Rajiv S. Desai

Regenerative Capacity of Old Muscle Stem Cells Declines without Significant Accumulation of DNA Damage

The performance of adult stem cells is crucial for tissue homeostasis but their regenerative capacity declines with age, leading to failure of multiple organs. In skeletal muscle this failure is manifested by the loss of functional tissue, the accumulation of fibrosis, and reduced satellite cell-mediated myogenesis in response to injury. While recent studies have shown that changes in the composition of the satellite cell niche are at least in part responsible for the impaired function observed with aging, little is known about the effects of aging on the intrinsic properties of satellite cells. For instance, their ability to repair DNA damage and the effects of a potential accumulation of DNA double strand breaks (DSBs) on their regenerative performance remain unclear. This work demonstrates that old muscle stem cells display no significant accumulation of DNA DSBs when compared to those of young, as assayed after cell isolation and in tissue sections, either in uninjured muscle or at multiple time points after injury. Additionally, there is no significant difference in the expression of DNA DSB repair proteins or globally assayed DNA damage response genes, suggesting that not only DNA DSBs, but also other types of DNA damage, do not significantly mark aged muscle stem cells. Satellite cells from DNA DSB-repair-deficient SCID mice do have an unsurprisingly higher level of innate DNA DSBs and a weakened recovery from gamma-radiation-induced DNA damage. Interestingly, they are as myogenic in vitro and in vivo as satellite cells from young wild type mice, suggesting that the inefficiency in DNA DSB repair does not directly correlate with the ability to regenerate muscle after injury. Overall, our findings suggest that a DNA DSB-repair deficiency is unlikely to be a key factor in the decline in muscle regeneration observed upon aging.

Genome-wide expression and copy number analysis identifies driver genes in gingivobuccal cancers.

The molecular mechanisms contributing to the development and progression of gingivobuccal complex (GBC) cancers—a sub‐site of oral cancer, comprising the buccal mucosa, the gingivobuccal sulcus, the lower gingival region, and the retromolar trigone–remain poorly understood. Identifying the GBC cancer‐related gene expression signature and the driver genes residing on the altered chromosomal regions is critical for understanding the molecular basis of its pathogenesis. Genome‐wide expression profiling of 27 GBC cancers with known chromosomal alterations was performed to reveal differentially expressed genes. Putative driver genes were identified by integrating copy number and gene expression data. A total of 315 genes were found differentially expressed (P ≤ 0.05, logFC > 2.0) of which 11 genes were validated by real‐time quantitative reverse transcriptase‐PCR (qRT‐PCR) in tumors (n = 57) and normal GBC tissues (n = 18). Overexpression of LY6K, in chromosome band 8q24.3, was validated by immunohistochemical (IHC) analysis. We found that 78.5% (2,417/3,079) of the genes located in regions of recurrent chromosomal alterations show copy number dependent expression indicating that copy number alteration has a direct effect on global gene expression. The integrative analysis revealed BIRC3 in 11q22.2 as a candidate driver gene associated with poor clinical outcome. Our study identified previously unreported differentially expressed genes in a homogeneous subtype of oral cancer and the candidate driver genes that may contribute to the development and progression of the disease.

Downregulation of keratin 76 expression during oral carcinogenesis of human, hamster and mouse

Background Keratins are structural marker proteins with tissue specific expression; however, recent reports indicate their involvement in cancer progression. Previous study from our lab revealed deregulation of many genes related to structural molecular integrity including KRT76. Here we evaluate the role of KRT76 downregulation in oral precancer and cancer development. Methods We evaluated KRT76 expression by qRT-PCR in normal and tumor tissues of the oral cavity. We also analyzed K76 expression by immunohistochemistry in normal, oral precancerous lesion (OPL), oral squamous cell carcinoma (OSCC) and in hamster model of oral carcinogenesis. Further, functional implication of KRT76 loss was confirmed using KRT76-knockout (KO) mice. Results We observed a strong association of reduced K76 expression with increased risk of OPL and OSCC development. The buccal epithelium of DMBA treated hamsters showed a similar trend. Oral cavity of KRT76-KO mice showed preneoplastic changes in the gingivobuccal epithelium while no pathological changes were observed in KRT76 negative tissues such as tongue. Conclusion The present study demonstrates loss of KRT76 in oral carcinogenesis. The KRT76-KO mice data underlines the potential of KRT76 being an early event although this loss is not sufficient to drive the development of oral cancers. Thus, future studies to investigate the contributing role of KRT76 in light of other tumor driving events are warranted.

Chromosomal Alterations and Gene Expression Changes Associated with the Progression of Leukoplakia to Advanced Gingivobuccal Cancer

We present an integrative genome-wide analysis that can be used to predict the risk of progression from leukoplakia to oral squamous cell carcinoma (OSCC) arising in the gingivobuccal complex (GBC). We find that the genomic and transcriptomic profiles of leukoplakia resemble those observed in later stages of OSCC and that several changes are associated with this progression, including amplification of 8q24.3, deletion of 8p23.2, and dysregulation of DERL3, EIF5A2, ECT2, HOXC9, HOXC13, MAL, MFAP5 and NELL2. Comparing copy number profiles of primary tumors with and without lymph-node metastasis, we identify alterations associated with metastasis, including amplifications of 3p26.3, 8q24.21, 11q22.1, 11q22.3 and deletion of 8p23.2. Integrative analysis reveals several biomarkers that have never or rarely been reported in previous OSCC studies, including amplifications of 1p36.33 (attributable to MXRA8), 3q26.31 (EIF5A2), 9p24.1 (CD274), and 12q13.2 (HOXC9 and HOXC13). Additionally, we find that amplifications of 1p36.33 and 11q22.1 are strongly correlated with poor clinical outcome. Overall, our findings delineate genomic changes that can be used in treatment management for patients with potentially malignant leukoplakia and OSCC patients with higher risk of lymph-node metastasis.

Altered immunohistochemical expression of mast cell tryptase and chymase in the pathogenesis of oral submucous fibrosis and malignant transformation of the overlying epithelium.

Mast cells (MCs) expressing serine proteases; tryptase and chymase, are associated with fibrosis in various diseases. However, little is known about their involvement in oral submucous fibrosis (OSF). Our goal was to evaluate the role of MC tryptase and chymase in the pathogenesis of OSF and its malignant transformation. Immunohistochemical expression of MC tryptase and chymase was evaluated in 20 cases of OSF, 10 cases of oral squamous cell carcinoma (OSCC) and 10 cases of healthy controls. Subepithelial zone of Stage 1 and 2 while deep zone of Stage 3 and 4 OSF demonstrated increased tryptase positive MCs. OSCC revealed a proportionate increase in tryptase and chymase positive MCs irrespective of areas of distribution. An altered balance in the subepithelial and deep distribution of tryptase and chymase positive MCs play an important role in the pathogenesis of OSF and its malignant transformation.

Evaluation of the diagnostic efficacy and spectrum of autofluorescence of benign, dysplastic and malignant lesions of the oral cavity using VELscope

OBJECTIVES Conventional oral examination and biopsy are the only reliable methods for the early detection of oral cancer at present. Autofluorescence examination of oral tissues using the VELscope has been suggested as an adjunctive tool for cancer detection and diagnosis. The aim of our study was to evaluate the efficacy of the VELscope in recognizing dysplastic and/or neoplastic changes in oral mucosal lesions that were identified on conventional oral examination. MATERIALS AND METHODS Two hundred patients with oral mucosal lesions were subjected to conventional oral examination followed by VELscope examination and their autofluorescence characteristics were compared with the histopathological diagnosis. The sensitivity, specificity, positive and negative predictive values of the VELscope examination was calculated. RESULTS The VELscope examination showed sensitivity and specificity values of 76% (95% CI: 54.87-90.64%) and 66.29% (95% CI: 58.76-73.24%) respectively while the positive and negative predictive values were 24.36% (95% CI: 19.22-30.36%) and 95.08% (95% CI: 90.52-97.51%) respectively. CONCLUSION The VELscope examination alone cannot provide a definitive diagnosis as to the presence of dysplastic tissue change. In spite of having a reasonable sensitivity, the high number of false-positive results limits its efficiency as an adjunct. However, a high negative predictive value can serve to alleviate patient anxiety regarding suspicious mucosal lesions in a general practice setting.

Multiple Calcifying Hyperplastic Dental Follicles: A Case Report and Literature Review

Enlarged follicles associated with multiple unerupted teeth always comprise an area of considerable interest for oral and maxillofacial surgeons. The condition of multiple calcifying hyperplastic dental follicles is extremely rare and is characterized by multiple unerupted teeth with abundant calcifications and odontogenic epithelial rests in the enlarged dental follicles. We report an interesting case of multiple calcifying hyperplastic dental follicles in a 16-year-old healthy male patient.

Calcifying Cystic Odontogenic Tumor in a 5-Year-Old Boy: A Case Report

The calcifying cystic odontogenic tumor (CCOT), formerly known as calcifying odontogenic cyst, is a rare developmental neoplasm/cyst of odontogenic epithelial origin with considerable histopathologic diversity and variable clinical behaviour. The occurrence of CCOT in the first decade of life is very uncommon. We report an interestingly rare variant of CCOT with ameloblastomatous proliferation affecting the mandibular left posterior region associated with an impacted permanent tooth in a 5-year-old boy.

Aggressive adenomatoid odontogenic tumor of the mandible: A rare case report and review of the literature

Adenomatoid odontogenic tumor (AOT) is a relatively rare and distinct odontogenic tumor that is exclusively odontogenic epithelium in origin. Although considerable numbers of reports are available with regard to the clinical and histological spectrum of AOT, very few have highlighted its rare aggressive nature. This article focuses on an AOT causing jaw swelling in the mandibular anterior region with cortical plate expansion and perforation, root resorption and paresthesia. The present case had remarkably unusual clinical and radiographic features that distinguished it from most conventional AOTs and supported its neoplastic nature.

Immunohistochemical characterization of stem cell and differentiation markers of the dental pulp of human natal teeth

Aim: Dental pulp stem cells, which are primarily derived from the pulp tissues of human teeth, have rarely been obtained from natal teeth. This study investigated the stem cell and differentiation markers of the dental pulp of natal teeth using immunohistochemistry. Materials & Methods: The pulp tissue from extracted natal teeth (n = 2) of a 20-day-old healthy male was examined for immunohistochemical expression of stem cell (Oct-4 and SOX 2) and differentiation markers (Nestin, CD 44, desmin, osteopontin and Ki- 67). Results: The pulp tissue of the natal teeth expressed immunopositivity for nestin, CD 44 and SOX2. Conclusion: Natal teeth, if preserved properly, could serve as sources of dental pulp stem cells that are an improvement on deciduous teeth.