Marked and rapid regression of hepatic amyloid deposition in a patient with systemic light chain (AL) amyloidosis after high-dose melphalan therapy with stem cell transplantation

Collagen inhibits phagocytosis of amyloid in vitro and in vivo and may act as a 'don't eat me' signal

BACKGROUND

Systemic amyloidosis refers to a group of protein misfolding disorders characterized by the extracellular deposition of amyloid fibrils in organs and tissues. For reasons heretofore unknown, amyloid deposits are not recognized by the immune system, and progressive deposition leads to organ dysfunction.

METHODS

In vitro and in vivo phagocytosis assays were performed to elucidate the impact of collagen and other amyloid associated proteins (eg serum amyloid p component and apolipoprotein E) had on amyloid phagocytosis. Immunohistochemical and histopathological staining regimens were employed to analyze collagen-amyloid interactions and immune responses.

RESULTS

Histological analysis of amyloid-laden tissue indicated that collagen is intimately associated with amyloid deposits. We report that collagen inhibits phagocytosis of amyloid fibrils by macrophages. Treatment of 15 patient-derived amyloid extracts with collagenase significantly enhanced amyloid phagocytosis. Preclinical mouse studies indicated that collagenase treatment of amyloid extracts significantly enhanced clearance as compared to controls, coincident with increased immune cell infiltration of the subcutaneous amyloid lesion.

CONCLUSIONS

These data suggest that amyloid-associated collagen serves as a 'don't eat me' signal, thereby hindering clearance of amyloid. Targeted degradation of amyloid-associated collagen could result in innate immune cell recognition and clearance of pathologic amyloid deposits.

Molecular Mechanisms of Cardiac Amyloidosis

Cardiac involvement has a profound effect on the prognosis of patients with systemic amyloidosis. Therapeutic methods for suppressing the production of causative proteins have been developed for ATTR amyloidosis and AL amyloidosis, which show cardiac involvement, and the prognosis has been improved. However, a method for removing deposited amyloid has not been established. Methods for reducing cytotoxicity caused by amyloid deposition and amyloid precursor protein to protect cardiovascular cells are also needed. In this review, we outline the molecular mechanisms and treatments of cardiac amyloidosis.

Significance of Oligomeric and Fibrillar Species in Amyloidosis: Insights into Pathophysiology and Treatment

Amyloidosis is a term referring to a group of various protein-misfolding diseases wherein normally soluble proteins form aggregates as insoluble amyloid fibrils. How, or whether, amyloid fibrils contribute to tissue damage in amyloidosis has been the topic of debate. In vitro studies have demonstrated the appearance of small globular oligomeric species during the incubation of amyloid beta peptide (Aβ). Nerve biopsy specimens from patients with systemic amyloidosis have suggested that globular structures similar to Aβ oligomers were generated from amorphous electron-dense materials and later developed into mature amyloid fibrils. Schwann cells adjacent to amyloid fibrils become atrophic and degenerative, suggesting that the direct tissue damage induced by amyloid fibrils plays an important role in systemic amyloidosis. In contrast, there is increasing evidence that oligomers, rather than amyloid fibrils, are responsible for cell death in neurodegenerative diseases, particularly Alzheimer’s disease. Disease-modifying therapies based on the pathophysiology of amyloidosis have now become available. Aducanumab, a human monoclonal antibody against the aggregated form of Aβ, was recently approved for Alzheimer’s disease, and other monoclonal antibodies, including gantenerumab, solanezumab, and lecanemab, could also be up for approval. As many other agents for amyloidosis will be developed in the future, studies to develop sensitive clinical scales for identifying improvement and markers that can act as surrogates for clinical scales should be conducted.

Giant Hepatomegaly with Spleno-testicular Enlargement in a Patient with Apolipoprotein A-I Amyloidosis: An Uncommon Type of Amyloidosis in Japan

Hereditary systemic amyloidosis aside from transthyretin-related familial amyloid polyneuropathy is quite uncommon in Japan. We herein report a sporadic case of hereditary apolipoprotein A-I (apoAI) amyloidosis. The patient was a 43-year-old Japanese man who exhibited marked hepatomegaly with spleno-testicular enlargement. While he was initially thought to have primary AL amyloidosis, a proteomics analysis revealed that the amyloid was composed of variant apoAI with an E34K variant. To date, only one patient with apoAI amyloidosis has been reported in Japan. However, our study suggests that more patients may be present in Japan, and the majority may have been diagnosed with other types of amyloidosis due to its clinical similarity.

Long-Term Outcomes of Patients With Amyloidosis Following Kidney Transplant

OBJECTIVES

Reported graft and patient survival rates in amyloidosis after renal transplant differ considerably between studies.

MATERIALS AND METHODS

Group 1 included 24 patients who had end-stage renal disease secondary to amyloidosis. Group 2 (the control group) included 24 consecutive patients who had kidney disease secondary to various causes other than amyloidosis. Comparisons between groups were made for kidney and patient survival rates and other complications following kidney transplant. We also compared survival rates of patients in group 1 versus another control group that included patients with amyloidosis who were treated with hemodialysis (group 3; n = 25).

RESULTS

Mean follow-up was 109.5 ± 79.8 months. Biopsy-proven acute rejection and graft failure rates were not significantly different between groups. In group 1 versus group 2, the cumulative 10-year and 20-year patient survival rates were 68.2% versus 86.1% and 36.9% versus 60.3%, respectively (P = .041). Survival was not significantly different in group 1 compared with group 2 and group 3, although patients in group 3 had significantly shorter duration of time to death after the start of renal replacement therapy.

CONCLUSIONS

Patient survival may be lower in kidney transplant recipients with amyloidosis compared with patients with end-stage renal disease due to other causes. However, graft failure and acute rejection rates seem to be similar.

Macrophage-Mediated Phagocytosis and Dissolution of Amyloid-Like Fibrils in Mice, Monitored by Optical Imaging

Light chain-associated amyloidosis is characterized by the extracellular deposition of amyloid fibrils in abdominothoracic organs, skin, soft tissue, and peripheral nerves. Phagocytic cells of the innate immune system appear to be ineffective at clearing the material; however, human light chain amyloid extract, injected subcutaneously into mice, is rapidly cleared in a process that requires neutrophil activity. To better elucidate the phagocytosis of light chain fibrils, a potential method of cell-mediated dissolution, amyloid-like fibrils were labeled with the pH-sensitive dye pHrodo red and a near infrared fluorophore. After injecting this material subcutaneously in mice, optical imaging was used to quantitatively monitor phagocytosis and dissolution of fibrils concurrently. Histologic evaluation of the residual fibril masses revealed the presence of CD68⁺, F4/80⁺, ionized calcium binding adaptor molecule 1^- macrophages containing Congo red-stained fibrils as well as neutrophil-associated proteins with no evidence of intact neutrophils. These data suggest an early infiltration of neutrophils, followed by extensive phagocytosis of the light chain fibrils by macrophages, leading to dissolution of the mass. Optical imaging of this novel murine model, coupled with histologic evaluation, can be used to study the cellular mechanisms underlying dissolution of synthetic amyloid-like fibrils and human amyloid extracts. In addition, it may serve as a test bed to evaluate investigational opsonizing agents that might serve as therapeutic agents for light chain-associated amyloidosis.

Hereditary Fibrinogen Aα-Chain Amyloidosis in Asia: Clinical and Molecular Characteristics

Hereditary fibrinogen Aα-chain amyloidosis (Aα-chain amyloidosis) is a type of autosomal dominant systemic amyloidosis caused by mutations in fibrinogen Aα-chain gene (FGA). Patients with Aα-chain amyloidosis have been mainly reported in Western countries but have been rarely reported in Asia, with only five patients with Aα-chain amyloidosis being reported in Korea, China, and Japan. Clinically, the most prominent manifestation in Asian patients with Aα-chain amyloidosis is progressive nephropathy caused by excessive amyloid deposition in the glomeruli, which is similar to that observed in patients with Aα-chain amyloidosis in Western countries. In molecular features in Asian Aα-chain amyloidosis, the most common variant, E526V, was found in only one Chinese kindred, and other four kindred each had a different variant, which have not been identified in other countries. These variants are located in the C-terminal region (amino acid residues 517–555) of mature Aα-chain, which was similar to that observed in patients with Aα-chain amyloidosis in other countries. The precise number of Asian patients with Aα-chain amyloidosis is unclear. However, patients with Aα-chain amyloidosis do exist in Asian countries, and the majority of these patients may be diagnosed with other types of systemic amyloidosis.

Amyloidosis of the gastrointestinal tract and the liver: clinical context, diagnosis and management

Amyloidosis is a group of disorders that can manifest in virtually any organ system in the body and is thought to be secondary to misfolding of extracellular proteins with subsequent deposition in tissues. The precursor protein that is produced in excess defines the specific amyloid type. This requires histopathological confirmation using Congo red dye with its characteristic demonstration of green birefringence under cross-polarized light. Gastrointestinal (GI) manifestations are common and the degree of organ involvement dictates the symptoms that a patient will experience. The small intestine usually has the most amyloid deposition within the GI tract. Patients generally have nonspecific findings such as abdominal pain, nausea, diarrhea, and dysphagia that can often delay the proper diagnosis. Liver involvement is seen in a majority of patients, although symptoms typically are not appreciated unless there is significant hepatic amyloid deposition. Pancreatic involvement is usually from local amyloid deposition that can lead to type 2 diabetes mellitus. In addition, patients may undergo either endoscopic or radiological evaluation; however, these findings are usually nonspecific. Management of GI amyloidosis primarily aims to treat the underlying amyloid type with supportive measures to alleviate specific GI symptoms. Liver transplant is found to have positive outcomes, especially in patients with specific variants of hereditary amyloidosis.

[Histological and immunohistochemical examinations in the diagnosis of hepatic amyloidosis]

OBJECTIVE

to investigate the histopathology of amyloid in liver biopsy specimens. MATERIAL AND METHODS. A total of 46 liver biopsy specimens were investigated in patients with histologically verified amyloidosis in 2006 to 2009 from the Amyloid Registry of the Charité University Hospital (Berlin). The liver biopsy specimens were fixed in formalin and embedded in paraffin. The paraffin sections were stained with hematoxylin and eosin and with Congo red. Amyloid was immunohistochemically classified using antibodies against amyloid P component, AA amyloid, apolipoprotein Al, lysozyme, fibrinogen, transthyretin, and κ and λ light chains.

RESULTS

Amyloid deposits were diagnosed in the 46 liver biopsy specimens from 17 women and 29 men (mean age 60 years). Immunohistochemical subtyping was successful in 91% of the cases. AL amyloidosis was diagnosed in 87% of the biopsy specimens and further classified as AL lambda-light chain amyloidosis (57%) and AL kappa-light chain amyloidosis (30%). The 46 liver biopsy specimens showed one case of AA amyloidosis (2%) and one case of transthyretin amyloidosis (2%). The type of amyloid could not be classified in 9% of the biopsy specimens.

CONCLUSION

The investigation revealed that the most common types of hepatic amyloidosis are AL lambda- and AL kappa-light chain amyloidosis associated with the signs of parenchymal atrophy and steatosis.

[Optimization of the immunohistochemical diagnosis of AL amyloidosis using novel antibodies]

OBJECTIVE

to improve the immunohistochemical diagnosis of AL amyloidosis, by generating novel peptide antibodies against the variable and constant regions of the κ-light chains.

MATERIAL AND METHODS

All amyloidogenic κ-light chains were sought in the scientific literature and the database of the National Center for Biotechnology Information. On the basis of the findings, a chain was formed from the most common amino acid residues that were used to choose peptide regions for immunization. Four antibodies were generalized via immunization of rabbits with two peptides that corresponded to the variant or constant regions of κ-light chains.

RESULTS

The specificity of the obtained antibodies was confirmed using a series of 222 biopsy specimens from 193 patients with AL, AA, transthyretin, or insulin amyloidosis. All the novel polyclonal peptide antibodies produced positive staining in cases of ALκ amyloidosis.

CONCLUSION

The generated polyclonal peptide antibodies against the variable and constant regions of κ-light chains are able to improve the immunohistochemical diagnosis of amyloidosis.