Evaluation of endoscopic examination of colon tumors in rats

Endoscopic submucosal injection of adipose-derived mesenchymal stem cells ameliorates TNBS-induced colitis in rats and prevents stenosis

Background

Mesenchymal stem cells have potential applications in inflammatory bowel disease due to their immunomodulatory properties. Our aim was to evaluate the feasibility, safety and efficacy of endoscopic administration of adipose-derived mesenchymal stem cells (ASCs) in a colitis model in rats.

Methods

Colitis was induced in rats by rectal trinitrobenzenesulfonic acid (TNBS). After 24 h ASCs (10⁷ cells) or saline vehicle were endoscopically injected into the distal colon. Rats were followed for 11 days. Daily weight, endoscopic score at days 1 and 11, macroscopic appearance at necropsy, colon length and mRNA expression of Foxp3 and IL-10 in mesenteric lymph nodes (MLN) were analyzed.

Results

Endoscopic injection was successful in all the animals. No significant adverse events or mortality due to the procedure occurred. Weight evolution was significantly better in the ASC group, recovering initial weight by day 11 (− 0.8% ± 10.1%, mean ± SD), whereas the vehicle group remained in weight loss (− 6.7% ± 9.2%, p = 0.024). The endoscopic score improved in the ASC group by 47.1% ± 5.3% vs. 21.8% ± 6.6% in the vehicle group (p < 0.01). Stenosis was less frequent in the ASC group (4.8% vs. 41.2%, p < 0.01). Colon length significantly recovered in the ASC group versus the vehicle group (222.6 ± 17.3 mm vs. 193.6 ± 17.9 mm, p < 0.001). The endoscopic score significantly correlated with weight change, macroscopic necropsy score and colon length. Foxp3 and IL-10 mRNA levels in MLN recovered with ASC treatment.

Conclusions

ASC submucosal endoscopic injection is feasible, safe and ameliorates TNBS-induced colitis in rats, especially stenosis.

Electronic supplementary material

The online version of this article (10.1186/s13287-018-0837-x) contains supplementary material, which is available to authorized users.

Development of a total colonoscopy rat model with endoscopic submucosal injection of the cecal wall

BACKGROUND

Experimental models of colorectal tumor require either laparotomy for induction or anastomosis following resection. The long murine cecum avoids the need for an anastomosis, making the cecum the preferred site for induction. This study aimed to evaluate total colonoscopy with submucosal injection of cecal wall (TCWI) in rats in terms of failure rate (FR), complication rate (CR), and reproducibility (R).

METHODS

A bolus of bowel prep was given. Anesthesia was injected intraperitoneally. A video fiberscope (5.9 mm outer diameter, 180/90 degrees up/down bending, 100/100 degrees right/left bending, 103 cm working length, 120 degrees view field, and 2.0 mm channel) allowed for irrigation and suction. Saline 1 ml was injected in the cecal wall through a 4-mm-long, 23-gauge needle placed on a 3-mm wire, resulting in a blister. FR was a failure to reach and inject the cecum. Rats were allowed to recover. CR was measured at necropsy. R was assessed by comparing TCWI time, FR, and CR for three investigators. Sample size of 120 (type I error, 0.05; power, 80%) was based on a pilot study. Data are presented as median (range).

RESULTS

A total of two of 122 rats (1.6%) died after prep or anesthesia. Bowel prep resulted in 99.1% evacuation of solid feces. A total of 120 male Sprague-Dawley retired breeders weighing 592 g (range, 349-780) underwent TCWI. Scope depth was 28 cm (range, 20-36). Irrigating fluid was 290 ml (range, 100-600). TCWI time was 7 min (range, 4-28). FR was 4%. In three failed cases, the scope reached the ascending colon. CR was 2%. There were two perforations in the ascending colon. All three operators had similar TCWI time (p = 0.673), FR (p > 0.1), and CR (p > 0.1). A total of 98.3% of rats survived to planned sacrifice. At 48-h necropsy, the injection site was macroscopically identified in 118 rats.

CONCLUSIONS

A safe and reproducible TCWI rat model has been achieved, which may provide a valuable tool in the future for studies of solid colorectal tumors.

Experimental chemical carcinogenesis in the stomach and colon

Experimental chemical carcinogenesis in the digestive tract is reviewed, mainly on the basis of information obtained in the laboratories of the National Cancer Center Research Institute. It is generally accepted that cancer is the outcome of DNA damage, resulting in mutation, loss, amplification and recombination of genes. Gastric cancer is no exception. It was shown very early that cancer of the glandular stomach can be produced in rats by administration of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), a widely used mutagen. However, this depends on the genotype. Whereas the ACI rat is susceptible to MNNG, the Buffalo rat is resistant and this is a dominantly inherited trait. Genes responsible for the sensitivity to gastric cancer induction are at present under investigation by linkage analysis of rat genome markers. With regard to cancer in humans, our finding that cooked proteinaceous foods can give rise to a series of heterocyclic amines (HCAs) is of major significance. 2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), one of the most abundant, causes colon cancers in male rats, whereas in females it induces breast cancers. The colon cancers induced by PhIP feature a deletion of G as represented by 5-GGGA-3-->5-GGA-3 in the Apc gene, resulting in a truncated Apc molecule. Microsatellite mutations have also been found in PhIP-induced colon tumors, as in human hereditary non-polyposis colorectal cancer cases. Similarly to the case of gastric cancer production by MNNG, there is a genetic component and F344 rats are more susceptible to PhIP colon carcinogenesis than the ACI/N strain and the gene responsible is being sought. Since carcinogenesis proceeds with accumulation of genetic alteration, often involving genomic instability, exposure to any kind of carcinogenic substances, either xeno- or autobiotics, needs to be reduced as far as possible, taking account of inconvenience at the individual and socio-economical levels.

Efficacy of dinaline and its methyl and acetyl derivatives against colorectal cancer in vivo and in vitro

Dinaline [4-amino-N-(2'-aminophenyl)-benzamide, Din], p-N-methyldinaline (Me-Din) and p-N-acetyldinaline (Ac-Din) were evaluated for their antineoplastic efficacy in acetoxymethylmethylnitrosamine-induced colorectal carcinomas in Sprague-Dawley rats and in two human colon cancer cell lines. Din was very effective at all dosages (10, 7.7 and 5.9 mg/kg) as indicated by the ratio of median tumour volume of treated and control groups (T/C%) values of 0.4, 16 and 10.6, respectively, but also caused a corresponding mortality of 87, 47 and 13%, respectively, as opposed to 15% in the control group. Me-Din also showed significant tumour growth inhibition at all dosages (13.8, 10.6, 8.2 and 6.2 mg/kg), as evidenced by T/C% values of 2, 5.7, 8.4 and 25, respectively. The corresponding mortality was 47, 20, 27 and 30%, respectively. Ac-Din showed the lowest mortality with 20, 13 and 20% at dosages of 9.1, 7.0 and 5.3 mg/kg, respectively, whereas application of 11.9 mg/kg resulted in 100% mortality. T/C values of 18.3, 11.1 and 21.6%, respectively, demonstrated again high anticancer efficacy. Compared to the combination therapy with 5-FU and leucovorin (25 mg/kg each), p-N-acetyldinaline (7.0 mg/kg) was 4-fold more effective as indicated by T/C% values of 81.4 versus 21.9 at similar toxicity. In vitro, all three compounds were similarly active with IC50 concentrations between 1 and 2.2 micrograms/ml after 48 h of exposure and 0.6 to 1.6 micrograms/ml after 72 h of incubation. The MTT dye conversion assay correlated well with cell counts obtained by cell counting except for low dosages after short incubation periods when it stimulated cell proliferation. These results suggest that dinaline and its derivatives have clinical potential.

Antineoplastic activity of three ruthenium derivatives against chemically induced colorectal carcinoma in rats

The antineoplastic activity of the ruthenium complexes trans-imidazolium[tetracholorobisimidazole-ruthenate(III)], HIm(RuIm2Cl4), trans-indazolium-[tetrachlorobis(1H-indazole)ruthenate (III, N2)], HInd [RuInd2Cl4(N2)], and trans-indazolium[tetrachloro-bis(2H-indazole)ruthenate(III,N 1)], HInd[RuInd2Cl4-(N1)] was assessed in acetoxymethylmethylnitrosamine-induced autochthonous colorectal carcinomas of Sprague-Dawley rats. The model is not sensitive to clinically established antineoplastic agents, including cisplatin. An exception is the combination therapy with 5-fluorouracil/leucovorin, which shows moderate activity against the tumour model. In contrast to this general trend, the new substances were all active against this tumour. HIm(RuIm2Cl4) was very effective at all dosages applied (7.5 mg/kg, 5.3 mg/kg, and 3.8 mg/kg), as indicated by percentage treated/control (T/C values of 23%, 34.5%, and 44%. Toxicity was considerable as shown by a body weight change of -30%, -19%, and -9%. Nevertheless, the medium dose seems to be the optimum in terms of mortality (0% vs 15% in the control group), whereas at the highest dose, mortality increased as a result of substance toxicity, and at the lowest dose mortality increased through tumor growth combined with substance toxicity. HInd[RuInd2Cl4(N2)] showed high efficacy at the highest dosage of 13 mg/kg, reaching a T/C value of 27% combined with 0% mortality versus 15% in the control group. In equimolar dosages (10 mg/kg, 7.1 mg/kg and 5.1 mg/kg), the compound is not as active as HIm-(RuIm2Cl4), as indicated by T/C values of 50.2%, 45.7%, and 38.6%. HInd[RuInd2Cl4(N1)] was slightly but not significantly better than HInd[RuInd2Cl4(N2)] at a dosage of 7.1 mg/kg and is advantageous over combination therapy with 5-fluorouracil and leucovorin (20/20 mg/kg) in terms of efficacy (T/C = 37.6% versus 44.7%) and mortality (6% versus 33.3%).

Activity of two platinum-linked phosphonic acids against autochthonous rat colorectal cancer as well as in two human colon-cancer cell lines

Two new platinum-containing phosphonate compounds, cis-diammine[nitrilotris(methylphosphonato)(2-)- O1,N1]platinum(II) (AMDP) and cis-cyclohexane-1,2-diamine[nitrilotris(methylphosphonato) (2-)-O1,N1]platinum(II) (DADP) were investigated in acetoxy-methyl-methylnitrosamine-induced autochthonous colorectal rat adenocarcinoma in vivo as well as in two human colon-cancer cell lines (SW707 and SW948) in vitro. In the in vivo model, the two compounds were given i.v. at doses of 8 and 13 mg/kg as well as p.o. at 16 and 26 mg/kg twice a week for 10 weeks, respectively. AMDP produced more intensive toxicity at both doses but showed higher antitumour activity only following i.v. administration. On the other hand, DADP caused significant tumour-growth inhibition after both modes of application, but as it produced only low toxicity, its use should be favoured. The in vitro assays were performed using two cell lines derived from human colorectal adenocarcinomas. According to the microculture tetrazolium test (MTT) AMDP (IC50, 34 and 59 microM in SW707 and SW948, respectively) was more effective than DADP (IC50, 412 and 660 microM in SW707 and SW948, respectively) in inhibiting cell growth. Based on cell counts AMDP (IC50, 8 and 11 microM in SW707 and SW948, respectively) and DADP (IC50, 266 and 285 microM in SW707 and SW948, respectively) showed more intensive antiproliferative efficacy as determined by the Coulter Counter method vs the MTT assay. The promising activities of these new platinum-linked phosphonic acids in autochthonous rat colorectal carcinoma and in human colorectal cancer cell lines warrant further investigations of compounds of this class to elucidate their role in the treatment of colorectal cancer.

Endoscopic and radiographic evaluation of the murine colon

Endoscopic and radiographic techniques have not been widely applicable in the evaluation of chemically induced murine colon cancer. The authors investigated methods of cleansing the rat colon and refined endoscopic and radiographic techniques. They compared total colonoscopy (TC) and air-contrast (ACBE) and single-contrast barium enema (SCBE) findings with those obtained at necropsy in rats with 1,2-dimethylhydrazine (DMH)-induced colon cancer. Gastrograffin enemas with bisacodyl suppositiories showed complete evacuation of solid feces. Sprague-Dawley rats treated with DMH had their colons cleansed and then underwent TC (5.0-mm Olympus bronchoscope) and either SCBE or ACBE. Colonoscopy and ACBE were equally sensitive (81.5% and 76.3%, respectively), although SCBE was significantly insensitive in identifying lesions (P less than 0.001). This study demonstrates that: (1) mechanical cleansing of the rat colon is feasible, (2) TC and barium radiology can be done routinely after mechanical cleansing, and (3) TC and double-contrast BE are sensitive in identifying colon lesions. These techniques will provide a means for manipulation of murine tumors and in vivo surveillance.

Possible role of acetaldehyde in ethanol-related rectal cocarcinogenesis in the rat

Prospective epidemiologic studies have reported an increased risk of rectal cancer following chronic ethanol ingestion. The effect of ethanol on chemically induced colorectal carcinogenesis is controversial depending on the experimental conditions. In the present study the effect of chronic ethanol administration on acetoxymethylmethylnitrosamine-induced rectal cancer and the possible role of acetaldehyde in this process were investigated. Chronic ethanol administration resulted in an earlier occurrence of rectal tumors in this animal model. Because the concomitant administration of cyanamide, a potent acetaldehyde dehydrogenase inhibitor, showed a positive trend toward increased incidences of tumors, acetaldehyde could be involved in the ethanol-associated carcinogenesis. To measure colonic acetaldehyde, 12 chronically ethanol-fed and control rats received an acute dose of ethanol (2.5 g/kg body wt). The mucosal concentration of acetaldehyde was significantly higher in the rectum compared with the cecum (198 +/- 23 vs. 120 +/- 23 nmoles.g colon-1, p less than 0.05), but was not affected by chronic ethanol feeding. Furthermore, 6 germ-free rats had significantly lower acetaldehyde concentrations in the rectum (84 +/- 11 vs. 234 +/- 33 nmoles.g colon-1, p less than 0.01) and in the cecum (59 +/- 13 vs. 121 +/- 33 nmoles.g colon-1, p less than 0.05) compared with 6 conventional animals, and this was paralleled by the number of fecal bacteria in the 2 intestinal segments. In addition, to determine the effect of chronic ethanol feeding on colorectal cell turnover, 30 animals were pair-fed liquid diets. Using the metaphase-arrest technique, alcohol feeding induced rectal (19.1 +/- 2.0 vs. 9.1 +/- 1.8 cells.crypt-1.h-1, p less than 0.01), but not cecal (18.9 +/- 1.3 vs. 22.2 +/- 3.3 cells.crypt-1.h-1, p greater than 0.05) hyperregeneration. This was accompanied by an increase in the crypt proliferative compartment and increased mucosal ornithine decarboxylase activity (63 +/- 18 vs. 22 +/- 6 pmoles.hr-1.mg protein-1, p less than 0.05). The data show that chronic ethanol ingestion accelerates chemically induced rectal carcinogenesis and raise the possibility that acetaldehyde probably generated through bacterial ethanol oxidation may be involved in this process. The secondary hyperregeneration of the mucosa, observed after alcohol feeding, could by itself favour carcinogenesis.

Serial observations of colonic carcinogenesis in the rat. Premalignant mucosa binds Ulex europeus agglutinin

We evaluated certain histochemical tests for their ability to detect premalignant mucosa in the dimethylhydrazine model of colonic carcinogenesis. Biweekly colonoscopic biopsies of the descending colon were performed for 29 wk in control and dimethylhydrazine-treated rats. Biopsy specimens of the splenic flexure, rectum, and any visualized tumors were taken. The specimens were stained with periodic acid-Schiff to detect neutral mucins, high-iron diamine alcian blue to detect sialylated and sulfated mucins, fluoresceinated peanut agglutinin, and fluoresceinated Ulex europeus agglutinin. None of the first three tests consistently detected premalignant mucosa. However, Ulex europeus agglutinin, which bound to only 3% of control biopsy specimens throughout the course of the study, bound to increasing numbers of biopsy specimens in the dimethylhydrazine-treated animals, reaching a maximum of 90% positivity by 13-16 wk. Moreover, Ulex europeus agglutinin bound strongly to all biopsy specimens from tissues adjacent to tumors and to 93% of tumors. Mucosal atrophy and focal dysplasia were present more frequently in specimens taken from the rectum (but not the splenic flexure) of dimethylhydrazine-treated animals than of control animals, but there was no correlation between the histochemical markers and either atrophy or dysplasia. We conclude that Ulex europeus agglutinin binding is a consistent feature of premalignant colonic mucosa in dimethylhydrazine-treated rats.

Growth characteristics of autochthonous experimental colonic tumors as assessed by serial colonoscopic measurement in rats

We report the growth characteristics of autochthonous experimental colonic tumors as assessed by serial measurements at colonoscopy. Male Fischer 344 rats were given 10 weekly subcutaneous injections of the bowel carcinogen azoxymethane, 10 mg/kg (weeks 1-10). Beginning in week 15, colonoscopy to the splenic flexure was performed weekly with a pediatric fiberoptic bronchoscope. Width of identified tumors was measured in photographs that included a scale passed through the biopsy channel, and tumor volume was calculated using computerized image analysis. Sensitivity, specificity, predictive values, and efficiency of colonoscopy for identification of tumors were 85%-100%. Cumulative tumor incidence in the descending colon increased in a relatively linear fashion from 3% at week 15 to 68% at week 30. Tumor width by colonoscopy correlated well with width at necropsy (r = 0.951). Growth curves of individual tumors were highly variable; however, tumor width showed stable mean weekly growth rates. By contrast, mean calculated tumor volume rose exponentially, with deviation from the fitted curve in the sixth week. All tumors greater than 3 mm in width or greater than 10 mm3 in volume showed invasion. Final tumor width and volume, and growth of tumor volume during the initial week but not the later weeks of observation, correlated with depth of invasion. Our findings suggest that colonoscopic measurement was useful to study the growth characteristics of autochthonous experimental colonic tumors; azoxymethane administration produced persistently altered colonic epithelium that had variable latent periods until development of visible tumors in individual rats; the growth curves of individual colonic tumors were exponential, although variable, during the initial weeks; invasion was found in small tumors and depth of invasion correlated with growth rate during the initial week but not the later weeks. This aggressive behavior of the tumors early in their course contrasts with colorectal adenomas in humans and argues against the routine occurrence of an adenoma-carcinoma sequence in the model we used.

[Effect of local moderate hyperthermia in combination with N-nitroso-1,3-bis-(2-chloroethyl)urea (BCNU) and 5-fluoro-(tetrahydro-2-furyl)uracil (ftorafur) on induced autochthonous colonic cancers in the rat. 3: Polychemotherapy in combination with hyperthermia]

The use of hyperthermia for the treatment of tumors has been tested in vitro and in vivo experiments as well as clinically for a long time. Combination of hyperthermia with chemotherapy was reported to result in overadditive cytostatic effects. In a clinically adapted, controlled animal experiment, local moderate hyperthermia (43.5 degrees C, 3 X 60 min) alone and in combination with polychemotherapy (BCNU) and Ftorafur) was used for the treatment of AMMN-(N-nitrosoacetoxymethyl-methylamine) induced autochthonous colonic carcinomas in Sprague-Dawley rats. Diagnosis and follow-up inspections were carried out endoscopically. The applied therapies did not result in prolonged survival times, nor was an additive effect seen after combined hyperthermia and chemotherapy in this "hard", i.e. relatively chemotherapy-resistent, tumor model.

Combination chemotherapy with 5-fluorouracil (5FU) and 1,3-bis(2-chloro-ethyl)-1-nitrosourea (BCNU) prolongs survival of rats with dimethylhydrazine-induced colon cancer

The effects of combination chemotherapy with 5FU and BCNU on rats with dimethylhydrazine (DMH)-induced colon cancer were investigated in a long term survival study. Eighty Wistar rats received a colon cancer producing regimen on DMH (40 mg/kg body weight/week, subcutaneously for 10 weeks). After presenting with signs of colonic disease, all rats underwent diagnostic laparotomy and colonoscopy when colon tumours were located, measured and the extent of the disease staged. Only animals with tumours (n = 63) were included and allocated to one of three tumour stages. Stage A (n = 17), had colonic tumours without serosal involvement; stage B (n = 28) had serosal involvement without metastases; stage C (n = 18) had serosal involvement with lymphadenopathy and/or metastases. Each group was randomly allocated into two subgroups, one serving as untreated controls while the other received 5FU (300 mg/m2 weekly intragastrically for life) together with BCNU (40 mg/m2 intraperitoneally on days 0, 42 and 84). The effect of chemotherapy on tumour growth was measured sequentially by colonoscopy. Animals were observed until death and necropsied, when colon carcinoma was histologically confirmed and survival analysed. The results indicate that chemotherapy significantly prolongs the survival of rats with the least advanced disease (stage A) but was of no benefit to rats with locally advanced or metastatic disease (stages B and C). Furthermore, chemotherapy was associated with a significant reduction in tumour size. Survival analyses in untreated animals show that the laparotomy staging system adopted provides accurate prognostic information. This study shows that DMH-induced colon tumours are chemosensitive, and suggests that this animal model may be a valuable testing ground for new chemotherapeutic agents.

Chemotherapeutic studies on N-nitrosoacetoxymethyl-methylamine-and 1,2-dimethylhydrazine-induced colonic tumors in rats: monotherapy with 5-fluorouracil, ftorafur, CGP 6809, and CGP 15'720A

Colonic tumors were induced in male Sprague-Dawley rats by ten applications of 2 mg/kg/week N-nitrosoacetoxymethyl-methylamine (AMMN) or by three applications of 100 mg/kg/month 1,2-dimethylhydrazine (1,2-DMH). Application of AMMN and 1,2-DMH induced selective colonic tumors in 97% and 29-42% of the initial animals, respectively. Colonic-tumor-bearing animals were subjected to monotherapy with 5-fluorouracil, ftorafur, CGP 6809, and CGP 15'720A. No cures were achieved. The different therapies did not exert any clear influence on the survival time of animals, except for animals pretreated with AMMN and then subjected to ftorafur therapy.

Chemoprevention of development of colonic adenomatosis and carcinomatosis with 5-fluorouracil and ftorafur on animal model

This study deals with the treatment by chemotherapy of carcinogen-induced tumors in the colon of rats. These tumors mimic colonic adenomatosis and carcinomatosis in man. The rats were given an intrarectal (i.r.) instillation of methylnitrosourea for producing colonic tumors, and thereafter received a long-term chemotherapy which was started on nascent microscopic lesions of carcinoma. The colonic tumor incidence was significantly lower in rats treated for 10 weeks than in untreated rats. An inhibition rate of tumor development was 100% in rats with i.r. doses of 5-FU, or 57% in rats with intraperitoneal (i.p.) doses of Ftorafur. However, it was found that a few microscopic lesions of carcinoma were still present in the normal-appearing colonic mucosa, even after the completion of the effective treatment. The 10-week cessation of the treatment following the 5-week chemotherapy permitted the tumor development. The results indicate that the nascent microscopic lesions of carcinoma (premalignant lesions) in the colon can be inhibited or regulated from developing into grossly visible tumors by the effective chemotherapy, i.e., intermittent and/or long-term treatment with sensitive chemotherapeutic agents and effective way of administration.

Chemoprevention of development of colonic adenomatosis and carcinomatosis with intrarectal dose of 5-FU on animal model

This study concerns the treatment by chemotherapy of carcinogenically-induced cancers in the colons of rats. These cancers mimic adenomatosis and carcinomatosis in humans. We believed that they could be prevented or regulated from growing into grossly visible tumors by the intrarectal administration of 5-fluorouracil if the treatment was started on nascent cancers. The incidence of colon carcinoma and the number of tumors per rat were significantly lower in rats treated by this method than in the control rats. Furthermore, some of the small tumors visible by endoscopy disappeared with treatment. This beneficial effect appeared to be due to the direct delivery of an active form of anticancer drug administered in high concentration to the target lesions in the colon mucosa, and carried fewer side effects when compared to other parenteral administrations.