Serum level of expressed in renal carcinoma (ERC)/ mesothelin in rats with mesothelial proliferative lesions induced by multi-wall carbon nanotube (MWCNT)

Continuous infiltration of small peritoneal macrophages in the mouse peritoneum through CCR2-dependent and -independent routes during fibrosis and mesothelioma development induced by a multiwalled carbon nanotube, MWNT-7

Although toxicities of multiwalled carbon nanotube (MWCNT) have been found to be related with activities of macrophages phagocytosing the fibers, the exact relationship between macrophage population and pathogenesis of fibrosis and mesotheliomas induced by MWCNTs is largely unknown. CCL2-CCR2 axis, a major monocyte/macrophage infiltration route, is thought to be involved in not only acute inflammation but also the formation of tumor microenvironment. We therefore described a time-course of alteration of macrophage population in an attempt to clarify the contribution of the Ccr2 gene to mesotheliomagenesis. Wild-type (WT) C57BL/6 mice and Ccr2-knockout (KO) mice were intraperitoneally administered with MWNT-7 and were sequentially necropsied at 1, 7, 28, 90, and 245 day(s) after the injection. Peritoneal fibrosis was prominent in all MWCNT-treated mice, with a lower severity in the KO mice. No differences were observed in the incidences of neoplastic lesions of mesothelia between WT and KO mice. A flow cytometric analysis revealed that after gross disappearance of macrophages after MWCNT exposure, small peritoneal macrophages (SPMs) were exclusively refurbished by the CCR2-dependent route at day 1 (as Ly-6C+MHC class II- cells), followed by additional CCR2-independent routes (as Ly-6C-MHC class II- cells); i.e., the only route in KO mice; with a delay of 1-7 days. The SPMs derived from both routes appeared to differentiate into maturated cells as Ly-6C-MHC class II+, whose ratio increased in a time-dependent manner among the total SPM population. Additionally, most macrophages expressed M1-like features, but a small fraction of macrophages exhibited an M1/M2 mixed status in MWCNT-treated animals. Our findings demonstrate a long-persistent activation of the CCL2-CCR2 axis after MWCNT exposure and enable a better understanding of the participation and potential roles of SPMs in fibrous material-induced chronic toxicities.

Spontaneous Primary Pleural Mesothelioma in Fischer 344 (F344) and Other Rat Strains: A Retrospective Review

Spontaneous primary pleural mesotheliomas in Fischer 344 (F344) or other rat strains have rarely been reported. The objectives of this retrospective study were to develop historical incidence data and better characterize the light-microscopic morphology of these naturally occurring neoplasms in a large cohort of rats of several strains. A retrospective review was performed of National Toxicology Program (NTP) studies in rats conducted between 1980 and 2019 and comprising a total of 104,029 rats (51,326 males, 52,703 females), predominantly (90%) of the F344 strain. Of the 94,062 F344 rats surveyed, there were 30 cases of primary pleural mesotheliomas (22 males, 8 females). Of the 2998 Wistar Han rats surveyed, primary pleural mesotheliomas were present in 2 male rats. No primary pleural mesotheliomas were noted in male and female rats of other strains (6669 Sprague Dawley; 300 Osborne-Mendel). All primary pleural mesotheliomas in control and treated F344 and Wistar Han rats were considered spontaneous and unrelated to treatment. Based on light-microscopic evaluation of paraffin-embedded hematoxylin and eosin stained sections, only epithelioid and biphasic histologic subtypes were observed: 18 and 12 in F344 rats, respectively, and one each in Wistar Han rats. No sarcomatoid subtype cases were noted in any strain of rat.

Recent Advances in the Synthesis and Biomedical Applications of Nanocomposite Hydrogels

Hydrogels sensitive to electric current are usually made of polyelectrolytes and undergo erosion, swelling, de-swelling or bending in the presence of an applied electric field. The electrical conductivity of many polymeric materials used for the fabrication of biomedical devices is not high enough to achieve an effective modulation of the functional properties, and thus, the incorporation of conducting materials (e.g., carbon nanotubes and nanographene oxide) was proposed as a valuable approach to overcome this limitation. By coupling the biological and chemical features of both natural and synthetic polymers with the favourable properties of carbon nanostructures (e.g., cellular uptake, electromagnetic and magnetic behaviour), it is possible to produce highly versatile and effective nanocomposite materials. In the present review, the recent advances in the synthesis and biomedical applications of electro-responsive nanocomposite hydrogels are discussed.

Malignant peritoneal mesothelioma with a sarcomatoid growth pattern and signet-ring-like structure in a female f344 rat

We report a biphasic malignant mesothelioma in an aged female F344/DuCrlCrlj rat. Macroscopically, multiple pale brown nodules were observed in the abdominal cavity with retention of bloody ascites. Histopathologically, the tumor cells spread over the peritoneum and formed masses on the surface and underlying adipose tissues. The tumor cells dominantly proliferated in a solid, nodular or nest-like pattern with modest amount of fibrillar connective tissues, which contained hyaluronan. The tumor consisted of ovoid, polygonal or spindle-shaped cells that possessed eosinophilic cytoplasms including glycogen; some tumor cells showed a signet-ring-like structure. Multinucleated cells and mitosis were found frequently, and direct invasion to intra-abdominal organs and intravascular metastasis to the liver were observed. Immunohistochemically, keratin and mesothelin were strongly positive in most of tumor cells, while vimentin was mainly positive in spindle-shaped cells. Podoplanin was also positive, particularly in the cell membrane of tumor cells. Electron microscopically, tumor cells showed an intercellular desmosome-like structure, basement membrane and microvillus. We diagnosed the case as a malignant peritoneal mesothelioma with a sarcomatoid growth pattern and signet-ring-like structure.

No toxicological effects on acute and repeated oral gavage doses of single-wall or multi-wall carbon nanotube in rats

Three female Crl:CD(SD) rats/group were dosed with single wall carbon nanotube (SWCNT) or multi wall carbon nanotube (MWCNT) four times by gavage at a total of 50 mg/kg bw or 200 mg/kg bw (four equally divided doses at one-hour intervals). Acute oral doses of SWCNT and MWCNT caused neither death nor toxicological effects, and thus the oral LD<inf>50 </inf>values for SWCNT and MWCNT were considered to be greater than 50 mg/kg bw and 200 mg/kg bw, in rats respectively. Five or ten Crl:CD(SD) rats/sex were dosed with SWCNT once daily by gavage at a dose of 0 (control), 0.125, 1.25 or 12.5 mg/kg bw/day for 28 days with a 14-day recovery period (0 and 12.5 mg/kg bw/day groups). Six or twelve Crl:CD(SD) rats/sex were dosed with MWCNT once daily by gavage at a dose of 0 (control), 0.5, 5.0 or 50 mg/kg bw/day for 28 days with a 14-day recovery period (0 and 50 mg/kg bw/day groups). Based on no toxicological effects, the no observed adverse effect levels (NOAELs) of repeated dose toxicity of SWCNT and MWCNT were considered to be 12.5 mg/kg bw/day and 50 mg/kg bw/day (the highest dose tested), respectively. It was suggested that SWCNT and MWCNT dosed by gavage reached the gastro-intestinal tract as agglomerates and were mostly excreted via feces.

Mesothelin overexpression promotes mesothelioma cell invasion and MMP-9 secretion in an orthotopic mouse model and in epithelioid pleural mesothelioma patients

PURPOSE

Mesothelin (MSLN) is a tumor-associated antigen, being investigated as a biomarker and therapeutic target in malignant pleural mesothelioma (MPM). The biologic function of MSLN overexpression in MPM is unknown. We hypothesized that MSLN may promote tumor invasion in MPM, a tumor characterized primarily by regional aggressiveness and rare distant metastases.

EXPERIMENTAL DESIGN

Human and murine MPM cells with MSLN forced expression and short hairpin RNA knockdown were examined for proliferation, invasion, and matrix metalloproteinase (MMP) secretion. The influence of MSLN overexpression on MPM cell invasion was assessed in an orthotopic mouse model and in patient samples.

RESULTS

MSLN expression promotes MPM cell invasion and MMP secretion in both human and murine MPM cells. In an orthotopic MPM mouse model characterized by our laboratory, MPM cells with MSLN overexpression preferentially localized to the tumor invading edge, colocalized with MMP-9 expression, and promoted decreased survival without an increase in tumor burden progression. In a tissue microarray from epithelioid MPM patients (n = 139, 729 cores), MSLN overexpression correlated with higher MMP-9 expression at individual core level. Among stage III MPM patients (n = 72), high MSLN expression was observed in 26% of T2 tumors and 51% of T3 tumors.

CONCLUSIONS

Our data provide evidence elucidating a biologic role for MSLN as a factor promoting tumor invasion and MMP-9 expression in MSLN expressing MPM. As regional invasion is the characteristic feature in MSLN expressing solid cancers (MPM, pancreas, and ovarian), our observations add rationale to studies investigating MSLN as a therapeutic target.