Hamster Cheek Pouch Model Research Articles

Detection of squamous neoplasia by fluorescence imaging comparing porfimer sodium fluorescence to tissue autofluorescence in the hamster cheek-pouch model

Early neoplastic changes in the oral cavity may be difficult to detect. Fluorescence imaging using porphyrin-derived drugs has been used to enhance detection of neoplasia. Autofluorescence has also been used for this purpose. This paper compares autofluorescence to porfimer sodium-induced fluorescence in the detection of neoplasia in the hamster cheek-pouch model. Neoplasia was induced in the hamster cheek pouch by the application of 9,10-dimethyl-1,2-benzanthracene. Animals were imaged either with injection of drug (porfimer sodium) or without drug (autofluorescence). Imaging was carried out using a laser-induced fluorescence detection system. Biopsies were performed on imaged sections and histologic grades were assigned. Porfimer sodium fluorescence provided 100% sensitivity and specificity in detection of neoplasia. The sensitivity and specificity with autofluorescence was 76% and 83%, respectively. Autofluorescence provides an accurate means of detecting early neoplastic changes in the hamster cheek-pouch model; however, porfimer sodium imaging does improve detection rates.

Hydrogen peroxide: a review of its use in dentistry.

Several dentifrices that contain hydrogen peroxide are currently being marketed. The increased use of bleaching agents containing (or generating) H2O2 prompted this review of the safety of H2O2 when used in oral hygiene. Daily exposure to the low levels of H2O2 present in dentifrices is much lower than that of bleaching agents that contain or produce high levels of H2O2 for an extended period of time. Hydrogen peroxide has been used in dentistry alone or in combination with salts for over 70 years. Studies in which 3% H2O2 or less were used daily for up to 6 years showed occasional transitory irritant effects only in a small number of subjects with preexisting ulceration, or when high levels of salt solutions were concurrently administered. In contrast, bleaching agents that employ or generate high levels of H2O2 or organic peroxides can produce localized oral toxicity following sustained exposure if mishandled. Potential health concerns related to prolonged hydrogen peroxide use have been raised, based on animal studies. From a single study using the hamster cheek pouch model, 30% H2O2 was referred to as a cocarcinogen in the oral mucosa. This (and later) studies have shown that at 3% or less, no cocarcinogenic activity or adverse effects were observed in the hamster cheek pouch following lengthy exposure to H2O2. In patients, prolonged use of hydrogen peroxide decreased plaque and gingivitis indices. However, therapeutic delivery of H2O2 to prevent periodontal disease required mechanical access to subgingival pockets. Furthermore, wound healing following gingival surgery was enhanced due to the antimicrobial effects of topically administered hydrogen peroxide. For most subjects, beneficial effects were seen with H2O2 levels above 1%.

Differential expression of cytokeratin mRNA in hamster squamous epithelia as observed by in situ hybridization using human cytokeratin cRNA probes.

In this hybridohistochemical study, we investigated the expression of cytokeratin (CK) mRNA in the keratinizing squamous epithelium of hamster cheek pouch and esophagus, using eight different digoxigenin-labelled RNA probes complementary to human CK mRNAs. CK 4, CK 6, CK 8, CK 14, and CK 15 RNA probe obviously hybridized with hamster counterpart mRNA(s) in the cheek pouch as well as in the esophageal epithelium. However, using the CK 10-specific RNA probe, only the cheek pouch epithelium exhibited a positive reaction. We were not able to detect any positive signal for the CK 18 or for the CK 19 RNA probe. We observed three different CK mRNA distribution patterns in the cheek pouch epithelium, and four in the esophageal epithelium. The differences in expression and distribution pattern of CK mRNAs between the two types of epithelia suggest that the hamster CK polypeptide family comprises at least six different species. We also conclude that human cRNA probes for CK mRNAs may provide a way to detect changes in CK expression and distribution during induced non-neoplastic and neoplastic changes in the hamster cheek pouch model. This may also help to elucidate the molecular pathogenesis of squamous-cell carcinoma.

Vasoconstrictive effects of cocaine and lidocaine with epinephrine in the hamster cheek pouch model

Vasoconstrictive effects of cocaine and lidocaine with epinephrine in the hamster cheek pouch model

Vasoconstrictive Effects of Cocaine and Lidocaine with Epinephrine in the Hamster Cheek Pouch Model

Otolaryngologists frequently use cocaine and lidocaine with epinephrine for their anesthetic and vasoconstrictive effects. However, no studies have visually compared the vasoconstrictive effects of cocaine to lidocaine with epinephrine. This study used the everted hamster cheek pouch model to assess the vasoconstrictive effects of cocaine and lidocaine with epinephrine by measuring the diameter changes of arterioles. Our results showed that locally injected 1% lidocaine with 1:100,000 units epinephrine caused the greatest diameter reduction in arterioles to 32% of the initial resting diameter. Topical 1% lidocaine with 1:100,000 units epinephrine caused a gradual reduction in diameter with findings equivalent to those of injected 1% lidocaine with 1:100,000 units epinephrine at 30 minutes. Topical 5% cocaine HCl showed a minimal response, with a reduction to only 85% of the resting arteriolar diameter. Topical NaCl and injected NaCl controls showed no significant arteriolar reduction. Vasoconstrictive differences between the preparations were statistically significant (p < 0.05). Five percent cocaine is a much weaker vasoconstrictor than locally injected 1% lidocaine with 1:100,000 units epinephrine.

Effects of sialoadenectomy and epidermal growth factor administration on 9,10-dimethyl-1,2-benzanthracene-induced tumor formation in hamster cheek pouch

The effects of removal of the submandibular gland (sialoadenectomy) and administration of human urinary epidermal growth factor on the 9,10-dimethyl-1,2-benzanthracene-induced tumor formation were investigated with the use of a hamster cheek pouch model. Syrian hamsters were treated with 0.5% 9,10-dimethyl-1,2-benzanthracene for 6 weeks. Thereafter hamsters in group 1 underwent a sham operation and those in groups 2 and 3 underwent a sialoadenectomy. Subsequently, hamsters in groups 1 and 2 were given 0.9% sodium chloride and group 3 received the human urinary epidermal growth factor at a dose of 0.25 mg/kg body weight subcutaneously three times a week for 8 weeks. Sixteen weeks after the start of the experiment, the mean number of tumors that were less than 3-mm in diameter in groups 1 and 3 was significantly greater than that in group 2 ( p < 0.05). The overall incidence and mean number of all carcinomas irrespective of size showed no differences among the experimental groups. These results indicate that epidermal growth factor synthesized in the submandibular gland may enhance the induction of cheek pouch tumor.

Photodynamic therapy of squamous cell carcinoma. An evaluation of a new photosensitizing agent, benzoporphyrin derivative and new photoimmunoconjugate

Photodynamic therapy for cancer depends on the relatively selective distribution of photosensitizing agents to malignant as compared with normal tissues, rendering the malignant cells more susceptible to light-mediated damage. Photodynamic therapy has been used with only moderate success to date. The purpose of this study was to compare a new photosensitizing agent, benzoporphyrin derivative (BPD), to the standard agent presently in use, photofrin II, in a hamster cheek pouch model of squamous cell carcinoma. As well we have investigated the potential of using a tumour-specific monoclonal antibody-BPD conjugate to improve the tumour localizing properties of BPD. Treatment consisted of photodynamic therapy with either photofrin II, BPD, or a tumour-specific anti-epidermal growth factor receptor-BPD conjugate. Control groups of light alone, anti-EGFr, tumour non-specific MoAb, and tumour nonspecific MoAb-BPD conjugate were included with the contralateral cheek pouch of each animal acting as a dark control. An assessment of differential delivery of BPD to tumour and to normal mucosa was undertaken using a spectrophotometric assay. Parametric statistical analysis included Student's t-tests and linear regression while non-parametric analysis was undertaken using Fisher's exact test. Animals receiving BPD alone demonstrated tumour-to-tissue levels of approximately 2:1 while animals receiving the tumour-specific anti-EGFr-BPD conjugate had significantly better tumour:tissue ratios of 26:1 ( P < 0.005). Animals treated with photofrin II had a 1 month cancer-free survival of 27% while animals treated with BPD had an improved survival of 67% ( P = 0.03) The group treated with the tumour-specific anti-EGFr-BPD conjugate at a twentieth the total dose of BPD had an 80% 1 month cancer-free survival which was not statistically different from the group treated with BPD alone. Benzoporphyrin appears to be a more effective photosensitizing agent than Photofrin II and its tumour selectivity can be improved using a tumour specific monoclonal antibody conjugate.

Beta-carotene and vitamin E in oral cancer prevention

The ultimate proof that a putative chemopreventive agent does prevent cancer is a demonstration of reduced cancer incidence in a targeted population. However, because of practical and logistical considerations, such trials are virtually impossible to conduct for the majority of cancers. Therefore, a conclusion regarding the efficacy of chemopreventive activity is based on consideration of a variety of indirect lines of evidence, including laboratory studies, animal model systems, epidemiologic surveys, intervention trials involving reversal of premalignant changes, and the prevention of malignancies in particularly high risk subjects. Furthermore, the only agents worth testing are those with limited, or preferably, no toxicity, since the final use will be prevention in a generally healthy population. Beta-carotene and vitamin E both fulfill all the criteria for suitable chemopreventive agents; several lines of evidence point toward preventive roles for them in oral cancer. In numerous epidemiologic studies, low intake of beta-carotene has been associated with higher cancer risk. Both intake and supplemental use of vitamin E have been associated with a lowered risk of cancer. Smokers, whose habit is a major risk factor, have lower beta-carotene levels in oral mucosal cells when compared with non-smokers. In several laboratory and animal model systems, including the very relevant hamster cheek pouch model, these agents strongly inhibit oral cavity carcinogenesis. Beta-carotene and vitamin E produce regression of oral leukoplakia, a premalignant lesion for oral cancer. This has now been shown in seven clinical trials: five with beta-carotene alone, one with vitamin E, and one with a combination of both.(ABSTRACT TRUNCATED AT 250 WORDS)

Detection of squamous cell cancer and pre-cancerous lesions by imaging of tissue autofluorescence in the hamster cheek pouch model

Early detection of invasive and pre-invasive neoplasms of the aerodigestive tract will ultimately improve the management of patients with these lesions. This paper describes the use of quantitative fluorescence imaging of early squamous cell carcinomas in an animal model. Dysplasia, carcinoma in situ and invasive cancers were imaged exploiting tumour autofluorescence. Mapped biopsies were obtained from areas imaged determining a sensitivity of 100% and specificity of 80%. Autofluorescence imaging is an excellent method of detecting neoplasms of the aerodigestive tract.

The hamster cheek pouch model of carcinogenesis and chemoprevention.

The Syrian golden hamster cheek pouch carcinogenesis model is probably the best-known animal system for studying events involved in the development of premalignancy and malignancy in human oral cancer. Like the mouse skin model of carcinogenesis, the hamster cheek pouch model provides data on the effect of carcinogens, promoters, and chemopreventive agents, which makes both these models very useful in selecting chemopreventive agents for human cancer intervention studies (1–8). Our first approach to understanding the important early events that occur in the hamster cheek pouch model of carcinogenesis was to compare this model with the mouse skin model, in which a number of critical events have already been well characterized (9–11). The carcinogenesis studies in the hamster cheek pouch were carried out using multiple applications of 7,12-dimethylbenz[a] an thracene (DMBA) (0.5% in mineral oil, 3 times a week). This protocol induced a hyperplastic response in the pouch epithelium after only a few applications, followed by the appearance after 6–8 weeks of treatment of a variety of dysplastic lesions resembling human premalignant lesions. Benign and malignant tumors (papillomas and squamous cell carcinomas [SCCs]) started to develop after 10 weeks of treatment (12,13).

Modulation of Acute Allergic Inflammation by Prostaglandins

In vivo microscopy of the hamster cheek pouch microvasculature of sensitised animals was used for in vivo quantification of mediator release and the dynamic microcirculatory changes during immunologically induced acute mast cell-dependent inflammation. The evoked micro-vascular allergic reaction is probably IgE mediated and includes vasoconstriction followed by partially prostaglandin-dependent vasodilatation and immediate histamine-dependent plasma extravasation. The histamine-independent phase of plasma leakage is associated with leucocyte accumulation and is predominantly mediated by leukotrienes. Vasodilating prostaglandins [e.g. PGE2 (dinoprostone) and PGI2 (epoprostenol)] exert both pro- and anti-inflammatory actions, i.e. blood flow-dependent enhancement of inflammatory mediator action (oedema formation and leucocyte emigration) on one hand, and blood flow-independent suppression of mediator release on the other. In the hamster cheek pouch model of allergic inflammation, inhibition of mediator release by endogenous prostaglandins predominates. However, the final outcome of these opposite actions of vasodilating prostanoids is likely to vary with differences in experimental design. Accordingly, such a dual prostaglandin action may contribute to the understanding of the variable results of studies where NSAIDs or prostaglandins are used to modify different types of inflammation.

Verdins in photodynamic therapy of squamous cell carcinoma

Photodynamic therapy (PDT) is a relatively new treatment modality employing photoactive drugs in combination with light to destroy malignant tissue. Porphyrins (ie, hematoporphyrin derivative and dihematoporphyrin ether) have been the most thoroughly investigated photoactive drugs. The primary limitation of the use of porphyrins in PDT is the shallow depth of effective tumor kill. Each photoactive drug is activated maximally by light of a particular wavelength, and longer wavelengths are able to penetrate tissue to a greater depth. Hematoporphyrin derivative and its semipurified form, dihematoporphyrin ether, are activated by light at 630 nm, which penetrates tissue to a maximum of 8 mm. The search for more effective photosensitizers is under way. Verdins, photoactive compounds in the class of chlorins, have recently been synthesized with activating wavelengths near 700 nm. This longer activation wavelength should theoretically allow a greater depth of tumor kill. Verdins have been shown to be effective photosensitizers in a urothelial carcinoma model in rats. In this study, we investigated the effectiveness of these compounds on squamous cell carcinoma in the hamster cheek pouch model.

Leukotriene B4-induced permeability increase in postcapillary venules and its inhibition by three different antiinflammatory drugs

Leukotriene B4 (LTB4) is a potent chemotactic and chemokinetic substance that causes leukocyte accumulation and increases vascular permeability. We have used the hamster cheek pouch model to study the effect of some different antiinflammatory drugs on the LTB4-induced microvascular permeability. Intravascular fluorescein-labeled dextran (mol wt 150,000) was used as a tracer of macromolecular leakage, which was measured as the number of venular leaky sites and as efflux of the vascular tracer. Topical application of LTB4 (10(-8) M, 5 min) resulted in a reversible increase of the vascular permeability and could be repeated with 40-min intervals without any significant reduction in permeability response. The LTB4-induced response could be inhibited by budesonide (a glucocorticoid) given locally, by iloprost (a prostacyclin analog) given intravenously and by a combined local and intravenous treatment with terbutaline (a beta 2-receptor agonist) but not by local terbutaline treatment only.

Reduced thrombus formation in vivo after administration of pentoxifylline (Trental R)

The hamster cheek pouch model of experimental thrombosis in which thrombi are induced in the microvasculature by iontophoretical administration of adenosine diphosphate (ADP) was used to test the antithrombotic potential of pentoxifylline (Trental R). Single intraperitoneal injections of 5, 10 and 20 mg/kg pentoxifylline reduced thrombus formation by 20 to 50 % from 30 to 105 min following drug administration. The effect of a single application of 10 mg/kg was exceeded significantly (p < 0.05) by the higher rate of inhibition after repeated injections of the same dose given three times daily. This suggests a residual antithrombotic effect from the preceeding administrations.

New Dimensions in Photodynamic Therapy

Richard E. Hayden, MD, and coworkers of Washington University, St Louis, have been exploring, in the laboratory, the role of photodynamic therapy in the treatment of squamous cell carcinoma. At the annual meeting of the American Academy of Otolaryngology–Head and Neck Surgery, Washington, DC, Sept 25-29, 1988, they reported that they have been utilizing a hamster cheek pouch squamous cell carcinoma model induced with dimethylbenzanthracene, and comparing the in vivo effectiveness of dihematoporphyrin ether (DHE), heretofore the standard photosensitizer, with a newer group of compounds: the verdins. They feel that the hamster cheek pouch model is a good one in that it utilizes an immunocompetent host. They point out, however, the labor intensiveness of actually inducing the tumors. The verdins have a theoretic superiority in that they are activated at light wavelengths of approximately 700 nm, a somewhat longer wavelength than that used to activate DHE. This would be expected

Toluidine blue staining for detection of oral premalignant lesions and carcinomas.

The discriminative value of toluidine blue vital staining for detecting oral premalignant lesions and carcinomas was tested in the hamster DMBA buccal pouch model. The stain technique was further tested for specificity using the turpentine liquid petrolatum (TLP) hamster cheek pouch model for hyperplasia. Although carcinomas frequently exhibited toluidine blue staining, a 27.8% false negative result was noted. Premalignant lesions (dysplasia and carcinoma in situ) seldom retained toluidine blue stain and yielded a histologically confirmed (95.2%) false negative result. DMBA induced papillomas yielded a 5% false positive result. The TLP model failed to produce either clinically or histologically evident hyperplastic/hyperkeratotic lesions.

Marked enhancement in antithrombotic activity of isocarbacyclin following its incorporation into lipid microspheres

Isocarbacyclin, (+)-9(0)-methano- Δ 6(9 α) -PGI 1 (TEI 7165) and its methyl ester (TEI 9090) were incorporated in lipid microspheres (LM) with a diameter of 0.2 μm, in an attempt to increase their efficacy, possibly by way of targeting the drugs to the site of vascular damage. When the two LM-preparations were incubated in 2% bovine serum albumin solution, it was shown that TEI 7165 was slow. rapidly from LM, while the release of TEI 9090 was slow. Thus, TEI 9090 in LM, injected intravenously, may not be released largely in plasma before the distribution of LM to the target sites. The antithrombotic activity of the LM preparation of TEI 9090 was then compared with that of TEI 9090 as such in the hamster cheek pouch model. It was found that TEI 9090 incorporated in LM was more than 500 times more potent as an inhibitor of ADP-induced thrombus growth. These data suggest that prostacyclin analogues incorporated in LM may be used safely as potent antithrombotic agents in the clinical application.

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Isocarbacyclin (TEI 7165), an analogue of prostacyclin, and its methylester (TEI 9090) were incorporated in lipid microspheres (LM) with a diameter of 0.2μm, in an attempt to increase the efficacy, probably by way of targeting the drugs to the vessel wall. When the two LM-preparations were incubated in 2% BSA-saline, it was shown that TEI 9090 was released from LM much more slowly than TEI 7165. It indicates that TEI 9090 in LM, injected intravenously, may not be released largely in plasma, and delivered to the target sites.Compared with TEI 9090 as such, TEI 9090 incorporated in LM was more than 500 times more potent as an inhibitor of ADP-induce thrombus growth in the hamster cheek pouch model. These data suggest that prostacyclin analogues incorporated in LM may be used safely as potent antithrombotic agents in the clinical application.

Acute tissue reactions to potassium alginate with and without colour/ flavour additives

The acute tissue reactions to potassium alginate, locally applied to a microvascular bed, were studied with the use of the vital microscopic hamster cheek pouch model combined with correlative histology. This experimental model permitted us to study microvascular permeability, blood flow, vessel diameters and leucocyte adhesion to vessel walls intravitally, and leucocyte migration and mastcell degranulation histologically. Deionized water alone and potassium alginate with flavour and colour mixed in saline was found to cause severe microvascular alterations, while potassium alginate, without flavour and colour, but mixed in saline and applied to the microvasculature resulted in a minor inflammatory reaction.

Diffusion during dehydrogenase reactions: the effects of intermediate electron acceptors.

A hamster cheek pouch model has been used to study the diffusion of reactants from the epithelium into adjacent muscle and connective tissue during the histochemical demonstration of glucose-6-phosphate dehydrogenase activity. The effects of the addition of intermediate electron acceptors to the incubation medium varied considerably from one acceptor to another, but were independent of the grade of polyvinyl alcohol incorporated into the medium. Menadione was the least effective intermediate both in transferring reducing equivalents from the primary dehydrogenase to Neotetrazolium chloride and in preventing diffusion. Phenazine methosulphate, Methylene Blue and Thionin were more efficient intermediates. Nevertheless, considerable diffusion occurred in the presence of Phenazine methosulphate, although very little diffusion was detectable with either of the thiazine dyes. It is suggested that these differences are related to different modes and sites of action of the carriers.