Salivary gland gene therapy

Development of a Primary Human Cell Model for the Study of Human Cytomegalovirus Replication and Spread within Salivary Epithelium

Various aspects of human cytomegalovirus (HCMV) pathogenesis, including its ability to replicate in specific cells and tissues and the mechanism(s) of horizontal transmission, are not well understood, predominantly because of the strict species specificity exhibited by HCMV. Murine CMV (MCMV), which contains numerous gene segments highly similar to those of HCMV, has been useful for modeling some aspects of CMV pathogenesis; however, it remains essential to build relevant human cell-based systems to investigate how the HCMV counterparts function. The salivary gland epithelium is a site of persistence for both human and murine cytomegaloviruses, and salivary secretions appear to play an important role in horizontal transmission. Therefore, it is important to understand how HCMV is replicating within the glandular epithelial cells so that it might be possible to therapeutically prevent transmission. In the present study, we describe the development of a salivary epithelial model derived from primary human "salispheres." Initial infection of these primary salivary cells with HCMV occurs in a manner similar to that reported for established epithelial lines, in that gH/gL/UL128/UL130/UL131A (pentamer)-positive strains can infect and replicate, while laboratory-adapted pentamer-null strains do not. However, while HCMV enters the lytic phase and produces virus in salivary epithelial cells, it fails to exhibit robust spread throughout the culture and persists in a low percentage of salivary cells. The present study demonstrates the utility of these primary tissue-derived cells for studying HCMV replication in salivary epithelial cells in vitro IMPORTANCE Human cytomegalovirus (HCMV) infects the majority of the world's population, and although it typically establishes a quiescent infection with little to no disease in most individuals, the virus is responsible for a variety of devastating sequelae in immunocompromised adults and in developing fetuses. Therefore, identifying the viral properties essential for replication, spread, and horizontal transmission is an important area of medical science. Our studies use novel human salivary gland-derived cellular models to investigate the molecular details by which HCMV replicates in salivary epithelial cells and provide insight into the mechanisms by which the virus persists in the salivary epithelium, where it gains access to fluids centrally important for horizontal transmission.

Gene Therapy for Bone Defects in Oral and Maxillofacial Surgery: A Systematic Review and Meta-Analysis of Animal Studies

Craniofacial bone defects are challenging problems for maxillofacial surgeons over the years. With the development of cell and molecular biology, gene therapy is a breaking new technology with the aim of regenerating tissues by acting as a delivery system for therapeutic genes in the craniofacial region rather than treating genetic disorders. A systematic review was conducted summarizing the articles reporting gene therapy in maxillofacial surgery to answer the question: Was gene therapy successfully applied to regenerate bone in the maxillofacial region? Electronic searching of online databases was performed in addition to hand searching of the references of included articles. No language or time restrictions were enforced. Meta-analysis was done to assess significant bone formation after delivery of gene material in the surgically induced maxillofacial defects. The search identified 2081 articles, of which 57 were included with 1726 animals. Bone morphogenetic proteins were commonly used proteins for gene therapy. Viral vectors were the universally used vectors. Sprague-Dawley rats were the frequently used animal model in experimental studies. The quality of the articles ranged from excellent to average. Meta-analysis results performed on 21 articles showed that defects favored bone formation by gene therapy. Funnel plot showed symmetry with the absence of publication bias. Gene therapy is on the top list of innovative strategies that developed in the last 10 years with the hope of developing a simple chair-side protocol in the near future, combining improvement of gene delivery as well as knowledge of the molecular basis of oral and maxillofacial structures.

Xerostomia: current streams of investigation

Xerostomia is the subjective feeling of dry mouth, and it is often related to salivary hypofunction. Besides medication-related salivary hypofunction, Sjögren syndrome and head-and-neck radiation are two common etiologies that have garnered considerable attention. Approaches to treating and/or preventing salivary hypofunction in patients with these conditions will likely incorporate gene therapy, stem cell therapy, and tissue engineering. Advances in these disciplines are central to current research in the cure for xerostomia and will be key to eventual treatment.

Advances in salivary gland gene therapy - oral and systemic implications

INTRODUCTION

Much research demonstrates the feasibility and efficacy of gene transfer to salivary glands. Recently, the first clinical trial targeting a salivary gland was completed, yielding positive safety and efficacy results.

AREAS COVERED

There are two major disorders affecting salivary glands: radiation damage following treatment for head and neck cancers and Sjögren's syndrome (SS). Salivary gland gene transfer has also been employed in preclinical studies using transgenic secretory proteins for exocrine (upper gastrointestinal tract) and endocrine (systemic) applications.

EXPERT OPINION

Salivary gland gene transfer is safe and can be beneficial in humans. Applications to treat and prevent radiation damage show considerable promise. A first-in-human clinical trial for the former was recently successfully completed. Studies on SS suffer from an inadequate understanding of its etiology. Proof of concept in animal models has been shown for exocrine and endocrine disorders. Currently, the most promising exocrine application is for the management of obesity. Endocrine applications are limited, as it is currently impossible to predict if systemically required transgenic proteins will be efficiently secreted into the bloodstream. This results from not understanding how secretory proteins are sorted. Future studies will likely employ ultrasound-assisted and pseudotyped adeno-associated viral vector-mediated gene transfer.

Expression and secretion of human proinsulin-B10 from mouse salivary glands: implications for the treatment of type I diabetes mellitus

Adenovirus (Ad) mediated expression of therapeutic proteins from salivary glands can result in the delivery of biologically active proteins into the circulation where they impart their physiological function. In recent years, Ad vector delivery to salivary glands (SGs) has emerged as a viable option for gene therapy. Here, we engineered a variant of human proinsulin (hProinsulin-B10) into an Ad vector and demonstrated its ability to transduce cell lines, and express a bioactive protein that induces the phosphorylation of AKT, a key insulin signaling molecule. We also examined its expression in mice following delivery of the vector to the parotid gland (PTG), the submandibular gland (SMG) or to the liver via the tail vein and assessed transgenic protein expression and vector containment for each delivery method. In all cases, hProinsulin-B10 was expressed and secreted into the circulation. Lower levels of circulating hProinsulin-B10 were obtained from the PTG while higher levels were obtained from the tail vein and the SMG; however, vector particle containment was best when delivered to the SMG. Expression of hProinsulin-B10 in the SMG of chemically induced diabetic mice prevented excessive hyperglycemia observed in untreated mice. These results demonstrate that hProinsulin-B10 can be expressed and secreted into the circulation from SGs and can function physiologically in vivo. The ability to remediate a diabetic phenotype in a model of type 1 diabetes mellitus is the first step in an effort that may lead to a possible therapy for diabetes.

Sjögren's syndrome: diagnosis and management

This article reviews current understanding of the clinical manifestations, diagnosis and treatment of Sjögren's syndrome. Sjögren's syndrome is a chronic inflammatory disorder of the exocrine glands with multiple nonexocrine features. It is found predominantly in middle-aged women but exists throughout the population. The diagnosis of Sjögren's syndrome can be challenging because the cardinal sicca symptoms may be subclinical or attributed to other causes, such as medications or aging. Differential diagnosis of Sjögren's syndrome can be confounded by the multiple exocrine manifestations in the mouth, eyes, ears, nose, skin, vagina, and respiratory and gastrointestinal tracts, as well as seemingly unrelated nonexocrine involvement in the thyroid, liver, kidneys and the musculoskeletal, vascular and nervous systems. This article concludes that early diagnosis of Sjögren's syndrome is crucial to prevent and/or minimize potentially life-threatening complications. Periodic follow-up of patients' status and collaboration between the primary-care physician and the rheumatologist, dentist, ophthalmologist and other specialists are indispensable.

New developments and opportunities in oral mucosal drug delivery for local and systemic disease

The oral mucosa's accessibility, excellent blood supply, by-pass of hepatic first-pass metabolism, rapid repair and permeability profile make it an attractive site for local and systemic drug delivery. Technological advances in mucoadhesives, sustained drug release, permeability enhancers and drug delivery vectors are increasing the efficient delivery of drugs to treat oral and systemic diseases. When treating oral diseases, these advances result in enhanced therapeutic efficacy, reduced drug wastage and the prospect of using biological agents such as genes, peptides and antibodies. These technologies are also increasing the repertoire of drugs that can be delivered across the oral mucosa to treat systemic diseases. Trans-mucosal delivery is now a favoured route for non-parenteral administration of emergency drugs and agents where a rapid onset of action is required. Furthermore, advances in drug delivery technology are bringing forward the likelihood of transmucosal systemic delivery of biological agents.

Glucagon-like peptide-1 gene therapy

Glucagon-like peptide 1 (GLP-1) is a small peptide component of the prohormone, proglucagon, that is produced in the gut. Exendin-4, a GLP-1 receptor agonist originally isolated from the saliva of H. suspectum or Gila monster, is a peptide that shares sequence and functional homology with GLP-1. Both peptides have been demonstrated to stimulate insulin secretion, inhibit glucagon secretion, promote satiety and slow gastric emptying. As such, GLP-1 and Exendin-4 have become attractive pharmaceutical targets as an adjunctive therapy for individuals with type II diabetes mellitus, with several products currently available clinically. Herein we summarize the cell biology leading to GLP-1 production and secretion from intestinal L-cells and the endocrine functions of this peptide and Exendin-4 in humans. Additionally, gene therapeutic applications of GLP-1 and Exendin-4 are discussed with a focus on recent work using the salivary gland as a gene therapy target organ for the treatment of diabetes mellitus.

IL17: potential therapeutic target in Sjögren's syndrome using adenovirus-mediated gene transfer

Sjögren's syndrome (SS) involves a chronic, progressive inflammation primarily of the salivary and lacrimal glands leading to decreased levels of saliva and tears that eventually result in dry mouth and dry eye diseases. T(H)17 cell populations secreting IL17A have been shown to have an important function in an increasing number of autoimmune diseases, including SS. In this study, we investigated the function of IL17A on SS development and onset. Adenovirus-5 vectors expressing either IL17R:fragment of crystallization (Fc) fusion protein or LacZ were injected through retrograde cannulation into the salivary glands of SS-susceptible (SS(S)) C57BL/6.NOD-Aec1Aec2 mice between 6 and 8 weeks of age (a pre-disease stage) or 15 and 17 weeks of age (a diseased stage). The mice were subsequently characterized for their SS phenotypes. Mice cannulated with the Ad5-IL17R:Fc viral vector at either 7 or 16 weeks of age exhibited a rapid temporal, yet persistent, decrease in the levels of serum IL17 as well as the overall numbers of CD4+IL17+T cells present in their spleens. Disease profiling indicated that these mice showed decreased lymphocytic infiltrations of their salivary glands, normalization of their antinuclear antibodies repertoire, and increased saliva secretion. In contrast, mice cannulated with the control Ad5-LacZ viral vector did not exhibit similar changes and progressed to the overt disease stage. The capacity of the Ad5-IL17R:Fc-blocking factor to reduce SS pathology in SS(S) mice strongly suggests that IL17 is an important inflammatory cytokine in salivary gland dysfunction. Thus, therapeutic approach targeting IL17 may be effective in preventing glandular dysfunction.

Bioengineering strategies for regeneration of craniofacial bone: a review of emerging technologies

Although advances in surgical techniques and bone grafting have significantly improved the functional and cosmetic restoration of craniofacial structures lost because of trauma or disease, there are still significant limitations in our ability to regenerate these tissues. The regeneration of oral and craniofacial tissues presents a formidable challenge that requires synthesis of basic science, clinical science, and engineering technology. Tissue engineering is an interdisciplinary field of study that addresses this challenge by applying the principles of engineering to biology and medicine toward the development of biological substitutes that restore, maintain, and improve normal function. This review will explore the impact of biomaterials design, stem cell biology and gene therapy on craniofacial tissue engineering.

Ultrasound-assisted non-viral gene transfer to the salivary glands

We report a non-viral gene transfer method using ultrasound induced microbubble destruction to allow the uptake of plasmid gene transfer vectors to the cells of the mouse salivary gland. The Luciferase (Luc) reporter gene, driven by a cytomegalovirus (CMV) promoter, was delivered unilaterally to the submandibular salivary gland via retroductal cannulation and Luc expression was monitored with in vivo imaging. The CMV-Luc plasmid was delivered to the salivary gland in a carrier solution containing microbubbles composed of lipid-encased perfluoropropane gas, with two different concentrations of microbubbles used (100 and 15% volume/volume). An Adenoviral (Ad) vector using an identical CMV-Luc expression cassette was used as a positive control at two different dosages. Whereas ultrasound-assisted gene transfer (UAGT) with 100% microbubbles was weak and rapidly extinguished, UAGT with the 15% microbubble solution was robust and stable for 28 days. UAGT seems to be a practicable and promising method for non-viral gene delivery to the salivary glands.

Science is the fuel for the engine of technology and clinical practice

BACKGROUND

The biological, chemical, behavioral and physical sciences provide the fuel for innovation, discovery and technology that continuously improves the quality of the human condition. Computer power derived from the dramatic breakthroughs of the digital revolution has made extraordinary computational capacity available for diagnostic imaging, bioinformatics (the science of information) and numerous aspects of how we practice dentistry in the 21st century.

OVERVIEW

The biological revolution was initiated by the identification of the structure for DNA in 1953, a discovery that continues to catalyze improvements in patient care through new and better diagnostics, treatments and biomaterials. Humanity's most basic and recognizable characteristics--including the face--are now better understood through the elucidation of our genome and proteome, the genes and proteins they encode. Health care providers are beginning to use personalized medicine that is based on a person's genetic makeup and predispositions to disease development.

CONCLUSIONS

Advances in the fields of genetics, developmental and stem cell biology, and many other disciplines continue to fuel innovative research findings that form the basis for new diagnostic tests, therapeutic interventions and procedures that improve the quality of life for patients. Scientists are on the threshold of applying knowledge in stem cell biology to regenerative medicine and dentistry, heralding an era when clinicians can consider using biological engineering to replace tissues and organs lost to disease or trauma.

In vivo secretion of the mouse immunoglobulin G Fc fragment from rat submandibular glands

BACKGROUND

Salivary glands have been proposed as target organs for gene therapy. They secrete endogenous, as well as transgenic proteins, in a polarized manner. Transgene-encoded regulated pathway proteins primarily follow the regulated pathway in rat salivary glands and are secreted into saliva in an exocrine manner. Conversely, constitutive pathway proteins generally are secreted more basolaterally and thus follow the endocrine route. In the present study, we studied in vivo the sorting of the mouse immunoglobulin G2b Fc fragment, which is physiologically secreted via the constitutive pathway.

METHODS

Adenoviral vectors encoding the Fc fragment and human growth hormone were delivered into rat and mouse submandibular glands in vivo to compare their serum-to-saliva distribution. We also compared the intracellular localization of the Fc fragment and growth hormone by confocal microscopy.

RESULTS

We found that the Fc fragment was secreted almost entirely into the bloodstream from rat and mouse submandibular glands via a constitutive or constitutive-like pathway. This sorting behaviour is clearly different from that of transgenic human growth hormone, which is secreted in a regulated pathway, both in neuroendocrine cells and as a transgenic protein from salivary gland cells. We also found that simultaneously expressed human growth hormone and the mouse Fc fragment do not appear to influence each other's sorting behaviour. The Fc fragment showed a primarily basal localization, whereas growth hormone showed an apical localization, in rat submandibular gland acinar cells.

CONCLUSIONS

The results obtained in the present study indicate that the mouse Fc fragment is a useful model protein for examining the basolateral versus apical secretory pathways employed by transgenic secretory proteins in salivary glands.

Adapting to changes in molecular biosciences and technologies

Dental education, like any other educational programme in a research-intensive university environment, must be research led or at least research informed. In this context, as the research and knowledge base of dentistry lies in the biological and physical sciences, dental education must be led by advances in research in both these areas. There is no doubt that biotechnology and nanotechnology have, over the past 25 years, led research in both these areas. It is therefore logical to assume that this has also impacted on dental education. The aim of this paper is twofold; on one hand to examine the effects of biotechnology and nanotechnology and their implications for dental education and on the other to make recommendations for future developments in dental education led by research in biotechnology and nanotechnology. It is now generally accepted that dental education should be socially and culturally relevant and directed to the community it serves. In other words, there can be no universal approach and each dental school or indeed curriculum must apply the outcomes in their own social, cultural and community settings.

[Cell-based strategies for salivary gland regeneration]

Xerostomia as a side effect of radiotherapy or due to Sjögren's disease leads to considerable impairment of the quality of life of the affected patients. Preventive treatment approaches such as intensity-modulated radiotherapy, surgical transfer of a submandibular gland to a site outside the radiation field or administration of amifostin during radiation treatment are not yet completely established in clinical practice and are not applicable for all patients. Symptomatic treatment with pilocarpin or synthetic saliva leads to an improvement of the symptoms only in some patients, and in the case of pilocarpin significant systemic anticholinergic side-effects might occur. Because large numbers of patients are affected and current treatment options are not satisfactory, it is essential to develop new treatment options. In parallel with the in vitro production of functional salivary gland constructs by means of tissue engineering techniques, attempts are currently under way to experimentally restore salivary gland function by genetic treatment approaches such as transfection of the affected salivary glands with aquaporins or pro-angiogenic factors. In addition, the in vivo application of stem cells is under investigation. In the present paper, we discuss the clinical and radiobiological background of xerostomia and highlight possible innovative future treatment options.

Reengineering salivary gland cells to enhance protein secretion for use in developing artificial salivary gland device

Salivary glands (SGs) are considered exocrine glands, which mainly secrete water into the oral cavity. Nevertheless, they also exhibit a smaller endocrine secretory pathway toward the bloodstream. The concept of an artificial SG device for exocrine fluid secretion into the oral region in xerostomic patients has been previously studied. The purpose of the current study was to examine the potential of such a device for enhancing bioactive protein secretion. We engineered a plasmid encoding a SG-specific signal peptide sequence adjacent to a normally nonsecreted encoded reporter gene creating a chimera protein, and examined if this construct can enhance secretion from salivary epithelial cells. An N-terminal encoding epidermal growth factor (EGF) sequence was synthesized and inserted into a pGL3 control vector 5' of a firefly luciferase gene, creating a pGL3-EGF signal peptide (pGL3-EGFSP) fused vector. This vector was cotransfected with a pRL-CMV vector containing a Renilla luciferase gene, in 293 cells (serving as controls), and human submandibular gland ductal epithelial (HSG), rat submandibular gland acinar epithelial (SMIE), and rat submandibular gland ductal epithelial (A5) salivary cell lines. The transfected 293, SMIE, and HSG cells showed 8-, 18-, and 40-fold higher luciferase activity, respectively. These observations lead to the concept of an envisioned secretory device, which can serve as a potential biological pump for bioactive proteins.