Adult stem cells: perspectives for therapeutic applications.

The use of adult stem cells in tissue regeneration appears to be a powerful research tool, due to the intrinsic characteristics of these cells, i.e., self-renewal and unlimited capacity for proliferation. In particular, mesenchymal stem cells (MSCs) obtained from bone marrow or peripheral blood can be easily isolated, cultivated, propagated and can be differentiated into several specialized cell types thanks to their plasticity. Among these cells, MSCs can evolve into cardiac cell lineages. Since heart damage leads to the irreversible loss of cardiac function, cell transplantation could be a potential therapy for heart injury. Our laboratory has focused on the purification and expansion of rat and sheep MSCs, their differentiation into cardiomyocytes and their characterisation. Numerous results indicate that MSCs could be promising for therapy, however we need to better understand the biology of stem cells to improve methods for delivery and/or pharmacological activation. These techniques can indeed track engrafted cells and systems to guarantee their safe use.

Hepatitis B virus antigens in primary hepatic carcinoma: immunofluorescent techniques on fixed liver tissue.

The presence of hepatitis B surface (HBsAg) and core (HBcAg) antigens was investigated by immunofluorescence in specimens of liver tissue obtained at necrospy in 107 patients with primary hepatic carcinoma. HBsAg was detected in the cytoplasm of liver cells in 16 cases, and in eight of them the antigen was also found in malignant cells. HBcAg, which was present in the nuclei of liver cells in eight cases, was detected in the nuclei of tumour cells in six of these and also in two other cases showing HBsAg, but not HBcAg, in the nonneoplastic tissue. Although most of the primary hepatic carcinomas studied were associated with cirrhotic changes in the non-neoplastic tissue, HBsAg and HBcAg were also detected in the absence of underlying cirrhosis. Hepatitis B virus markers were demonstrated in non-neoplastic tissue, mainly in patients with a well-differentiated carcinoma, and only in these cases were they found also in the neoplastic tissue. These results show that hepatitis B virus antigens, including HBcAg, can be detected in the neoplastic cells of well-differentiated carcinoma of the liver. Although these cells could have been infected after the malignant transformation, a direct oncogenic role of the virus cannot be excluded.

Expression of HBsAg on the membrane of hepatocytes in chronic carriers of hepatitis B virus infection.

Liver cell membrane localization of hepatitis B surface antigen (HBsAg) was investigated in 31 asymptomatic chronic carriers by a direct immunofluorescence technique. A close relationship was found between absence of inflammatory liver disease, presence of large amounts of HBsAg in the liver and expression of the antigen at the hepatocyte surface. Capping of HBsAg after the addition of anti-HBs serum could be inhibited by factors (temperature, metabolic inhibition) that are known to influence viral antigenic mobility at the cell surface. In two patients with chronic active hepatitis as well as in some cases showing histological features of focal parenchymal necrosis, HBsAg could be detected in the cytoplasm of a few scattered hepatocytes but never at the surface of the cells. Both the cases with CAH and one with focal parenchymal necrosis had IgG bound to the liver cell membrane. These findings are in agreement with the hypothesis that the absence of liver damage in HBsAg healthy chronic carriers is related to immune tolerance to the antigen. In chronic active liver disease the presence of IgG on the membrane of hepatocytes suggests a possible role of blocking antibodies directed against viral antigens expressed at the hepatocyte surface.