Kumi Obara

Ultrastructural spectrum of solitary fibrous tumor: a unique perivascular tumor with alternative lines of differentiation

Eight tumors diagnosed as solitary fibrous tumor (SFT) of the oral cavity were studied. Histologic spectrum was entirely comparable with the extrapleural SFT of other sites. One tumor had glomus tumor-like foci. Immunohistochemical results confirmed most of the previous observations, indicating characteristic expression of vimentin, CD34, bcl-2, and CD99. Factor XIIIa and α-smooth muscle actin were less commonly reactive and a very few cells were faintly positive for factor VIII-related antigen and Ulex europaeus agglutinin 1. All were essentially negative for S-100 protein, desmin, CD31, and CD68. In stark contrast to the conclusive immunoprofile, ultrastructural investigation of six tumors demonstrated considerable cellular heterogeneity. Other than fibroblasts, perivascular undifferentiated cells and pericytes predominated, but endothelial cells were regularly present. There was a distinctive proliferation of pericytic cells in four tumors, one of which had glomoid foci of myopericytes. The extreme increase in number of Weibel-Palade bodies occurred in voluminous capillary endothelium. Occasional single and clustered cells with consistent features of endothelium showed intracytoplasmic lumen formation. Such composite cells constituted an integral segment of richly vascularized SFT. Myofibroblastic form smooth muscle differentiation was present in only a minority of cells. From phenotypic analysis by electron microscopy, SFT may originate from a unique, perivascular multipotent mesenchyme sharing with its lineage with pericytes, fibroblasts, and infrequently, endothelium. Consequently, morphological features of SFT may become diversely varied by whether predominantly constituent cells are undifferentiated, pericytic or fibroblastic in nature.

Possible Involvement of Oxidative Stress in Salivary Gland of Patients with Sjögren’s Syndrome

Objective: To determine the involvement of oxidative stress in the salivary gland of patients with Sjögren’s syndrome (SS). Methods: Oxidative damage to the gland was measured by 8-hydroxy-2′-deoxyguanosine (8-OHdG) and hexanoyl-lysine (HEL) using the SS saliva. In addition, lactate dehydrogenase (LDH) and mitochondrial glutamic-oxaloacetic transaminase (m-GOT), both general markers for cell damage, were also analyzed. Results: Increased levels of 8-OHdG and HEL were found in the saliva of SS patients, but not in that of patients with other salivary gland dysfunction or of healthy individuals. Levels of LDH and m-GOT were significantly correlated with 8-OHdG and HEL levels, respectively. Furthermore, the increased levels of 8-OHdG and HEL were also correlated in the SS saliva. Conclusion: These findings suggested the involvement of oxidative stress in glandular tissue destruction in SS. It was indicated that the detection of 8-OHdG and HEL in the saliva may become a useful tool for the diagnosis of SS.

Cellular basis of verruciform xanthoma: immunohistochemical and ultrastructural characterization.

BACKGROUND Verruciform xanthoma (VX) holds two basic pathogenic interests: (1) Why and how do macrophage foam cells accumulate exclusively in the sub-basal papillae? and (2) What underlies the disease chronicity? Moreover, an unsolved question is which came first - epithelial hyperplasia or foam cell collection? MATERIALS AND METHODS We analyzed 36 oral mucosal lesions to dissect a series of linked cellular changes in VX using immunohistochemical and ultrastructural techniques. RESULTS Macrophage scavenger receptor-1 (MSR-1), monocyte chemoattractant protein-1 (MCP-1), CCR2, and oxidized low-density lipoprotein (ox-LDL) were all expressed by foam cells. VX epithelium showed reactivity for MCP-1, HLA-DR and IL8 in varying degrees, and showed a nearly 40% reduction in Langerhans cell density. In sub-epithelial inflammatory infiltrates, CD8+ T cells preponderated (>70%), but only a minority were positive for granzyme B (<1%). Keratinocyte/basal lamina complex exhibited disruption of basal lamina, squamatization and cytolysis of basal cells, fragmentation of desmosomes, and intraepithelial migration of macrophages. In severely inflamed papillae, necrotic foam cells were scavenged by adjacent macrophages. CONCLUSIONS Under synergistic regulation of T cells, MCP-1/CCR2-mediated macrophage recruitment in the sub-basal papillae and the lysosomal engulfment of epithelial lipids by MSR-1-bearing macrophages may be central in VX formation. Once developed, ox-LDL-induced foam cell necrosis and macrophage-dependent debris disposal may cyclically perpetuate VX.

Intravascular myopericytoma of the oral mucosa: a rare histologic variant in an uncommon location

Dear Editor: Myopericytoma (MPC) belongs to a family of benign tumors showing a myoid/pericytic line of differentiation [8]. The most common anatomic setting for MPC is the skin and superficial soft tissues of distal extremities. With increased recognition, a wider distribution is described [10]; however, an intraoral lesion appears never to have been recorded. The patient was a 45-year-old woman with a painless, slowly expanding mass that had been present in her right buccal mucosa for more than 2 years. Clinical examination revealed a freely movable, 2-cm spherical nodule with a purplish hue in the submucosal space (Fig. 1a). The smooth-surfaced tumor attached to the buccal fat pad was excised, and 9 years later, there was no evidence of recurrence. Microscopically, the lesion presented as a discrete intravenous solid mass filling the distended lumen (Fig. 1b). It was focally attached to the attenuated vessel wall by the stalk, and both internal elastic lamella and smooth muscle layer were interrupted at this site. The luminal aspect of the tumor was covered by a single layer of endothelium. There was no formation of thrombus. The tumor was typified by a hemangiopericytomatous growth pattern of thin-walled branching vessels, ranging from slitlike capillary size (Fig. 1c) to gaping cavernous spaces (Fig. 1d). A multilayered, concentric perivascular orientation of myoid-appearing oval-to-spindle cells was easily identified (Fig. 1e). Often, myoid tumor cells spun off from the thick-walled vessels (Fig. 1f), and at high magnification, intervascular sweeping fascicles of elongated cells with abundant eosinophilic cytoplasm and cigar-shaped nuclei showed morphology of smooth muscle differentiation (Fig. 1g). Also of note were scattered nodules of glomoid cytomorphology. Tumor cells, irrespective of their shape, expressed immunopositivity for α-smooth muscle actin (Fig. 1h) and h-caldesmon (Fig. 1i), but were desmin negative (Fig. 1j). No reactivity for CD34 was obtained in tumor cells. Ultrastructurally, prominent external lamina, numerous pinocytotic vesicles, thin filaments with dense bodies, and attachment plaques that suggest myoid differentiation were all appealing (Fig. 2a,b). The fine structure of uniform rounded cells with distinct cell borders corresponded exactly to a glomus line (Fig. 2b). Within MPC, the intravascular type is a rare histologic variant [10]. To our knowledge, this particular subset has been documented only two (a total of six cases) [9, 10] or three times, if we accept the case of Sajben et al. [14] as the first example. All tumors were located in the subcutis, including elbow, thigh, hand, trunk, and foot; the present lesion arose in the noncutaneous submucosal site, further expanding the list of locations. The differential diagnostic alternatives include a number of other reactive or neoplastic processes that can be intravascular, i.e., glomus tumor [1], papillary endothelial hyperplasia [6], pyogenic granuloma [3], nodular fasciitis [12], leiomyomatosis [2]. The points of microscopic diagnostic separation were summarized in the previous report [9]. Considering no detectable tumor outside the vessel, none of the intravascular MPC represented a vascular invasion, as occasionally seen in glomus tumors. The present tumor is referred to as angioleiomyoma-like MPC, depending on the predominant growth pattern [10]. In contrast to classic angioleiomyoma, myoid tumor cells Virchows Arch (2007) 450:475–477 DOI 10.1007/s00428-007-0368-9

Functional Analysis of an Established Mouse Vascular Endothelial Cell Line

Background: In vitrostudies using cell lines are useful for the understanding of cellular mechanisms. The purpose of our study is to develop a new immortalized aortic vascular endothelial cell (EC) line that retains endothelial characteristics and can facilitate the study of ECs. Methods: A mouse aortic vascular EC line (MAEC) was established from p53-deficient mouse aorta and cultured for over 100 passages. The expression of endothelial markers was assessed, and the function of this cell line was analyzed by tube formation and binding assays. Results: MAEC retained many endothelial properties such as cobblestone appearance, contact-inhibited growth, active uptake of acetylated low-density lipoprotein, existence of Weibel-Palade bodies and several EC markers. MAECs exhibited tube formation activity both in vitro and in vivo. Furthermore, crucially, tumor necrosis factor α, an inflammatory cytokine, promoted lymphocyte adhesion to MAECs, suggesting that MAECs may facilitate the study of atherosclerosis and local inflammatory reactions in vitro. Conclusion: We describe the morphological and cell biological characteristics of MAEC, providing strong evidence that it retained endothelial properties. This novel cell line can be a useful tool for studying the biology of ECs.

Up-Regulated PAR-2-Mediated Salivary Secretion in Mice Deficient in Muscarinic Acetylcholine Receptor Subtypes

Protease-activated receptor-2 (PAR-2) is expressed in the salivary glands and is expected to be a new target for the treatment of exocrine dysfunctions, such as dry mouth; however, the salivary secretory mechanism mediated by PAR-2 remains to be elucidated. Therefore, mechanism of the PAR-2-mediated salivary secretion was investigated in this study. We found that a PAR-2 agonist peptide, SLIGRL-OH, induced salivary flow in vivo and dose-dependent increase in [Ca2+]i submandibular gland (SMG) acinar cells in wild-type (WT) mice and mice lacking M3 or both M1 and M3 muscarinic acetylcholine receptors (mAChRs), whereas secretions in PAR-2 knockout (PAR-2KO) mice were completely abolished. The saliva composition secreted by SLIGRL-OH was similar to that secreted by mAChR stimulation. Ca2+ imaging in WT acinar cells and β-galactosidase staining in PAR-2KO mice, in which the β-galactosidase gene (LacZ) was incorporated into the disrupted gene, revealed a nonubiquitous, sporadic distribution of PAR-2 in the SMG. Furthermore, compared with the secretion in WT mice, PAR-2-mediated salivary secretion and Ca2+ response were enhanced in mice lacking M3 or both M1 and M3 mAChRs, in which mAChR-stimulated secretion and Ca2+ response in acinar cells were severely impaired. Although the mechanism underlying the enhanced PAR-2-mediated salivary secretion in M3-deficient mice is not clear, the result suggests the presence of some compensatory mechanism involving PAR-2 in the salivary glands deficient in cholinergic activation. These results indicate that PAR-2 present in the salivary glands mediates Ca2+-dependent fluid secretion, demonstrating potential usefulness of PAR-2 as a target for dry mouth treatment.

Balloon cell nevus of the soft palate: an immunohistochemical and ultrastructural study.

An ultrastructural analysis of oral balloon cell nevus of intramucosal type complemented with an immunohistochemical study was performed for the first time. The lesion was composed of large balloon cells with an admixture of small nevus cells and melanophages at the periphery. Balloon cells showed cytoplasmic accumulation of vacuoles of varying sizes and the presence of microgranular and vacuolated melanosomes were found. Residual cytoplasm contained no identifiable organelles. A spectrum of transitional forms between balloon cells and conventional nevus cells with microvacuoles was readily observed. Both cells exhibited intense immunoreactivity to multiple melanocytic markers. Ballooning phenomenon was not evident in melanophages containing a large amount of melanosome complex. It can be inferred, from the present and previous observations, that progressive vacuolization of melanosomes in nevomelanocytes may be responsible for the formation of peculiar ballooning appearance, suggesting an aberrant melanogenesis.

Biological and Oncogenic Properties of p53-Deficient Salivary Gland Epithelial Cells with Particular Emphasis on Stromal-Epithelial Interactions in Tumorigenesis

Objective: To understand the salivary gland pathobiology, we established an immortalized duct/basal cell line (MSE) from the submandibular glands of p53-deficient mice. Methods: A variety of culture assays and xenograft experiments were conducted. Cellular characteristics were analyzed using histological, immunohistochemical, ultrastructural, and molecular techniques. Results: Inoculation of a mixture of MSE and Matrigel reconstructed polarized ducts whereas cotransplantation of MSE with both Matrigel and NIH3T3 (3T3) cells developed mixed tumors of adenoma and sarcoma. A daughter adenoma line (MSA) showed some transformed phenotype in vitro, but was marginally tumorigenic in vivo. Notably, pleomorphic adenoma gene 1 (PLAG1) was expressed in MSA but not in MSE. As compared with MSE, MSA showed higher levels of insulin-like growth factor-I receptor (IGF-IR). Interestingly, 3T3 sarcoma secreted insulin-like growth factor-II (IGF-II), while MSA did not. Conclusion: The intrinsic tumorigenic programs of p53 null salivary epithelium are promoted by 3T3 sarcoma-derived IGF-IIin a paracrine manner through overexpression of PLAG1 and IGF-IR.