We describe here isolation and characterization of CD133+ cells derived from normal adult human kidney. These cells lacked the expression of hematopoietic markers and expressed PAX-2, an embryonic renal marker, suggesting their renal origin. Renal tissue-derived CD133+ cells and clones of individual cells were capable of expansion and limited self-renewal and differentiated in vitro into epithelial or endothelial cells. On subcutaneous implantation in SCID mice, the undifferentiated cells formed tubular structures expressing renal epithelial markers. At variance, when differentiated in endothelial cells, these cells formed functional vessels. On intravenous injection in SCID mice with glycerol-induced tubulonecrosis, the in vitro expanded renal-derived CD133+ cells homed into the injured kidney and integrated in tubules. We propose that CD133+ cells from kidney represent a multipotent adult resident stem cell population that may contribute to the repair of renal injury.

Several studies suggested the presence of stem cells in the adult normal human liver; however, a population with stem cell properties has not yet been isolated. The purpose of the present study was to identify and characterize progenitor cells in normal adult human liver. By stringent conditions of liver cell cultures, we isolated and characterized a population of human liver stem cells (HLSCs). HLSCs expressed the mesenchymal stem cell markers CD29, CD73, CD44, and CD90 but not the hematopoietic stem cell markers CD34, CD45, CD117, and CD133. HLSCs were also positive for vimentin and nestin, a stem cell marker. The absence of staining for cytokeratin-19, CD117, and CD34 indicated that HLSCs were not oval stem cells. In addition, HLSCs expressed albumin, ␣-fetoprotein, and in a small percentage of cells, cytokeratin-8 and cytokeratin-18, indicating a partial commitment to hepatic cells. HLSCs differentiated in mature hepatocytes when cultured in the presence of hepatocyte growth factor and fibroblast growth factor 4, as indicated by the expression of functional cytochrome P450, albumin, and urea production. Under this condition, HLSCs downregulated ␣-fetoprotein and expressed cytokeratin-8 and cytokeratin-18. HLSCs were also able to undergo osteogenic and endothelial differentiation when cultured in the appropriated differentiation media, but they did not undergo lipogenic differentiation. Moreover, HLSCs differentiated in insulin-producing islet-like structures. In vivo, HLSCs contributed to regeneration of the liver parenchyma in severe-combined immunodeficient mice. In conclusion, we here identified a pluripotent progenitor population in adult human liver that could provide a basis for cell therapy strategies.

CD40 has been involved in tumor and inflammatory neoangiogenesis. In this study we determined that stimulation of endothelial CD40 with sCD154 induced resistance to apoptosis and in vitro vessel-like formation by human microvascular endothelial cells (HMEC). These effects were determined to be mediated by CD40-dependent signaling because they were inhibited by a soluble CD40-muIg fusion protein. Moreover, apoptosis of HMEC was associated with an impairment of Akt phosphorylation, which was restored by stimulation with sCD154. The anti-apoptotic effect as well as in vitro vessel-like formation and Akt phosphorylation were inhibited by treatment of HMEC with two unrelated pharmacological inhibitors of phosphatidylinositol 3-kinase (PI3K), wortmannin and LY294002. CD40 stimulation induced a rapid increase in Akt enzymatic activity that was not prevented by cycloheximide, an inhibitor of protein synthesis. The enhanced Akt activity induced by stimulation of endothelial CD40 was temporarily correlated with the association of CD40 with TRAF6, c-Cbl, and the p85 subunit of PI3K. Expression of negativedominant Akt inhibited the activation of endogenous Akt through CD40 stimulation, despite the observation that association of CD40 with TRAF6, c-Cbl, and PI3K was intact. The defective activation of Akt abrogated not only the anti-apoptotic effect of CD40 stimulation but also the proliferative response, the enhanced motility, and the in vitro formation of vessel-like tubular structures by CD40-stimulated HMEC. In conclusion, these results suggest that endothelial CD40, through activation of the PI3K/Akt signaling pathway, regulates cell survival, proliferation, migration, and vessel-like structure formation, all steps considered critical for angiogenesis.CD40 is a member of the tumor necrosis factor (TNF) 1 receptor superfamily, which provides activation signals in antigen-presenting cells such as B cells, macrophages, and dendritic cells (1, 2). Among the molecular mechanisms that link immunity to inflammation, the interaction between CD40 and its counterreceptor CD154 has rapidly emerged as a key system in the regulation of vascular pathophysiological processes such as atherogenesis (3, 4), tumor neoangiogenesis (5, 6), and inflammation (2, 8). Under physiological conditions, CD40 is expressed at low levels on endothelial cells but is up-regulated in areas of inflammation (9). Ligation of endothelial CD40 by CD154, either expressed on activated monocytes or T cells (2) or disgorged by platelets upon activation (10), induces production of various inflammatory cytokines and chemokines, procoagulant activity, adhesion molecules, metalloproteinases, and inflammatory mediators (11-14). These mediators have been implicated in the development and progression of atherosclerosis. In situ analysis of human atherosclerotic lesions revealed the co-expression of CD154 and CD40 on vascular endothelium and smooth muscle cells (15). Blockade of CD40-CD154 interaction in atherosclerosis was found not only to diminish the formation and pr...

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The way a tumor cell dies is believed to influence both its engulfment by dendritic cells (DC) and access of the relevant antigen(s) to the cross-presentation pathway. Here we have studied the effect of lymphokine activated killer (LAK) cells, gamma-radiation and the antimetabolite drug 5-fluorouracil (5-FU) on tumor uptake by HLA-matched DC, and DC presentation of tumor antigens to autologous T lymphocytes. LAK cells and radiation were the best inducers of apoptotic death (Annexin-V+/propidium iodide-) on the gastric cell line KATO III and a primary gastric carcinoma, respectively. The highest rate of tumor uptake by monocyte-derived, granulocyte macrophage colony stimulating factor/interleukin (IL)-4-driven DC was associated with 5-FU, followed by radiation. These treatments also induced high levels of heat shock protein (hsp70). In contrast, only DC that had been taken up 5-FU- or LAK-treated tumors up-modulated IL-12 and presented tumor-associated antigens with increased efficiency, as shown by class I MHC-restricted interferon-gamma release and cytotoxic responses by autologous lymphocytes. Together, these data indicate that apoptotic death induced by anti-cancer therapies can induce distinct patterns of class I MHC cross-presentation of gastric carcinoma-associated antigens to cytotoxic T lymphocyte precursors.

Thiamine and benfotiamine correct increased apoptosis due to high glucose in cultured vascular cells. Further elucidations of the mechanisms through which they work could help set the basis for clinical use of this vitamin in the prevention and/or treatment of diabetic microangiopathy.

Here we have studied the effects of apoptotic cell death induced by chemotherapic agents on tumor phagocytosis by dendritic cells (DC) and presentation of the relevant antigen to T lymphocytes. Annexin-V-FITC (Ann-V) and propidium iodide (PI) staining was used to assess early apoptotic (Ann-V ؉ /PI ؊ ) vs. late apoptotic/secondary necrotic (Ann-V ؉ /PI ؉ ) death after a 24 hr observation of untreated and drug-treated gastric carcinoma cells. After treatments, the HLA-A*0201 ؉ tumor cell line KATO III was exposed for 24 hr to allogeneic, HLA-related GM-CSF, IL-4-driven immature (i) DC. Tumorloaded iDC were tested for IL-12 release in an ELISA assay, incubated with the DC-maturating factor TNF-␣ and used as stimulators for autologous T lymphocytes. Generation of antitumor T response against KATO cells was evaluated in an anti-MHC class I MAb-blocked Interferon-␥ ELISPOT assay. After treatment with Cis-platin (cis), all dying cells were in early apoptosis, whereas secondary necrosis was the prevalent death pattern observed after epirubicin (epi) and doxorubicin (doxo). Doxo and epi increased tumor expression of heat shock protein (hsp) 70 and uptake of tumor cell components by DC, whereas cis treatment had no effect on hsp70 and was associated with poor tumor uptake by DC. Significant upmodulation of IL-12 was observed by DC that had taken up the doxo-and epi-treated tumors (p< 0.005 and p< 0.01, respectively). Increased IFN-␥ release was also observed after stimulation of T lymphocytes with DC loaded with doxo-and epi-treated (p< 0.02 and p< 0.005, respectively) but not with cis-treated DC. These data show that the products of early apoptosis cannot efficiently cross-activate MHC class I-restricted anti-tumor lymphocytes even in the presence of DC maturating factors, whereas secondary necrosis is associated with robust T cell response.

In this study, we found that Kaposi's sarcoma cells but not human microvascular endothelial cells expressed PAX2, a gene coding for a transcription factor involved both in organogenesis and tumorigenesis. Moreover