Microextraction and purification techniques applicable to chemical characterization of amyloid proteins in minute amounts of tissue

Diagnostic Challenges and Solutions in Systemic Amyloidosis

Amyloidosis refers to a clinically heterogeneous group of disorders characterized by the extracellular deposition of amyloid proteins in various tissues of the body. To date, 42 different amyloid proteins that originate from normal precursor proteins and are associated with distinct clinical forms of amyloidosis have been described. Identification of the amyloid type is essential in clinical practice, since prognosis and treatment regimens both vary according to the particular amyloid disease. However, typing of amyloid protein is often challenging, especially in the two most common forms of amyloidosis, i.e., the immunoglobulin light chain amyloidosis and transthyretin amyloidosis. Diagnostic methodology is based on tissue examinations as well as on noninvasive techniques including serological and imaging studies. Tissue examinations vary depending on the tissue preparation mode, i.e., whether it is fresh-frozen or fixed, and they can be carried out by ample methodologies including immunohistochemistry, immunofluorescence, immunoelectron microscopy, Western blotting, and proteomic analysis. In this review, we summarize current methodological approaches used for the diagnosis of amyloidosis and discusses their utility, advantages, and limitations. Special attention is paid to the simplicity of the procedures and their availability in clinical diagnostic laboratories. Finally, we describe new methods recently developed by our team to overcome limitations existing in the standard assays used in common practice.

Conservation of the Amyloid Interactome Across Diverse Fibrillar Structures

Several human proteins cause disease by misfolding and aggregating into amyloid fibril deposits affecting the surrounding tissues. Multiple other proteins co-associate with the diseased deposits but little is known about how this association is influenced by the nature of the amyloid aggregate and the properties of the amyloid-forming protein. In this study, we investigated the co-aggregation of plasma and cerebrospinal proteins in the presence of pre-formed amyloid fibrils. We evaluated the fibril-associated proteome across multiple amyloid fibril types that differ in their amino acid sequences, ultrastructural morphologies, and recognition by amyloid-binding dyes. The fibril types included aggregates formed by Amyloid β, α-synuclein, and FAS4 that are associated with pathological disorders, and aggregates formed by the glucagon and C-36 peptides, currently not linked to any human disease. Our results highlighted a highly similar response to the amyloid fold within the body fluid of interest. Fibrils with diverse primary sequences and ultrastructural morphologies only differed slightly in the composition of the co-aggregated proteins but were clearly distinct from less fibrillar and amorphous aggregates. The type of body fluid greatly affected the resulting amyloid interactome, underlining the role of the in vivo environment. We conclude that protein fibrils lead to a specific response in protein co-aggregation and discuss the effects hereof in the context of amyloid deposition.

Kidney disease and plasma cell dyscrasias: ambiguous cases solved by serum free light chain dimerization analysis

BACKGROUND

Plasma cell dyscrasias (PCD) comprise a wide spectrum of disorders, which may adversely affect the kidney. However, in some PCD cases associated with kidney disease, the routine laboratory tests may be incapable to determine precisely the form of PCD, i.e., benign or malignant. Moreover, the kidney biopsy needed for precise diagnosis may be risky or declined. To overcome these limitations, we have developed and reported a new non-invasive technique based on serum free light chains (FLC) monomer (M) and dimer (D) pattern analysis (FLC MDPA), which allowed differentiation between malignant and benign PCD forms. The objective of our retrospective study was to demonstrate the utility of FLC MDPA in solving ten puzzling PCD cases complicated with kidney disease (patients 1-10).

METHODS

Ten patients with uncertain form of PCD or with a questionable response to treatment were studied. In addition to routine laboratory tests and clinical evaluation of the PCD patients, our previously developed FLC MDPA in sera and biochemical amyloid typing in biopsy tissues were applied.

RESULTS

The FLC MDPA aided the diagnosis of the PCD underlying or accompanying the kidney disease in patients 1-5, and helped to interpret properly the response to treatment in patients 1, 6-10. The FLC MDPA findings were confirmed by a biochemical analysis of tissue amyloid deposits and subsequently by the outcome of these patients.

CONCLUSIONS

FLC MDPA is a non-invasive diagnostic test useful in the management of ambiguous cases of PCD associated with kidney disease.

Cardiac amyloidosis: pathology, nomenclature, and typing

Amyloidosis is an increasingly recognized cause of heart disease, caused by the deposition of misfolded protein within the heart. These proteins may deposit systemically and include the heart or deposit only within the heart muscle itself. In either case, cardiac symptoms may be the primary manifestation. The diagnosis is usually made by the pathologist identifying amyloid within a tissue sample. The diagnosis, however, does not end with such visual recognition of the presence of amyloid. Newer generation pharmacotherapeutic agents that are protein specific necessitate a closer evaluation to determine the type of protein being deposited and accurately conveying this to the treating clinician. Herein, the gross and histopathologic features of cardiac amyloidosis are reviewed along with a review of amyloid typing strategies (both direct and indirect) that may be employed in the diagnostic workup as well as the nomenclature standards for reporting.

Amyloid fibrils containing fragmented ATTR may be the standard fibril composition in ATTR amyloidosis

Abstract The clinical phenotype of familial ATTR amyloidosis depends to some extent on the particular mutation, but differences exist also within mutations. We have previously described that two types of amyloid fibril compositions exist among Swedish ATTRV30M amyloidosis patients, one consisting of a mixture of intact and fragmented ATTR (type A) and one consisting of mainly intact ATTR (type B). The fibril types are correlated to phenotypic differences. Patients with ATTR fragments have a late onset and develop cardiomyopathy, while patients without fragments have an early onset and less myocardial involvement. The present study aimed to determine whether this correlation between fibril type and phenotype is valid for familial ATTR amyloidosis in general. Cardiac or adipose tissues from 63 patients carrying 29 different TTR non-V30M mutations as well as 13 Japanese ATTRV30M patients were examined. Fibril type was determined by western blotting and compared to the patients' age of onset and degree of cardiomyopathy. All ATTR non-V30M patients had a fibril composition with ATTR fragments, except two ATTRY114C patients. No clear conclusions could be drawn about a phenotype to fibril type correlation among ATTR non-V30M patients. In contrast, Japanese ATTRV30M patients showed a similar correlation as previously described for Swedish ATTRV30M patients. This study shows that a fibril composition with fragmented ATTR is very common in ATTR amyloidosis, and suggests that fibrils composed of only full-length ATTR is an exception found only in a subset of patients.

Aged vervet monkeys developing transthyretin amyloidosis with the human disease-causing Ile122 allele: a valid pathological model of the human disease

Mutant forms of transthyretin (TTR) cause the most common type of autosomal-dominant hereditary systemic amyloidosis. In addition, wild-type TTR causes senile systemic amyloidosis, a sporadic disease seen in the elderly. Although spontaneous development of TTR amyloidosis had not been reported in animals other than humans, we recently determined that two aged vervet monkeys (Chlorocebus pygerythrus) spontaneously developed systemic TTR amyloidosis. In this study here, we first determined that aged vervet monkeys developed TTR amyloidosis and showed cardiac dysfunction but other primates did not. We also found that vervet monkeys had the TTR Ile122 allele, which is well known as a frequent mutation-causing human TTR amyloidosis. Furthermore, we generated recombinant monkey TTRs and determined that the vervet monkey TTR had lower tetrameric stability and formed more amyloid fibrils than did cynomolgus monkey TTR, which had the Val122 allele. We thus propose that the Ile122 allele has an important role in TTR amyloidosis in the aged vervet monkey and that this monkey can serve as a valid pathological model of the human disease. Finally, from the viewpoint of molecular evolution of TTR in primates, we determined that human TTR mutations causing the leptomeningeal phenotype of TTR amyloidosis tended to occur in amino acid residues that showed no diversity throughout primate evolution. Those findings may be valuable for understanding the genotype-phenotype correlation in this inherited human disease.

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

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.

A proposed histopathologic classification, scoring, and grading system for renal amyloidosis: standardization of renal amyloid biopsy report

CONTEXT

A disease associated with amyloid deposits, called amyloidosis, is associated with characteristic electron microscopic appearance, typical x-ray pattern, and specific staining. Renal involvement mainly occurs in AA amyloidosis and AL amyloidosis and usually progresses to renal failure.

OBJECTIVE

The renal histopathologic changes with amyloidosis comprise a spectrum. Clear relationships between the extent of amyloid deposition and the severity of clinical manifestations have not been demonstrated. Whether there is a lack of clinicopathologic correlation is not clear, but studies have revealed the need for standardization of the renal amyloid biopsy report. With these objectives in mind, we proposed a histopathologic classification, scoring, and grading system. Renal amyloidosis was divided into 6 classes, similar to the classification of systemic lupus erythematosus. Amyloid depositions and other histopathologic lesions were scored. The sum of these scores was termed the renal amyloid prognostic score and was divided into 3 grades.

DATA SOURCES

AA amyloidosis was detected in 90% of cases, mostly related to familial Mediterranean fever. Positive correlations between class I and grade I, class VI and grade III, and class III and grade II were observed. Also, a positive correlation was identified between severity of glomerular amyloid depositions, interstitial fibrosis, and inflammation. Because of the inadequacy of the patients' records and outcomes, different therapy regimes, and etiologies, clinical validation of this study has not been completed.

CONCLUSIONS

Standardization of the renal amyloid pathology report might be critical for patients' medication and comparison of outcome and therapeutic trials between different clinics. Because of our AA to AL amyloidosis ratio and the predisposition of familial Mediterranean fever-related AA amyloidosis, there is a need for further international collaborative studies.

Diagnosis and typing of systemic amyloidosis: The role of abdominal fat pad fine needle aspiration biopsy

Introduction:

Systemic amyloidosis (SA) has a broad nonspecific clinical presentation. Its diagnosis depends on identifying amyloid in tissues. Abdominal fat pad fine needle aspiration (FPFNA) has been suggested as a sensitive and specific test for diagnosing SA.

Materials and Methods:

Thirty-nine FPFNA from 38 patients (16 women and 20 men, age range 40–88 years) during a 15-year period were reviewed. Smears and cell blocks were stained with Congo red (CR). A panel of antibodies (serum amyloid protein, serum amyloid A, albumin, transthyretin, kappa light chain and lambda light chain) was used on six cell blocks from five patients. The FNA findings were correlated with clinical and histological follow-up.

Results:

FPFNAs were positive, confirmed by CR in 5/39 (13%), suspicious in 1/39 (3%), negative in 28/39 (72%), and insufficient for diagnosis in 5/39 (13%) of cases. In all the positive cases, SA was confirmed within 2–16 weeks. Among the 28 negative cases, SA was diagnosed in 21, the rest were lost to follow-up. Among the insufficient cases, SA was diagnosed in four and one was lost to follow-up. Specificity was 100%, whereas sensitivity was 19%. SA typing using cell block sections was successful in three, un-interpretable in one, and negative in two cases.

Conclusion:

FPFNA for SA is not as good as previously reported. This may be due to different practice setting, level of experience, diagnostic technique, or absence of abdominal soft tissue involvement. A negative result of FPFNA does not exclude SA. Immune phenotyping of amyloid is possible on cell block.

Distinct characteristics of amyloid deposits in early- and late-onset transthyretin Val30Met familial amyloid polyneuropathy

Late-onset transthyretin Val30Met-associated familial amyloid polyneuropathy (FAP ATTR Val30Met) cases unrelated to endemic foci in Japan show different clinicopathological features from the conventional early-onset cases in endemic foci. We compared the characteristics of amyloid deposits in early-onset FAP ATTR Val30Met cases in endemic foci and late-onset cases in non-endemic areas. Amyloid deposits in three early-onset cases from endemic foci and five late-onset cases from non-endemic areas were systematically examined post-mortem. Amyloid deposits in early-onset cases were highly congophilic and showed strong apple-green birefringence with Congo red staining and had long, parallel fibrils in most organs. On the other hand, those in late-onset cases were generally weakly congophilic and showed faint apple-green birefringence with Congo red staining and had short, haphazard fibrils. In the renal glomus and adrenal gland of early-onset cases, the characteristics of amyloid deposits were similar to those observed in late-onset cases. Analysis of cardiac amyloid using surface enhanced desorption/ionization time-of-flight mass spectrometry indicated that most transthyretin (TTR) was variant in early-onset cases, while more than half was composed of wild-type TTR in late-onset cases. Although characteristics of amyloid deposits may differ among individual organs of respective cases, especially in early-onset cases, the pattern was distinct between early- and late-onset cases. Amyloid deposition in late-onset cases may be similar to that observed in senile systemic amyloidosis with wild-type TTR deposition, suggesting that aging may play an important role in these cases.

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.

[Amyloid diagnostics in rheumatic diseases]

Amyloid is a pathological protein deposit in tissue which has a red eosin color when the slice preparation is stained with traditional hematoxylin and eosin and after Congo red staining under polarized light exhibits a characteristic apple-green polarization color. Over 26 different autologous physiological proteins have been described that can form amyloid. In surgical pathology, immunoglobulin light chain-associated AL amyloidosis is the most frequent generally occurring amyloidosis, followed by hereditary and nonhereditary ATTR amyloidosis and AA amyloidosis. AA amyloidosis mostly develops subsequent to chronic infectious or inflammatory underlying disease and can represent a potentially life threatening complication. The spectrum of causes for AA amyloidosis has changed in the past few decades and is now determined by chronic rheumatic diseases and hereditary periodic fever syndromes. Early diagnosis of an amyloidosis and its correct classification continue to pose a great challenge. Precise classification of the amyloid and amyloidosis is essential for prognosis assessment and treatment planning. In addition to anti-inflammatory management of AA amyloidosis, specific treatment strategies may possibly become available in the future.

Demonstration of a common artifact in immunosorbent assays of brain extracts: Development of a solid-phase extraction protocol to enable measurement of amyloid-β from wild-type rodent brain

In the process of developing species-specific, immunosorbent assays for brain amyloid-beta (Abeta) in non-transgenic animals, we have demonstrated an artifact that impedes accurate quantitation of Abeta in this assay format. Using synthetic peptides, cerebrospinal fluid (CSF), or plasma samples, no nonspecific binding or cross-species immunoreactivity was detected in human or rodent Abeta assays. However, extracts of guinea pig brain (human Abeta sequence) or rat brain (rodent Abeta sequence) demonstrated immunoreactivity regardless of which capture antibody, detection antibody, or reporter method (colorimetric or fluorescent) was used. This immunoreactivity remained even in the absence of a capture antibody. Various blocking conditions failed to resolve the nonspecific binding of detection antibodies in the presence of brain extracts. Fractionation of DEA-extracted guinea pig brain over Sephadex G-50 demonstrated the feasibility of separating specific from nonspecific binding components in the brain extracts. Thus, a solid phase extraction method, compatible with multiple extraction buffers, has been developed to isolate and concentrate Abeta from brain extracts. This isolation method eliminates non-specific binding components from brain extracts and allows for accurate quantitation and robust detection of multiple Abeta peptides in extracts from wild-type animals.

Immunohistochemical Classification of Amyloid in Surgical Pathology Revisited

We aimed to reassess the suitability of immunohistochemical classification of amyloid in surgical pathology. One hundred sixty-nine biopsies from 121 patients diagnosed with amyloid during the period from 1994 to 2004 were included. Amyloid was classified immunohistochemically, using antibodies directed against amyloid P-component, AA amyloid, apolipoprotein AI, fibrinogen, keratoepithelin, lactoferrin, lysozyme, beta2-microglobulin (beta2M), immunoglobulin-derived lambda-light and kappa-light chains, and transthyretin. Amyloid was most commonly present in biopsies from the hepatogastrointestinal tract. The deposits were classified immunohistochemically in 156 (92%) biopsies. In 13 biopsies of 12 patients, amyloid remained unclassified. AL amyloidosis was diagnosed in 76 (45%) biopsies and was further categorized into AL amyloid of kappa-light chain origin [32 (42%) biopsies] or lambda-light chain origin [20 (26%)]. In 24 (32%) biopsies, the amyloid deposits did not show unequivocal staining for lambda-light or kappa-light chain. However, these cases were categorized as "probably AL amyloid, not otherwise specified", because no other antibody showed unequivocal staining of the amyloid deposits. AA amyloidosis was diagnosed in 32, ATTR amyloidosis in 21, and AApoAI amyloidosis in 3 biopsies. Other types of amyloid included AKer and ALac amyloids each in 1, and ALys and ACal amyloids each in 2 biopsies. Abeta2M amyloid was not diagnosed in any case. Immunohistochemical classification of amyloid still poses problems. Although classification of AA, AApoAI, ALys, ALac, and ATTR amyloids is relatively straightforward, classification of AL amyloid and rare hereditary amyloidoses is a serious obstacle and sometimes even impossible when conclusive clinical information or additional protein biochemical or molecular biologic studies are not available.

Immunohistochemical study of immunoglobulin light chain amyloidosis with antibodies to the immunoglobulin light chain variable region

To detect immunoglobulin (Ig) light chain amyloidosis (AL amyloidosis) in formalin-fixed, paraffin-embedded tissue sections by immunohistochemistry, polyclonal antibodies were generated against synthetic peptides corresponding to amino acids 1-19 of the Ig lambda light chain V lambda VI subgroup (anti-V lambda VI (1-19)) and the Ig kappa light chain Vkappa I subgroup (anti-Vkappa I (1-19)). Anti-V lambda VI (1-19) antibody reacted with amyloid deposits in 21 of 22 Alambda amyloidosis cases, and anti-Vkappa I (1-19) antibody reacted with amyloid deposits in 10 of 11 Akappa amyloidosis cases. Immunoreactivity varied in intensity by case and within specimens. Surprisingly, amyloid deposits were positive for anti-V kappa I (1-19) staining in one case of Alambda amyloidosis. Analysis of anti-V lambda VI (1-19) and anti-Vkappa I (1-19) antibody reactivity by ELISA showed some cross-reactivity with peptides other than antigen peptides. The antibodies were not reactive in all cases of AL amyloidosis examined but may be useful, together with anti-Ig constant region antibodies, for immunohistochemical diagnosis of AL amyloidosis.

AH Amyloidosis Associated With Lymphoplasmacytic Lymphoma Secreting a Monoclonal γ Heavy Chain Carrying an Unusual Truncated D Segment

To date, the presence of amyloidosis associated with immunoglobulin heavy chain (AH amyloidosis) was reported in only 7 cases. Although AH amyloidosis is caused mainly by plasma cell dyscrasia, as in AL amyloidosis, we report a 61-year-old patient who presented with nephrotic syndrome caused by AH amyloidosis associated with lymphoplasmacytic lymphoma. Biochemical and molecular analyses of the deposited amyloid fibrils and heavy-chain genes of lymphocytes showed that proliferative lymphoma cells produced a gamma heavy chain, not a mu heavy chain, which carried an unusual truncated diversity (D) segment of the variable region. Our results indicate that production of the abnormal heavy chain caused by the partially deleted D segment gene is responsible for gamma heavy-chain-related amyloid fibril formation in this patient.

Cathepsin protease activity modulates amyloid load in extracerebral amyloidosis

In cerebral amyloidoses, such as Alzheimer's disease, proteolytic processing of the precursor protein is a fundamental mechanism of the disease, since it generates the amyloid protein. However, the putative significance of proteases in extracerebral amyloidoses is less well defined. In this study, we investigated the biological significance of cathepsin (Cath) B, CathK, and CathL in the pathology and pathogenesis of extracerebral amyloidoses by using the murine model of reactive or secondary AA amyloidosis with three different cathepsin-deficient mouse strains. Extracerebral AA amyloid was induced by injecting amyloid-enhancing factor and silver nitrate into CathB(-/-), CathK(-/-), and CathL(-/-) mice. Wild-type mice served as a control. CathK(-/-) mice deposited over 90% more amyloid and CathL(-/-) mice 60% less amyloid than the control (p < 0.0001). The amyloid load in CathB(-/-) mice did not differ from that in wild-type mice. In vitro degradation experiments with recombinant human and murine serum amyloid A (SAA) 1.1 and CathK and CathL showed that CathL generates a large number of differently sized SAA cleavage products. One of these fragments spans the heparin/heparan sulphate binding site and the neutral cholesterol ester hydrolase activating region of SAA. CathK showed only endoproteolytic activity and did not generate any AA amyloid-like peptides. This study provides unequivocal evidence that proteases modulate amyloid load in extracerebral amyloidosis. CathL was identified as an amyloid-promoting and CathK as an amyloid-retarding cysteine protease. CathB may only modulate the primary structure of the amyloid peptide without affecting amyloid load.

Characterization of Systemic Amyloid Deposits by Mass Spectrometry

The human systemic (noncerebral) amyloidoses represent a heterogeneous group of disorders characterized by the widespread deposition of proteins as fibrils in organs or tissues throughout the body. The unequivocal identification of the type of amyloid deposited is critical to the correct diagnosis and treatment of patients with these illnesses. Heretofore, this information was inferred from clinical data, ancillary laboratory tests, and results of immunohistochemical, as well as genetic, analyses. However, to establish definitively the type of amyloid present, the chemical composition of the fibrillar components must be determined. For this purpose, we have developed micro-methods, whereby this information can be obtained by tandem mass spectrometry (MS/MS) using material extracted from formalin-fixed, amyloid-containing tissue biopsy specimens or subcutaneous fat aspirates. The ability to identify precisely the protein nature of the pathologic deposits has diagnostic, therapeutic, and prognostic implications for patients with amyloid-associated disease.

Gastrointestinal beta2microglobulin amyloidosis in hemodialysis patients: biochemical analysis of amyloid proteins in small formalin-fixed paraffin-embedded tissue specimens

We present here a first report on the biochemical analysis of intestinal amyloid deposits found in two cases of hemodialysis-related amyloidosis. A new microtechnique was applied for extraction and immunochemical/chemical characterization of amyloid proteins in small amounts of fixed tissue, thus allowing precise identification of beta2microglobulin amyloid (Abeta2M) in both cases studied. The molecular mass of the identified amyloid beta2M was close to that of intact beta2M (12 kDa), with no evidence of the products of proteolytic fragmentation of these molecules. The isoelectrofocusing of the purified Abeta2M demonstrated a shift to more acidic pI as compared to the normal beta2M analyzed under the same experimental conditions. The obtained data suggest that the intestinal amyloid deposits in dialysis-related amyloidosis contain disease-specific beta2M isoforms, which could play a role in the pathogenesis of amyloid disease. The new methodology used might be useful in obtaining precise diagnosis of amyloidosis that is necessary for appropriate therapy, and also provide new important information on the chemical structure of amyloid proteins.

Influence of tissue fixation on the microextraction and identification of amyloid proteins

In surgical pathology, correct immunohistochemical identification of AL amyloidosis poses a particular problem. Immunostaining for lambda- or kappa-light chains is commonly encountered even in non-immunoglobulin-derived amyloidoses, which leads to a false-positive classification as AL amyloidosis. In this respect, microextraction of amyloid proteins from surgical pathology specimens and their subsequent biochemical characterization may prove useful in reaching the correct diagnosis. In this study, we investigated systematically the influence of fixation on the extraction of amyloid proteins from amyloid-containing tissue samples. Tissue samples were obtained from a patient with generalized AA amyloidosis and from a second patient with generalized AL amyloidosis. The samples were stored either unfixed or fixed in phosphate buffered 4% p-formaldehyde, methacarn, or Bouin for 3 days, 1 week, or 1 month. Thereafter, proteins were extracted according to the procedure of Layfield et al, separated by SDS-PAGE and subjected to Western blotting, using antibodies directed against AA amyloid and immunoglobulin-derived lambda-light chain. Following this procedure, a variety of differently sized AA amyloid or lambda-light chain immunoreactive protein bands were found in both patients, which is typical for amyloid proteins. Fixation time did not per se prohibit the extraction of these amyloid proteins from tissue samples, which remained detectable irrespective of fixation time. Although all three fixatives impaired the resolution of some, but not all, individual amyloid proteins, this procedure may help to confirm or reject a diagnosis of AL amyloidosis, because detection of several lambda- or kappa-light chain immunoreactive protein bands in the low-molecular-weight range (<20 kDa) is a common characteristic of their amyloid nature.

Definition of organ involvement and treatment response in immunoglobulin light chain amyloidosis (AL): a consensus opinion from the 10th International Symposium on Amyloid and Amyloidosis, Tours, France, 18-22 April 2004

We undertook this study to develop uniformly accepted criteria for the definition of organ involvement and response for patients on treatment protocols for immunoglobulin light-chain amyloidosis (AL). A consensus panel was convened comprising 13 specialists actively involved in the treatment of patients with amyloidosis. Institutional criteria were submitted from each, and a consensus was developed defining each organ involved and the criteria for response. Specific criteria have been developed with agreed on definitions of organ and hematologic response as a result of discussions at the 10th International Symposium on Amyloid and Amyloidosis held in Tours, France, April 2004. These criteria now form the working definition of involvement and response for the purposes of future data collection and reporting. We report criteria that centers can now use to define organ involvement and uniform response criteria for reporting outcomes in patients with light-chain AL.

Co-deposition of amyloidogenic immunoglobulin light and heavy chains in localized pulmonary amyloidosis

Localized pulmonary amyloidosis is a rare condition whose pathogenesis is insufficiently understood. In the present study, we report a case of localized pulmonary amyloidosis associated with lung-restricted lymphoplasmacytoid lymphoma, monoclonal for immunoglobulin (Ig) G lambda (lambda). Biochemical microtechniques have been applied for extraction, purification, and characterization of amyloid proteins. Surprisingly, chemical analysis of these proteins revealed a not-previously-described case of combined deposits containing Ig fragments of gamma heavy chain (variable domain) and lambda light chain (constant domain). In view of the absence of circulating monoclonal Ig, this case supports the hypothesis that localized amyloid is formed by local plasmacytoid cells.

Amyloid deposits in transthyretin-derived amyloidosis: cleaved transthyretin is associated with distinct amyloid morphology

The pathological fibrillar deposits found in the heart and other organs of patients with senile systemic amyloidosis (SSA) and Swedish familial amyloidotic polyneuropathy (FAP) contain wild-type (wt) and a mutant form of transthyretin (TTR), respectively. Previously, it was reported that these two forms of amyloid have different molecular features and it was thus postulated that the mechanism responsible for TTR fibrillogenesis in SSA and FAP may differ. To document further the nature of the amyloid in these entities, detailed morphological, histochemical, immunological, and structural analyses of specimens obtained from 14 individuals with SSA and 11 Swedish FAP patients have been performed. Two distinct patterns of amyloid deposition (designated A and B) were evident. In pattern A, found in all SSA and five of 11 FAP cases, the amyloid had a homogeneous but patchy distribution within the sub-endocardium, sub-epicardium, and myocardium; exhibited weak congophilia and green birefringence; and was composed of tightly packed, short, unorientated fibrils. This material contained mainly approximately 79-residue C-terminal fragments of the amyloidogenic precursor protein. In pattern B, seen in the six other FAP patients, the amyloid appeared as thin streaks throughout the cardiac tissue; often surrounded individual muscle cells; was strongly congophilic and birefringent; had long fibrils arranged in parallel bundles, often penetrating into myocytes; and was composed of virtually intact TTR molecules. These findings provide substantive evidence for the morphological and structural heterogeneity of TTR fibrils and suggest that the two types of deposition may reflect fundamental differences in the pathogenesis of the TTR-associated amyloidoses.

Primary local orbital amyloidosis: biochemical identification of the immunoglobulin light chain kappaIII subtype in a small formalin fixed, paraffin wax embedded tissue sample

BACKGROUND

Amyloidosis refers to a heterogeneous group of disorders associated with the deposition of chemically distinct amyloid fibril proteins. Precise determination of chemical amyloid type has diagnostic, therapeutic, and prognostic relevance. Although immunohistochemical techniques are used routinely to determine the amyloid type, the results can be negative or inconclusive, so that biochemical characterisation is often required. The development and application of new biochemical microtechniques suitable for examination of extremely small tissue samples is essential for precise identification of the deposited amyloid proteins.

AIMS

To investigate biochemically the amyloid proteins present in a formalin fixed paraffin wax embedded orbital tissue from a patient with localised orbital amyloidosis in whom immunohistochemistry was not helpful in the determination of amyloid type.

METHODS

Extraction of amyloid proteins from fixed tissue and their identification was carried out by a recently developed microtechnique. An extremely small tissue sample was dewaxed and extracted with formic acid. The extracted material was analysed using electrophoresis, western blotting, and amino acid sequencing.

RESULTS

Biochemical examination of the extracted proteins showed the presence of immunoglobulin (Ig) derived amyloid proteins, which were composed of the N-terminal fragments of the Ig light chain kappaIII subtype (AL-kappaIII) (16, 8, and 3 kDa).

CONCLUSIONS

This is the first chemically proved AL case reported in association with primary localised orbital amyloidosis. The biochemical microtechnique used was useful in achieving a precise diagnosis of amyloid disease, in a case where the results of routine immunohistochemical examination of amyloid were inconclusive.

The systemic amyloidoses: clearer understanding of the molecular mechanisms offers hope for more effective therapies

Knowledge about the systemic amyloidoses has increased considerably during the last few years. This group of diseases is characterized by great biochemical variability, including at least 11 different amyloid fibril proteins and a remarkable range of clinical manifestations. With the understanding that the pathogenesis is different in the various forms of amyloidosis, it is now being increasingly accepted that an early and accurate diagnosis, including that of the underlying biochemical nature, is crucial for a successful treatment. The elucidation of the molecular mechanisms involved in amyloidogenesis is at the basis of the recent blossoming of new, innovative and more effective therapeutic approaches.

Search for peptidic “middle molecules” in uremic sera: isolation and chemical identification of fibrinogen fragments

According to the "middle molecule" (MM) hypothesis, the uremic solutes ranging from 500 to 5,000 Da are insufficiently eliminated by conventional hemodialysis and may act as uremic toxins. However, because of the methodological difficulties of MM purification, their chemical analysis is complicated and the precise structure of these molecules remains obscure. In the present study, a new micro-preparative procedure including SDS electrophoresis and liquid chromatography was applied for isolation of MM peptides from uremic sera. Microsequencing and MS/MS analyses of these peptides showed that most of the identified MM (22 out of 23) represented the N- and C-terminal fragments of the alpha- and beta-chains of fibrinogen. The obtained data provide new information on the precise structure of fibrinogen fragments accumulating in uremic serum as MM.

A high-yield method to extract peptides from rat brain tissue

A process to extract and enrich extracellular peptides and proteins from tissues should have broad utility in the burgeoning proteomics field. To address this need, a novel three-step protocol was developed to extract polypeptides from whole tissue samples and enrich the extracellular components. The initial homogenization of rat brain was carried out at neutral pH to optimize protein and peptide stability and solubility. Subsequent covalent chromatography on an activated thiopropyl resin was employed to debulk the tissue extract by selectively removing a substantial fraction of the intracellular protein component under nondenaturing conditions. Finally, extraction with 0.1% trifluoroacetic acid was used to selectively precipitate large proteins while enhancing the solubility of smaller proteins and peptides. The fractions from each step in the process were compared to a single extract obtained by homogenization in 0.5 M acetic acid. The recovery and yields of endogenous neuropeptides and an exogenously added peptide were evaluated by enzyme immunoassay and Western blotting, respectively. In summary, the three-step protocol was superior to the extraction of tissue with 0.5 M acetic acid in terms of peptide recovery, enrichment, and sample stability. Enrichment of the extracellular protein compartment from tissues should be valuable in proteomics experiments aimed at identifying biomarkers that can partition into serum.

Immunoglobulin heavy chain can be amyloidogenic: morphologic characterization including immunoelectron microscopy

It is not well recognized that monoclonal immunoglobulin heavy chains or their fragments can be amyloidogenic. Amyloidosis due to heavy chains, referred to as AH amyloidosis, is rare with only three cases previously reported. An additional case of AH amyloidosis is reported. To the best of our knowledge, this is the first case of IgM heavy chain amyloidosis. A 59-year-old man presented with nephrotic syndrome. Immunoelectrophoresis detected a monoclonal IgM lambda in his serum and free lambda light chains in his urine. A renal biopsy showed amyloidosis, in which the amyloid deposits stained only for mu heavy chain by immunofluorescent and immunoelectron microscopic studies. This case suggests that monoclonal immunoglobulin heavy chains can be amyloidogenic. Furthermore, this type of amyloidosis shares the same morphologic features with other types of amyloidosis and can involve the kidney to produce nephrotic syndrome.

Micropurification techniques in the analysis of amyloid proteins

This review describes the different microtechniques developed for the extraction and purification of amyloid proteins from small specimens of fresh and formalin fixed tissues. These procedures differ with respect to solvent type, extraction conditions, and protein purification strategy. The advantages and disadvantages of the different microtechniques are discussed by taking into consideration tissue type (fresh of fixed) and size, amyloid type, and its content in the tissue. The review demonstrates the applicability of these techniques for the immunochemical and chemical characterisation of amyloid in different clinical forms of amyloidosis and in experimental small animal models. The clinical value of the applied microtechniques and their importance in the study of the pathogenesis of amyloid related diseases are outlined.

Codeposition of apolipoprotein A-IV and transthyretin in senile systemic (ATTR) amyloidosis

Protein material was extracted from amyloid-rich sections of formalin-fixed and paraffin-embedded heart tissue from an individual with senile systemic amyloidosis, known to contain wild-type transthyretin as major amyloid fibril protein. Amino acid sequence analysis of tryptic peptides of this material revealed in addition to transthyretin sequences, also amino acid sequence corresponding to an N-terminal fragment of apolipoprotein A-IV. In immunohistochemistry, an antiserum to a synthetic apolipoprotein A-IV peptide labeled amyloid specifically. This peptide formed spontaneously amyloid-like fibrils in vitro and enhanced fibril formation from wild-type transthyretin. We conclude that several apolipoproteins, including apolipoprotein A-IV, may be important minor amyloid constituents, promoting fibril formation.

Chemical typing of amyloid protein contained in formalin-fixed paraffin-embedded biopsy specimens

The human amyloidoses represent a heterogeneous group of disorders characterized by the deposition of fibrillar protein in vital organs. Given the fact that at least 20 different molecules can form fibrils, the unambiguous identification of the type of amyloid deposited is critical to the correct diagnosis and treatment of patients with these disorders. Heretofore, this information has been inferred from particular clinical features of the disease, ancillary laboratory tests, and results of immunohistochemical analyses. However, to establish unequivocally the kind of protein that is deposited as amyloid, it is necessary to determine its chemical composition through amino acid sequencing or mass spectroscopy of material extracted from fibrillar deposits. We have developed a micromethod whereby such studies can be performed readily using sections of formalin-fixed, paraffin-embedded biopsy specimens. The ability to identify precisely the nature of the tissue deposits has diagnostic, therapeutic, and prognostic implications for patients with amyloid-associated disorders.

Apolipoprotein AI and transthyretin as components of amyloid fibrils in a kindred with apoAI Leu178His amyloidosis

We found a new C-terminal amyloidogenic variant of apolipoprotein AI (apoAI), Leu178His in a French kindred, associated with cardiac and larynx amyloidosis and skin lesions with onset during the fourth decade. This single-point mutation in exon 4 of the apoAI gene was detected by DNA sequencing of polymerase chain reaction amplified material and restriction fragment length polymorphism analysis in two siblings. Blood, larynx, and skin biopsies were available from one sibling. Anti-apoAI immunoblotting of isoelectric focusing of plasma showed a +1 alteration in the charge of the protein. Extraction of fibrils from the skin biopsy revealed both full-length and N-terminal fragments of apoAI and transthyretin (TTR). ApoAI and TTR co-localized in amyloid deposits as demonstrated by immunohistochemistry. The present report, together with the first recently described C-terminal amyloidogenic variant of apoAI, Arg173Pro, shows that amyloidogenicity of apoAI is not a feature exclusive to N-terminal variants. The most striking characteristic of amyloid fibrils in Leu178His is that wild-type TTR is co-localized with apoAI in the fibrils. We have previously determined that a fraction of plasma TTR circulates in plasma bound to high-density lipoprotein and that this interaction occurs through binding to apoAI. Therefore we hypothesize that nonmutated TTR might influence deposition of apoAI as amyloid.