The hamster cheek pouch model for field cancerization studies

Serum Raman spectroscopy: Evaluation of tumour load variations in experimental carcinogenesis

Several serum Raman spectroscopy (RS) studies have demonstrated its potential as an oral cancer screening tool. This study investigates influence of low tumour load (LTL) and high tumour load (HTL) on serum RS using hamster buccal pouch model of experimental oral carcinogenesis. Sera of untreated control, LTL, and HTL groups at week intervals during malignant transformation were employed. Serum Raman spectra were subjected to multivariate analyses-principal component analysis, principal component-based linear discriminant analysis (for stratification of study groups), and multivariate curve resolution-alternating least squares (MCR-ALS) (to comprehend biomolecular differences). Multivariate analysis revealed misclassifications between LTL and HTL at all week intervals. MCR-ALS components showed statistically significant abundances between control versus LTL and control versus HTL, but could not discern LTL and HTL. MCR-ALS components exhibited spectral mixtures of proteins, lipids, heme and nucleic acids. Thus, these findings support use of serum RS as a screening tool as varying tumour load is not a confounding factor influencing the technique.

Using the photon isoeffective dose formalism to compare and combine BNCT and CIRT in a head and neck tumour

Boron Neutron Capture Therapy (BNCT) is a radiotherapy technique based on the enrichment of tumour cells with suitable 10-boron concentration and on subsequent neutron irradiation. Low-energy neutron irradiation produces a localized deposition of radiation dose caused by boron neutron capture reactions. Boron is vehiculated into tumour cells via proper borated formulations, able to accumulate in the malignancy more than in normal tissues. The neutron capture releases two high-LET charged particles (i.e., an alpha particle and a lithium ion), losing their energy in a distance comparable to the average dimension of one cell. Thus BNCT is selective at the cell level and characterized by high biological effectiveness. As the radiation field is due to the interaction of neutrons with the components of biological tissues and with boron, the dosimetry requires a formalism to express the absorbed dose into photon-equivalent units. This work analyzes a clinical case of an adenoid cystic carcinoma treated with carbon-ion radiotherapy (CIRT), located close to optic nerve and deep-seated as a practical example of how to apply the formalism of BNCT photon isoeffective dose and how to evaluate the BNCT dose distribution against CIRT. The example allows presenting different dosimetrical and radiobiological quantities and drawing conclusions on the potential of BNCT stemming on the clinical result of the CIRT. The patient received CIRT with a dose constraint on the optic nerve, affecting the peripheral part of the Planning Target Volume (PTV). After the treatment, the tumour recurred in this low-dose region. BNCT was simulated for the primary tumour, with the goal to calculate the dose distribution in isoeffective units and a Tumour Control Probability (TCP) to be compared with the one of the original treatment. BNCT was then evaluated for the recurrence in the underdosed region which was not optimally covered by charged particles due to the proximity of the optic nerve. Finally, a combined treatment consisting in BNCT and carbon ion therapy was considered to show the consistency and the potential of the model. For the primary tumour, the photon isoeffective dose distribution due to BNCT was evaluated and the resulted TCP was higher than that obtained for the CIRT. The formalism produced values that are consistent with those of carbon-ion. For the recurrence, BNCT dosimetry produces a similar TCP than that of primary tumour. A combined treatment was finally simulated, showing a TCP comparable to the BNCT-alone with overall dosimetric advantage in the most peripheral parts of the treatment volume. Isoeffective dose formalism is a robust tool to analyze BNCT dosimetry and to compare it with the photon-equivalent dose calculated for carbon-ion treatment. This study introduces for the first time the possibility to combine the dosimetry obtained by two different treatment modalities, showing the potential of exploiting the cellular targeting of BNCT combined with the precision of charged particles in delivering an homogeneous dose distribution in deep-seated tumours.

Optimizing Boron Neutron Capture Therapy (BNCT) to Treat Cancer: An Updated Review on the Latest Developments on Boron Compounds and Strategies

Boron neutron capture therapy (BNCT) is a tumor-selective particle radiotherapy. It combines preferential boron accumulation in tumors and neutron irradiation. The recent initiation of BNCT clinical trials employing hospital-based accelerators rather than nuclear reactors as the neutron source will conceivably pave the way for new and more numerous clinical trials, leading up to much-needed randomized trials. In this context, it would be interesting to consider the implementation of new boron compounds and strategies that will significantly optimize BNCT. With this aim in mind, we analyzed, in this review, those articles published between 2020 and 2023 reporting new boron compounds and strategies that were proved therapeutically useful in in vitro and/or in vivo radiobiological studies, a critical step for translation to a clinical setting. We also explored new pathologies that could potentially be treated with BNCT and newly developed theranostic boron agents. All these radiobiological advances intend to solve those limitations and questions that arise during patient treatment in the clinical field, with BNCT and other therapies. In this sense, active communication between clinicians, radiobiologists, and all disciplines will improve BNCT for cancer patients, in a cost- and time-effective way.

Understanding the process of angiogenesis in regenerating earthworm

Developing blood vessels from the existing vasculature is vital for the growth of the organism, as well as for systematic wound healing and the repair process. In this study, we investigated the role of angiogenesis during the regeneration process in the earthworm, Eudrilus eugeniae, animal model. Briefly, the morphological examination of blood vessels in juvenile and mature worms is documented, along with the development of new blood vessels in regenerating blastema. However, in vivo and in vitro experiments with juvenile worms revealed that geraniol retards blastemal regeneration growth with undeveloped blood vessels, as compared to the control. The results of qRT-PCR, western blotting, and immunohistochemistry confirmed a reduced expression of VEGFR2 and WNT5A in the day 3 regenerating blastema of geraniol-treated worms, as compared to the control. We conclude that geraniol acts as a potent natural inhibitor of angiogenesis, thereby retarding the regeneration process in earthworms. In addition, for studying angiogenesis and screening effective angiogenesis inhibitors as drug candidates, the earthworm is an ambient animal model system.

Syrian hamster as an ideal animal model for evaluation of cancer immunotherapy

Cancer immunotherapy (CIT) has emerged as an exciting new pillar of cancer treatment. Although benefits have been achieved in individual patients, the overall response rate is still not satisfactory. To address this, an ideal preclinical animal model for evaluating CIT is urgently needed. Syrian hamsters present similar features to humans with regard to their anatomy, physiology, and pathology. Notably, the histological features and pathological progression of tumors and the complexity of the tumor microenvironment are equivalent to the human scenario. This article reviews the current tumor models in Syrian hamster and the latest progress in their application to development of tumor treatments including immune checkpoint inhibitors, cytokines, adoptive cell therapy, cancer vaccines, and oncolytic viruses. This progress strongly advocates Syrian hamster as an ideal animal model for development and assessment of CIT for human cancer treatments. Additionally, the challenges of the Syrian hamster as an animal model for CIT are also discussed.

Boron Neutron Capture Therapy (BNCT) Mediated by Maleimide-Functionalized Closo-Dodecaborate Albumin Conjugates (MID:BSA) for Oral Cancer: Biodistribution Studies and In Vivo BNCT in the Hamster Cheek Pouch Oral Cancer Model

Background: BNCT (Boron Neutron Capture Therapy) is a tumor-selective particle radiotherapy that combines preferential boron accumulation in tumors and neutron irradiation. Although p-boronophenylalanine (BPA) has been clinically used, new boron compounds are needed for the advancement of BNCT. Based on previous studies in colon tumor-bearing mice, in this study, we evaluated MID:BSA (maleimide-functionalized closo-dodecaborate conjugated to bovine serum albumin) biodistribution and MID:BSA/BNCT therapeutic effect on tumors and associated radiotoxicity in the hamster cheek pouch oral cancer model. Methods: Biodistribution studies were performed at 30 mg B/kg and 15 mg B/kg (12 h and 19 h post-administration). MID:BSA/BNCT (15 mg B/kg, 19 h) was performed at three different absorbed doses to precancerous tissue. Results: MID:BSA 30 mg B/kg protocol induced high BSA toxicity. MID:BSA 15 mg B/kg injected at a slow rate was well-tolerated and reached therapeutically useful boron concentration values in the tumor and tumor/normal tissue ratios. The 19 h protocol exhibited significantly lower boron concentration values in blood. MID:BSA/BNCT exhibited a significant tumor response vs. the control group with no significant radiotoxicity. Conclusions: MID:BSA/BNCT would be therapeutically useful to treat oral cancer. BSA toxicity is a consideration when injecting a compound conjugated to BSA and depends on the animal model studied.

Emerging approaches of wound healing in experimental models of high-grade oral mucositis induced by anticancer therapy

Clinical guidelines for oral mucositis (OM) still consist in palliative care. Herein, we summarize cellular and molecular mechanisms of OM ulceration in response to chemical therapies in animal models. We discuss evidenced anti-inflammatory and anti-oxidant drugs which have not been ever used for OM, such as synthetic peptides as well as cell therapy with mesenchymal stem cells; amniotic membranes, mucoadhesive polymers loaded with anti-inflammatory agents and natural or synthetic electrospun. These approaches have been promising to allow the production of drug-loaded membranes, scaffolds for cells encapsulation or guided tissue regeneration.

Photodynamic therapy in the treatment of oral squamous cell carcinoma - The state of the art in preclinical research on the animal model

BACKGROUND

Oral cavity squamous cell carcinoma is a common cancer of the head and neck region. Due to the frequency of diagnoses, high rate of mortality, mutilating nature of classic therapy and numerous complications, new methods of treatment are being sought. One promising solution for treatment that is utilized in many fields of oncology is photodynamic therapy. The purpose of this article is to present a general overview of the use of photodynamic therapy in preclinical in vivo studies on the animal model.

MATERIAL AND METHODS

A literature search for articles corresponding to the topic of this review was performed using the PubMed and MEDLINE databases using the following keywords: 'oral cavity squamous cell carcinoma,' 'photodynamic therapy,' 'photosensitizer(s),' 'in vivo', and 'animal model'.

RESULTS

Based on the literature review, the two most used animal models can be distinguished in research on the use of photodynamic therapy for oral squamous cell carcinoma. Studies mainly focus on the evaluation of tumor growth inhibition after using therapies with various photosensitizers on the murine or hamster cheek pouch models.

CONCLUDING REMARKS

The animal model is a part of preclinical research. Unfortunately, each of the models has its limitations, so it is difficult to extrapolate the results to clinical trials.

Optimization of the classical oral cancerization protocol in hamster to study oral cancer therapy

OBJECTIVE(S)

The hamster carcinogenesis model recapitulates oral oncogenesis. Dimethylbenz[a]anthracene (DMBA) cancerization induces early severe mucositis, affecting animal's welfare and causing tissue loss and pouch shortening. "Short" pouches cannot be everted for local irradiation for boron neutron capture therapy (BNCT). Our aim was to optimize the DMBA classical cancerization protocol to avoid severe mucositis, without affecting tumor development. We evaluated BNCT in animals cancerized with this novel protocol.

MATERIALS AND METHODS

We studied: Classical cancerization protocol (24 applications) and Classical with two interruptions (completed at the end of the cancerization protocol). BNCT mediated by boronophenylalanine (BPA) was performed in both groups.

RESULTS

The twice-interrupted group exhibited a significantly lower percentage of animals with severe mucositis versus the non-interrupted group (17% versus 71%) and a significantly higher incidence of long pouches (100% versus 53%). Tumor development and the histologic characteristics of tumor and precancerous tissue were not affected by the interruptions. For both groups, overall tumor response was more than 80%, with a similar incidence of BNCT-induced severe mucositis.

CONCLUSION(S)

The twice-interrupted protocol reduced severe mucositis during cancerization without affecting tumor development. This favored the animal's welfare and reduced the number of animals to be cancerized for our studies, without affecting BNCT response.

Nucleolar organizer regions in human oral verrucous carcinoma and adjacent lining epithelium

The epithelium adjacent to an oral squamous cell carcinoma is at risk of undergoing precancerous changes. Even after such changes occur, however, the adjacent epithelium remains histologically similar to normal mucosa. We investigated five argyrophilic nucleolar organizer region (AgNOR)-related features in samples of oral verrucous carcinoma (VeCa) and their corresponding adjacent lining epithelium (adj. VeCa). Morphometric characteristics of AgNORs in oral adj. VeCa and oral VeCa were compared to normal mucosa epithelium, squamous cell carcinoma and oral mucosa epithelium adjacent to squamous cell carcinoma findings that we published earlier. Although adj. VeCa and normal oral mucosa were histologically similar, total AgNOR volume differentiated adj. VeCa from normal oral mucosa, but revealed no significant difference between VeCa and adj. VeCa. Total AgNOR volume/nuclear volume discriminated VeCa from adj. VeCa and normal oral mucosa. Certain AgNOR parameters provide a complementary tool for discriminating VeCa from adj. VeCa and normal oral mucosa, and also for detecting incipient malignant changes in epithelium adjacent to VeCa. Use of the AgNOR technique is cost-effective, because it can be performed on paraffin sections.

DMBA-Induced Oral Carcinoma in Syrian Hamster: Increased Carcinogenic Effect by Dexamethasone Coexposition

Objectives

To investigate the effect of systemic administration of the immunosuppressant dexamethasone (DM) while inducing hamster buccal pouch DMBA carcinogenesis. Materials and Methods. Two different experiments were performed. In the first experiment, hamsters' right buccal pouches in group A (n = 10) were painted three times per week with 7,12-dimethylbenzanthracene (DMBA) 0.5%, while pouches of animals in group B (n = 10) were painted three times per week with 7,12-dimethylbenzanthracene (DMBA) 0.5%, while pouches of animals in group B (

Results

The time of macroscopic neoplasm development was reduced when DM-DMBA coexposition was employed, finding tumors after 10–12 weeks of exposition. In addition, the frequency of histopathological lesions was higher.

Conclusion

Immunomodulatory action of dexamethasone may reduce the time of oral squamous cell carcinoma (OSCC) induction and may increase the incidence of neoplasms developed.

Electroporation optimizes the uptake of boron-10 by tumor for boron neutron capture therapy (BNCT) mediated by GB-10: a boron biodistribution study in the hamster cheek pouch oral cancer model

Boron neutron capture therapy (BNCT) is a promising cancer binary therapy modality that utilizes the nuclear capture reaction of thermal neutrons by boron-10 resulting in a localized release of high- and low-linear energy transfer (LET) radiation. Electrochemotherapy (ECT) is based on electroporation (EP) that induces opening of pores in cell membranes, allowing the entry of compounds. Because EP is applied locally to a tumor, the compound is incorporated preferentially by tumor cells. Based on the knowledge that the therapeutic success of BNCT depends centrally on the boron content in tumor and normal tissues and that EP has proven to be an excellent facilitator of tumor biodistribution of an anti-tumor agent, the aim of this study was to evaluate if EP can optimize the delivery of boronated compounds. We performed biodistribution studies and qualitative microdistribution analyses of boron employing the boron compound sodium decahydrodecaborate (GB-10) + EP in the hamster cheek pouch oral cancer model. Syrian hamsters with chemically induced exophytic squamous cell carcinomas were used. A typical EP treatment was applied to each tumor, varying the moment of application with respect to the administration of GB-10 (early or late). The results of this study showed a significant increase in the absolute and relative tumor boron concentration and optimization of the qualitative microdistribution of boron by the use of early EP + GB-10 versus GB-10 without EP. This strategy could be a tool to improve the therapeutic efficacy of BNCT/GB-10 in vivo.

Different oral cancer scenarios to personalize targeted therapy: Boron Neutron Capture Therapy translational studies

Boron neutron capture therapy (BNCT) is a targeted therapy, which consists of preferential accumulation of boron carriers in tumor followed by neutron irradiation. Each oral cancer patient has different risks of developing one or more carcinomas and/or oral mucositis induced after treatment. Our group proposed the hamster oral cancer model to study the efficacy of BNCT and associated mucositis. Translational studies are essential to the advancement of novel boron delivery agents and targeted strategies. Herein, we review our work in the hamster model in which we studied BNCT induced mucositis using three different cancerization protocols, mimicking three different clinical scenarios. The BNCT-induced mucositis increases with the aggressiveness of the carcinogenesis protocol employed, suggesting that the study of different oral cancer patient scenarios would help to develop personalized therapies.

Amifostine reduces inflammation and protects against 5-fluorouracil-induced oral mucositis and hyposalivation

Oral mucositis (OM) is a common and dose-limiting side effect of cancer treatment, including 5-fluorouracil (5-FU) and radiotherapy. The efficacy of the therapeutic measures to prevent OM is limited and disease prevention is not fully observable. Amifostine is a cytoprotective agent with a described anti-inflammatory potential. It is clinically used to reduce radiotherapy and chemotherapy-associated xerostomia. This study investigated the protective effect of amifostine on an experimental model of OM. Hamsters were divided into six groups: saline control group (5 mL/kg), mechanical trauma (scratches) of the right cheek pouch; 5-FU (60 and 40 mg/kg, ip, respectively, administered on days 1 and 2); amifostine (12.5, 25, or 50 mg/kg) + 5-FU + scratches. Salivation rate was assessed and the animals were euthanized on day 10 for the analysis of macroscopic and microscopic injury by scores. Tissue samples were harvested for the measurement of neutrophil infiltration and detection of inflammatory markers by ELISA and immunohistochemistry. 5-FU induced pronounced hyposalivation, which was prevented by amifostine (P<0.05). In addition, 5-FU injection caused pronounced tissue injury accompanied by increased neutrophil accumulation, tumor necrosis factor-alpha (TNF-α), and interleukin-1 beta (IL-1β) tissue levels, and positive immunostaining for TNF-α, IL-1β, and inducible nitric oxide synthase (iNOS). Interestingly, amifostine prevented the inflammatory reaction and consequently improved macroscopic and microscopic damage (P<0.05 vs 5-FU group). Amifostine reduced inflammation and protected against 5-FU-associated oral mucositis and hyposalivation.

Sextuple Tumors in Head and Neck Area: Evidence of Field Cancerization

Background

Field cancerization is a phenomenon in which prolonged exposure to carcinogens induces changes throughout the epithelium leaving the field ready for the appearance of premalignant or malignant lesions. These alterations can promote the development of multiple carcinomas and explain the appearance of recurrences and second primary tumors. The objective of this study was to report the case of a patient who developed six oral cavity tumors in five years of treatment and, also, demonstrate the immunohistochemical changes for p53 and Ki-67, routinely used to assess dysplasic regions.

Case Report

When altered, p53 and Ki-67 suggest the presence of field cancers, an area with genetically altered cells, presenting a high risk of developing premalignant and malignant lesions. This phenomenon explains the recurrence of malignant neoplasms after tumor resections.

Conclusion

In addition, early identification of potentially malignant lesions in cases of second primary tumors is essential for effective treatment and patient survival, which usually have an unwelcoming prognosis.

Smokeless tobacco impacts oral microbiota in a Syrian Golden hamster cheek pouch carcinogenesis model

The use of smokeless tobacco products (STPs) can cause many serious health problems. The oral microbiota plays important roles in oral and systemic health, and the disruption in the oral microbial population is linked to periodontal disease and other health problems. To assess the impact of smokeless tobacco on oral microbiota in vivo, high-throughput sequencing was used to examine the oral microbiota present in Syrian Golden hamster cheek pouches. Sixteen hamsters were divided into four groups and treated with the STP Grizzly snuff (0, 2.5, 25, or 250 mg) twice daily for 4 weeks. After 0, 1, 2, 3, and 4 weeks of treatment, bacterial genomic DNA was extracted from oral swabs sampled from the cheek pouches of the hamsters. The oral bacterial communities present in different hamster groups were characterized by sequencing the hypervariable regions V1-V2 and V4 of 16S rRNA using the Illumina MiSeq platform. Fifteen phyla, 27 classes, 59 orders, 123 families, and 250 genera were identified from 4,962,673 sequence reads from the cheek pouch samples. The bacterial diversity and taxonomic abundances for the different treatment groups were compared to the non-treated hamsters. Bacterial diversity was significantly decreased after 4 weeks of exposure to 2.5 mg, and significantly increased by exposure to 250 mg STP. Treatment with 250 mg STP significantly increased Firmicutes, transiently increased Cyanobacteria and TM7, and decreased Bacteroidetes and Fusobacteria compared to the control group. At the genus level, 4 weeks of administration of 250 mg STP significantly increased Granulicatella, Streptococcus, Oribacterium, Anaerococcus, Acidaminococcus, Actinomyces, Eubacterium, Negativicoccus, and Staphylococcus, and decreased Bacteroides, Buleidia, Dialister, and Leptotrichia, and transiently decreased Arcanobacterium compared to the control group. For the first time, an animal model was used for evaluating the effects of STP on oral microbiota by metagenomic sequencing. Our results provide a view of the shift of the oral microbiota in response to STP exposure in Syrian Golden hamster. Our findings indicate that the use of smokeless tobacco significantly disrupts the oral microbiota.

Boron neutron capture therapy (BNCT) translational studies in the hamster cheek pouch model of oral cancer at the new "B2" configuration of the RA-6 nuclear reactor

Boron neutron capture therapy (BNCT) is based on selective accumulation of B-10 carriers in tumor followed by neutron irradiation. We demonstrated, in 2001, the therapeutic effect of BNCT mediated by BPA (boronophenylalanine) in the hamster cheek pouch model of oral cancer, at the RA-6 nuclear reactor. Between 2007 and 2011, the RA-6 was upgraded, leading to an improvement in the performance of the BNCT beam (B2 configuration). Our aim was to evaluate BPA-BNCT radiotoxicity and tumor control in the hamster cheek pouch model of oral cancer at the new "B2" configuration. We also evaluated, for the first time in the oral cancer model, the radioprotective effect of histamine against mucositis in precancerous tissue as the dose-limiting tissue. Cancerized pouches were exposed to: BPA-BNCT; BPA-BNCT + histamine; BO: Beam only; BO + histamine; CONTROL: cancerized, no-treatment. BNCT induced severe mucositis, with an incidence that was slightly higher than in "B1" experiments (86 vs 67%, respectively). BO induced low/moderate mucositis. Histamine slightly reduced the incidence of severe mucositis induced by BPA-BNCT (75 vs 86%) and prevented mucositis altogether in BO animals. Tumor overall response was significantly higher in BNCT (94-96%) than in control (16%) and BO groups (9-38%), and did not differ significantly from the "B1" results (91%). Histamine did not compromise BNCT therapeutic efficacy. BNCT radiotoxicity and therapeutic effect at the B1 and B2 configurations of RA-6 were consistent. Histamine slightly reduced mucositis in precancerous tissue even in this overly aggressive oral cancer model, without compromising tumor control.

Objective Detection of Oral Carcinoma with Multispectral Fluorescence Lifetime Imaging In Vivo

Successful early detection and demarcation of oral carcinoma can greatly impact the associated morbidity and mortality rates. Current methods for detection of oral cancer include comprehensive visual examination of the oral cavity, typically followed by tissue biopsy. A noninvasive means to guide the clinician in making a more objective and informed decision toward tissue biopsy can potentially improve the diagnostic yield of this process. To this end, we investigate the potential of fluorescence lifetime imaging (FLIM) for objective detection of oral carcinoma in the hamster cheek pouch model of oral carcinogenesis in vivo. We report that systematically selected FLIM features can differentiate between low-risk (normal, benign and low-grade dysplasia) and high-risk (high-grade dysplasia and cancer) oral lesions with sensitivity and specificity of 87.26% and 93.96%, respectively. We also show the ability of FLIM to generate "disease" maps of the tissue which can be used to evaluate relative risk of neoplasia. The results demonstrate the potential of multispectral FLIM with objective image analysis as a noninvasive tool to guide comprehensive oral examination.

Zebrafish as an Emerging Model Organism to Study Angiogenesis in Development and Regeneration

Angiogenesis is the process through which new blood vessels are formed from preexisting ones and plays a critical role in several conditions including embryonic development, tissue repair and disease. Moreover, enhanced therapeutic angiogenesis is a major goal in the field of regenerative medicine and efficient vascularization of artificial tissues and organs is one of the main hindrances in the implementation of tissue engineering approaches, while, on the other hand, inhibition of angiogenesis is a key therapeutic target to inhibit for instance tumor growth. During the last decades, the understanding of cellular and molecular mechanisms involved in this process has been matter of intense research. In this regard, several in vitro and in vivo models have been established to visualize and study migration of endothelial progenitor cells, formation of endothelial tubules and the generation of new vascular networks, while assessing the conditions and treatments that either promote or inhibit such processes. In this review, we address and compare the most commonly used experimental models to study angiogenesis in vitro and in vivo. In particular, we focus on the implementation of the zebrafish (Danio rerio) as a model to study angiogenesis and discuss the advantages and not yet explored possibilities of its use as model organism.

A Latin American perspective of periodontology

Periodontal diseases occur worldwide, and Latin American populations are significantly affected by different manifestations of periodontal disease. The interest in periodontics and periodontal therapy first developed in the early 1930s in the southernmost countries of Latin America, and spread, as the years went by, throughout the region. Today, periodontal research is vibrant in Latin America. The aim of this volume of Periodontology 2000 was to present an overview of the periodontal research currently being performed in different countries of Latin America. The epidemiology of periodontal diseases in adults, children and adolescents, and the pathogenesis of such diseases (including microbiological characteristics and risk factors), are discussed. The role of systemic antibiotic therapy and the effect of smoking are discussed in relation to the progression and the treatment of periodontitis. In addition, the benefit of lasers in periodontal therapy is evaluated. Latin American research groups have been active in exploring new venues of regenerative periodontal treatment, addressing the role of cementum proteins, growth factors and oral mesenchymal stem cells in tissue engineering. Finally, basic research to study cancerization is reported.