Proliferating Cell Nuclear Antigen Labeling Research Articles

Myometrial Apoptosis: Activation of the Caspase Cascade in the Pregnant Rat Myometrium at Midgestation1

In the present study, we determined the contribution of myometrial hyperplasia, hypertrophy, and apoptosis to uterine growth during pregnancy. The changes in two endogenous markers of cell replication, proliferating cell nuclear antigen (PCNA) protein expression and bromodeoxyuridine (BrdU) incorporation, were studied. Myocyte hypertrophy was assessed by measuring the protein:DNA ratio. The expression levels of antiapoptotic regulatory proteins (BCL2 and BCL2L1) and enzymes involved in apoptosis (caspases 3, 6, 7, 9, and 10) were assessed by immunoblotting throughout gestation and postpartum. Myometrial cell apoptosis was determined by TUNEL staining and DNA fragmentation assays. Both BrdU incorporation and PCNA labeling were elevated in early pregnant myometrium and decreased dramatically after midgestation, with a simultaneous increase in cellular hypertrophy. Levels of BCL2 were high during early gestation, followed by significantly elevated levels of BCL2L1 at midgestation. The expression of caspase 10 in myometrial samples declined from a high nonpregnant level to a complete loss at early gestation. The cleaved forms of caspases (CC) 3, 6, 7, and 9, as well as poly(ADP-ribose)polymerase-1, were undetectable in the myometrial samples at early or late gestation but were transiently elevated at midgestation. Immunohistochemical staining of CC3 confirmed the activation of the caspase cascade, but TUNEL-positive staining or the increase in DNA fragmentation was not detected. Collectively, two distinct phases of myometrial growth were observed: myocyte hyperplasia associated with an increase in antiapoptotic proteins during the first half of gestation, and cellular hypertrophy during the second part of gestation. The transition between these phases was associated with transient activation of the caspase cascade that triggered the differentiation of uterine smooth muscle.

Inhibition of Putrescine Aminopropyltransferase Influences Rat Liver Regeneration

A close relationship between rat liver regeneration and the concentration ratio of spermidine to spermine (spd:spm) was demonstrated by the oral administration of trans-4-methylcyclohexylamine (MCHA), a specific inhibitor of putrescine aminopropyltransferase. A decrease in recovery rate of remnant liver with MCHA, as a percentage index of remnant liver weight to body weight, correlated well with a decrease of the spd:spm value, with a correlation coefficient of 0.952 for the remnant livers on day 3 after partial hepatectomy. The decrease in recovery rate could be explained by a prolonged cell cycle based on the data of the proliferating cell nuclear antigen labelling index and mitotic cell index in both livers of day 2 and day 3 after partial hepatectomy. The results presented here will give a new aspect in the field of polyamine regulation to control cell growth in vivo.

Inhibitory effect of dietary monoglucosylceramide 1‐O‐β‐glucosyl‐N‐2′‐hydroxyarachidoyl‐4,8‐sphingadienine on two different categories of colon preneoplastic lesions induced by 1,2‐dimethylhydrazine in F344 rats

Sphingolipids display a wide spectrum of biological activities, including cell growth, differentiation and apoptosis. However, precise mechanisms by which these compounds exert anticancer or cancer-preventive effects are not known. In the present study, we evaluated the preventive efficacy of enriched dietary monoglucosylceramide 1-O-beta-glucosyl-N-2'-hydroxyarachidoyl-4,8-sphingadienine (G(1)CM) on 1,2-dimethylhydrazine (DMH)-induced aberrant crypt foci (ACF) and beta-catenin-accumulated crypt (BCAC) formation in F344 rats during initiation stage. We also examined whether G(1)CM affects cell proliferation and apoptosis in these lesions. Pure G(1)CM was isolated from rice bran. Forty-two rats were divided randomly into five experimental groups. Rats in groups 1-3 were given subcutaneous injections of DMH (40 mg/kg body weight) once a week for 2 weeks. One week before the first injection of DMH, rats in groups 2 and 3 were fed a diet containing 200 and 1,000 p.p.m. G(1)CM, respectively, for 5 weeks. Rats in group 4 were fed a diet containing 1,000 p.p.m. G(1)CM. Rats in group 5 were given the basal diet alone and served as untreated controls. The experiment was terminated 5 weeks after the start. Dietary G(1)CM at both doses (groups 2 and 3) significantly inhibited the induction of ACF and BCAC (P<0.001) when compared to group 1 treated with DMH alone. In groups 2 and 3, the proliferating cell nuclear antigen labeling indices of epithelial cells in ACF and BCAC were also lower than in group 1 (P<0.0001 for ACF, P<0.05 for BCAC). These results, that dietary G(1)CM has possible chemopreventive effects in the present short-term colon carcinogenesis bioassays, suggest that longer exposure may cause suppression of tumor development.

Indole-3-carbinol inhibits the growth of human colon carcinoma cells but enhances the tumor multiplicity and volume of azoxymethane-induced rat colon carcinogenesis

Indole-3-carbinol (I3C) is a naturally occurring phytochemical which exerts a broad range of biological activities. The purpose of this study was to examine the effects of I3C on colon carcinogenesis, cell proliferation, cell-cycle progression and apoptosis, and on the levels of expression of several cell-cycle control molecules. We used a long-term rat model by using azoxymethane (AOM) to induce tumors (adenomas and adenocarcinomas) in the colon. In the present study, we found that after AOM injection, the treatment of male F344 rats with 0.01 and 0.05% I3C caused a significant increase in the tumor multiplicity of adenocarcinomas by 2.2- (P<0.05 for 0.01% I3C) and 2.1-fold (P<0.0002 for 0.05% I3C) respectively, when compared to the control rats. In addition, the tumor multiplicity of adenoma plus adenocarcinoma and the volume of adenocarcinoma were also increased by 2.0- (P<0.00001) and 2.1-fold (P<0.05) respectively, compared to the control. I3C significantly increased the proliferating cell nuclear antigen labeling index (PCNA LI) (P<0.008) and decreased the apoptotic index (P<0.05) of the colon adenocarcinoma. In contrast, in HCT 116 and HT29 human colon carcinoma cells, I3C inhibited growth and induced G1-phase cell-cycle arrest and apoptosis. Furthermore, I3C caused approximately a 2- to 4-fold increase in the cellular levels of p27KIP1 and p21CIP1 mRNA. These results suggest that I3C inhibits the growth of human colon carcinoma cells, at least in part, by inducing p27KIP1 and p21CIP1-mediated G1 cell-cycle arrest but dietary I3C promotes AOM-induced rat colon carcinogenesis by inhibiting the apoptosis of colon tumors. Therefore, the present study may provide further evidence for the ambivalent modulatory activity of I3C and this information may be useful when including I3C in cancer chemoprevention and/or extensive clinical therapy trials.

Epithelioid hemangioendothelioma of tongue: A case report with immunohistochemical studies

A very rare case of epithelioid hemangioendothelioma (EH) in the tongue is reported. The immunohistochemical studies for Factor VIII, proliferating cell nuclear antigen (PCNA) and vascular endothelial growth factor (VEGF) were performed. The tumour cell kinetics in EH was evaluated by PCNA immunohistochemistry. PCNA labeling index in the tumour was 57.0%. Furthermore, strong immunohistochemical expression of VEGF was recognized in the cytoplasm of tumour cells. The intense expression of VEGF in EH may indicate its aggressive proliferative activity and metastatic behavior.

Histological and biological characteristics of esophageal dysplasia

Dysplasia is an important problem in esophageal carcinogenesis, and there are controversial opinions concerning whether esophageal squamous dysplasia is a cancerous lesion. In the present study, it was histopathologically and biologically confirmed that dysplasia has a close correlation with cancer. Dysplasia was frequently observed with early stages of carcinoma. Although continuity of dysplastic lesions into the carcinoma area is not frequently observed, this continuity is observed in severe dysplasia more often than in mild or moderate dysplasia. The proliferating cell nuclear antigen labeling index (PCNA LI) showed no substantial difference in the cell proliferative activities of dysplasia and intraepithelial carcinoma. In addition, p53 immunohistochemical analysis revealed that p53 positivities in carcinomas and dysplasias were contiguous to each other. These findings indicate that the relationship between the severity of dysplasia and carcinoma has high potential for leading to malignancy. Therefore, dysplasias can be treated as early cancerous lesions of the esophagus to prevent serious results.

The change of proliferating cell nuclear antigen and apoptosis of the MM46 mammary cancer cells of the mouse after single high-dose irradiation

The effects of intraoperative radiotherapy on tumor cells were elucidated by immunohistochemical examination of changes in the level of proliferating cell nuclear antigen. In addition, the terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling method was used to examine the level of apoptosis in mouse MM46 tumor cells after a single high dose of irradiation (30 Gy, 6 MeV). A significant decrease in the number of tumor cells compared to controls was observed on the 3rd, 7th, and 14th days following irradiation, but not on the 1st day. Consistent with these results, the proliferating cell nuclear antigen labeling index of irradiated cells decreased significantly on the 3rd, 7th, and 14th days following irradiation, but not on the 1st day. By comparison, the regrowth area on day 14 only showed no difference compared to the control group. The apoptotic index increased on the 7th and 14th day after irradiation, but at a lower rate than the observed decrease in the level of proliferating cell nuclear antigen. We speculate that the major mechanism of single high-dose radiation effect is inhibition of DNA synthesis.

Administration of rhHGF-Activator Via Portal Vein Stimulates the Regeneration of Cirrhotic Liver After Partial Hepatectomy in Rats 1

Cirrhotic liver has less ability to regenerate than normal liver, but it can produce the precursor of hepatocyte growth factor (proHGF) similarly to normal liver after resection. Studies were performed to examine whether the exogenous administration of recombinant human (rh) HGF-activator converts proHGF to biologically active (mature) HGF, inducing an enhancement of liver regeneration in cirrhosis. Rats with liver cirrhosis were treated by 45% partial hepatectomy, and rhHGF-activator or vehicle was injected via the portal vein 24 h after resection. Liver injury and its regeneration, the conversion of proHGF to mature HGF, and the activation of its signal through HGF receptor (c-Met) were analyzed. rhHGF-activator improved the recovery of liver function after resection in cirrhotic liver as compared with the control group. rhHGF-activator also enhanced the proliferating cell nuclear antigen labeling index and liver regeneration rate. rhHGF-activator converted the proHGF to mature HGF, showing the maximal effect at 10 min after injection, which was followed by tyrosine phosphorylation of insulin receptor substrate (IRS)-1, and the association of IRS-1 with c-Met and phosphatidylinositol 3-kinase. Results demonstrate that the administration of rhHGF-activator stimulates the recovery of liver function and regeneration after resection in cirrhotic liver through the activation of proHGF and its intracellular signal. It may be potentially useful treatment for patients with liver cirrhosis.

The Effect of Amrinone on Liver Regeneration in Experimental Hepatic Resection Model 1

The phosphodiesterase inhibitors (PDEIs) have been proposed to improve hepatic reperfusion injury and hepatosplanchnic circulation, but the effects of these agents on liver regeneration have not been investigated thoroughly. The aim of this study was to investigate the effect of amrinone, a PDEI, on liver regeneration in rats. Sixty rats were divided into two groups, control and amrinone. Each group was then divided into three groups (n=10). An infusion of amrinone to the study group and of 0.9% NaCl to the control group was performed. Seventy percent liver resection was performed to the rats during the first hour of infusion. The infusion was maintained for 17 h after resection. A total of 18 h infusion was performed. Rats were allowed to survive for 24, 48, and 72 h, and then they were sacrificed. Biochemical, morphological, hematological, and histopathologic measurements and assessments were performed. There were statistically significant differences between the amrinone and control groups in alkaline phosphatase and relative liver weights at 24, 48, and 72 h (P<0.05). There also were statistically significant differences between the groups in AST, bilirubin, and albumine levels at 24 h, ALT and prothrombine time levels at 48 h, and aspartate aminotransferase and alanine aminotransferase levels at 72 h (P<0.05). Hepatic ATP levels, mitotic index, and proliferating cell nuclear antigen labeling index were significantly higher in amrinone group compared with control group at all three time intervals (P<0.05). Amrinone improves both morphological and functional liver regeneration after liver resection.

Beneficial Effect of Hyperbaric Oxygenation on Liver Regeneration in Cirrhosis

Underlying hepatic injury and cirrhosis are leading factors that interfere with the post-operative liver regeneration and function. Hyperbaric oxygenation (HBO) has been reported to ameliorate the ischemia-reperfusion injury of the liver, to induce compensatory hypertrophy of the predicted remnant liver in rats after portal vein ligation and to augment liver regeneration after hepatectomy in non-cirrhotic rats. Our aim was to determine the effect of HBO treatment on liver regeneration after partial hepatectomy in normal and cirrhotic mice in this experimental study. The effect of HBO on liver regeneration was studied in a mice model combining carbon tetrachloride induced cirrhosis and partial hepatectomy. Mice were divided into four groups: Control, cirrhotic, non-cirrhotic HBO-treated, and cirrhotic HBO-treated. All animals underwent 40% hepatectomy. Liver regeneration was evaluated by the proliferating cell nuclear antigen-labeling index. Serum aspartate aminotransferase and alanine aminotransferase levels were measured to evaluate liver injury. Serum alanine aminotransferase and aspartate aminotransferase levels were significantly decreased in HBO-treated cirrhotic group compared to cirrhosis group after hepatectomy (P = 0.001 and P = 0.014, respectively). The proliferating cell nuclear antigen labeling index was significantly higher in HBO treated cirrhotic group than in cirrhotic group after hepatectomy (P = 0.022). Our results suggest that HBO treatment improves liver functions and augments hepatocyte regeneration in cirrhotic mice after hepatectomy. Post-operative HBO treatment may have a beneficial effect on post-operative liver function and regeneration in cirrhotic patients.

Lung Alveolar Septation Defects in Ltbp-3-Null Mice

Latent transforming growth factor (TGF)-beta binding proteins (LTBPs) modulate the secretion and activation of latent TGF-beta. To explore LTBP function in vivo, we created an Ltbp-3(-/-) mouse that has developmental emphysema with decreased septation in terminal alveoli. Differences in distal airspace enlargement were obvious at day 6 after birth. Secondary septation was inhibited, so by days 21 to 28 the mean linear intercept was approximately twofold greater in mutant versus control lungs. There were no differences in lung collagen and elastin, visualized by immunohistochemistry, or in myofibroblast numbers, determined by alpha-smooth muscle actin-positive cells, between mutant or wild-type lungs as the animals aged, other than differences associated with altered lung structure in mutant animals. However, from day 10 there was twice the number of alveolar type II cells in mutant alveoli compared to controls. At days 6 and 10, a transient enhancement in cell proliferation in the mutant lungs was observed by both 5-bromo-2'-deoxy-uridine and proliferating cell nuclear antigen labeling, accompanied by enhanced numbers of terminal dUTP nick-end labeling-positive cells at days 4, 6, and 10. Finally, there was a transient decrease in TGF-beta signaling at days 4 to 6 in Ltbp-3(-/-) lungs. These results indicate that in the absence of Ltbp-3, a temporary decrease in TGF-beta signaling in the lungs at days 4 to 6 alters cell proliferation, correlating with inhibition of septation and developmental emphysema.

Relationship between expression of cyclin D1 and impaired liver regeneration observed in fibrotic or cirrhotic rats

The mechanisms responsible for impaired regenerative ability after hepatic resection observed in chronic liver disease are not fully understood. We have examined the relationships between an altered expression of cell cycle-related proteins in regenerating liver after partial hepatectomy and the impaired regenerative process observed in fibrotic and cirrhotic rats. We performed 70% partial hepatectomy in both control and porcine serum-induced fibrotic rats, and 45% partial hepatectomy in thioacetamide-induced cirrhotic rats because of the high mortality associated with 70% partial hepatectomy. Liver regeneration was monitored by proliferating cell nuclear antigen labeling index and the expression of G1 regulatory cell cycle-related proteins was determined by immunoblot analysis. Compared with controls, hepatocyte DNA synthesis, and induction of cyclin D1 and p21(CIP1) proteins were delayed but not suppressed in porcine serum-induced fibrotic rats and markedly inhibited in thioacetamide-induced cirrhotic rats. p27(KIP1) protein levels were unaffected by partial hepatectomy and did not differ among all three groups. Two distinct rat models of liver fibrosis and cirrhosis showed markedly different proliferative responses after partial hepatectomy. The delay or failure of cyclin D1 induction, but not the increase of p21(CIP1) or p27(KIP1) might be responsible for their impaired liver regeneration.

Inhibitory effect of meloxicam, a cyclooxygenase-2 inhibitor, on N -nitrosobis (2-oxopropyl) amine induced biliary carcinogenesis in Syrian hamsters

Pancreaticobiliary maljunction (PBM) is a high risk factor in biliary tract carcinoma. The chemopreventive action of a cyclooxygenase (COX)-2 inhibitor (meloxicam) on N-nitrosobis (2-oxopropyl) amine (BOP)-induced gallbladder cancer in hamster PBM models was investigated. In 7-week-old female Syrian golden hamsters, the extrahepatic bile duct at the distal end of the common duct was ligated and cholecystoduodenostomy was performed (group I). In group II, the same surgery was performed and from week 4 after surgery, 10 mg/kg of BOP was injected subcutaneously once a week with a 1-week interval. In group III, in addition to the measures employed in group II, 5 mg/kg/day of meloxicam was administered once a day, every weekday. Pathological findings in the gallbladder in week 20 after surgery were as follows. In group I, proper epithelium (PE) was predominant and there was no cancer. In group II, PE was predominant, but there was also hyperplasia and atypical epithelium (AE) recognized in 8 of 11 cases (72.7%); the area of AE was more extensive than that in group I. Carcinoma in situ (CIS) was recognized in 4 of 11 cases (36.4%) in group II. Group III showed the same pathological findings as group I. However, compared with group II, the incidence of AE decreased to 27.3% and no cancerous lesion was observed. In week 20 after surgery, the proliferative cell nuclear antigen labeling index in group III was statistically significantly lower than in group II (P = 0.045). No statistically significant differences were noted among the groups in terms of apoptosis labeling index in week 20 after surgery. In conclusion, it was confirmed that meloxicam suppresses carcinogenesis in hamster PBM models and its mechanism may be based on the suppression of cell growth.

Hepatic proliferation in Gunn rats transplanted with hepatocytes: effect of retrorsine and tri‐iodothyronine

Hepatocyte transplantation would offer an attractive alternative to liver transplantation in the treatment of inborn errors of liver metabolism. However, a major problem in most transplantation studies to date has been the limited growth of transplanted cells in the recipient organ. We performed a strategy for selective proliferation of transplanted cells by interfering with the proliferative capacity of resident hepatocytes, using the pyrrolizidine alkaloid retrorsine and then transplanting liver cells in conjunction with repeated administration of triiodothyronine, an inducer of hepatocyte proliferation in rats. In the present study, foetal and adult syngeneic hepatocyte transplantation into spleen was performed in retrorsine-treated hyperbilirubinemic Gunn rats. In parallel, repeated injections of triiodothyronine were given to recipients. Rats were sacrificed at 1, 7, 30 and 90 days after transplantation and blood and bile samples were taken to assess the functionality of transplanted cells. The proliferative activity of transplanted hepatocytes was evaluated using proliferating cell nuclear antigen labelling index. In summary, both adult and foetal hepatocyte transplantation were effective in correcting a metabolic abnormality in Gunn rats for as long as 3 months. The RS/T3 model, as a measure to increase graft function, could represent an important advance to future clinical application of hepatocyte transplantation.

Biological behavior of myoepithelial cells in the regeneration of rat atrophied sublingual glands following release from duct ligation

The present study aimed to clarify how myoepithelial cells behave during regeneration of an atrophied sublingual gland by investigating cell proliferation and ultrastructure. Atrophy of rat sublingual glands was induced by unilateral ligation of the excretory duct near the hilum with metal clips, which were then removed after one week of ligation for regeneration. The sublingual glands 0-14 days after unligation were examined with single immunohistochemistry for actin as a marker of myoepithelial cells, double immunohistochemistry for actin and proliferating cell nuclear antigen (PCNA) as a marker of proliferating cells, and transmission electron microscopy (TEM). The single immunohistochemistry and TEM showed that myoepithelial cells surrounded residual ducts in the atrophied glands and immature and mature acini in the regenerating glands. Although PCNA-positive myoepithelial cells were identified during regeneration, PCNA labeling indices of myoepithelial cells were low at all time points except at day 7. Ultrastructurally, myoepithelial cells showing bizarre shaped structures in the atrophy changed with maturation of differentiating acinar cells and appeared normal in the regenerated glands. There was no differentiation of the remaining duct cells to myoepithelial cells. These observations suggest that proliferation of myoepithelial cells and differentiation to myoepithelial cells do not commonly participate in the regeneration of atrophied sublingual glands and that the bizarre shaped myoepithelial cells in the atrophied sublingual glands recover the original shapes with acinar cell regeneration.

Expression of cellular FLICE/caspase-8 inhibitory protein is associated with malignant potential in endometrial carcinoma

This study aimed to investigate the expression of cellular Fas-associated death domain-like interleukin-1β-converting enzyme (FLICE)/caspase-8 inhibitory protein (c-FLIP) in endometrial carcinoma and its possible implications. c-FLIP protein was detected in 42 endometrial carcinoma tissues and in 22 normal proliferative endometrial tissues by immunohistochemistry. In addition, c-FLIP messenger ribonucleic acid (mRNA) was evaluated in 20 endometrial carcinomas and in 18 normal proliferative endometria by semiquantitative reverse transcriptase–polymerase chain reaction (RT-PCR) using SYBR Green I™. The relationship between c-FLIP protein level and tumor cell proliferation and that between c-FLIP protein level and clinicopathologic parameters of patients with endometrial carcinoma was analyzed. c-FLIP protein expression was significantly higher in neoplastic tissues than in normal tissues (P&lt; 0.01), and similar result was obtained from RT-PCR analysis of c-FLIP mRNA (P&lt; 0.01). Furthermore, c-FLIP protein was significantly associated with proliferating cell nuclear antigen–labeling index (P&lt; 0.01), clinical stage (P&lt; 0.05), the presence of invasion to &gt;1/2 myometrium (P&lt; 0.05), and lymph node metastasis (P&lt; 0.01). Multivariate analysis of variance also confirmed the association of c-FLIP with clinical stage (P&lt; 0.05) and with lymph node metastasis (P&lt; 0.05), while its association with myometrial invasion was marginal (P= 0.059). It is concluded that c-FLIP might contribute to the carcinogenesis and aggressiveness of endometrial carcinoma and might be a useful prognostic factor in the tumor.

Early Detection of Tumor Response to Chemotherapy by 3′-Deoxy-3′-[18F]Fluorothymidine Positron Emission Tomography: The Effect of Cisplatin on a Fibrosarcoma Tumor Model In vivo

We have assessed the potential of [18F]fluorothymidine positron emission tomography ([18F]FLT-PET) to measure early cytostasis and cytotoxicity induced by cisplatin treatment of radiation-induced fibrosarcoma 1 (RIF-1) tumor-bearing mice. Cisplatin-mediated arrest of tumor cell growth and induction of tumor shrinkage at 24 and 48 hours, respectively, were detectable by [18F]FLT-PET. At 24 and 48 hours, the normalized uptake at 60 minutes (tumor/liver radioactivity ratio at 60 minutes after radiotracer injection; NUV60) for [18F]FLT was 0.76 +/- 0.08 (P = 0.03) and 0.51 +/- 0.08 (P = 0.03), respectively, compared with controls (1.02 +/- 0.12). The decrease in [18F]FLT uptake at 24 hours was associated with a decrease in cell proliferation assessed immunohistochemically (a decrease in proliferating cell nuclear antigen labeling index, LI(PCNA), from 14.0 +/- 2.0% to 6.2 +/- 1.0%; P = 0.001), despite the lack of a change in tumor size. There were G1-S and G2-M phase arrests after cisplatin treatment, as determined by cell cycle analysis. For the quantitative measurement of tumor cell proliferation, [18F]FLT-PET was found to be superior to [18F]fluorodeoxyglucose-PET (NUV60 versus LIPCNA: r = 0.89, P = 0.001 and r = 0.55, P = 0.06, respectively). At the biochemical level, we found that the changes in [18F]FLT and [18F]fluorodeoxyglucose uptake were due to changes in levels of thymidine kinase 1 protein, hexokinase, and ATP. This work supports the further development of [18F]FLT-PET as a generic pharmacodynamic readout for early quantitative imaging of drug-induced changes in cell proliferation in vivo.

Modifying effects of Terminalia catappa on azoxymethane-induced colon carcinogenesis in male F344 rats

The modifying effects of dietary administration of an herb, Terminalia catappa (TC), were investigated on rat colon carcinogenesis induced by a carcinogen azoxymethane (AOM). The number of aberrant crypt foci (ACF) and beta-catenin accumulated crypts (BCACs) in the colon, and proliferating cell nuclear antigen (PCNA) labelling index in the colonic epithelium were examined in a total of 36 male F344 rats. All animals were randomly divided into five experimental groups (4-10 rats in each group). At 6 weeks of age, rats in groups 1, 2 and 3 were given s.c. injections of AOM once a week for 2 weeks at a concentration of 20 mg/kg body weight. One week before the first injection of AOM, rats in groups 2 and 3 were fed a diet containing 0.02 and 0.1% TC, respectively, throughout the experiment. Rats in group 4 were fed a diet containing 0.1% TC. Rats in group 5 were served as untreated controls. All animals were sacrificed at the experimental week 5 after the start of the experiment. Oral administration of TC at both doses significantly decreased the numbers of both ACF/colon/rat (P<0.05 for 0.02% TC, P<0.005 for 0.1% TC) and BCAC/cm/rat (P<0.05 for both 0.02 and 0.1% TC), when compared with the control group (group 1). Colonic PCNA labelling index in groups 2 and 3 was also significantly lower than that in group 1 (P<0.001 for 0.02% TC, P<0.005 for 0.1% TC). These results suggest that TC has a potent short-term chemopreventive effect on biomarkers of colon carcinogenesis and this effect may be associated with the inhibition of the development of ACF and BCACs.

Development and resolution of experimental colitis in mice with targeted deletion of dipeptidyl peptidase IV

Glucagon-like peptide-2 (GLP-2) is a potent intestinotrophic growth factor that enhances repair of damaged intestinal tissue. However, its bioactivity is limited by dipeptidyl peptidase IV (DPIV)-mediated degradation. We hypothesized that DPIV(-/-) mice would display an increased resistance to, and an enhanced recovery from, dextran sulfate sodium (DSS)-induced colitis compared to DPIV(+/+) mice. DPIV(+/+) and DPIV(-/-) mice consumed 2% DSS for 6 days, followed by a 15 day recovery period. Mice were killed at days 0, 3, 6, 9, 14, and 21 (n = 6-8) and the small intestine and colon removed for histological assessment of villus height, crypt depth, and crypt area. The epithelial cell proliferative labeling index was determined by proliferating cell nuclear antigen (PCNA) immunostaining. Small intestine, colon, and total body weight did not differ between DPIV(+/+) and DPIV(-/-) mice. Distal colon crypt depth did not differ significantly between DPIV(+/+) and DPIV(-/-) mice during the development of DSS-colitis or during the recovery phase. Similarly no significant effects were apparent on distal colon crypt area or PCNA labeling index between DPIV(+/+) and DPIV(-/-) during the development of and recovery from DSS-colitis. However, DPIV(-/-) mice still possessed significant levels of plasma DPIV-like activity. We conclude that loss of DPIV activity does not increase resistance to experimental colitis and hypothesize that other DPIV family members may also be involved in the cleavage of GLP-2.

Activin and Activin Receptor Expression Changes in Liver Regeneration in Rat

This study aimed to investigate regulatory mechanisms of hepatocyte proliferation by comparing liver regeneration of the remnant lobe after 70% partial hepatectomy (PH) and portal vein branch ligation (PBL) in rat. Expressions of activins betaA, betaC, and betaE and their receptors were investigated after PH and PBL. The proliferating cell nuclear antigen (PCNA) labeling index was used to monitor hepatocyte proliferation. The PCNA labeling index in the regenerative lobe of PBL rats reached a peak at 48 h, a delay of 24 h compared with the remnant lobe in PH rats. In the postoperative early stage, the expression of activin betaA, betaC, and betaE mRNAs was stronger in PBL than PH. At 72 h the expression of activin receptor type IIA mRNA reached a peak in PH but was significantly lower in PBL. Hepatocyte proliferation, and the regulated expression of activins and their receptors, differs during liver regeneration after PH and PBL in the rat. Thus, regulation of activin signaling through receptors is one of the factors determining liver regeneration after PH and PBL.