Journal of Indian Society of Periodontology
Journal of Indian Society of Periodontology
Home | About JISP | Search | Accepted articles | Online Early | Current Issue | Archives | Instructions | SubmissionSubscribeLogin 
Users Online: 1229  Home Print this page Email this page Small font size Default font size Increase font sizeWide layoutNarrow layoutFull screen layout


 
   Table of Contents    
REVIEW ARTICLE
Year : 2013  |  Volume : 17  |  Issue : 2  |  Page : 156-161  

Gene therapy in periodontics


Department of Periodontics, Institute of Dental Sciences, Bareilly, Uttar Pradesh, India

Date of Submission18-Aug-2010
Date of Acceptance17-Aug-2012
Date of Web Publication6-Jun-2013

Correspondence Address:
Nidhi Singh
Department of Periodontics, Institute of Dental Sciences, Pilibhit, Bypass Road, Near Suresh Sharma Nagar, Bareilly, Uttar Pradesh - 243 006
India
Login to access the Email id

Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0972-124X.113062

Rights and Permissions
   Abstract 

GENES are made of DNA - the code of life. They are made up of two types of base pair from different number of hydrogen bonds AT, GC which can be turned into instruction. Everyone inherits genes from their parents and passes them on in turn to their children. Every person's genes are different, and the changes in sequence determine the inherited differences between each of us. Some changes, usually in a single gene, may cause serious diseases. Gene therapy is 'the use of genes as medicine'. It involves the transfer of a therapeutic or working gene copy into specific cells of an individual in order to repair a faulty gene copy. Thus it may be used to replace a faulty gene, or to introduce a new gene whose function is to cure or to favorably modify the clinical course of a condition. It has a promising era in the field of periodontics. Gene therapy has been used as a mode of tissue engineering in periodontics. The tissue engineering approach reconstructs the natural target tissue by combining four elements namely: Scaffold, signaling molecules, cells and blood supply and thus can help in the reconstruction of damaged periodontium including cementum, gingival, periodontal ligament and bone.

Keywords: Designer drug therapy, gene therapy, gene delivery, scaffold, signaling molecule


How to cite this article:
Chatterjee A, Singh N, Saluja M. Gene therapy in periodontics. J Indian Soc Periodontol 2013;17:156-61

How to cite this URL:
Chatterjee A, Singh N, Saluja M. Gene therapy in periodontics. J Indian Soc Periodontol [serial online] 2013 [cited 2019 Apr 24];17:156-61. Available from: http://www.jisponline.com/text.asp?2013/17/2/156/113062


   Introduction Top


Periodontal diseases, have a broad spectrum of inflammatory and destructive responses, and are thought to be multi-factorial in origin. Genetic variance has been considered as a major risk factor for periodontitis. With the advent of gene therapy in dentistry, significant progress has been made in controlling the periodontal disease and reconstruction of damaged periodontal tissue.

A broad definition of gene therapy is the genetic modification of cells for therapeutic purposes. [1] This approach is becoming possible owing to the increased understanding of the molecular basis for many diseases and the advances in the technology of gene transfer. The goal of gene therapy is to transfer the DNA of interest (for example, growth factor and thrombolytic genes) into cells, thereby allowing the DNA to be synthesized in these cells and its protein (termed recombinant protein) expressed [Figure 1].
Figure 1: Approaches for regenerating tooth supporting structure

Click here to view


Currently genetic principles are being applied along with tissue engineering for periodontal rehabilitation. This article reviews the fundamentals of gene therapy, and its implication in periodontal disease.


   History Top


The first gene therapy trials on humans began in 1990 on patients with Severe Combined Immunodeficiency (SCID). In 2000, the first gene therapy "success" resulted in SCID patients with a functional immune system. These trials were stopped when it was discovered that two of ten patients in one trial had developed leukemia resulting from the insertion of the gene-carrying retrovirus near an oncogene.


   Fundamentals of Gene Therapy Top


There are a variety of different methods to replace or repair the genes targeted in gene therapy.

  • A normal gene may be inserted into a nonspecific location within the genome to replace a nonfunctional gene. This approach is most common
  • An abnormal gene could be swapped for a normal gene through homologous recombination
  • The abnormal gene could be repaired through selective reverse mutation, which returns the gene to its normal function
  • The regulation (the degree to which a gene is turned on or off) of a particular gene could be altered
  • Spindle transfer is used to replace entire mitochondria that carry defective mitochondrial DNA. [2]

   Types of Gene Therapy Top
[3]

Gene therapy may be classified into the following types:

Germ line gene therapy

In the case of germ line gene therapy, germ cells, i.e., sperm or eggs are modified by the introduction of functional genes, which are ordinarily integrated into their genomes. Therefore, the change due to therapy would be heritable and would be passed on to later generations.

Somatic gene therapy

In the case of somatic gene therapy, the therapeutic genes are transferred into the somatic cells of a patient. Any modifications and effects will be restricted to the individual patient only, and will not be inherited by the patient's offspring.


   Gene Delivery Top


In general, gene therapy involves the transfer of genetic information to target cells, which enables them to synthesize a protein of interest to treat disease. [4],[5],[6] The technology can be used to treat disorders that result from single point mutations. [7] The preferred strategy for gene transfer depends on the required duration of protein release and the morphology of the target site production. [8] There are various methods for gene delivery:

Viral

A carrier molecule called a vector must be used to deliver the therapeutic gene to the patient's target cells. Currently, the most common vector is a virus that has been genetically altered to carry normal human DNA. Viruses have evolved a way of encapsulating and delivering their genes to human cells in a pathogenic manner. Scientists have tried to take advantage of this capability and manipulate the virus genome to remove disease-causing genes and insert therapeutic genes.

Some of the different types of viruses used as gene therapy vectors: [9]

  • Retroviruses: A class of viruses that can create double-stranded DNA copies of their RNA genomes. These copies of its genome can be integrated into the chromosomes of host cells. Human immunodeficiency virus (HIV) is a retrovirus
  • Adenoviruses: A class of viruses with double-stranded DNA genomes that cause respiratory, intestinal, and eye infections in humans. The virus that causes the common cold is an adenovirus
  • Adeno-associated viruses: A class of small, single-stranded DNA viruses that can insert their genetic material at a specific site on chromosome 19
  • Herpes simplex viruses: A class of double-stranded DNA viruses that infect a particular cell type, neurons. Herpes simplex virus type 1 is a common human pathogen that causes cold sores.
Non viral

  • The simplest method is the direct introduction of therapeutic DNA into target cells. This approach is limited in its application because it can be used only with certain tissues and requires large amounts of DNA
  • Another non viral approach involves the use of an artificial lipid sphere with an aqueous core. This liposome, which carries the therapeutic DNA, is capable of passing the DNA through the target cell's membrane.

   Major Developments in Gene Therapy Top


In 1999

Trial treatments of SCID have been gene therapy's only success; since 1999, gene therapy has restored the immune systems of at least 17 children with two forms (ADA-SCID and X-SCID) of the disorder.

In 2002

In 2002 a question was raised when two of the ten children treated developed a leukemia-like condition. [10]

In 2006

Scientists have successfully treated metastatic melanoma in two patients using killer T cells genetically retargeted to attack the cancer cells. [11] As well as in March again, scientists announced the successful use of gene therapy to treat two adult patients for a disease affecting myeloid cells. [12]

Italy reported a breakthrough for gene therapy in which they developed a way to prevent the immune system from rejecting a newly delivered gene. Similar to organ transplantation. [13]

In 2007

The world's first gene therapy trial was done for inherited retinal disease. [14] The sub retinal delivery of recombinant adeno associated virus (AAV) carrying RPE65 gene, was found to be safe and yielded positive results. [15]

In 2009

The journal Nature reported that researchers at the University of Washington and University of Florida were able to give trichromatic vision to squirrel monkeys using gene therapy, a hopeful precursor to a treatment for color blindness in humans. [16]

Technical difficulties in using gene therapy

  1. Difficulty in delivering of gene: Delivery of successful gene in gene therapy is not easy or predictable, even for single gene disorders. For example genetic basis of cystic fibrosis is well known but delivery of gene therapy is still difficult because of presence of mucus in lungs. [2]
  2. Short-lived nature of gene therapy: Before gene therapy can become a permanent cure for any condition, the therapeutic DNA introduced into target cells must remain functional and the cells containing the therapeutic DNA must be long-lived and stable. Problems with integrating therapeutic DNA into the genome and the rapidly dividing nature of many cells prevent gene therapy from achieving any long-term benefits. Patients will have to undergo multiple rounds of gene therapy.
  3. Activation of immune response: Viral vector may be recognized as antigen and leads to activation of immune response. This may lead the efficacy of gene therapy and can induce serious side effect.
  4. Chance of inducing a tumor (insertion mutagenesis): If the DNA is integrated in the wrong place in the genome, for example in a tumor suppressor gene, it could induce a tumor. This has occurred in clinical trials for X-linked severe combined immunodeficiency (X-SCID) patients, in which hematopoietic stem cells were transduced with a corrective transgene using a retrovirus, and this led to the development of T cell leukemia in 3 of 20 patients.
  5. Safety of vector: Viruses, the carrier of choice in most gene therapy studies, present a variety of potential problems to the patient toxicity, immune and inflammatory responses, and gene control and targeting issues. In addition, there is always the fear that the viral vector, once inside the patient, may recover its ability to cause disease.
  6. Difficulty to treat multigene disorders: Conditions or disorders that arise from mutations in a single gene are the best candidates for gene therapy. Unfortunately, some of the most commonly occurring disorders, such as heart disease, high blood pressure, Alzheimer's disease, arthritis, and diabetes, are caused by the combined effects of variations in many genes. Multigene or multifactorial disorders such as these would be especially difficult to treat effectively using gene therapy.
  7. Expensive: Gene therapy is costly and very expensive procedure.

   Implications of Gene Therapy in Periodontics Top


There have been tremendous advances in gene therapy relevant to dentistry since 1995. Even in the field of periodontics, it has been studied extensively. Currently genetic principles are being applied along with tissue engineering for periodontal rehabilitation.

Approaches for regenerating tooth-supporting structures (A) Guided tissue regeneration uses a cell occlusive barrier membrane to restore periodontal tissues. (B) Alternatively, an example of gene therapy uses vector-encoding growth factors aimed at stimulating the regeneration of host cells derived from the periodontium [Figure 2].
Figure 2: In vivo

Click here to view


There are three approach of tissue engineering in periodontics:

  1. Protein based approach

    Growth and differentiation factors are used for regeneration of periodontal tissues likes TGF-β, BMP-2, 6, 7, 12, bFGF, VEGF and PDGF. [17]
  2. Cell based approach

    Several studies using mesengymal stem cell have demonstrated efficient reconstruction of bone defect that are too large to heal spontaneously. [18]
  3. Gene delivery approach [19]

    To overcome the short half-lives of growth factor peptides in vivo, gene therapy that uses a vector that encodes the growth factor is utilized to stimulate tissue regeneration. So far, two main strategies of gene vector delivery have been applied to periodontal tissue engineering.


Gene vectors can be introduced directly to the target site (in vivo technique) or selected cells can be harvested, expanded, genetically transduced, and then reimplanted (ex vivo technique).

IN VIVO

Gene therapy is done by targeting the gene delivery system to the desired cell type in the patient using either physical means such as tissue injection (brain tumor) or biolistics (dermal DNA vaccination), or potentially in the future, using systemic infusion of cell-specific receptor-mediated DNA carriers (reconstructed liposome's or viruses). Importantly, neither of these gene therapy strategies involve reproductive germline cells nor therefore the genetic alteration will not be transmitted to the next generation. In many countries, human germ line gene therapy is considered unethical or even illegal [Figure 2].

EX VIVO

Ex-vivo
gene therapy is performed by transfecting or infecting patient-derived cells in culture with vector DNA and then reimplanting the transfected cells into the patient. Two types of ex-vivo gene therapies under development are those directed at fibroblasts and hematopoietic stem cells [Figure 3].
Figure 3: Ex vivo

Click here to view



   Clinical Trials Using Gene Therapy Top


The application of PDGF-gene transfer strategies to tissue engineering originally was generated to improve healing in soft tissue wounds, such as skin lesions. [20] But, recently various trial have been done PDGF using Plasmid [21] and Ad/PDGF gene deliver, [22] for regeneration of periodontal tissue.

Platelet-derived growth factor gene delivery

Early studies in dental applications using recombinant adenoviral vectors that encode PDGF demonstrated the ability of these vectors constructs to transduce potently the cells isolated from the periodontium (eg osteoblasts, cementoblats, PDL cells, and gingival fibroblasts). [23] continuous exogenous delivery of PDGF-α may delay mineral formation induced by cementoblasts, whereas PDGF clearly is required for mineral neogenesis. [24]

  1. Jin et al., demonstrated in their study that direct in vivo gene transfer of PDGF-B stimulated tissue regeneration in large periodontal defects. [25]
  2. Anusaksathien et al., reported that in an ex vivo investigation, showed that the expression of PDGF genes was prolonged for up to 10 days in gingival wounds. [26]
  3. Giannobile et al., reviewed different mechanisms of drug delivery and novel approaches to reconstruct and engineer oral- and tooth-supporting structures, namely the periodontium and alveolar bone. [27]
Bone morphogenetic protein delivery

  1. Franceschi et al., investigated in vitro and in vivo Ad gene transfer of BMP-7 for bone formation. [28]
  2. Dunn et al., demonstrated that in case of direct in vivo gene delivery of Ad/BMP-7 in a collagen gel carrier promoted successful regeneration of alveolar bone defects around dental implants. [29]

   Gene Enhanced Tissue Engineering Top


The general strategy of tissue engineering is to supplement the regenerative site with a therapeutic protein like growth factors. However the problem with the delivery of growth factor is its short life. This is due to protelytic breakdown and receptor mediated exocytosis and solubility of delivery vehicle. To overcome these problems, gene therapy has been developed which provides long term exposure of growth factor to periodontal wound [Figure 4].
Figure 4: Tissue engineering

Click here to view



   Applications Top


They are as following:

  1. Gene Therapeutics-Periodontal Vaccination
  2. Genetic Approach to Biofilm Antibiotic Resistance
  3. An In vivo Gene Transfer by Electroporation for Alveolar Remodeling
  4. Antimicrobial Gene Therapy to Control Disease Progression
  5. Designer Drug Therapy in Treating Periodontal Disease
Gene therapeutics-periodontal vaccination

  • A salivary gland of a mouse when immunized using plasmid DNA encoding the  Porphyromonas gingivalis Scientific Name Search P. gingivalis) fimbrial gene produces fimbrial protein locally in the salivary gland tissue resulting in the subsequent production of specific salivary immunoglobulin's A, or IgA and immunoglobulin G, or IgG, antibodies and serum IgG antibodies. This secreted IgA could neutralize P. gingivalis and limit its ability to participate in plaque formation.
  • Scientists have also demonstrated the efficacy of immunization with genetically engineered Strepto-cocci gordoni vectors expressing P. Gingivalis is fimbrial antigen as vaccine against P. gingivalis associated periodontitis in rats. [30]
  • The gene hemagglutinin which is an important virulence factor of P. gingivalis has been identified, cloned and expressed in  Escherichia More Details coli. The recombinant hemagglutinin B (rHag B) when injected subcutaneously in Fischer rats infected with P. gingivalis showed serum IgG antibody and interleukin-2 (IL-2), IL-10, and the IL-4 production which gave protection against P. gingivalis induced bone loss. [31]
Genetic approach to biofilm antibiotic resistance

  • Researchers have found bacteria growing in biofilms become up to 1,000 fold more resistant to antibiotics as compared to a planktonic counterpart making them hard to control.
  • Recently Mah et al., identified gene ndvB [32] encoding for glycosyltransferase required for the synthesis of periplasmic glucans in wild form of Pseudomonas aeuroginosa RA14 strain.
  • This remarkably protected them from the effects of antibiotics biocides, and disinfectant [Figure 5].
    Figure 5: Genetic approach to biofilim antibiotic resistance

    Click here to view
  • Using a genetic approach.
Researchers have isolated ndvB mutant of Pseudomonas aeuroginosa still capable of forming biofilm but lacking the characteristic of periplasmic glucans there by render- ing microbial communities in biofilm more susceptible to conventional antibiotic therapy [Figure 6].
Figure 6: Electroporation for alveolar bone

Click here to view


An in-vivo gene transfer by electroporation for alveolar remodeling [33]

  • Using an in vivo transfer of LacZ gene (gene encoding for various remodeling molecules) into the periodontium and using plasmid DNA as a vector along with electroporation (electric impulse) for driving the gene into cell, has shown predictable alveolar bone remodeling
  • Step A- Cells obtained from outpatient skin biopsy
  • Step B- Gene of therapeutic interest is introduced into cells by electroporation
  • Step C- Genetically engineered cells are propagated and characterized
  • Step D- Genetically engineered cells are returned back to clinician [Figure 6] and [Figure 7].
    Figure 7: Electroporation for alveolar bone

    Click here to view
Antimicrobial gene therapy to control disease progression [34]

  • One way to enhance host defense mechanism against infection is by transfecting host cells with an antimicrobial peptide/protein- encoding gene
  • Researchers have shown when host cells were infected in vivo with β defensin-2 (HBD-2) gene via retroviral vector; there was a potent antimicrobial activity which enhanced host antimicrobial defenses.
Designer drug therapy in treating periodontal disease [34]

  • If genes necessary for normal development are known, then "designer drug therapies" aimed at one area of the gene or the other can be developed.
  • These designer drugs will be safer than today's medicines because they would only affect the defect in a gene clearly identified through genetic research.

   Conclusion Top


Gene therapy has a promising role in the field of periodontics but it does encompass serious ethical issue to be dealt with. It is evident that gene therapy has emerged from its stage of infancy of mere theoretical and hypothetical quotations to factual scientific researches, which reveals potential hopes. There are still lots of research and details of mechanisms to be understood to include these practically in day to day treatment modalities.

 
   References Top

1.Kinane DF, Shiba H, Hart TC. The genetic basis of periodontitis. Periodontol 2000 2005;39:91-117.  Back to cited text no. 1
    
2.Human Genome Project Information. Available from: http://www.genomics.energy.gov. Clinical Genetics-Kaya Lahiri. [Last accessed on 2012 Aug 2].  Back to cited text no. 2
    
3.Friedmann T. The maturation of human gene therapy. Acta Paediatr 1996;85:1261-5.  Back to cited text no. 3
    
4.Baum BJ, Kok M, Tran SD, Yamano S. The impact of gene therapy on dentistry: A revisiting after six years. J Am Dent Assoc 2002;133:35-44.  Back to cited text no. 4
    
5.Baum BJ, O′Connell BC. The impact of gene therapy on dentistry. J Am Dent Assoc 1995;126:179-89.  Back to cited text no. 5
    
6.Parekh-Olmedo H, Ferrara L, Brachman E, Kmiec EB. Gene therapy progress and prospects: Targeted gene repair. Gene Ther 2005;12:639-46.  Back to cited text no. 6
    
7.Muramatsu S, Tsukada H, Nakano I, Ozawa K. Gene therapy for Parkinson′s disease using recombinant adeno-associated viral vectors. Expert Opin Biol Ther 2005;5:663-71.  Back to cited text no. 7
    
8.Lakshminarayana P. Vectors in gene therapy. In: Lakshminarayana P, Laxmi S, Editors. Medical genetics. 1 st Ed, Paras, 2008.  Back to cited text no. 8
    
9.Morgan RA, Dudley ME, Wunderlich JR, Hughes MS, Yang JC, Sherry RM, et al. Cancer regression in patients after transfer of genetically engineered lymphocytes. Science 2006;314:126.  Back to cited text no. 9
    
10.Ott MG, Schmidt M, Schwarzwaelder K, Stein S, Siler U, Koehl U, et al. Correction of X-linked chronic granulomatous disease by gene therapy, augmented by insertional activation of MDS1-EVI1, PRDM16 or SETBP1. Nat Med 2006;12:401-9.  Back to cited text no. 10
    
11.Brown BD, Venneri MA, Zingale A, Sergi Sergi L, Naldini L. Endogenous microRNA regulation suppresses transgene expression in hematopoietic lineages and enables stable gene transfer. Nat Med 2006;12:585-91.  Back to cited text no. 11
    
12.Gene therapy first for poor sight". BBC News. May 1, 2007. Retrieved May 3, 2010.  Back to cited text no. 12
    
13.Maguire AM, Simonelli F, Pierce EA, Pugh EN Jr, Mingozzi F, Bennicelli J, et al. Safety and efficacy of gene transfer for Leber′s congenital amaurosis. N Engl J Med 2008;358:2240-8.  Back to cited text no. 13
    
14.Available from: http://www.nature.com/news/2009/090916/full/news.2009.921.html [Last accessed on 2012 Aug 2].  Back to cited text no. 14
    
15.Jocelya K. Seeking the cause of induced leukemia in X-SCID trial. Science 2003;299;495.  Back to cited text no. 15
    
16.Jin QM, Anusaksathien O, Webb SA, Rutherford RB, Giannobile WV. Gene therapy of bone morphogenetic protein for periodontal tissue engineering. J Periodontol 2003;74:202-13.  Back to cited text no. 16
    
17.Lee JY, Peng H, Usas A, Musgrave D, Cummins J, Pelinkovic D, et al. Enhancement of bone healing based on ex vivo gene therapy using human muscle derived cells expressing BMP-2. Hum Gene Ther 2002;13:1201-11.  Back to cited text no. 17
    
18.Baum BJ, O′Connell BC. The impact of gene therapy on dentistry. J Am Dent assoc 1995;126:179-89.  Back to cited text no. 18
    
19.Crombleholme TM. Adenoviral-mediated gene transfer in wound healing. Wound Repair Regen 2000;8:460-72.  Back to cited text no. 19
    
20.Hijjawi J, Mogford JE, Chandler LA, Cross KJ, Said H, Sosnowski BA, et al. Platelet-derived growth factor B, but not fibroblast growthfactor 2, plasmid DNA improves survival of ischemic mucocutaneous flaps. Arch Surg 2004;139:142-7.  Back to cited text no. 20
    
21.Printz MA, Gonzalez AM, Cunningham M, Gu DL, Ong M, Pierce GF, et al. Fibroblast growth factor 2-retargeted adenoviral vectors exhibit a modified biolocalization pattern and display reduced toxicity relative to native adenoviral vectors. Hum Gene Ther 2000;11:191-204.  Back to cited text no. 21
    
22.Zhu Z, Lee CS, Tejeda KM, Giannobile WV. Gene transfer and expression of platelet-derived growth factors modulate periodontal cellular activity. J Dent Res 2001;80:892-7.  Back to cited text no. 22
    
23.Anusaksathien O, Jin Q, Zhao M, Somerman MJ, Giannobile WV. Effect of sustained gene delivery of platelet-derived growth factor or its antagonist (PDGF-1308) on tissue-engineered cementum. J Periodontol 2004;75:429-40.  Back to cited text no. 23
    
24.Jin QM, Anusaksathien O, Webb SA, Rutherford `RB, Giannobile WV. Engineering of tooth- supporting structures by delivery of PDGF gene therapy vectors. Mol Ther 2004;9:519-26.  Back to cited text no. 24
    
25.Anusaksathien O, Webb SA, Jin QM, Giannobile WV. Platelet- derived growth factor gene delivery stimulates ex vivo gingival repair. Tissue Eng 2003;9:745-56.  Back to cited text no. 25
    
26.Kaiger D, Cirelli JA, Giannobile WV. Growth factor delivery for oral and periodontal tissue engineering. Expert Opin Drug Deliv 2006;3:647-62.  Back to cited text no. 26
    
27.Franceschi RT, Wang D, Krebsbach PH, Rutherford RB. Gene therapy for bone formation: In vitro and in vivo osteogenic activity of an adenovirus expressing BMP-7. J Cell Biochem 2000;78:476-86.  Back to cited text no. 27
    
28.Dunn CA, Jin QM, Taba MJr, Franceshi RT, Bruce Rutherford R, Giannobile WV. BMP gene delivery for alveolar bone engineering at dental implant defects. Mol Ther 2005:11:294-9  Back to cited text no. 28
    
29.Sharma A, Honma K, Evans TR, Hruby DE. Oral immunization with recombinant Streptococcus gordonii expressing Porphyromonas gingivalis Fim A Domains. Infect Immun 2001;69:2928-34.  Back to cited text no. 29
    
30.Katz J, Black KP, Michalek MS. Host response to recombinant hemagglutinin B of Porphyromonas gingivalis in an experiment rat model. Infect Immun 1999;67:4352-59.  Back to cited text no. 30
    
31.Mah TF, Pitts B, Pellock B, Walker GC, Stewart PS, O′Toole GA. A genetic basis for Pseudomonas aeruginosa biofilm antibiotic resistance. Nature 2003;426:306-10.  Back to cited text no. 31
    
32.Tsuchiya S. Gene transfer into periodontal tissue by in vivo electroporation. 2002. Available from: http://www.Iadr.confex.com. [Last accessed on 2012 Aug 2].  Back to cited text no. 32
    
33.Schreiner HC, Sinatra K, Kaplan JB, Furgang D, Kachlany SC, Planet PJ, et al. Tight-adherence genes of Actinobacillus actinomycetemcomitans are required for virulence in a rat model. Proc Natl Acad Sci 2003;100:7295-300.  Back to cited text no. 33
    
34.Cathy AJ. Teeth-We′re going to grow them back! Available from: http://www.Filipinodentist.Com. [Last accessed on 2005 April 17].  Back to cited text no. 34
    


    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]



 

Top
   
 
  Search
 
  
    Similar in PUBMED
   Search Pubmed for
   Search in Google Scholar for
 Related articles
    Access Statistics
    Email Alert *
    Add to My List *
* Registration required (free)  

 
  In this article
    Abstract
   Introduction
   History
    Fundamentals of ...
    Types of Gene Th...
   Gene Delivery
    Major Developmen...
    Implications of ...
    Clinical Trials ...
    Gene Enhanced Ti...
   Applications
   Conclusion
    References
    Article Figures

 Article Access Statistics
    Viewed3308    
    Printed63    
    Emailed2    
    PDF Downloaded1029    
    Comments [Add]    

Recommend this journal