergo liver transplantation. Results: The mortality and occurrence of cerebral hemorrhage and dementia in patients having transplantations were reduced compared with those in patients not having transplantations. The two groups did not differ with regard to the frequency of episodes of fluctuating consciousness and TIAs. The group undergoing transplantations had significantly smaller volumes of intracranial hemorrhage than did the no-transplantation group. Conclusion: Liver transplantation was effective for CNS manifestations of cerebral amyloid angiopathy associated with amyloidogenic transthyretin Tyr114Cys.

Effects of tafamidis treatment on transthyretin (TTR) stabilization, efficacy, and safety in Japanese patients with familial amyloid polyneuropathy (TTR-FAP) with Val30Met and non-Val30Met: A phase III, open-label study

INTRODUCTION The efficacy and safety of tafamidis in transthyretin (TTR) familial amyloid polyneuropathy (TTR-FAP) were evaluated in this open-label study. METHODS Japanese TTR-FAP patients (n=10; mean age 60.1 years) received tafamidis meglumine (20mg daily; median treatment duration 713.5 days). The primary endpoint was TTR stabilization at Week 8. Secondary endpoints included Neuropathy Impairment Score-Lower Limb (NIS-LL), Norfolk QOL-DN total quality of life (TQOL), and modified body mass index (mBMI). RESULTS TTR stabilization was achieved in all patients at Weeks 8 and 26, 9 out of 10 patients at Week 52, and 8 out of 10 patients at Week 78. The percentage (95% CI) of NIS-LL responders (increase from baseline in NIS-LL<2) was 80.0% (44.4, 97.5), 60.0% (26.2, 87.8), and 40.0% (12.2, 73.8) and mean(SD) NIS-LL change from baseline was 2.1 (5.6), 3.6 (4.4), and 3.3 (4.7), at Weeks 26, 52, and 78, respectively. Mean (SD) changes from baseline in TQOL and mBMI at Weeks 26, 52, and 78 were 11.8 (20.0), 9.1 (12.5), and 10.8 (13.7) for TQOL, and 26.6 (61.9), 64.9 (80.0), and 53.7 (81.4) for mBMI, respectively. Ambulation status was preserved in 4 out of 8 patients at Week 78. Most adverse events (AEs) were mild/moderate, with no discontinuations due to AEs. CONCLUSIONS Tafamidis stabilized TTR, was safe and well-tolerated, and was effective over 1.5 years in slowing neurologic progression and maintaining TQOL and nutrition status in TTR-FAP.

Effect of age and sex differences on wild-type transthyretin amyloid formation in familial amyloidotic polyneuropathy: A proteomic approach

BACKGROUND Age and sex differences are closely related to the onset of senile systemic amyloidosis (SSA) caused by wild-type (WT) transthyretin (TTR). However, the effects of these differences on the amyloid formation mechanism in familial amyloid polyneuropathy (FAP) caused by variant TTR, have remained unclear. To elucidate age and sex differences in FAP, we investigated biochemical characteristics of amyloid deposits in different tissue sites of FAP by proteomic analysis. METHODS We used shotgun liquid chromatography/tandem mass spectrometry to analyze the proportions of variant and WT TTR in amyloid deposits in different tissues, such as cardiac, kidney, peripheral nerves, and gastrointestinal tissues, from 23 autopsied FAP cases. RESULTS AND CONCLUSIONS The analysis revealed a highly significant correlation between the proportion of WT TTR and age at autopsy in cardiac tissues, whereas the analysis indicated no correlation in kidney, peripheral nerves, and gastrointestinal tissues. In addition, we demonstrated age-related significantly increased WT TTR deposits, but not variant TTR deposits, in cardiac tissues of male patients. Taken together, these data suggest that both age and sex differences affect cardiac amyloid formation, mainly derived from WT TTR, in FAP.

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

Amyloidosis is a protein conformational disorder with the distinctive feature of extracellular accumulation of amyloid fibrils that come from different proteins. In the ligamentum flavum of the lumbar spine, amyloid deposits were frequently found in elderly patients with lumbar spinal canal stenosis and were at least partially formed by wild-type transthyretin. However, how amyloid deposits in the ligamentum flavum affect lumbar spinal canal stenosis has remained unclear. In this study, we analyzed clinical, pathologic, and radiologic findings of patients with lumbar spinal canal stenosis who had amyloid deposits in the ligamentum flavum. We studied 95 ligamentum flavum specimens obtained from 56 patients with lumbar spinal canal stenosis and 21 ligamentum flavum specimens obtained from 19 patients with lumbar disk herniation. We evaluated histopathologic findings and clinicoradiologic manifestations, such as thickness of the ligamentum flavum and lumbar spinal segmental instability. We found that all 95 ligamentum flavum specimens resected from patients with lumbar spinal canal stenosis had amyloid deposits, which we classified into two types, transthyretin-positive and transthyretin-negative, and that transthyretin amyloid formation in the ligamentum flavum of patients with lumbar spinal canal stenosis was an age-associated phenomenon. The amount of amyloid in the ligamentum flavum was related to clinical manifestations of lumbar spinal canal stenosis, such as thickness of the ligamentum flavum and lumbar spinal segmental instability, in the patients with lumbar spinal canal stenosis with transthyretin-positive amyloid deposits. To our knowledge, this report is the first to show clinicopathologic correlations in transthyretin amyloid deposits of the ligamentum flavum. In conclusion, transthyretin amyloid deposits in the ligamentum flavum may be related to the pathogenesis of lumbar spinal canal stenosis in elderly patients.

Novel function of transthyretin in pancreatic alpha cells

Although transthyretin (TTR) is expressed in pancreatic alpha (glucagon) cells in the islets of Langerhans, the function of TTR in pancreatic alpha cells remains unknown. In this study, by using TTR knockout (TTR KO) mice, we determined the novel role of TTR in glucose homeostasis. We demonstrated that TTR KO mice evidenced impaired recovery of blood glucose and glucagon levels. Lack of TTR induced significantly lower levels of glucagon in the islets of Langerhans. These results suggest that TTR expressed in pancreatic alpha cells may play important roles in glucose homeostasis via regulating the expression of glucagon.