Semiautomated computer-assisted image analysis to quantify 3,3'-diaminobenzidine tetrahydrochloride-immunostained small tissues

Histological and immunohistochemical guide to tendon tissue

Tendons are unique dense connective tissues with discrete zones having specific structure and function. They are juxtaposed with other tissues (e.g., bone, muscle, and fat) with different compositional, structural, and mechanical properties. Additionally, tendon properties change drastically with growth and development, disease, aging, and injury. Consequently, there are unique challenges to performing high quality histological assessment of this tissue. To address this need, histological assessment was one of the breakout session topics at the 2022 Orthopaedic Research Society (ORS) Tendon Conference hosted at the University of Pennsylvania. The purpose of the breakout session was to discuss needs from members of the ORS Tendon Section related to histological procedures, data presentation, knowledge dissemination, and guidelines for future work. Therefore, this review provides a brief overview of the outcomes of this discussion and provides a set of guidelines, based on the perspectives from our laboratories, for histological assessment to assist researchers in their quest to utilize these techniques to enhance the outcomes and interpretations of their studies.

Implication of RAS in Postnatal Cardiac Remodeling, Fibrosis and Dysfunction Induced by Fetal Undernutrition

Fetal undernutrition is a risk factor for cardiovascular diseases. Male offspring from rats exposed to undernutrition during gestation (MUN) exhibit oxidative stress during perinatal life and develop cardiac dysfunction in ageing. Angiotensin-II is implicated in oxidative stress-mediated cardiovascular fibrosis and remodeling, and lactation is a key developmental window. We aimed to assess if alterations in RAS during lactation participate in cardiac dysfunction associated with fetal undernutrition. Control dams received food ad libitum, and MUN had 50% nutrient restriction during the second half of gestation. Both dams were fed ad libitum during lactation, and male offspring were studied at weaning. We assessed: ventricular structure and function (echocardiography); blood pressure (intra-arterially, anesthetized rats); collagen content and intramyocardial artery structure (Sirius red, Masson Trichromic); myocardial and intramyocardial artery RAS receptors (immunohistochemistry); plasma angiotensin-II (ELISA) and TGF-β1 protein expression (Western Blot). Compared to Control, MUN offspring exhibited significantly higher plasma Angiotensin-II and a larger left ventricular mass, as well as larger intramyocardial artery media/lumen, interstitial collagen and perivascular collagen. In MUN hearts, TGF-β1 tended to be higher, and the end-diastolic diameter and E/A ratio were significantly lower with no differences in ejection fraction or blood pressure. In the myocardium, no differences between groups were detected in AT1, AT2 or Mas receptors, with MrgD being significantly lower in the MUN group. In intramyocardial arteries from MUN rats, AT1 and Mas receptors were significantly elevated, while AT2 and MrgD were lower compared to Control. Conclusions. In rats exposed to fetal undernutrition, RAS disbalance and associated cardiac remodeling during lactation may set the basis for later heart dysfunction.

Adenosine A2A and A3 Receptors as Targets for the Treatment of Hypertensive-Diabetic Nephropathy

Diabetic nephropathy (DN) and hypertension are prime causes for end-stage renal disease (ESRD) that often coexist in patients, but are seldom studied in combination. Kidney adenosine levels are markedly increased in diabetes, and the expression and function of renal adenosine receptors are altered in experimental diabetes. The aim of this work is to explore the impact of endogenous and exogenous adenosine on the expression/distribution profile of its receptors along the nephron of hypertensive rats with experimentally-induced diabetes. Using spontaneously hypertensive (SHR) rats rendered diabetic with streptozotocin (STZ), we show that treatment of SHR-STZ rats with an agonist of adenosine receptors increases A_2A immunoreactivity in superficial glomeruli (SG), proximal tubule (PCT), and distal tubule (DCT). Differently, treatment of SHR-STZ rats with a xanthinic antagonist of adenosine receptors decreases adenosine A₃ immunoreactivity in SG, PCT, DCT, and collecting duct. There is no difference in the immunoreactivity against the adenosine A₁ and A_2B receptors between the experimental groups. The agonist of adenosine receptors ameliorates renal fibrosis, probably via A_2A receptors, while the antagonist exacerbates it, most likely due to tonic activation of A₃ receptors. The reduction in adenosine A₃ immunoreactivity might be due to receptor downregulation in response to prolonged activation. Altogether, these results suggest an opposite regulation exerted by endogenous and exogenous adenosine upon the expression of its A_2A and A₃ receptors along the nephron of hypertensive diabetic rats, which has a functional impact and should be taken into account when considering novel therapeutic targets for hypertensive-diabetic nephropathy.

Diabetes downregulates renal adenosine A2A receptors in an experimental model of hypertension

Studies on diabetic nephropathy rarely take into account that the co-existence of diabetes and hypertension is frequent and further aggravates the prognosis of renal dysfunction. Adenosine can activate four subtypes of adenosine receptors (A₁, A_2A, A_2B and A₃) and has been implicated in diabetic nephropathy. However, it is not known if, in hypertensive conditions, diabetes alters the presence/distribution profile of renal adenosine receptors. The aim of this work was to describe the presence/distribution profile of the four adenosine receptors in six renal structures (superficial/deep glomeruli, proximal/distal tubules, loop of Henle, collecting tubule) of the hypertensive kidney and to evaluate whether it is altered by diabetes. Immunoreactivities against the adenosine receptors were analyzed in six renal structures from spontaneously hypertensive rats (SHR, the control group) and from SHR rats with diabetes induced by streptozotocyin (SHR-STZ group). Data showed, for the first time, that all adenosine receptors were present in the kidney of SHR rats, although the distribution pattern was specific for each adenosine receptor subtype. Also, induction of diabetes in the SHR was associated with downregulation of adenosine A_2A receptors, which might be relevant for the development of hypertensive diabetic nephropathy. This study highlights the adenosine A_2A receptors as a potential target to explore to prevent and/or treat early diabetes-induced hyperfiltration, at least in hypertensive conditions.

Cellular HIV Reservoirs and Viral Rebound from the Lymphoid Compartments of 4'-Ethynyl-2-Fluoro-2'-Deoxyadenosine (EFdA)-Suppressed Humanized Mice

Although antiretroviral therapy (ART) greatly suppresses HIV replication, lymphoid tissues remain a sanctuary site where the virus may replicate. Tracking the earliest steps of HIV spread from these cellular reservoirs after drug cessation is pivotal for elucidating how infection can be prevented. In this study, we developed an in vivo model of HIV persistence in which viral replication in the lymphoid compartments of humanized mice was inhibited by the HIV reverse transcriptase inhibitor 4′-ethynyl-2-fluoro-2′-deoxyadenosine (EFdA) to very low levels, which recapitulated ART-suppression in HIV-infected individuals. Using a combination of RNAscope in situ hybridization (ISH) and immunohistochemistry (IHC), we quantitatively investigated the distribution of HIV in the lymphoid tissues of humanized mice during active infection, EFdA suppression, and after drug cessation. The lymphoid compartments of EFdA-suppressed humanized mice harbored very rare transcription/translation-competent HIV reservoirs that enable viral rebound. Our data provided the visualization and direct measurement of the early steps of HIV reservoir expansion within anatomically intact lymphoid tissues soon after EFdA cessation and suggest a strategy to enhance therapeutic approaches aimed at eliminating the HIV reservoir.

Vascular impairment of adenosinergic system in hypertension: increased adenosine bioavailability and differential distribution of adenosine receptors and nucleoside transporters

Adenosinergic system regulates vascular tonicity through the complex system of adenosine, adenosine receptors (ARs) and nucleoside transporters. This work aimed at evaluating the impact of hypertension on adenosine bioavailability and expression/distribution profile of AR subtypes (A₁, A_2A, A_2B, A₃) and equilibrative nucleoside transporters (ENT1, ENT2, ENT3, ENT4). Adenosine was measured in vascular tissue extracts by HPLC (fluorescence detection); immunoreactivities (ARs/ENTs) in mesenteric arteries/veins from normotensive Wistar Kyoto (WKY) and spontaneously hypertensive rats (SHR) were analyzed by histomorphometry. Significantly higher adenosine bioavailability occurred in arteries than in veins. Adenosine bioavailability was even more increased in SHR vessels. Expression/distribution of ARs and ENTs observed in all vascular layers (intima, media, adventitia), with more intensified expression in arteries than in veins. In SHR arteries, a downregulation of all ENT along with downregulated and punctuated distribution of A₁ and A_2B receptors occurred comparatively to WKY arteries. By contrast, expressions of ARs and ENTs were unaltered, exception for an A_2A receptor upregulation, and ENT2 downregulation in SHR veins relatively to WKY veins. Our data evidenced clear alterations of adenosinergic dynamics occurring in hypertension, particularly in arterial vessels. An increased adenosine bioavailability was observed, for the first time, in hypertensive vascular tissues.

Immunohistochemical quantification of expression of a tight junction protein, claudin-7, in human lung cancer samples using digital image analysis method

BACKGROUND AND OBJECTIVES

Tight junction proteins are correlated with cancer development. As the pivotal proteins in epithelial cells, altered expression and distribution of different claudins have been reported in a wide variety of human malignancies. We have previously reported that claudin-7 was strongly expressed in benign bronchial epithelial cells at the cell-cell junction while expression of claudin-7 was either altered with discontinued weak expression or completely absent in lung cancers. Based on these results, we continued working on the expression pattern of claudin-7 and its relationship with lung cancer development. We herein proposed a new Digital Image Classification, Fragmentation index, Morphological analysis (DICFM) method for differentiating the normal lung tissues and lung cancer tissues based on the claudin-7 immunohistochemical staining.

METHODS

Seventy-seven lung cancer samples were obtained from the Second Affiliated Hospital of Zhejiang University and claudin-7 immunohistochemical staining was performed. Based on C++ and Open Source Computer Vision Library (OpenCV, version 2.4.4), the DICFM processing module was developed. Intensity and fragmentation of claudin-7 expression, as well as the morphological parameters of nuclei were calculated. Evaluation of results was performed using Receiver Operator Characteristic (ROC) analysis.

RESULTS

Agreement between these computational results and the results obtained by two pathologists was demonstrated. The intensity of claudin-7 expression was significantly decreased while the fragmentation was significantly increased in the lung cancer tissues compared to the normal lung tissues and the intensity was strongly positively associated with the differentiation of lung cancer cells. Moreover, the perimeters of the nuclei of lung cancer cells were significantly greater than that of the normal lung cells, while the parameters of area and circularity revealed no statistical significance.

CONCLUSIONS

Taken together, our DICFM approach may be applied as an appropriate approach to quantify the immunohistochemical staining of claudin-7 on the cell membrane and claudin-7 may serve as a marker for identification of lung cancer.

Matrix metalloproteinase-2 of human carotid atherosclerotic plaques promotes platelet activation

Purified active matrix metalloproteinase-2 (MMP-2) is able to promote platelet aggregation. We aimed to assess the role of MMP-2 expressed in atherosclerotic plaques in the platelet-activating potential of human carotid plaques and its correlation with ischaemic events. Carotid plaques from 81 patients undergoing endarterectomy were tested for pro-MMP-2 and TIMP-2 content by zymography and ELISA. Plaque extracts were incubated with gel-filtered platelets from healthy volunteers for 2 minutes before the addition of a subthreshold concentration of thrombin receptor activating peptide-6 (TRAP-6) and aggregation was assessed. Moreover, platelet deposition on plaque extracts immobilised on plastic coverslips under high shear-rate flow conditions was measured. Forty-three plaque extracts (53%) potentiated platelet aggregation (+233 ± 26.8%), an effect prevented by three different specific MMP-2 inhibitors (inhibitor II, TIMP-2, moAb anti-MMP-2). The pro-MMP-2/TIMP-2 ratio of plaques potentiating platelet aggregation was significantly higher than that of plaques not potentiating it (3.67 ± 1.21 vs 1.01 ± 0.43, p<0.05). Moreover, the platelet aggregation-potentiating effect, the active-MMP-2 content and the active MMP-2/pro-MMP-2 ratio of plaque extracts were significantly higher in plaques from patients who developed a subsequent major cardiovascular event. In conclusion, atherosclerotic plaques exert a prothrombotic effect by potentiating platelet activation due to their content of MMP-2; an elevated MMP-2 activity in plaques is associated with a higher rate of subsequent ischaemic cerebrovascular events.

nNOS is involved in cardiac remodeling induced by chronic ethanol consumption

Chronic ethanol consumption has deleterious effects on the cardiovascular system by directly damaging the myocardial structure and/or by neurohormonal activation. Moreover, nitric oxide (NO) derived from neuronal NO synthase (nNOS) seems to be important to balance the harmful effects of ethanol consumption, because it influences several aspects of cardiac physiology and attenuates pathological cardiac remodeling. However, the impact of chronic ethanol consumption on nNOS expression is unknown. We address this subject in the present study by evaluating whether chronic ethanol consumption induces cardiac remodeling and hypertension, and if these changes are associated with alterations in the expression of nNOS. Male Wistar rats were examined after ingesting a 20% alcohol solution for 6 months. Blood alcohol concentration and brain natriuretic peptide (BNP) levels were measured. The cardiac remodeling was assessed by histomorphometric analysis and the nNOS expression was evaluated by immunofluorescence and western blot analysis. Our results show that chronic ethanol consumption induces cardiac remodeling, namely thinning of left ventricular wall, cardiomyocyte hypertrophy and increased fibrosis, and elevations of arterial blood pressure. They also show that in rats fed with ethanol for 6 months, the circulating BNP levels had decreased as well as the expression of nNOS in left ventricle cardiomyocytes. These findings suggest that the effects of chronic ethanol consumption on BNP levels and/or on nNOS expression in cardiomyocytes may contribute to aggravate the cardiac remodeling and leads to progression of cardiomyopathy.

PET imaging of cardiac wound healing using a novel [68Ga]-labeled NGR probe in rat myocardial infarction

PURPOSE

Peptides containing the asparagine-glycine-arginine (NGR) motif bind to aminopeptidase N (CD13), which is expressed on inflammatory cells, endothelial cells, and fibroblasts. It is unclear whether radiolabeled NGR-containing tracers could be used for in vivo imaging of the early wound-healing phase after myocardial infarction (MI) using positron emission tomography (PET).

PROCEDURES

Uptake of novel tracer [(68)Ga]NGR was assessed together with [(68)Ga]arginine-glycine-aspartic acid ([(68)Ga]RGD) and 2-deoxy-2-[(18) F]fluoro-D-glucose after myocardial ischemia/reperfusion (MI/R) injury using μ-PET and autoradiography, and relative expressions of CD13 and integrin β3 were assessed in fibroblasts, inflammatory cells, and endothelial cells by immunohistochemistry.

RESULTS

In the infarcted myocardium, uptake of [(68)Ga]NGR was maximal from days 3 to 7 after MI/R, and correlated with fibroblast and inflammatory cell infiltration as well as [(68)Ga]RGD uptake.

CONCLUSIONS

[(68)Ga]NGR allows noninvasive and sequential determination of CD13 expression in fibroblasts and inflammatory cells by PET. This will facilitate monitoring of CD13 in the individual wound healing processes, allowing patient-specific therapies to improve outcome after MI.

Impaired inhibitory function of presynaptic A1-adenosine receptors in SHR mesenteric arteries

In hypertension, vascular reactivity alterations have been attributed to numerous factors, including higher sympathetic innervation/adenosine. This study examined the modulation of adenosine receptors on vascular sympathetic nerves and their putative contribution to higher noradrenaline spillover in hypertension. We assessed adenosine receptors distribution in the adventitia through confocal microscopy, histomorphometry, and their regulatory function on electrically-evoked [(3)H]-noradrenaline overflow, using selective agonists/antagonists. We found that: i) A1-adenosine receptor agonist (CPA: 100 nM) inhibited tritium overflow to a lower extent in SHR (25% ± 3%, n = 14) compared to WKY (38% ± 3%, n = 14) mesenteric arteries; ii) A2A-adenosine receptor agonist (CGS 21680: 100 nM) induced a slight increase of tritium overflow that was similar in SHR (22% ± 8%, n = 8) and WKY (24% ± 5%, n = 8) mesenteric arteries; iii) A2B- and A3-adenosine receptors did not alter tritium overflow in either strain; iv) all adenosine receptors were present on mesenteric artery sympathetic nerves and/or some adventitial cells of both strains; and v) A1-adenosine receptor staining fractional area was lower in SHR than in WKY mesenteric arteries. We conclude that there is an impaired inhibitory function of vascular presynaptic A1-adenosine receptors in SHR, likely related to a reduced presence of these receptors on sympathetic innervation, which might lead to higher levels of noradrenaline in the synaptic cleft and contribute to hypertension in this strain.

Mitochondrial abnormality associates with type-specific neuronal loss and cell morphology changes in the pedunculopontine nucleus in Parkinson disease

Cholinergic neuronal loss in the pedunculopontine nucleus (PPN) associates with abnormal functions, including certain motor and nonmotor symptoms. This realization has led to low-frequency stimulation of the PPN for treating patients with Parkinson disease (PD) who are refractory to other treatment modalities. However, the molecular mechanisms underlying PPN neuronal loss and the therapeutic substrate for the clinical benefits following PPN stimulation remain poorly characterized, hampering progress toward designing more efficient therapies aimed at restoring the PPN's normal functions during progressive parkinsonism. Here, we investigated postmortem pathological changes in the PPN of PD cases. Our study detected a loss of neurons producing gamma-aminobutyric acid (GABA) as their output and glycinergic neurons, along with the pronounced loss of cholinergic neurons. These losses were accompanied by altered somatic cell size that affected the remaining neurons of all neuronal subtypes studied here. Because studies showed that mitochondrial dysfunction exists in sporadic PD and in PD animal models, we investigated whether altered mitochondrial composition exists in the PPN. A significant up-regulation of several mitochondrial proteins was seen in GABAergic and glycinergic neurons; however, cholinergic neurons indicated down-regulation of the same proteins. Our findings suggest an imbalance in the activity of key neuronal subgroups of the PPN in PD, potentially because of abnormal inhibitory activity and altered cholinergic outflow.

Elevated levels of endothelin-1 in hepatic venous blood are associated with intrapulmonary vasodilatation in humans

BACKGROUND

Hepatopulmonary syndrome is a pulmonary vascular complication of cirrhosis in which intrapulmonary vasodilatation (IPV) results in hypoxemia. Endothelin-1 (ET-1), produced by proliferating cholangiocytes, has been identified as a mediator of IPV in an animal model of HPS, but the pathophysiology of IPV in humans has not been defined.

AIM

The purpose of this study was to assess whether cirrhosis with IPV, which often leads to HPS, is associated with increased hepatic venous ET-1 blood levels.

METHODS

We performed a prospective cohort pilot study of 40 patients with liver disease undergoing transjugular liver biopsy from November 1, 2008 to September 1, 2009. Patients were categorized according to absence (-) or presence (+) of IPV as determined by bubble-contrasted echocardiography. Hepatic venous blood was assayed for ET-1 by ELISA. The percent volume of cholangiocytes in the liver biopsy specimen was determined by morphometric analysis, as a measure of bile duct proliferation.

RESULTS

Nine subjects were excluded, due to absence of cirrhosis (6) and patent foramen ovale (3). Of the remaining 31 subjects, IPV was present in 18 (58%). Median hepatic venous ET-1 was higher with IPV+ than IPV- at levels of 9.1 pg/mL (range 7.5-11.7) versus 2.1 pg/mL (1.3-5.6), respectively (P = 0.004). ET-1 levels correlated positively with cholangiocyte percent volume (r = 0.72, P < 0.001) but not with measures of liver dysfunction (bilirubin, INR, MELD score, or hepatic venous pressure gradient).

CONCLUSION

In human cirrhosis, increased hepatic venous ET-1 is associated with IPV and increased hepatic cholangiocyte volume.

Automation of immunohistochemical evaluation in breast cancer using image analysis

AIM: To automate breast cancer diagnosis and to study the inter-observer and intra-observer variations in the manual evaluations.

METHODS: Breast tissue specimens from sixty cases were stained separately for estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor-2 (HER-2/neu). All cases were assessed by manual grading as well as image analysis. The manual grading was performed by an experienced expert pathologist. To study inter-observer and intra-observer variations, we obtained readings from another pathologist as the second observer from a different laboratory who has a little less experience than the first observer. We also took a second reading from the second observer to study intra-observer variations. Image analysis was carried out using in-house developed software (TissueQuant). A comparison of the results from image analysis and manual scoring of ER, PR and HER-2/neu was also carried out.

RESULTS: The performance of the automated analysis in the case of ER, PR and HER-2/neu expressions was compared with the manual evaluations. The performance of the automated system was found to correlate well with the manual evaluations. The inter-observer variations were measured using Spearman correlation coefficient r and 95% confidence interval. In the case of ER expression, Spearman correlation r = 0.53, in the case of PR expression, r = 0.63, and in the case of HER-2/neu expression, r = 0.68. Similarly, intra-observer variations were also measured. In the case of ER, PR and HER-2/neu expressions, r = 0.46, 0.66 and 0.70, respectively.

CONCLUSION: The automation of breast cancer diagnosis from immunohistochemically stained specimens is very useful for providing objective and repeatable evaluations.

Antibody treatment promotes compensation for human cytomegalovirus-induced pathogenesis and a hypoxia-like condition in placentas with congenital infection

Human cytomegalovirus (HCMV) is the major viral cause of birth defects worldwide. Affected infants can have temporary symptoms that resolve soon after birth, such as growth restriction, and permanent disabilities, including neurological impairment. Passive immunization of pregnant women with primary HCMV infection is a promising treatment to prevent congenital disease. To understand the effects of sustained viral replication on the placenta and passive transfer of protective antibodies, we performed immunohistological analysis of placental specimens from women with untreated congenital infection, HCMV-specific hyperimmune globulin treatment, and uninfected controls. In untreated infection, viral replication proteins were found in trophoblasts and endothelial cells of chorionic villi and uterine arteries. Associated damage included extensive fibrinoid deposits, fibrosis, avascular villi, and edema, which could impair placental functions. Vascular endothelial growth factor and its receptor fms-like tyrosine kinase 1 (Flt1) were up-regulated, and amniotic fluid contained elevated levels of soluble Flt1 (sFlt1), an antiangiogenic protein, relative to placental growth factor. With hyperimmune globulin treatment, placentas appeared uninfected, vascular endothelial growth factor and Flt1 expression was reduced, and sFlt1 levels in amniotic fluid were lower. An increase in the number of chorionic villi and blood vessels over that in controls suggested compensatory development for a hypoxia-like condition. Taken together the results indicate that antibody treatment can suppress HCMV replication and prevent placental dysfunction, thus improving fetal outcome.

Hypoxia-inducible factor 1 alpha in oral squamous cell carcinoma and its relation to prognosis

The aim of this study was to investigate the correlation between the expression of hypoxia-inducible factor 1 alpha (HIF-1 alpha) and proliferative activity in tumor cells, lymph node metastasis, as well as prognosis in patients with oral squamous cell carcinoma (OSCC). Fifty-seven biopsy specimens of OSCC were investigated for the expression of HIF-1 alpha and proliferating cell nuclear antigen (PCNA) by immunohistochemistry. None of the patients had received any prior treatments. The percentage of HIF-1 alpha immunopositive area (PHIA) was calculated using computer-assisted image analysis for quantitative assessment of HIF-1 alpha expression. The PCNA labeling index (LI) was evaluated as a proliferation marker. We found that the mean PHIA in all stages was 12.1% in the poor prognosis patients, and it was 6.4% in the good prognosis patients. There was a significant difference of PHIA between poor prognosis and good prognosis patients (P=0.0065). Furthermore, the mean PHIA in the patients who had no metastatic lymph nodes was 7.5%, while it was 11.7% in the patients who had metastatic lymph nodes. There was also a significant difference of PHIA between patients who had no metastatic lymph nodes and those who had metastatic lymph nodes (P=0.0487). On the other hand, significant correlation between PHIA and PCNA LI was not observed. These results provide the clinical data indicating that HIF-1 alpha may play an important role in lymph node metastasis and prognosis in patients with OSCC.

Immunohistochemical characterization of adenosine receptors in rat aorta and tail arteries

Adenosine plays an important role in the cardiovascular system, activating adenosine A(1), A(2A), A(2B), and A(3) receptors, and regulating blood flow either by acting directly on vascular cells or indirectly because of its effects on the central or peripheral nervous systems. The aim of the present study was to investigate whether the pattern of distribution of adenosine receptor subtypes is different on elastic and muscular, using abdominal aorta and tail arteries as models. Immunohistochemistry using anti-A(1), anti-A(2A), anti-A(2B), and anti-A(3) receptor antibodies was performed on perfused-fixed/paraffin-embedded arteries from Wistar rats. 3,3'-Diaminobenzidine tetrahydrochloride (DAB; activated by hydrogen peroxide) staining revealed significant differences in the abundance of A(1), A(2A), and A(3) receptors between abdominal aorta and tail artery and allowed the identification of distinct distribution patterns for A(1), A(2A), A(2B), and A(3) receptors in the tunica adventitia, media, and intima of muscular and elastic arteries. Data are compatible with several previous functional reports supporting that different adenosine receptor subtype expression and/or their distribution in the vessel wall may influence their respective contribution to the control of blood flow.

Immunohistochemical localization of angiotensin II receptor types 1 and 2 in the mesenteric artery from spontaneously hypertensive rats

Angiotensin II plays a crucial role in the control of blood pressure, acting at AT1 or AT2 receptors, and can act as a potent vasoconstrictor of the peripheral vasculature inducing hypertrophy, hyperplasia, or both, in resistance arteries. The aim of the present study was to investigate whether the pattern of distribution of angiotensin AT1 and AT2 receptors on mesenteric artery sections differs in spontaneously hypertensive rats (SHR) versus their respective controls (Wistar-Kyoto [WKY] rats). Immunohistochemistry using anti-AT1 or anti-AT2 antibodies was performed on perfused-fixed/paraffin-embedded mesenteric arteries from SHR and WKY rats. 3,3'-Diaminobenzidine tetrahydrochloride (DAB; activated by hydrogen peroxide) staining revealed distinct AT1 and AT2 labeling of all artery layers (adventitia, media and intima) from WKY rats, whereas in SHR an abundant AT1 labeling was found in both intima and adventitia and a sparser labeling in the media. There was a vast reduction of AT2 labeling throughout all layers. These results suggest a crucial role for AT2 receptors in the pathogenesis of hypertension.

Quantitative image analysis of immunohistochemical stains using a CMYK color model

Background

Computer image analysis techniques have decreased effects of observer biases, and increased the sensitivity and the throughput of immunohistochemistry (IHC) as a tissue-based procedure for the evaluation of diseases.

Methods

We adapted a Cyan/Magenta/Yellow/Key (CMYK) model for automated computer image analysis to quantify IHC stains in hematoxylin counterstained histological sections.

Results

The spectral characteristics of the chromogens AEC, DAB and NovaRed as well as the counterstain hematoxylin were first determined using CMYK, Red/Green/Blue (RGB), normalized RGB and Hue/Saturation/Lightness (HSL) color models. The contrast of chromogen intensities on a 0–255 scale (24-bit image file) as well as compared to the hematoxylin counterstain was greatest using the Yellow channel of a CMYK color model, suggesting an improved sensitivity for IHC evaluation compared to other color models. An increase in activated STAT3 levels due to growth factor stimulation, quantified using the Yellow channel image analysis was associated with an increase detected by Western blotting. Two clinical image data sets were used to compare the Yellow channel automated method with observer-dependent methods. First, a quantification of DAB-labeled carbonic anhydrase IX hypoxia marker in 414 sections obtained from 138 biopsies of cervical carcinoma showed strong association between Yellow channel and positive color selection results. Second, a linear relationship was also demonstrated between Yellow intensity and visual scoring for NovaRed-labeled epidermal growth factor receptor in 256 non-small cell lung cancer biopsies.

Conclusion

The Yellow channel image analysis method based on a CMYK color model is independent of observer biases for threshold and positive color selection, applicable to different chromogens, tolerant of hematoxylin, sensitive to small changes in IHC intensity and is applicable to simple automation procedures. These characteristics are advantageous for both basic as well as clinical research in an unbiased, reproducible and high throughput evaluation of IHC intensity.