Increased Diagnostic Specificity of Congo Red Stain for Amyloid: The Potential Role of Texas Red-Filtered Fluorescence Microscopy

The evaluation of Congo red staining combined with fluorescence microscopy in the diagnosis of primary cutaneous amyloidosis

Primary cutaneous amyloidosis (PCA) is a chronic pruritic skin disease. The apple-green birefringence of Congo red-stained amyloid under a polarized light microscope (CR-PLM) remains the gold standard in the diagnosis of PCA. However, there are some limitations to this approach. In this study, eighty-two paraffin-embedded biopsy skin samples were collected from patients with a clinical diagnosis of PCA. The sections were respectively stained with hematoxylin-eosin (HE), crystal violet (CV), and Congo red (CR) and observed under a light microscope. CR-stained sections were also observed under a polarized light microscope (CR-PLM) or an ultraviolet (UV)-emitted fluorescence microscope (CR-UFM). Further, 35 cases clinically diagnosed with psoriasis, lichen planus, and prurigo nodularis were selected as the negative control group. The positive rate of amyloid protein detected by CR-UFM (81.71%) was significantly higher than that detected by CR-PLM (70.73%, p = 0.004), CR staining (56.10%, p < 0.001), CV staining (30.49%, p < 0.001), or HE staining (28.05%, p < 0.001). In the control group, 34 (97.14%) cases were negative for amyloid deposits in CR staining, CR-PLM, and CR-UFM sections. The relative number of positive dermal papillae observed by CR-UFM (0.35 ± 0.27) was much more than that observed by CR-PLM (0.15 ± 0.17, p<0.001), CR staining (0.12 ± 0.16, p < 0.001), CV staining (0.07 ± 0.12, p < 0.001), or HE staining (0.05 ± 0.12, p < 0.001). The intensity of fluorescence by CR-UFM was significantly greater than that of the appl-green birefringence by CR-PLM (p < 0.001). Moreover, the amyloid was easily distinguished from the surrounding tissues using the CR-UFM method. In conclusion, the CR-UFM method was superior to CR-PLM, CR staining, CV staining, and HE staining in diagnosing PCA.

Novel MOF-based vanadium and 2,2 -bipyridine-4,4 -dicarboxylic acid as phenomenal dye adsorbent and antimicrobial agent

In this study, a new MOF (metal-organic framework) based on vanadium and 2,2-bipyridine-4,4-dicarboxylic acid (V/BP-MOF) was synthesized. Synthesized V/BP-MOF was introduced as a strong adsorbent of Congo Red (CR) and an effective agent in eliminating microbial species. In the investigation of CR absorption activity, several factors such as concentration of V/BP-MOF, pH, time, and temperature were investigated. Antimicrobial evaluations were carried out on Common bacterial strains in wastewater and values of MIC (minimum inhibitory concentration) and MBC (Minimum Bactericidal Concentration) were reported. The V/BP-MOF was confirmed and characterized by EA, EDS, EDS mapping, FT-IR, XRD, TGA, BET, SEM, and TEM. In checking the characteristics of V/BP-MOF, size, specific surface area, and thermal stability were obtained, respectively, 68 nm, 325 m2/g, and 320°C. The highest adsorption of CR, at 94%, was obtained at natural pH, ambient temperature, and after 150 min. In kinetic studies, a correlation coefficient of 0.99 was observed with the pseudo-second-order kinetic model, while in isotherm studies, a correlation coefficient of 0.97 was observed with the Freundlich isotherm model. In the biological evaluations, the best inhibition was against Escherichia coli, and MIC and MBC were observed as 4 μg/mL and 2 μg/mL, respectively. As a general result, V/BP-MOF can be introduced as a potent absorbent agent of CR dye and antimicrobial properties. Therefore, the compound synthesized in this study can be introduced as a suitable option for the wastewater treatment industry, with multiple capabilities including the removal of chemical pollutants and pathogenic agents.

Prostatic amyloidosis: pathological features of an underdiagnosed condition

Amyloidosis is a rare disease that can affect genitourinary organs but the involvement of the prostate has been documented in a limited number of cases. We have reviewed morphologic and immunohistochemical features of prostate biopsies or surgical specimens in which an initial diagnosis of amyloidosis was made. Prostatic amyloidosis was diagnosed in 25 patients, 21 of them were needle biopsies (1.16% of these ones). Amyloid was observed inside vessel walls (25 cases) and the stroma (3). No significant differences in the number of affected biopsy samples between patients with and without cardiac amyloidosis were found. In prostatectomies, amyloid was visualized in all the regions of the prostate, being more abundant in the periphery and the posterolateral tissue. Three patients with abundant amyloid in the prostatectomy did not have cardiac amyloidosis. Immunohistochemically prostatic amyloid was positive for transthyretin and P amyloid (24 cases). A amyloid, kappa, and lambda chains were negative. The genetic analysis revealed transthyretin wild-type amyloidosis. Immunohistochemistry was not conclusive in one case of immunoglobulin light chain amyloidosis. In conclusion, prostate amyloidosis is an infrequent finding characterized by the deposition of amyloid inside small vessel walls, and less often in the stroma. It occurs mainly in the periphery of the gland. Amyloid deposits are often subtle and overlooked but relevant as this may be the first sample in which systemic amyloidosis is diagnosed. Immunohistochemistry can be used to subtype amyloid, although there are limitations when confronted with immunoglobulin light chain amyloidosis. Most cases have corresponded to wild-type transthyretin amyloidosis.

[Amyloidosis - The pathologist's perspective]

Despite the advent of scintigraphic diagnosis of transthyretin amyloidosis, the role of pathologists remains central for the diagnosis and typing of amyloidosis. The anatomo-pathological diagnosis and typing of amyloidosis are hindered by pitfalls that should be known, linked to the Congo red staining (technical implementation and interpretation) and the difficulties of immunohistochemistry. The use of expert centers is recommended for difficult cases and when the type cannot be confirmed.

Down regulation of the c-Fos/MAP kinase signaling pathway during learning memory processes coincides with low GnRH levels in aluminum chloride-induced Alzheimer's male rats

Aluminum chloride (Al) is associated with Alzheimer's disease (AD) and reproductive disorders. But the relationship between gonadotropin-releasing hormone (GnRH) and c-Fos levels, the end product of MAP-kinase signaling, in AD is unknown, so we aimed to investigate this relationship. We exposed rats to Al dissolved in drinking water (10 and 50 mg/kg) for two and four weeks. The control group received only drinking water. At the end, the blood sample was collected under deep anesthesia and the brain was dissected on ice, and the testicular tissue was fixed in formalin. Amyloid beta (βA) plaques in brain regions and the number of CA1 neurons were evaluated by Congo red staining and cresyl violet staining. Activation of neuronal nitric oxide synthase (nNOS) was studied using NADPH-diaphorase. The levels of c-Fos and testosterone receptors in the target area were examined immunohistochemically. Brain GnRH levels were determined by blotting, and serum levels of gonadotropins and steroids were measured by enzyme-linked immunosorbent assay (ELISA). All data were analyzed using analysis of variance (ANOVA) at α = 0.05 level. The accumulation of βA plaque was observed along with a decrease in the number of CA1 pyramidal neurons and a significant decrease in the levels of c-Fos and GnRH in the brains of rats receiving Al, which was aligned with a significant decrease in serum levels of testosterone and LH. This study, for the first time, showed a link between dementia and a concomitant decrease in brain GnRH and c-Fos levels.

Congo Red Staining in Digital Pathology: The Streamlined Pipeline for Amyloid Detection Through Congo Red Fluorescence Digital Analysis

Renal amyloidosis is a rare condition caused by the progressive accumulation of misfolded proteins within glomeruli, vessels, and interstitium, causing functional decline and requiring prompt treatment due to its significant morbidity and mortality. Congo red (CR) stain on renal biopsy samples is the gold standard for diagnosis, but the need for polarized light is limiting the digitization of this nephropathology field. This study explores the feasibility and reliability of CR fluorescence on virtual slides (CRFvs) in evaluating the diagnostic accuracy and proposing an automated digital pipeline for its assessment. Whole-slide images from 154 renal biopsies with CR were scanned through a Texas red fluorescence filter (NanoZoomer S60, Hamamatsu) at the digital Nephropathology Center of the Istituto di Ricovero e Cura a Carattere Scientifico San Gerardo, Monza, Italy, and evaluated double-blinded for the detection and quantification through the amyloid score and a custom ImageJ pipeline was built to automatically detect amyloid-containing regions. Interobserver agreement for CRFvs was optimal (k = 0.90; 95% CI, 0.81-0.98), with even better concordance when consensus-based CRFvs evaluation was compared to the standard CR birefringence (BR) (k = 0.98; 95% CI, 0.93-1). Excellent performance was achieved in the assessment of amyloid score overall by CRFvs (weighted k = 0.70; 95% CI, 0.08-1), especially within the interstitium (weighted k = 0.60; 95% CI, 0.35-0.84), overcoming the misinterpretation of interstitial and capsular collagen BR. The application of an automated digital pathology pipeline (Streamlined Pipeline for Amyloid detection through CR fluorescence Digital Analysis, SPADA) further increased the performance of pathologists, leading to a complete concordance with the standard BR. This study represents an initial step in the validation of CRFvs, demonstrating its general reliability in a digital nephropathology center. The computational method used in this study has the potential to facilitate the integration of spatial omics and artificial intelligence tools for the diagnosis of amyloidosis, streamlining its detection process.