Histopathological study on the prevalence of trichosporonosis in formalin-fixed and paraffin-embedded tissue autopsy sections by in situ hybridization with peptide nucleic acid probe.

Trichosporon species are some of the most common pathogenic yeasts in Asia, and many are resistant to echinocandin antifungal drugs. Effective treatment of fungal infections requires the selection of appropriate antifungals and the accurate identification of the causal organism. However, in histopathological specimens Trichosporon spp. are often misidentified as Candida species due to morphological similarities. In situ hybridization (ISH) is a useful technique for identifying fungal species in formalin-fixed and paraffin-embedded (FFPE) tissue sections. Although many novel probes for ISH are available, the practical use of ISH for identification of fungi remains limited, in part due to the lack of adequate verifications. We conducted a two-center retrospective observational study in which the ISH technique was used to differentiate Trichosporon spp. and C. albicans in FFPE tissue from autopsy specimens. The study included 88 cases with blood stream yeast infection without Cryptococci extracted from 459 autopsy files of cases with proven invasive fungal infection (IFI). Positive signals for the Trichosporon spp. protein nucleic acid (PNA) probe and C. albicans PNA probe were seen for 7 and 35 cases, respectively, whereas the remaining 46 were negative for both. For the Trichosporon spp.- positive specimens, 5/7 were reported as candidiasis in autopsy records. Our results suggested that accurate histological identification of fungal infections remains challenging, but ISH may be a suitable approach to support histological findings. In addition, this retrospective study suggested that trichosporonosis may have high prevalence among cases of bloodstream yeast infections in Japan.

Gangliocytic paraganglioma: a multi-institutional retrospective study in Japan.

BACKGROUND: Gangliocytic paraganglioma (GP) is an extremely rare benign tumor that commonly arises from the second part of the duodenum. Since GP exhibit neither prominent mitotic activity nor Ki-67 immunoreactivity, this tumor is often misdiagnosed as neuroendocrine tumor (NET) G1 (carcinoid tumor). However, patients with GP may have a better prognosis than patients with NET G1. This fact emphasizes the importance of differentiating GP from NET G1, but few studies have reported the epidemiology and histopathology of GP because of its rarity. To differentiate GP from NET G1 with ease, we conducted a multi-institutional retrospective study analyzing the morphometric and immunohistochemical features of this tumor. METHODS: Since only a limited number of patients with GP could be identified in our institute, we conducted a multi-institutional retrospective study of GP in Japan, which was approved by the Ethics Committee of our medical institute. The obtained tissue sections underwent detailed morphometric and immunohistochemical analyses. Additionally, to differentiate GP from NET G1 with ease, immunohistochemical findings were compared. RESULTS: In our examination of 12 cases of duodenal GP, we found that epithelioid cells of GP exhibited positive reactivity for progesterone receptor and pancreatic polypeptide, whereas tumor cells of NET G1 were completely negative reactivity for both. Additionally, although GP is considered to be an extremely rare NET, we found that four (40.0%) of the ten patients at our institute with duodenal NET G1 actually had GP. CONCLUSIONS: Although GP is regarded as a rare NET, our results suggest that it accounts for a substantial percentage of duodenal NETs. Additionally, confirmation of immunoreactivity for progesterone receptor and pancreatic polypeptide can assist in differentiating GP from NET G1.

Exacerbation of invasive Candida albicans infection by commensal bacteria or a glycolipid through IFN-γ produced in part by iNKT cells.

BACKGROUND: The commensal yeast Candida albicans is a major cause of invasive fungal infections. Despite treatment with antifungal agents, the mortality rate attributed to these types of infection is high. Although numerous cases have been reported regarding a poor outcome for patients with bacterial and C. albicans coinfection, the mechanisms by which the coinfecting bacteria exacerbate the C. albicans infection remain elusive. METHODS AND RESULTS: We evaluated how glycolipid-mediated activation of invariant natural killer T (iNKT) cells affects the clearance of C. albicans. Surprisingly, C. albicans-infected, glycolipid-treated mice exhibited significantly lower survival rates, increased fungal burden, and higher interleukin (IL)-6 production in the kidneys compared with control mice. Glycolipid-induced exacerbation of C. albicans infection was not observed in interferon-gamma knockout (IFN-γKO) mice. In the C. albicans-infected, glycolipid-treated mice, the number of neutrophils in the blood and bone marrow dramatically decreased in an IFN-γ-dependent manner. Furthermore, mice that were coinfected with C. albicans and nonfermentative gram-negative commensal bacteria exhibited increased fungal burden and inflammatory cytokine production in the kidneys that were dependent on IFN-γ and iNKT cells. CONCLUSIONS: Our results indicate that coinfecting commensal bacteria exacerbate C. albicans infection through IFN-γ produced, in part, by iNKT cells.

Remodeling of the pulmonary artery induced by metastatic gastric carcinoma: a histopathological analysis of 51 autopsy cases.

BACKGROUND: Gastric carcinoma remains the second commonest cause of cancer deaths worldwide. Presence of the carcinoma cell in the pulmonary artery is serious condition that might cause remodeling of the pulmonary artery. The present study conducted detailed histopathological analyses to elucidate how gastric carcinoma cells may affect the structure and hemodynamics of pulmonary arteries. METHODS: Remodeling of the pulmonary artery was assessed based on measurements of arterial diameters and stenosis rates from the autopsies, and their correlation were also validated. We additionally calculated 95 percent confidential intervals (CIs) for the rate of stenosis in groups of pulmonary arteries of different caliber zones (under 100, 100 to 300, and over 300 micrometer). The right ventricular thickness was measured and examined whether it correlated with the rate of pulmonary arterial stenosis. RESULTS: A total of 4612 autopsy cases were recorded at our institute, among which 168 had gastric carcinoma. Finally, 51 cases of the gastric carcinoma were employed for the study which had carcinoma cells in the lumen of the pulmonary artery. The mean right ventricular wall thickness of these cases was 3.14 mm. There were significant positive associations between the rates of pulmonary arterial stenosis and right ventricular thickness from pulmonary arteries of diameter under 100, 100 to 300, and over 300 micrometer. In these zones, 31, 31, and 33 cases had rates of pulmonary arterial stenosis that were below the lower limit of the 95 percent CI values, respectively. On the other hand, among cases with significant pulmonary stenosis, 17 of 18 cases with stenosis in the over 300 micrometer zone involved pulmonary arteries of both in the under 100 and 100 to 300 micrometer zones. CONCLUSION: One-third of autopsy with advanced gastric carcinoma had carcinoma cells in lumen of pulmonary artery, but implantation and proliferation may be essential to induce intimal thickening that causes an increasing of pulmonary arterial pressure, because our study revealed a significant positive association between the rate of pulmonary arterial stenosis and right ventricular thickness. In addition, diffuse type gastric carcinoma may be apt to cause the remodeling of the pulmonary artery.

Development of a peptide nucleic acid probe to Trichosporon species and identification of trichosporonosis by use of in situ hybridization in formalin-fixed and paraffin-embedded (FFPE) sections.

In order to identify Trichosporon species in formalin-fixed and paraffin-embedded sections from which visual discrimination of non-glabrata Candida species is mostly ineffective but critical for the choice of antifungals, we tested the usefulness of a newly designed peptide nucleic acid probe (PNA) for in situ hybridization (ISH). Results confirmed the usefulness of ISH with our PNA probe in identifying Trichosporon species from Candida albicans.

Histopathological implications of Aspergillus infection in lung.

This paper opens with a discussion on the significance of invasive fungal infections in advanced contemporary medicine, with an emphasis on the intractability of disease management and the difficulties of diagnosis. This is followed by a discussion concerning classification, histopathological features, and pathophysiology. While it has been largely accepted that Aspergillus species is recognized by cellular receptors and attacked by neutrophils, the radiological and macroscopic findings linking infection with neutropenia remain unconfirmed. In an effort to gain a better understanding of the pathophysiology and pathogenesis of invasive aspergillosis, we wish to emphasize the utility of radiological and histopathological examinations since these can provide detailed information on the extremely complex interaction between the causative microbes and tissue responses. A review of noninvasive or semi-invasive aspergillosis is also provided, with particular emphasis on chronic necrotizing pulmonary aspergillosis, which is recognized as a transition form of simple pulmonary aspergilloma and invasive pulmonary aspergillosis, although few findings have been reported in this area.

How histopathology can contribute to an understanding of defense mechanisms against cryptococci.

Invasive fungal infections, particularly those considered opportunistic, have become a common and significant complication of procedures performed in advanced contemporary medicine. Among such infections, cryptococcosis, which is usually caused by infection with Cryptococcus neoformans and Cryptococcus gattii, is particularly problematic because this fungal infection occurs in immunocompromised and apparently immunocompetent individuals. It has been largely accepted that Cryptococcus species are recognized by cellular receptors and that Th1-type immune responses play an important role in defense mechanisms against the yeast. However, the interaction between the yeast and host tissue varies depending on the characteristics of the yeast and the immune status of the host. To gain a better understanding of the pathophysiology of cryptococcosis, we wish to emphasize the usefulness of histopathological examinations, because it allowed more detailed information of an extremely complex interaction between the causative yeasts and tissue response. In the present review, we describe the pathophysiology of cryptococcosis as largely revealed in our previous histopathological investigations of the experimental infection.

Gene expression analysis of a murine model with pulmonary vascular remodeling compared to end-stage IPAH lungs.

BACKGROUND: Idiopathic pulmonary arterial hypertension (IPAH) continues to be one of the most serious intractable diseases that might start with activation of several triggers representing the genetic susceptibility of a patient. To elucidate what essentially contributes to the onset and progression of IPAH, we investigated factors playing an important role in IPAH by searching discrepant or controversial expression patterns between our murine model and those previously published for human IPAH. We employed the mouse model, which induced muscularization of pulmonary artery leading to hypertension by repeated intratracheal injection of Stachybotrys chartarum, a member of nonpathogenic and ubiquitous fungus in our envelopment. METHODS: Microarray assays with ontology and pathway analyses were performed with the lungs of mice. A comparison was made of the expression patterns of biological pathways between our model and those published for IPAH. RESULTS: Some pathways in our model showed the same expression patterns in IPAH, which included bone morphogenetic protein (BMP) signaling with down-regulation of BMP receptor type 2, activin-like kinase type 1, and endoglin. On the other hand, both Wnt/planar cell polarity (PCP) signaling and its downstream Rho/ROCK signaling were found alone to be activated in IPAH and not in our model. CONCLUSIONS: Activation of Wnt/PCP signaling, in upstream positions of the pathway, found alone in lungs from end stage IPAH may play essential roles in the pathogenesis of the disease.

Trends in the prevalence of invasive fungal infections from an analysis of annual records of autopsy cases of Toho University.

Clinical diagnosis of invasive fungal infections (IFIs) is sometimes difficult, and obtaining an accurate assessment of trends concerning the prevalence of IFIs is a challenge. The aim of this study was to determine trends in the prevalence of IFIs from an autopsy survey. The retrospective review of autopsy records stored in Toho University was performed on all documented cases with fungal infection from 1955 to 2006. A total of 411 cases of IFIs were detected among 10 297 autopsies. The prevalence of candidiasis decreased from 3.6% (1981-93) to 2.0% (1994-2006), and that of aspergillosis increased throughout the 52-year period and reached 2.0% (1994-2006). The prevalence of IFIs in the patient group comprising haematological disorders was significantly higher (19.9%) than in other patient groups (2.9%), of which the odds ratio was 18.4 for mucormycosis and 10.0 for aspergillosis. The lung was the most common organ involved irrespective of major fungal species, and most cases with candidiasis showed multiple-organ infection. Results confirmed the increasing prevalence of aspergillosis and high risk of IFIs in the patient group with haematological disorders. IFIs were also detected in an immunocompromised state caused not only by primary disease but also by treatment with anti-tumour drugs and corticosteroids.

Comparison Approach for Identifying Missed Invasive Fungal Infections in Formalin-Fixed, Paraffin-Embedded Autopsy Specimens.

Invasive fungal infection (IFI) has a high mortality rate in patients who undergo hematopoietic stem cell transplantation, and it is often confirmed by postmortem dissection. When IFI is initially confirmed after an autopsy, the tissue culture and frozen section are challenging to secure, and in many cases, formalin-fixed, paraffin-embedded (FFPE) samples represent the only modality for identifying fungi. Histopathological diagnosis is a useful method in combination with molecular biological methods that can achieve more precise identification with reproducibility. Meanwhile, polymerase chain reaction (PCR) using fungal-specific primers helps identify fungi from FFPE tissues. Autopsy FFPE specimens have a disadvantage regarding the quality of DNA extracted compared with that of specimens obtained via biopsy or surgery. In the case of mucormycosis diagnosed postmortem histologically, we examined currently available molecular biological methods such as PCR, immunohistochemistry (IHC), and in situ hybridization (ISH) to identify fungi. It is reasonable that PCR with some modification is valuable for identifying fungi in autopsy FFPE specimens. However, PCR does not always correctly identify fungi in autopsy FFPE tissues, and other approaches such as ISH or IHC are worth considering for clarifying the broad classification (such as the genus- or species-level classification).

Identification of Fusarium species in formalin-fixed and paraffin-embedded sections by in situ hybridization using peptide nucleic acid probes.

Fusarium has recently emerged as an opportunistic pathogen of humans, but the histological differentiation of Fusarium from Aspergillus and Scedosporium is particularly difficult because these fungi may induce similar clinical features and exhibit filamentous development in host tissues. Thus, there is a need to establish rapid and reliable methods that are applicable to pathological diagnoses. The aim of this study was to evaluate and establish in situ hybridization (ISH) using peptide nucleic acid (PNA) probes targeting the 28S rRNA to identify Fusarium species in tissue sections. This technique was validated using both formalin-fixed and paraffin-embedded pulmonary tissues from mice infected with seven different species of fungi and cell blocks from fungal cultures of 30 strains. As a result, strong positive signals were observed within fungal organisms present in tissues of the lung from mice infected with Fusarium solani. Furthermore, this probe reacted strongly with both F. solani and Fusarium oxysporum in sections from cell blocks. Although some cross-reactivity occurred with the Pseudallescheria boydii in sections from cell blocks, the signal intensity was low and most hyphae were not reactive. In conclusion, it was confirmed that ISH with PNA probes is accurate and is a valuable tool for identifying Fusarium spp. among organisms that have identical morphological features in formalin-fixed and paraffin-embedded sections.

Leiomyosarcoma with partial rhabdomyoblastic differentiation: first case report of primary cardiac origin.

BACKGROUND: Leiomyosarcoma occurring as a primary cardiac tumor has been known as an extremely rare condition. Previous studies of leiomyosarcoma with rhabdomyoblastic differentiation have conducted to those arisen from another site, and they indicated a poorer prognosis of this tumor. CASE PRESENTATION: A 69-year-old woman was referred to our hospital for an operation concerning umbilical hernia. Subsequent imaging examinations before an operation indicated the presence of primary cardiac malignant tumor due to its atypical shape. And then, it was surgically removed. Histopathologically, tumor cells consisted of two different types: spindle and polyhedral cells. Immunohistochemically, it is interesting to note that 2.1% of spindle cells and 23.1% of polyhedral cells showed positive reactivity for myogenin. Furthermore, we performed double-immunostaining for alpha-smooth muscle actin (SMA) and myogenin. The rates of alpha-SMA and myogenin double negative, alpha-SMA single positive, myogenin single positive, and alpha-SMA and myogenin double positive in spindle cells were estimated as 69.1%, 28.8%, 1.1% and 1.0%, respectively. In contrast, the rates in polyhedral cells were estimated as 76.9%, 0.0%, 23.1%, and 0.0%, respectively. CONCLUSION: Our immunohistochemical evaluation suggested that rhabdomyoblastic differentiation in leiomyosarcoma might be generated not only by de novo generation from mesenchymal cells. To the best of our knowledge, this is the first case of primary cardiac leiomyosarcoma with partial rhabdomyoblastic differentiation.

α-galactosylceramide-stimulated invariant natural killer T-cells play a protective role in murine vulvovaginal candidiasis by Candida albicans.

BACKGROUND: Vulvovaginal candidiasis is a common superficial candidiasis; however, a host's immunological mechanism against vaginal Candida infection remains unknown. OBJECTIVES: In this study, we aimed to elucidate the effect of iNKT cell activation on vulvovaginal candidiasis. METHODS: Using a vulvovaginal candidiasis model with estrogenized mice, we evaluated the fungal burden and number of leukocyte infiltrations in the vaginal lavage of wild-type C57BL/6J mice after Candida albicans inoculation. One day before C. albicans inoculation, α-galactosylceramide (the α-GalCer group) or sterile phosphate-buffered saline (the sham group) was intraperitoneally injected into the mice. We also evaluated the level of antimicrobial peptide S100A8 in the vaginal lavage and analyzed the correlation between S100A8 concentration and the number of vaginal leukocyte infiltrations. Moreover, the number of uterine and vaginal immune cells were evaluated using flow cytometry. RESULTS: The number of vaginal leukocyte infiltrations was significantly higher in the α-GalCer group than in the sham group 3 days after C. albicans inoculation. In addition, the fungal burden was significantly lower in the α-GalCer group than the sham group at 7 days after inoculation. In the analysis of S100A8 concentration of vaginal lavage, there were no significant differences between these two groups, although S100A8 concentration and the number of vaginal leukocyte infiltrations were positively correlated in the α-GalCer group. Moreover, the number of vaginal iNKT cells, NK cells and CD8+ T-cells was significantly higher in the α-GalCer group 3 days after inoculation. CONCLUSIONS: α-GalCer-stimulated iNKT cells likely play a protective role against vulvovaginal candidiasis.

Comparison in Quantities from Including Angles Comprising Lines of Hypha Themselves in Histological Images between Mucorales and Aspergillus.

BACKGROUND: The rate of aspergillosis has decreased due to improvements in therapy. The rate of mucormycosis, however, has gradually increased in recent years. Both aspergillosis and mucormycosis produce histologically similar hyphae, pointing to the need for an objective tool to distinguish between them. METHODS: Three aspergillosis cases and three mucormycosis cases were selected from autopsy cases in our hospital. Representative histological images were captured and hyphal angles in extravascular and intravascular lesions were calculated. RESULTS: For both extravascular and intravascular lesions, the average hyphal angle of aspergillosis was acute, and the standard deviation was less than that of mucormycosis. In aspergillosis, the average hyphal angle for extravascular lesions was acute, and the standard deviation was less than that for intravascular lesions. However, for mucormycosis, there was no significant difference in both the average and standard deviation of the hyphal angles. CONCLUSION: Surgical pathologists should carefully examine the histological characteristics of the fungus to correctly identify specimens and be able to administer proper therapies.

A dendritic cell-based systemic vaccine induces long-lived lung-resident memory Th17 cells and ameliorates pulmonary mycosis.

Tissue-resident memory T cells (TRMs) are a novel nonvascular memory T cell subset. Although CD8+ TRMs are well-characterized, CD4+ TRMs-especially lung-resident memory Th17 cells-are still being defined. In this study, we characterized lung-resident memory Th17 cells (lung TRM17) and their role in protection against the highly virulent fungus Cryptococcus gattii. We found that intravenously transferred DCs preferentially migrated to lungs and attracted recipient DCs and led to the induction of long-lived Th17 cells expressing characteristic markers. This population could be clearly discriminated from circulating T cells by intravascular staining and was not depleted by the immunosuppressive agent FTY720. The C. gattii antigen re-stimulation assay revealed that vaccine-induced lung Th17 cells produced IL-17A but not IFNγ. The DC vaccine significantly increased IL-17A production and suppressed fungal burden in the lungs and improved the survival of mice infected with C. gattii. This protective effect was significantly reduced in the IL-17A knockout (KO) mice, but not in the FTY720-treated mice. The protective effect also coincided with the activation of neutrophils and multinucleated giant cells, and these inflammatory responses were suppressed in the vaccinated IL-17A KO mice. Overall, these data demonstrated that the systemic DC vaccine induced lung TRM17, which played a substantial role in anti-fungal immunity.

[Pathophysiology of invasive fungal infection in diabetic patients].

It has been known that diabetes mellitus impairs functioning of neutrophil, macrophage, cellular immunity, humoral immunity, and iron metabolism. In addition to them, diabetes-related angiopathy leads a patient to being at high-risk individual for several kinds of infectious diseases. Therefore, diabetes has been accepted as one of the important risk factors for invasive fungal infection. From the viewpoint of pathology, the present review describes both pathophysiology of immunosuppression induced by diabetes and histopathological characteristics of typical forms in invasive fungal infection when it occurred as an opportunistic infection; those are candidiasis, aspergillosis, and cryptococcosis. We wish to draw that pathophysiological explanation still remains obscuring of relationship between diabetes and invasive fungal infection.

[Histopathological Diagnosis of Invasive Fungal Infections in Formalin-Fixed and Paraffin-Embedded Tissues in Conjunction with Molecular Methods].

The main objective of this study was to evaluate the relationship between histopathology, polymerase chain reaction (PCR), and in situ hybridization (ISH) for the identification of causative fungi in formalin-fixed and paraffin-embedded (FFPE) tissue specimens. Since pathogenic fungi in tissue specimens can be difficult to identify morphologically, PCR and ISH have been usually employed as auxiliary procedures. However, little comparison has been made on the sensitivity and specificity of PCR and ISH using FFPE specimens. Therefore, to compare and clarify the reproducibility and usefulness of PCR and ISH as auxiliary procedures for histological identification, we performed histopathological review, PCR assays, and ISH to identify pathogenic fungi in 59 FFPE tissue specimens obtained from 49 autopsies. The following are the main findings for this retrospective review: i) even for cases classified as "mold not otherwise specified" (MNOS), two cases could be identified as Aspergillus species by molecular methods; ii) all cases classified as non-zygomycetes mold (NZM) were Aspergillus species and were not identified by molecular methods as other fungi; iii) all 3 cases classified as zygomycetes mold (ZM) could be identified by molecular methods as Mucorales; iv) except for 1 case identified by molecular methods as Trichosporon spp., 5 cases were originally identified as dimorphic yeast (DY). As a measure of nucleic acid integrity, PCR and ISH successfully detected human and fungal nucleic acids in approximately 60% of the specimens. Detection of Aspergillus DNA by nested PCR assay and by ISH against the A. fumigatus ALP gene were similarly sensitive and significant (p<0.01). Thus, our findings demonstrated the potential risk of error in the classification of fungi based on pathological diagnosis. Combining molecular methods such as ISH and PCR on FFPE specimens with pathological diagnosis should improve diagnostic accuracy of fungal infection.

Differences in Ocular Complications Between Candida albicans and Non-albicans Candida Infection Analyzed by Epidemiology and a Mouse Ocular Candidiasis Model.

Objectives: Candida species are a major cause of hospital infections, including ocular candidiasis, but few studies have examined the propensities of specific species to invade the eye or the unique immunological responses induced. This study examined the frequency and characteristics of species-specific Candida eye infections by epidemiology and experiments using a mouse ocular candidiasis model. Methods: We reviewed medical records of candidemia patients from January 2012 to March 2017. We also evaluated ocular fungal burden, inflammatory cytokine and chemokine profiles, and inflammatory cell profiles in mice infected with Candida albicans, Candida glabrata, or Candida parapsilosis. Results: During the study period, 20 ocular candidiasis cases were diagnosed among 99 candidemia patients examined by ophthalmologists. Although C. parapsilosis was the most frequent candidemia pathogen, only C. albicans infection was significantly associated with ocular candidiasis by multivariate analysis. In mice, ocular fungal burden and inflammatory mediators were significantly higher during C. albicans infection, and histopathological analysis revealed invading C. albicans surrounded by inflammatory cells. Ocular neutrophil and inflammatory monocyte numbers were significantly greater during C. albicans infection. Conclusion: Candida albicans is strongly associated with ocular candidiasis due to greater capacity for invasion, induction of inflammatory mediators, and recruitment of neutrophils and inflammatory monocytes.

Technical Aspects and Applications for Developing in situ Hybridization Procedures for Formalin-Fixed and Paraffin-Embedded (FFPE) Tissues for Diagnosis of Fungal Infections.

Although histopathology is required for definitive diagnosis of fungal infections, conclusive identification and discrimination of fungi in tissue sections and cytological preparations remain technically difficult. Therefore, new diagnostic tools are needed for the routine diagnosis of pathogenic fungi. In situ hybridization (ISH) is a non-culture based procedure that has many advantages over traditional diagnostics for identification of pathogenic fungi in histological specimens. This review highlights the basic ISH technique, with particular emphasis on using pretreatment of tissue sections prior to hybridization to solve problems associated with formalin fixation. With this modification, ISH has become a valuable tool that complements conventional histopathological diagnoses in formalin-fixed and paraffinembedded (FFPE) tissues. However, understanding the limitations imposed by formalin fixation is essential in developing suitable ISH protocols for fungal identification.

Implication of overexpression of dishevelled-associated activator of morphogenesis 1 (Daam-1) for the pathogenesis of human Idiopathic Pulmonary Arterial Hypertension (IPAH).

BACKGROUND: Idiopathic pulmonary arterial hypertension (IPAH) is a rare, fatal disease of unknown pathogenesis. Evidence from our recent study suggests that IPAH pathogenesis is related to upregulation of the Wnt/planar cell polarity (Wnt/PCP) pathway. We used microscopic observation and immunohistochemical techniques to identify expression patterns of cascading proteins-namely Wnt-11, dishevelled-2 (Dvl-2), and dishevelled-associated activator of morphogenesis 1 (Daam-1)-in pulmonary arteries. METHODS: We analyzed sections of formalin-fixed and paraffin-embedded autopsied lung tissues obtained from 9 IPAH cases, 7 associated pulmonary arterial hypertension cases, and 16 age-matched controls without pulmonary arterial abnormalities. Results of microscopic observation were analyzed in relation to the cellular components and size of pulmonary arteries. RESULTS: Varying rates of positive reactivity to Dvl-2 and Daam-1 were confirmed in all cellular components of pulmonary arteries, namely, endothelial cells, myofibroblasts, and medial smooth muscle cells. In contrast, none of these components was reactive to Wnt-11. No specific expression patterns were observed for endothelial cells or myofibroblasts under any experimental conditions. However, marked expression of Dvl-2 and Daam-1 was confirmed in smooth muscle cells. In addition, Dvl-2 was depleted while Daam-1 expression was elevated in IPAH, in contrast with specimens from associated pulmonary arterial hypertension cases and controls. CONCLUSIONS: High Daam-1 expression may upregulate the Wnt/PCP pathway and cause IPAH.