LTF induces senescence and degeneration in the meniscus via the NF-κB signaling pathway: A study based on integrated bioinformatics analysis and experimental validation.

Background: The functional integrity of the meniscus continually decreases with age, leading to meniscal degeneration and gradually developing into osteoarthritis (OA). In this study, we identified diagnostic markers and potential mechanisms of action in aging-related meniscal degeneration through bioinformatics and experimental verification. Methods: Based on the GSE98918 dataset, common differentially expressed genes (co-DEGs) were screened using differential expression analysis and the WGCNA algorithm, and enrichment analyses based on Gene Ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways were further performed. Next, the co-DEGs were imported into the STRING database and Cytoscape to construct a protein‒protein interaction (PPI) network and further validated by three algorithms in cytoHubba, receiver operating characteristic (ROC) curve analysis and the external GSE45233 dataset. Moreover, the diagnostic marker lactotransferrin (LTF) was verified in rat models of senescence and replicative cellular senescence via RT‒qPCR, WB, immunohistochemistry and immunofluorescence, and then the potential molecular mechanism was explored by loss of function and overexpression of LTF. Results: According to the analysis of the GSE98918 dataset, we identified 52 co-DEGs (42 upregulated genes and 10 downregulated genes) in the OA meniscus. LTF, screened out by Cytoscape, ROC curve analysis in the GSE98918 dataset and another external GSE45233 dataset, might have good predictive power in meniscal degeneration. Our experimental results showed that LTF expression was statistically increased in the meniscal tissue of aged rats (24 months) and senescent passage 5th (P5) meniscal cells. In P5 meniscal cells, LTF knockdown inhibited the NF-κB signaling pathway and alleviated senescence. LTF overexpression in passage 0 (P0) meniscal cells increased the expression of senescence-associated secretory phenotype (SASP) and induced senescence by activating the NF-κB signaling pathway. However, the senescence phenomenon caused by LTF overexpression could be reversed by the NF-κB inhibitor pyrrolidine dithiocarbamate (PDTC). Conclusion: For the first time, we found that increased expression of LTF was observed in the aging meniscus and could induce meniscal senescence and degeneration by activating the NF-κB signaling pathway. These results revealed that LTF could be a potential diagnostic marker and therapeutic target for age-related meniscal degeneration.

Inorganic arsenic exposure promotes malignant progression by HDAC6-mediated down-regulation of HTRA1.

Inorganic arsenic (iAs) has been a human health concern and is associated with intestinal malignancies. However, the molecular mechanisms of the iAs-induced oncogenic process in intestine epithelial cells remain elusive, partly because of the known hormesis effect of arsenic. Here, we established that six-month exposure to iAs at a concentration similar to those found in contaminated drinking water could promote malignant characteristics, including enhanced proliferation and migration, resistance to apoptosis, and mesenchymal-like transition in Caco-2 cells. Transcriptome analysis and mechanism study revealed that key genes and pathways involved in cell adhesion, inflammation and oncogenic regulation were altered during chronic iAs exposure. Specifically, we uncovered that down-regulation of HTRA1 was essential for the iAs-induced acquisition of the cancer hallmarks. Further, we evidenced that the loss of HTRA1 during iAs-exposure could be restored by HDAC6 inhibition. Caco-2 cells with chronic exposure to iAs exhibited enhanced sensitivity to WT-161, a specific inhibitor of HDAC6, when used alone than in combination with a chemotherapeutic agent. These findings provide valuable information for understanding the mechanisms of arsenic-induced carcinogenesis and facilitating the health management of populations in arsenic-polluted areas.

Asymptomatic Hyperuricemia Is Associated with Achilles Tendon Rupture through Disrupting the Normal Functions of Tendon Stem/Progenitor Cells.

Hyperuricemia is a metabolic disorder that is essential to the development of inflammatory gout, with increasing prevalence over recent years. Emerging clinical findings has evidenced remarkable tendon damage in individuals with longstanding asymptomatic hyperuricemia, yet the impact of hyperuricemia on tendon homeostasis and associated repercussions is largely unknown. Here, we investigated whether asymptomatic hyperuricemia was associated with spontaneous ruptures in the Achilles tendon and the pathological effect of hyperuricemia on the tendon stem/progenitor cells (TSPCs). Significantly higher serum uric acid (SUA) levels were found in 648 closed Achilles tendon rupture (ATR) patients comparing to those in 12559 healthy volunteers. In vitro study demonstrated that uric acid (UA) dose dependently reduced rat Achilles TSPC viability, decreased the expressions of tendon collagens, and deformed their structural organization while significantly increased the transcript levels of matrix degradative enzymes and proinflammatory factors. Consistently, marked disruptions in Achilles tendon tissue structural and functional integrity were found in a rat model of hyperuricemia, together with enhanced immune cell infiltration. Transcriptome analysis revealed a significant elevation in genes involved in metabolic stress and tissue degeneration in TSPCs challenged by hyperuricemia. Specifically, reduced activity of the AKT-mTOR pathway with enhanced autophagic signaling was confirmed. Our findings indicate that asymptomatic hyperuricemia may be a predisposition of ATR by impeding the normal functions of TSPCs. This information may provide theoretical and experimental basis for exploring the early prevention and care of ATR.

Isorhynchophylline ameliorates the progression of osteoarthritis by inhibiting the NF-κB pathway.

Osteoarthritis (OA), a progressive and degenerative joint disease, is characterized by cartilage degradation, synovitis, subchondral bone remodeling and osteophyte formation. Isorhynchophylline (IRN) is an oxindole alkaloid isolated from the traditional Chinese herb Uncaria rhynchophylla. In this study, we evaluated the protective effects of IRN on human OA chondrocytes. IRN treatment dose-dependently decreased the interleukin-1ß (IL-1ß)-induced expressions of nitric oxide (NO; p < 0.001), prostaglandin E2 (PGE2; p < 0.001), tumor necrosis factor alpha (TNF-α; p < 0.001), interleukin-6 (IL-6; p < 0.001), cyclooxygenase-2 (COX-2; p < 0.001) and inducible nitric oxide synthase (iNOS; p < 0.001) in chondrocytes. Meanwhile, the production of metalloproteinase 13 (MMP13; p < 0.001) and a disintegrin and metalloproteinase with thrombospondin motifs 5 (ADAMTS5; p < 0.001) was inhibited by IRN treatment. Molecular docking studies revealed that IRN directly interacted with the nuclear factor kappa B (NF-κB) complex, which was associated with a reduced level of NF-κB nuclear translocation and the inhibition of NF-κB signaling activity. Furthermore, administration of IRN generated marked in vivo protective effects during OA development. Collectively, our results demonstrate that IRN may exhibit therapeutic benefits against OA, potentially by ameliorating the inflammative and degenerative progression of OA via inhibiting the NF-κB pathway.

Mechanical Overloading Induced-Activation of mTOR Signaling in Tendon Stem/Progenitor Cells Contributes to Tendinopathy Development.

Despite the importance of mechanical loading in tendon homeostasis and pathophysiology, the molecular responses involved in the mechanotransduction in tendon cells remain unclear. In this study, we found that in vitro mechanical loading activated the mammalian target of rapamycin (mTOR) in rat patellar tendon stem/progenitor cells (TSCs) in a stretching magnitude-dependent manner. Application of rapamycin, a specific inhibitor of mTOR, attenuated the phosphorylation of S6 and 4E-BP1 and as such, largely inhibited the mechanical activation of mTOR. Moreover, rapamycin significantly decreased the proliferation and non-tenocyte differentiation of PTSCs as indicated by the reduced expression levels of LPL, PPARγ, SOX-9, collagen II, Runx-2, and osteocalcin genes. In the animal studies, mice subjected to intensive treadmill running (ITR) developed tendon degeneration, as evidenced by the formation of round-shaped cells, accumulation of proteoglycans, and expression of SOX-9 and collagen II proteins. However, daily injections of rapamycin in ITR mice reduced all these tendon degenerative changes. Collectively, these findings suggest that mechanical loading activates the mTOR signaling in TSCs, and rapamycin may be used to prevent tendinopathy development by blocking non-tenocyte differentiation due to mechanical over-activation of mTOR in TSCs.

Rapamycin Treatment of Tendon Stem/Progenitor Cells Reduces Cellular Senescence by Upregulating Autophagy.

The elderly population is prone to tendinopathy due to aging-related tendon changes such as cellular senescence and a decreased ability to modulate inflammation. Aging can render tendon stem/progenitor cells (TSCs) into premature senescence. We investigated the effects of rapamycin, a specific mTOR inhibitor, on the senescence of TSCs. We first showed that after treatment with bleomycin in vitro, rat patellar TSCs (PTSCs) underwent senescence, characterized by morphological alterations, induction of senescence-associated ß-galactosidase (SA-ß-gal) activity, and an increase in p53, p21, and p62 protein expression. Senescence of PTSCs was also characterized by the elevated expression of MMP-13 and TNF-α genes, both of which are molecular hallmarks of chronic tendinopathy. We then showed that rapamycin treatment was able to reverse the above senescent phenotypes and increase autophagy in the senescent PTSCs. The activation of autophagy and senescence rescue was, at least partly, due to the translocation of HMGB1 from the nucleus to the cytosol that functions as an autophagy promoter. By reducing TSC senescence, rapamycin may be used as a therapeutic to inhibit tendinopathy development in the aging population by promoting autophagy.

Moderate and intensive mechanical loading differentially modulate the phenotype of tendon stem/progenitor cells in vivo.

To examine the differential mechanobiological responses of specific resident tendon cells, we developed an in vivo model of whole-body irradiation followed by injection of either tendon stem/progenitor cells (TSCs) expressing green fluorescent protein (GFP-TSCs) or mature tenocytes expressing GFP (GFP-TNCs) into the patellar tendons of wild type C57 mice. Injected mice were subjected to short term (3 weeks) treadmill running, specifically moderate treadmill running (MTR) and intensive treadmill running (ITR). In MTR mice, both GFP-TSC and GFP-TNC injected tendons maintained normal cell morphology with elevated expression of tendon related markers collagen I and tenomodulin. In ITR mice injected with GFP-TNCs, cells also maintained an elongated shape similar to the shape found in normal/untreated control mice, as well as elevated expression of tendon related markers. However, ITR mice injected with GFP-TSCs showed abnormal changes, such as cell morphology transitioning to a round shape, elevated chondrogenic differentiation, and increased gene expression of non-tenocyte related genes LPL, Runx-2, and SOX-9. Increased gene expression data was supported by immunostaining showing elevated expression of SOX-9, Runx-2, and PPARγ. This study provides evidence that while MTR maintains tendon homeostasis by promoting the differentiation of TSCs into TNCs, ITR causes the onset of tendinopathy development by inducing non-tenocyte differentiation of TSCs, which may eventually lead to the formation of non-tendinous tissues in tendon tissue after long term mechanical overloading conditions on the tendon.

Effect of Metformin on Development of Tendinopathy Due to Mechanical Overloading in an Animal Model.

BACKGROUND: Tendinopathy is a debilitating tendon disorder that affects millions of Americans and costs billions of health care dollars every year. High mobility group box 1 (HMGB1), a known tissue damage signaling molecule, has been identified as a mediator in the development of tendinopathy due to mechanical overloading of tendons in mice. Metformin (Met), a drug approved by the Food and Drug Administration used for the treatment of type 2 diabetes, specifically inhibits HMGB1. This study tested the hypothesis that Met would prevent mechanical overloading-induced tendinopathy in a mouse model of tendinopathy created by intensive treadmill running (ITR). METHODS: C57BL/6J mice (female, 3 months old) were equally separated into 4 groups and treated for 24 weeks as follows: group 1 had cage control activities, group 2 received a single intraperitoneal injection of Met (50 mg/kg body weight) daily, group 3 underwent ITR to induce tendinopathy, and group 4 received daily Met injection along with ITR to inhibit HMGB1. Tendinopathic changes were assessed in Achilles tendons of all mice using histology, immunohistochemistry, and enzyme-linked immunosorbent assays. RESULTS: ITR induced HMGB1 release into the tendon matrix and developed characteristics of tendinopathy as evidenced by the expression of macrophage marker CD68, proinflammatory molecules (COX-2, PGE2), cell morphological changes from normal elongated cells to round cells, high levels of expression of chondrogenic markers (SOX-9, collagen type II), and accumulation of proteoglycans in tendinopathic tendons. Daily injection of Met inhibited HMGB1 release and decreased these degenerative changes in ITR tendons. CONCLUSIONS: Inhibition of HMGB1 by injections of Met prevented tendinopathy development due to mechanical overloading in the Achilles tendon in mice. CLINICAL RELEVANCE: Met may be able to be repurposed as a therapeutic option for preventing the development of tendinopathy in high-risk patients.

Extracellular HMGB-1 activates inflammatory signaling in tendon cells and tissues.

BACKGROUND: Increasing evidence indicates that secretion of high mobility group box 1 protein (HMGB-1) is functionally associated with tendinopathy development. However, the underlying effect and mechanism of extracellular HMGB-1 on tendon cells are unclear. METHODS: We tested the effect of exogenous HMGB-1 on cell growth, migration, and inflammatory signaling responses with isolated rat Achilles tendon cells. Also, we studied the role of extracellular HMGB-1, when administrated alone or in combination with mechanical overloading induced by intensive treadmill running (ITR), in stimulating inflammatory effects in tendon tissues. RESULTS: By using in vitro and in vivo models, we show for the first time that exogenous HMGB-1 dose-dependently induces inflammatory reactions in tendon cells and tendon tissue. Extracellular HMGB-1 promoted redistribution of HMGB-1 from the nucleus to the cytoplasm, and activated canonical nuclear factor kappa B (NF-κB) signaling and mitogen-activated protein kinase (MAPK) signaling. Short-term administration of HMGB-1 induced hyper-cellularity of rat Achilles tendon tissues, accompanied with enhanced immune cell infiltration. Additional ITR to HMGB-1 treatment worsens these responses, and application of HMGB-1 specific inhibitor glycyrrhizin (GL) completely abolishes such inflammatory effects in tendon tissues. CONCLUSION: Collectively, these results confirm that HMGB-1 plays key roles in the induction of tendinopathy. Our findings improve the understanding of the molecular and cellular mechanisms during tendinopathy development, and provide essential information for potential targeted treatments of tendinopathy.

RNA editing enzyme ADAR1 is required for early T cell development.

The RNA editing enzyme ADAR1 has been shown to be an essential molecule for hematopoietic cell differentiation, embryonic development, and regulation of immune responses. Here, we present evidence in a T-cell-specific gene knockout mouse model that ADAR1 is required for early T cell development. Loss of ADAR1 led to cell death of the progenitors at the double negative stage and prevented T cell maturation in the thymus. Furthermore, ADAR1 deletion in pre-T cells preferentially affected TCRß-expressing cells causing TCRß positive cell depletion. Interruption of IFN signaling occurred in the premature T cells, indicating a role of IFN signaling in the survival of TCRß-expressing cells regulated by ADAR1. This study demonstrated an essential role for the RNA editing enzyme ADAR1 as a potential regulator for T-cell fate determination during clonal selection, which, in turn, contributes to immunologic homeostasis.

HMGB1 mediates the development of tendinopathy due to mechanical overloading.

Mechanical overloading is a major cause of tendinopathy, but the underlying pathogenesis of tendinopathy is unclear. Here we report that high mobility group box1 (HMGB1) is released to the tendon extracellular matrix and initiates an inflammatory cascade in response to mechanical overloading in a mouse model. Moreover, administration of glycyrrhizin (GL), a naturally occurring triterpene and a specific inhibitor of HMGB1, inhibits the tendon's inflammatory reactions. Also, while prolonged mechanical overloading in the form of long-term intensive treadmill running induces Achilles tendinopathy in mice, administration of GL completely blocks the tendinopathy development. Additionally, mechanical overloading of tendon cells in vitro induces HMGB1 release to the extracellular milieu, thereby eliciting inflammatory and catabolic responses as marked by increased production of prostaglandin E2 (PGE2) and matrix metalloproteinase-3 (MMP-3) in tendon cells. Application of GL abolishes the cellular inflammatory/catabolic responses. Collectively, these findings point to HMGB1 as a key molecule that is responsible for the induction of tendinopathy due to mechanical overloading placed on the tendon.

Selectively activated PRP exerts differential effects on tendon stem/progenitor cells and tendon healing.

To understand the variable efficacy with platelet rich plasma (PRP) treatments for tendon injury, we determined the differential effects of proteinase-activated receptor (PAR)1- or PAR4-activated PRP (PAR1-PRP, PAR4-PRP) from humans on human patellar tendon stem/progenitor cells (TSCs) and tendon healing. We show that PAR1-PRP released VEGF, whereas PAR4-PRP released endostatin. Treatment of TSCs with PAR1-PRP increased collagen I expression and matrix metalloproteinase-1 (MMP-1), but cells treated with PAR4-PRP increased less collagen I and higher MMP-2 expression. The wound area treated with PAR4-PRP formed tendon-like tissues with well-organized collagen fibers and fewer blood vessels, while PAR1-PRP treatment resulted in the formation of blood vessels and unhealed tissues. These findings indicate that differential activation of PRP leads to different effects on TSCs and tendon healing. We suggest that based on acute or chronic type of tendon injury, selective activation of PRP should be applied in clinics in order to treat injured tendons successfully.

Characterization of the structure of rabbit anterior cruciate ligament and its stem/progenitor cells.

BACKGROUND: It is known that anterior cruciate ligament (ACL) of the knee joint is prone to injuries with poor healing potential. The healing capacity of a tissue-like ACL is dependent on its structural components and the properties of the stem cells (SCs). Therefore, this study aimed to characterize the structure of ACL tissue and the properties of the SCs derived from the tissue components. METHODS: The tissue structure of rabbit ACL was determined using a scanning electron microscope, hematoxylin and eosin, and immunohistochemical staining. The biological properties of SCs derived from the structural components of ACL were studied by colony formation, cell proliferation assay, SC marker expression and collagen exhibition, and multidifferentiation potential. RESULTS: The two distinct components of ACL are classified as sheath and core, which possess differential properties in terms of collagen type, organization, and presence of blood vessels. The sheath tissue contains vascular SCs and the core tissue contains ligamentous SCs, respectively. The two types of SCs differ in clonogenicity, proliferation, and multidifferentiation potential. CONCLUSION: This study shows that ACL consists of sheath and core tissues, which contain sheath and core SCs with distinctive biological properties. These findings highlight the need for use of both sheath and core SCs to promote the repair of the complex structure of injured ACL.

Characterization of the structure, cells, and cellular mechanobiological response of human plantar fascia.

In this study, we report that human plantar fascia consists of two distinct tissues with differential structural properties. These tissues also contain stem/progenitor cells with differential biological properties. The mechanobiological responses of these two plantar fascia stem cells also differ in terms of expression of collagen I and IV, non-ligament-related genes, and proinflammatory genes. The production of inflammatory agents (prostaglandin E2, interleukin-6) and matrix degradative enzymes (matrix metalloproteinase-1, matrix metalloproteinase-2) are also different between the two types of plantar fascia stem cells. Based on the findings from this study, we suggest that plantar fasciitis results from the aberrant mechanobiological responses of the stem cells from plantar fascia sheath and core tissues. Our findings may also be used to devise tissue engineering approaches to treat plantar fascia injury effectively.

Lymphatic Endothelial Cells under Mechanical Stress: Altered Expression of Inflammatory Cytokines and Fibrosis.

BACKGROUND: Secondary lymphedema, resulting from damage to lymphatic vessels, is a common sequela following surgical removal of lymph nodes for cancer. Current therapeutics for treating lymphedema are limited and further research on underlying causes is warranted. Published studies on molecular mechanisms of lymphedema primarily focus on lymphatic endothelial cells (LECs), which comprise the innermost lining of lymphatic capillaries and collecting vessels. However, traditional static culture of LECs may not adequately recapitulate the lymphedemous cell phenotype as transcriptomal comparison of human dermal LECs has shown significant differences in ex vivo and in vitro LEC gene expression. In this study, we designed a dynamic culture system, in which LECs were exposed to physiologic and excess mechanical strain to determine if native and lymphedemous phenotypes could be reproduced in vitro. METHODS AND RESULTS: Purified human LECs were cultured in silicon dishes and subjected to 0% (control), 4%, and 8% mechanical strain for 72 hours. Our results indicate that control and stretched LECs maintained a mature phenotype. Extreme stretching at 8% strain significantly increased LEC proliferation and significantly increased Prox1 expression, suggesting a lymphedemous cell phenotype resulting with lymphangiogenesis. CONCLUSION: Mechanical strain reinforced a mature lymphatic phenotype and excess strain promoted lymphangiogenesis, while altering collagen deposition and cytokine secretion.

Fat-1 gene inhibits human oral squamous carcinoma cell proliferation through downregulation of ß-catenin signaling pathways.

The ω-3 fatty acid desaturase (fat-1) gene encodes the enzyme that converts ω-6 polyunsaturated fatty acids (PUFAs) to ω-3 PUFAs. Numerous studies have suggested that the ratio of ω-6/ω-3 PUFAs has an impact on tumorigenesis. To investigate the biological function of the fat-1 gene in human oral squamous cell carcinoma (OSCC), the fat-1 gene was introduced into OSCC cells by transfection. The uptake of the gene was confirmed by reverse transcription-polymerase chain reaction and analyzed using gas chromatography. The antitumor effects and mechanisms of the fat-1 gene were evaluated by studying cell survival and tumor growth in vitro and in vivo. Gas chromatography results revealed that the cells transfected with the fat-1 gene had a higher ω-3/ω-6 PUFA ratio than cells transfected with the control vector. An MTT and DNA fragmentation assay indicated that the presence of the fat-1 gene in vitro significantly decreased OSCC cell proliferation and significantly increased the rate of apoptosis. Similar antitumor effects of the fat-1 gene were also observed in vivo. Immunohistochemistry analysis confirmed that Tca8113 cell tumors displayed a significant reduction in cell growth and cell survival following the introduction of the fat-1 gene. The current study suggests that the inhibitory effect of the fat-1 gene on tumor growth may be a result of a reduction in the expression of the tumor survival protein ß-catenin. The results also support the theory that the ratio of ω-3/ω-6 PUFAs has an impact on OSCC tumor growth. The findings of the study provide notable molecular insight into the theory suggesting that ω-3 PUFAs are an intermediate for the chemoprevention and treatment of human OSCC.

ADAR1 ablation decreases bone mass by impairing osteoblast function in mice.

Bone mass is controlled through a delicate balance between osteoblast-mediated bone formation and osteoclast-mediated bone resorption. We show here that RNA editing enzyme adenosine deaminase acting on RNA 1 (ADAR1) is critical for proper control of bone mass. Postnatal conditional knockout of Adar1 (the gene encoding ADAR1) resulted in a severe osteopenic phenotype. Ablation of the Adar1 gene significantly suppressed osteoblast differentiation without affecting osteoclast differentiation in bone. In vitro deletion of the Adar1 gene decreased expression of osteoblast-specific osteocalcin and bone sialoprotein genes, alkaline phosphatase activity, and mineralization, suggesting a direct intrinsic role of ADAR1 in osteoblasts. ADAR1 regulates osteoblast differentiation by, at least in part, modulation of osterix expression, which is essential for bone formation. Further, ablation of the Adar1 gene decreased the proliferation and survival of bone marrow stromal cells and inhibited the differentiation of mesenchymal stem cells towards osteoblast lineage. Finally, shRNA knockdown of the Adar1 gene in MC-4 pre-osteoblasts reduced cyclin D1 and cyclin A1 expression and cell growth. Our results identify ADAR1 as a new key regulator of bone mass and suggest that ADAR1 functions in this process mainly through modulation of the intrinsic properties of osteoblasts (i.e., proliferation, survival and differentiation).

[Expression of X-linked inhibitor of apoptosis protein in Tca8113 cell and its relationship to chemoresistance].

OBJECTIVE: To explore the expression of X-linked inhibitor of apoptosis protein (XIAP) in Tca8113 cell, and to investigate its relationship to the chemoresistance. METHODS; The Tca8113 cell line was cultured by IMDM and the concentration of Pingyangmycin (PYM) added to Tca8113 cell line was increased gradually and continually, which was to induce the PYM-resistance in Tca8113 cell line. The sensitivity of Tca8113 cell to PYM and expression of XIAP were measured with methyl thiazolyl tetrazolium (MTT) chromatometry and reverse transcription-polymerase chain raction (RT-PCR). The XIAP level in the cells and its chemoresistance to PYM were analyzed by linear regression. RESULTS: The IC50 of Tca8113-1-10 group and Tca8113-10-10 group were(12.758 +/- 0.030), (18.986 +/- 0.150) microg x mL(-1) respectively. The IC50 of Tca8113-1-20 group and Tca8113-10-20 group increased to (26.302 +/- 0.072), (35.294 +/- 0.115) microg x mL(-1) respectively. There was a relation between XIAP and the drug-resistance in Tca8113 cell. CONCLUSION: XIAP may play an important role in the chemoresistance which might serve as a new therapeutic target for oral squamous cell carcinoma.

Establishment of a transgenic pig fetal fibroblast reporter cell line for monitoring Cre recombinase activity.

The pig is considered to be the most suitable nonhuman source of organs for xenotransplantation and is widely used as a model of human disease. The Cre-LoxP system provides a powerful means of cell- or tissue-specific deletion of a targeted gene in cells or tissues of interest. Pigs expressing Cre recombinase have a profound impact on the study of gene function and the generation of animal models of human diseases. To monitor Cre recombinase expression in vivo, it is important to create reporter strains. As a first step in the production of such transgenic pigs, we generated porcine fetal fibroblast cell lines conditionally expressing the gene for enhanced green fluorescent protein (EGFP). The EGFP gene is expressed only after Cre-mediated excision of LoxP-flanked stop sequences. These fetal fibroblast cell lines will be of great value for constructing reporter transgenic pigs.

Production of a reporter transgenic pig for monitoring Cre recombinase activity.

The pig is thought to be the most suitable non-human source of organs for xenotransplantation and is widely used as a model of human disease. Using pigs as disease models requires the design of conditional Cre recombinase-loxP gene modifications, which, in turn, requires a Cre-expressing pig with defined patterns of expression controlled by the use of a tissue-specific promoter. In order to monitor Cre recombinant expression in vivo, it is important to create a reporter strain. We have generated reporter a pig that is based on a single vector that drives the ubiquitous expression of the enhanced green fluorescent protein (EGFP). The EGFP gene is expressed only after Cre-mediated excision of loxP-flanked stop sequences. These reporter transgenic pigs will be of great value for monitoring Cre recombinase activity in vivo.