Participation of Tumor-Associated Myeloid Cells in Progression of Amelanotic Melanoma (RMM Tumor Line) in F344 Rats, with Particular Reference to MHC Class II- and CD163-Expressing Cells.

Tumor progression is often influenced by infiltration of myeloid cells; depending on the M1- or M2-like activation status, these cells may have either inhibitory or promoting effects on tumor growth. We investigated the properties of tumor-associated myeloid cells in a previously established homotransplantable amelanotic melanoma (RMM tumor line) in F344 rats. RMM tumor nodules were allowed to reach the sizes of 0.5, 1, 2 and 3 cm, respectively. Immunohistochemistry and flow cytometry was performed for macrophage markers CD68 and CD163, and for the antigen-presenting cell marker, MHC class II. Although no significant change was observed in the number of CD68+ and CD163+ macrophages during RMM progression, the number of MHC class II+ antigen-presenting cells was reduced in 3 cm nodules. Real-time RT-PCR of laser microdissection samples obtained from RMM regions rich in MHC class II+ cells demonstrated high expressions of M1-like factors: IFN-γ, GM-CSF and IL-12a. Furthermore, fluorescence-activated cell sorting, followed by real-time RT-PCR for CD11b+ MHC class II+ (myeloid antigen-presenting cells), CD11b+ CD163+ (M2 type myeloid cells), CD11b+ CD80+ (M1 type myeloid cells) and CD11b+ CD11c+ (dendritic cells) cells was performed. Based on the levels of inflammation- and tumor progression-related factors, MHC class II+ antigen-presenting cells showed polarization towards M1, while CD163+ macrophages, towards M2. CD80+ and CD11c+ myeloid cells did not show clear functional polarization. Our results provide novel information on tumor-associated myeloid cells in amelanotic melanoma, and may become useful in further research on melanoma immunity.

Multiple Histiocytic Foam Cell Nodules in the Tongue of Miniature Dachshund Dogs.

Miniature dachshund dogs are a common breed in Japan and are known to be predisposed to granulomatous diseases. Here we report the pathologic features of multiple lingual nodules in 7 miniature dachshunds. Seven dogs had multiple nodules of variable sizes mainly on the ventral and lateral surface of the tongue. In addition, 1 dog also had masses on the left oral mucosa. Three cases had recurrence after surgical resection. Histologically, the lingual nodules were composed of aggregates of foam cells with clear vacuolated cytoplasm that were negative for oil red O, PAS, and alcian blue. They stained positively for CD204 (macrophage scavenger receptor) and MHC class II and negatively for Iba-1, E-cadherin, adipophilin, cytokeratins, S-100, and nestin. These findings indicate that the multiple lingual nodules in miniature dachshunds are an unusual, unique lesion consisting of macrophage-derived foam cells, which does not correspond to canine lingual diseases reported to date.

Expression of nestin in remodelling of α-naphthylisothiocyanate-induced acute bile duct injury in rats.

The function of the intermediate filament protein nestin is poorly understood. The significance of nestin expression was assessed in α-naphthylisothiocyanate (ANIT)-induced cholangiocyte injury lesions in F344 rats. Liver samples obtained from rats injected intraperitoneally with ANIT (75 mg/kg) on post-injection days 0 (control) and 1-12 were labelled immunohistochemically for expression of nestin and markers specific for mesenchymal cells (vimentin), hepatic stellate cells (HSCs) (desmin and glial fibrillary acidic protein [GFAP]), endothelial cells (rat endothelial cell antigen [RECA]-1), cholangiocytes (cytokeratin [CK] 19) and cellular proliferation (Ki67). Cholangiocyte injury led to infiltration of neutrophils and macrophages followed by aggregation of mesenchymal cells and regeneration of bile ducts. Nestin expression was detected in mesenchymal cells (vimentin positive) on days 1-7 with a peak on days 3-5 and in newly-formed RECA-1-positive endothelial cells on day 3. Nestin expression was also observed in regenerating CK19-positive cholangiocytes on days 2-5, with a peak on day 3. Labelling for Ki67 showed proliferation of cholangiocytes, mesenchymal cells and HSCs. Real-time reverse transcriptase polymerase chain reaction with microdissected samples showed significantly elevated nestin mRNA on day 3. The findings suggest an association between nestin expression and cellular proliferation. Based on these findings, it was considered that nestin-expressing mesenchymal cells, HSCs and endothelial cells may be possible progenitors of repopulating cholangiocytes. Nestin expression may serve as an indicator for cellular remodelling and behaviour of injured and repopulating bile ducts.