The up-regulation of "tissue" transglutaminase (TG2) gene has been shown to occur in various pathologies and can lead to severe liver injury; however, its role in the onset of liver damage has not yet been clarified. To address this issue, we have used two experimental settings: carbon tetrachloride (CCl(4))-induced liver injury in wild-type and TG2 knockout mice; and liver biopsies obtained from a large cohort of hepatitis C virus (HCV)-infected patients. Mice lacking TG2 failed to clear the hepatic necrotic tissue formed in response to prolonged CCl(4) exposure (5 weeks) and 60% of them died before the end of the treatment. By contrast, wild-type mice were able to recover after the toxic insult. CCl(4)-treated TG2 null mice showed a derangement of the hepatic lobular architecture and a progressive accumulation of extracellular matrix (ECM) components and inflammatory cells which were not observed in the liver of control animals. Consistent with this protective role, we observed that TG2 levels were much higher (up to 15-fold) during the initial stages of liver fibrosis in HCV-infected individuals (METAVIR = F2) compared with uninfected controls, in which the enzyme protein localized in the hepatocytes facing the periportal infiltrate. By contrast, the enzyme levels decreased in the advanced stages (METAVIR = F3 and F4) and their localization was limited to the ECM. Our data demonstrate that TG2 plays a protective role in the liver injury by favoring tissue stability and repair.

Summary. Haematological abnormalities frequently occur in patients infected by human immunodeficiency virus‐type 1 (HIV‐1). Increasing evidence indicates that bone marrow suppression (BM) results from viral infection of accessory cells, with impaired stromal function and alteration of haematopoietic growth factor network. We have investigated the effects of antiretroviral therapy on cytokine and chemokine production by BM cells and stromal cells in a group of HIV‐1‐infected subjects before and during treatment. Compared with uninfected controls, an altered cytokine and chemokine production by BM cells was observed before treatment, characterized by decreased interleukin 2 (IL‐2) and elevated tumour necrosis factor‐α, macrophage inflammatory protein (MIP)‐1α, MIP‐1β, and RANTES (regulated on activation, normal T cell‐expressed and secreted) levels, along with a defective BM clonogenic activity. Antiretroviral therapy showed increased BM clonogenic capability, associated with normalization of IL‐2 production and chemokine receptors expression on CD34+ cells. Pre‐therapy, BM accessory cells were represented by macrophage‐like cells, in some cases positive for HIV‐1 DNA, suggesting that these cells are the main target of HIV‐1 infection. During therapy, the stromal cells became predominantly fibroblastoid‐like, as observed in normal controls, and were negative for HIV‐1 DNA. Controlling HIV‐1 replication may produce amelioration of stem cell activity, and restoration of stromal cell pattern and functions, with increased IL‐2 production at BM level.

Mucinous carcinoma of the thyroid gland is an uncommon tumour that from the histological point of view, resembles mucinous carcinoma of others sites. Although a mucinous appearance has sometimes been reported in association with cases of typical thyroid carcinoma, true mucinous carcinoma is exceptionally rare. We describe two cases of thyroid tumours with mucinous differentiation studied with immunohistochemistry. Both cases disclosed a similar histological appearance, with small nests and sheets of malignant epithelial cells associated with extensive extracellular mucin that substituted and entrapped the follicular parenchyma of the thyroid. Thyroglobulin and focally thyroid transcription factor (TTF) 1 were positive in one case. From these findings, we classified this tumour as primary mucinous thyroid carcinoma. Thyroglobulin and TTF-1 were negative in tumour cells of second case; on the contrary, positivity to the carcinoembryonic antigen and CA-125 was strong and generalized. However, successfully, the patient presented ascites associated to right ovarian mass. In this case, thyroid tumour represents the first clinical sign of an ovarian mucinous adenocarcinoma, and it has not been previously described in literature. Both patients died after few months to diagnosis. In conclusion, primary and secondary mucinous carcinoma are rare and unusual tumours of the thyroid gland that can be a cause of pitfall in differential diagnosis. In these cases, for a correct diagnosis, a complete clinical history, restricted histological criteria and immunohistochemical panel are necessary.

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