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 Table of Contents  
REVIEW ARTICLE
Year : 2019  |  Volume : 11  |  Issue : 1  |  Page : 48-51

Periodontal implications of argyrophilic nucleolar organizer region: A mini reviewPeriodontal implications of argyrophilic nucleolar organizer region: A mini review


1 Department of Periodontics, College of Dental Sciences, Davangere, Karnataka, India
2 Department of Oral Pathology and Microbiology, College of Dental Sciences, Davangere, Karnataka, India
3 Faculty of Dental Sciences, SGT University, Gurgaon, Haryana, India

Date of Submission18-Mar-2018
Date of Acceptance30-Nov-2018
Date of Web Publication6-Mar-2019

Correspondence Address:
Vandana Kharidi Laxman
Department of Periodontics, College of Dental Sciences, Davangere . 577 004, Karnataka
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jorr.jorr_5_18

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  Abstract 


The periodontal lesions with cellular proliferation can be assessed by various methods. One of the methods to determine the proliferative activity is silver-staining argyrophilic nucleolar organizer region (AgNOR) staining. AgNOR can be used as diagnostic and prognostic tool for many of periodontal lesions which are proliferative in nature and may be quantitative marker of incipient cellular alterations before the histologic hallmarks appear. Hence, this paper reviewed about the periodontal applications of AgNOR staining.

Keywords: Histology, periodontal lesions, proliferative marker, silver staining


How to cite this article:
Laxman VK, Madhushankari G S, Saluja M, Singh S. Periodontal implications of argyrophilic nucleolar organizer region: A mini reviewPeriodontal implications of argyrophilic nucleolar organizer region: A mini review. J Oral Res Rev 2019;11:48-51

How to cite this URL:
Laxman VK, Madhushankari G S, Saluja M, Singh S. Periodontal implications of argyrophilic nucleolar organizer region: A mini reviewPeriodontal implications of argyrophilic nucleolar organizer region: A mini review. J Oral Res Rev [serial online] 2019 [cited 2019 May 19];11:48-51. Available from: http://www.jorr.org/text.asp?2019/11/1/48/253434




  Introduction Top


The clinical presentation of hyperplastic (inflammatory and neoplastic) lesions affecting periodontium may generate diagnostic challenges for the periodontist. Several methods have been used in the past for the identification of proliferating cells in tissue sections such as assessment of mitosis, use of DNA flow cytometry, autoradiographic methods, application of RNA and DNA, and use of monoclonal antibodies to detect proliferating-related antigens.[1] The major disadvantages in the above techniques are that they are time-consuming, expensive and require sophisticated equipment with technical expertise. Various other methods which have been employed to indicate the proliferative activity in normal tissues and both benign and malignant tumors are immunohistochemical staining for proliferating cell nuclear antigen, Ki67, bromodeoxyuridine-labelling (Brdu), and AgNOR staining. Silver-staining argyrophilic nucleolar organizer regions (AgNORs) have recently been utilized in the healthy status[2],[3],[4] and diagnosis of periodontal lesions.[4],[5],[6] The early attraction of this method was that it was inexpensive and needed no special resources other than time and patience. An attempt is made in this short communication to provide periodontal application of AgNOR staining.


  Nucleolar Organizer Regions Top


Nucleolar organizer regions (NORs) are loops of ribosomal DNA which occur in the nuclei of cells possessing the genes for synthesizing r-RNA. These genes are transcribed by RNA polymerase I and ultimately direct ribosome formation and protein synthesis.

Location

In the homosapiens, they are located on the short arm of five acrocentric chromosomes, i.e., chromosome numbers 13, 14, 15, 21, and 22. Many of these bind silver, a property attributed to proteins attributed to these sites, particularly the acidic nonhistone compounds. The amount of silver deposited in this cytochemical reaction is a reflection of the transcriptional activity of ribosomal genes, and the frequency of NORs per nucleus may prove useful as replicatory marker.

Physiologic consideration of argyrophilic nucleolar organizer region

Although 20 AgNOR sites should theoretically be present in a human diploid nucleus, AgNORs are typically aggregated within one or two nuclei during interphase in normal cells. The number of AgNORs visualized depend on (a) the number of NOR-bearing chromosomes in the karyptope, (b) the level of (RNA) transcriptional activity, and (c) the stage of cell cycle, as the nucleolus disperses before mitosis and reorganizes afterward.[7]

Pathologic conditions

A decreased size of AgNOR which is normally 0.3–1.5 μ, an increased number, and more dispersed distribution has been reported in malignant lesions and the converse for benign lesions. However, AgNORs staining is also useful for studying normal proliferating cells, as it may be a quantitative marker of incipient cellular alterations before the histological hallmarks appear.


  Implications of Argyrophilic Nucleolar Organizer Region Top


Diagnostic implications of argyrophilic nucleolar organizer region

Tumor pathology

AgNOR count is more commonly used for the diagnostic purpose as compared to the prognostic determination. Crocker[8] demonstrated that malignant cells can be distinguished from corresponding benign or normal cells on the basis of a higher quantity of interphase. It has been suggested that AgNOR count may be more reflective of the biologic nature of the condition, and hence, the degree of malignant potential rather than proliferative status.

It has been employed to study the proliferative activity of various other tumor cells, including malignant lymphoma, salivary gland, sarcoma, breast cancer, and pleural malignancy. It has also been used in the diagnosis of cutaneous tumors.

Cysts

It has been reported that difference in AgNOR number is not of diagnostic significance and cannot be used to distinguish various odontogenic cysts from one another nor from unicystic ameloblastoma.[9]

Prognostic implication of argyrophilic nucleolar organizer region

Although AgNOR estimation is used for diagnostic aspect, it has been found to serve as a reliable prognostic marker too. The prognostic significance of the AgNOR technique was reported in carcinomas of the sigmoid colon and rectum. AgNOR count may provide information on breast cancer prognosis supplementary to that obtained from DNA flow cytometric analysis.[10]

Implications in oral conditions

Different Implications of silver-staining nucleolar organizer region in other oral conditions are presented in [Table 1].
Table 1: Implications of silver-staining nucleolar organizer region in other oral conditions

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Various Implications of silver-staining nucleolar organizer region in healthy and periodontal conditions are presented in [Table 2]
Table 2: Implications of silver-staining nucleolar organizer region in healthy and periodontal conditions

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Oral medicine and oral pathology

  • Studies on oral malignancies and submucous fibrosis have revealed high count in squamous cell carcinoma with the AgNOR count increasing further with poor differentiation of the neoplasm[11]
  • The lesions with higher counts were reported to exhibit poor prognosis[12]
  • The increased proliferative activity and poor prognosis of ossifying fibroma compared with peripheral ossifying fibroma was suggested through AgNORs expression.[13] [14]


Periodontics

In healthy situations

AgNOR in periodontics was a new found interest in the 80s and 90s, as many periodontal lesions are proliferative in nature. In few studies, the proliferative activity of long junctional epithelium (LJE) using AgNOR method has been reported.[2],[3],[4] Uno et al. in 1998[2] conducted a study to examine the proliferative activity of the LJE in rats using stains for argyrophilic proteins of the nucleolar organizer region (AgNORs protein). The results suggested that the proliferative activity of the LJE is maintained continuously at a high level on the connective tissue interface supplying the epithelial cells. Usuda et al. in 2004[3] showed that LJE could not supply sufficient epithelial cells because of their significantly low rates of proliferation, consequently LJE becomes shorter after 12 weeks whereas the proliferative activity of regenerative connective tissue maintains the same level of proliferation, and ultimately, LJE is replaced by regenerative connective tissue.

Gingivitis

AgNOR count can be used as a histopathological indicator in cases of nonresponsive gingivitis to assess the severity of gingival inflammation.[6]

Neoplastic and nonneoplastic periodontal conditions

A study by Saluja and Vandana evaluated the diagnostic and prognostic ability of AgNOR in various neoplastic (squamous cell carcinoma) and nonneoplastic periodontal conditions (fibrous hyperplasia, peripheral ossifying fibroma, gingival bromatosis, pyogenic granuloma, drug-induced enlargement, and gingival polyp) showed that AgNOR has a limited diagnostic value, with a definite prognostic value in nonneoplastic periodontal lesions.[5]


  Indications Top


AgNOR estimation can be additional diagnostic criteria histologically. Its feasible indications are

  1. All types of gingival/periodontal enlargements which undergoes excision or biopsy

    It is not popular because it's time-consuming and its implications are minimally understood specially in the periodontal field
  2. It is a useful tool to assess gingival changes pre- to post-treatment (scaling and root planing)[6]
  3. Its not expensive but laborious so usually not considered. However, after trying out in two of our projects, it is valuable more of prognostic criteria than diagnostic criteria.



  Argyrophilic Nucleolar Organizer Region Evaluation Methods Top


It includes enumeration of AgNOR dots, measurement of area of AgNORs, and analysis of their distribution pattern. Microscopically, the AgNOR were clearly recognized as variable sized black dots with yellowish background in the nuclei and the counting was done using two methods-individual count and cluster count [Figure 1]a and b].
Figure 1: Histological section (argyrophilic nucleolar organizer region staining) showing increased argyrophilic nucleolar organizer region count pretreatment (a) and posttreatment (b)

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  Significance of Argyrophilic Nucleolar Organizer Region Top


AgNOR count rise with increased cell ploidy, with increased transcriptional activity and stages of active cell proliferation. Thus, AgNOR counting may enable to predict the biologic behavior of various periodontal lesions and to correlate the clinical and histologic grading of the condition, thus rendering prognosis more reliably. However, further investigations are required to clarify these techniques in large series of periodontal lesions.

Limitations of argyrophilic nucleolar organizer region

As the AgNOR depends on active cell proliferation, the specific range of AgNOR count is not determined so far. There is a need to study the normal healthy tissue and to determine the normal range of AgNOR count. This will facilitate the oral pathologists and clinicians to discriminate healthy and diseased tissues. It may be a difficult issue since cell proliferation in health itself is variable.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Layfield LJ, Hall TL, Fu YS. Discrimination of benign versus malignant mixed tumors of the salivary gland using digital image analysis. Cytometry 1989;10:217-21.  Back to cited text no. 1
    
2.
Uno T, Hashimoto S, Shimono M. A study of the proliferative activity of the long junctional epithelium using argyrophilic nucleolar organizer region (AgNORs) staining. J Periodontal Res 1998;33:298-309.  Back to cited text no. 2
    
3.
Usuda J, Hashimoto S, Enokiya Y, Inoue T, Shimono M. Proliferative activities of epithelial and connective tissue cells in the rat periodontal regeneration using argyrophilic nucleolar organizer regions staining. J Periodontal Res 2004;39:175-87.  Back to cited text no. 3
    
4.
Coletta RD, Almeida OP, Graner E, Page RC, Bozzo L. Differential proliferation of fibroblasts cultured from hereditary gingival fibromatosis and normal gingiva. J Periodontal Res 1998;33:469-75.  Back to cited text no. 4
    
5.
Saluja M, Vandana KL. The diagnostic and prognostic implications of silver-binding nucleolar organizer regions in periodontal lesions. Indian J Dent Res 2008;19:36-41.  Back to cited text no. 5
[PUBMED]  [Full text]  
6.
Sapna N, Vandana KL. Evaluation of hyaluronan gel (Gengigel(®)) as a topical applicant in the treatment of gingivitis. J Investig Clin Dent 2011;2:162-70.  Back to cited text no. 6
    
7.
Underwood JC, Giri DD. Nucleolar organizer regions as diagnostic discriminants for malignancy. J Pathol 1988;155:95-6.  Back to cited text no. 7
    
8.
Crocker J. Nucleolar organiser regions. Curr Top Pathol 1990;82:91-149.  Back to cited text no. 8
    
9.
Allison RT, Spencer S. Nucleolar organiser regions in odontogenic cysts and ameloblastomas. Br J Biomed Sci 1993;50:309-12.  Back to cited text no. 9
    
10.
Giri DD, Nottingham JF, Lawry J, Dundas SA, Underwood JC. Silver-binding nucleolar organizer regions (AgNORs) in benign and malignant breast lesions: Correlations with ploidy and growth phase by DNA flow cytometry. J Pathol 1989;157:307-13.  Back to cited text no. 10
    
11.
Chattopadhyay A. AgNORs in oral squamous cell carcinoma. In: Varma AK, editor. Oral Oncology: Proceedings of the International Congress on oral Cancer. Vol. 2. New Delhi, India: Macmillan India Ltd.; 1991. p. 78-81.  Back to cited text no. 11
    
12.
Sano K, Takahashi H, Fujita S, Inokuchi T, Pe MB, Okabe H, et al. Prognostic implication of silver-binding nucleolar organizer regions (AgNORs) in oral squamous cell carcinoma. J Oral Pathol Med 1991;20:53-6.  Back to cited text no. 12
    
13.
Mesquita RA, Orsini SC, Sousa M, de Araújo NS. Proliferative activity in peripheral ossifying fibroma and ossifying fibroma. J Oral Pathol Med 1998;27:64-7.  Back to cited text no. 13
    
14.
Garg KN, Raj V, Chandra S. Evaluation of the efficacy of AgNOR as a proliferative marker in oral leukoplakia: A morphometric analysis. Natl J Maxillofac Surg 2013;4:40-5.  Back to cited text no. 14
[PUBMED]  [Full text]  


    Figures

  [Figure 1]
 
 
    Tables

  [Table 1], [Table 2]



 

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