Spatial and temporal distribution of Ki-67 proliferation marker, Bcl-2 and Bax proteins in the developing human tooth.
OBJECTIVE
To investigate the spatial and temporal expression of proliferation Ki-67 marker, pro-apoptotic Bax and anti-apoptotic Bcl-2 proteins during early development of the human tooth.


METHODS
Histological sections of eight human conceptuses, 5-10 postovulatory weeks old, were used for immunolocalization for Ki-67, Bax and Bcl-2 markers. Quantification was performed by calculating the fraction of Ki-67 positive cells, expressed as a mean ± SD, and analysed by Mann-Whitney test, Kruskal-Wallis and Dunn's post hoc test.


RESULTS
In 6th-7th developmental weeks, the tooth germ and dental crest contained 37% of proliferating cells, which increased to 40% in the 8th week, and then decreased to 15% in the 10th week, whilst the proliferation in the ectomesenchyme subsequently dropped from 37% to 23%. Epithelial parts of the enamel organ displayed similar proliferation activity (31-36%), dental crest 10%, whilst enamel knot showed no proliferating activity. The tooth ectomesenchyme contained more proliferating cells (50%) than the jaw ectomesenchyme (35%), and both dropped to 28% in the 10th week. Ectomesenchyme between the tooth germs contained 23%, whilst the jaw ectomesenchyme contained 15% of proliferating cells. Bcl-2 expression had following pattern: strong in proliferating cells, moderate in tooth germs and dental crest, and weak in the ectomesenchyme. Bax co-expressed with Bcl-2 in the tooth germ and dental crest. In the reticulum and inner enamel epithelium Bcl-2 had prevalent expression, whilst Bax prevailed in the outer enamel epithelium and tooth ectomesenchyme.


CONCLUSIONS
Proliferating cells most likely influence growth of the tooth germ, Bcl-2 affects proliferation and differentiation of specific cell lineages, whilst Bax influences process of cell death.
Kalibović Govorko
Danijela
D
School of Dental Medicine, University of Split, Šoltanska 2, 21000 Split, Croatia. danijela.kalibovic.govorko@mefst.hr
Bečić
Tina
T
Vukojević
Katarina
K
Mardešić-Brakus
Snježana
S
Biočina-Lukenda
Dolores
D
Saraga-Babić
Mirna
M
D016923:Cell Death / Q000502:physiology; D002454:Cell Differentiation / Q000502:physiology; D019070:Cell Lineage; D049109:Cell Proliferation; D003743:Dental Enamel / Q000166:cytology / Q000196:embryology; D003771:Dental Papilla / Q000166:cytology / Q000196:embryology; D003795:Dental Sac / Q000166:cytology / Q000196:embryology; D004475:Ectoderm / Q000166:cytology / Q000196:embryology; D004658:Enamel Organ / Q000166:cytology / Q000196:embryology; D004847:Epithelial Cells / Q000166:cytology; D004848:Epithelium / Q000196:embryology; D005455:Fluorescent Antibody Technique; D005865:Gestational Age; D006801:Humans; D007150:Immunohistochemistry; D019394:Ki-67 Antigen / Q000032:analysis*; D008648:Mesoderm / Q000166:cytology / Q000196:embryology; D009024:Morphogenesis / Q000502:physiology; D009805:Odontogenesis / Q000502:physiology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000032:analysis*; D014083:Tooth Germ / Q000166:cytology / Q000196:embryology*; D051028:bcl-2-Associated X Protein / Q000032:analysis*
C494826:BAX protein, human; D019394:Ki-67 Antigen; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein