Nonirradiated human fibroblasts and irradiated 3T3-J2 murine fibroblasts as a feeder layer for keratinocyte growth and differentiation in vitro on a fibrin substrate.

The standard method for producing graftable epithelia relies on the presence of a feeder layer of lethally irradiated 3T3-J2 murine fibroblasts (Rheinwald and Green technique). Here, we studied a new keratinocyte culture system, which envisages the utilization of nonirradiated human fibroblasts embedded into a fibrin substrate, in cultures destined for a future clinical application. We tested this culture system using keratinocytes grown on a fibrin gel precoated with 3T3-J2 murine fibroblasts as a control. In order to evaluate the new technology, we compared the clonogenic potential and the proliferative, differentiative and metabolic characteristics of keratinocytes cultured on the fibrin gel under the two culture conditions. The results demonstrated that the proposed technology did not impair the behavior of cultured keratinocytes and revealed that cells maintained their proliferative potential and phenotype under the experimental conditions. In particular, the demonstration of stem cell maintenance under the adopted culture conditions is very important for acute burn treatment with skin substitutes. This work is a first step in the evaluation of a new keratinocyte culture system, which has been studied in order to take advantage of an additional human cell population (i.e. nonirradiated, growing fibroblasts) for future transplantation purposes in acute and chronic wounds. Additional research will allow us to attain (1) the removal of murine cells in the initial phase of keratinocyte cultures, and (2) the removal of other potentially dangerous animal-derived materials from the entire culture system.

Tissue engineering for damaged surface and lining epithelia: stem cells, current clinical applications, and available engineered tissues.

Tissue engineering is an important tool for the treatment of damaged surface and lining epithelia. A source of cells and biocompatible substrates upon which cells can grow and differentiate are key components of this technology. Cultured normal human epithelial cells reconstitute sheets of stratified epithelia that retain biochemical and histological characteristics as well as specific differentiation features of the original donor site. Maintenance of epithelial stem cells in culture and a well-prepared receiving wound bed allow to permanently regenerate full-thickness wounds by means of in vitro reconstituted epithelia. Further, cultured cells produce growth factors and extracellular matrix (ECM) components that help resident cells to contribute to the wound-healing process. Biological matrices enhance the performance of the in vitro reconstituted epithelia. Owing to their similarity to the ECM, natural polymers offer the advantage of being similar to macromolecules that the human environment is prepared to recognize. They also maintain biological information and physical and chemical features that are instructive for cells used to populate them. This article discusses the developments of tissues engineered for cutaneous and mucosal regeneration. Native tissues and their stem cells are also considered, to enhance understanding of the extensive field of tissue reconstruction.

High-mobility group box 1 protein in human and murine skin: involvement in wound healing.

High-mobility group box 1 (HMGB1) protein is a multifunctional cytokine involved in inflammatory responses and tissue repair. In this study, it was examined whether HMGB1 plays a role in skin wound repair both in normoglycemic and diabetic mice. HMGB1 was detected in the nucleus of skin cells, and accumulated in the cytoplasm of epidermal cells in the wounded skin. Diabetic human and mouse skin showed more reduced HMGB1 levels than their normoglycemic counterparts. Topical application of HMGB1 to the wounds of diabetic mice enhanced arteriole density, granulation tissue deposition, and accelerated wound healing. In contrast, HMGB1 had no effect in normoglycemic mouse skin wounds, where endogenous HMGB1 levels may be adequate for optimal wound closure. Accordingly, inhibition of endogenous HMGB1 impaired wound healing in normal mice but had no effect in diabetic mice. Finally, HMGB1 had a chemotactic effect on skin fibroblasts and keratinoyctes in vitro. In conclusion, lower HMGB1 levels in diabetic skin may play an important role in impaired wound healing and this defect may be overcome by the topical application of HMGB1.

3,3',5-Triiodo-L-thyronine inhibits ductal pancreatic adenocarcinoma proliferation improving the cytotoxic effect of chemotherapy.

The pancreatic adenocarcinoma is an aggressive and devastating disease, which is characterized by invasiveness, rapid progression, and profound resistance to actual treatments, including chemotherapy and radiotherapy. At the moment, surgical resection provides the best possibility for long-term survival, but is feasible only in the minority of patients, when advanced disease chemotherapy is considered, although the effects are modest. Several studies have shown that thyroid hormone, 3,3',5-triiodo-l-thyronine (T(3)) is able to promote or inhibit cell proliferation in a cell type-dependent manner. The aim of the present study is to investigate the ability of T(3) to reduce the cell growth of the human pancreatic duct cell lines chosen, and to increase the effect of chemotherapeutic drugs at conventional concentrations. Three human cell lines hPANC-1, Capan1, and HPAC have been used as experimental models to investigate the T(3) effects on pancreatic adenocarcinoma cell proliferation. The hPANC-1 and Capan1 cell proliferation was significantly reduced, while the hormone treatment was ineffective for HPAC cells. The T(3)-dependent cell growth inhibition was also confirmed by fluorescent activated cell sorting analysis and by cell cycle-related molecule analysis. A synergic effect of T(3) and chemotherapy was demonstrated by cell kinetic experiments performed at different times and by the traditional isobologram method. We have showed that thyroid hormone T(3) and its combination with low doses of gemcitabine (dFdCyd) and cisplatin (DDP) is able to potentiate the cytotoxic action of these chemotherapic drugs. Treatment with 5-fluorouracil was, instead, largely ineffective. In conclusion, our data support the hypothesis that T(3) and its combination with dFdCyd and DDP may act in a synergic way on adenopancreatic ductal cells.

3,5,3'-triiodothyronine (T3) is a survival factor for pancreatic beta-cells undergoing apoptosis.

3,5,3'-triiodothyronine (T3) is essential for the growth and the regulation of metabolic functions, moreover, the growth-stimulatory effect of T3 has largely been demonstrated and the pathways via which T3 promotes cell growth have been recently investigated. Type 1 diabetes (T1D) is due to the destruction of beta-cells, which occurs even through apoptosis. Aim of our study was to analyze whether T3 could have an antiapoptotic effect on cultured beta-cells undergoing apoptosis. We have demonstrated that T3 promotes cell proliferation in islet beta-cell lines (rRINm5F and hCM) provoking an increment in cell number (up to 55%: rRINm5F and 45%: hCM), cell viability, and BrdU incorporation, and regulating the cell cycle-related molecules (cyc A, D1, E, and p27(kip1)). T3 inhibited the apoptotic process induced by streptozocin, S-Nitroso-N-Acetylpenicylamine (SNAP), and H2O2 via regulation of the pro- and anti-apoptotic factors Bcl-2, Bcl-XL, Bad, Bax, and Caspase 3. The T3 protective effect was PI-3 K-, but not MAPK- or PKA-mediated, involving pAktThr308. Thus, T3 could be considered a survival factor protecting islet beta-cells from apoptosis.

3,5,3'-Triiodo-L-thyronine enhances the differentiation of a human pancreatic duct cell line (hPANC-1) towards a beta-cell-Like phenotype.

The thyroid hormone, 3,5,3'-Triiodo-L-thyronine (T3), is essential for growth, differentiation, and regulation of metabolic functions in multicellular organisms, although the specific mechanisms of this control are still unknown. In this study, treatment of a human pancreatic duct cell line (hPANC-1) with T3 blocks cell growth by an increase of cells in G(0)/G(1) cell cycle phase and enhances morphological and functional changes as indicated by the marked increase in the synthesis of insulin and the parallel decrease of the ductal differentiation marker cytokeratin19. Expression analysis of some of the genes regulating pancreatic beta-cell differentiation revealed a time-dependent increase in insulin and glut2 mRNA levels in response to T3. As last step of the acquisition of a beta-cell-like phenotype, we present evidence that thyroid hormones are able to increase the release of insulin into the culture medium. In conclusion, our results suggest, for the first time, that thyroid hormones induce cell cycle perturbations and play an important role in the process of transdifferentiation of a human pancreatic duct line (hPANC-1) into pancreatic-beta-cell-like cells. These findings have important implications in cell-therapy based treatment of diabetes and may provide important insights in the designing of novel therapeutic agents to restore normal glycemia in subjects with diabetes.

Omomyc, a potential Myc dominant negative, enhances Myc-induced apoptosis.

The Myc basic helix-loop-helix zipper domain determines dimerization with Max and binding to the DNA E-box, both of which play a critical role in Myc regulation of growth, proliferation, tumorigenesis, and apoptosis. The mutant basic helix-loop-helix zipper domain, Omomyc, dimerizes with Myc, sequestering it in complexes unable to bind the E-box, and so acting as a potential dominant negative. Consistent with this, Omomyc reverses Myc-induced cytoskeletal disorganization in C2C12 myoblasts. Surprisingly, however, Omomyc strongly potentiates Myc-induced apoptosis in a manner dependent on Myc expression level. Expression analysis of known Myc target genes indicates that Omomyc inhibits transcriptional activation but enhances repression. These findings suggest that Omomyc can selectively trigger apoptosis in cells overexpressing Myc, possibly through the transcriptional repression of specific genes.