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Head: Assoc. Prof. Miroslav Peterka, MD, DSc

Phone: +420 241 062 604
The main focuses of the Department of Teratology are studies on the developmental abnormalities in humans as well as in the experimental models. The causes and mechanisms of the inborn defects formation are studied using two experimental models (developing chick embryo and mouse tooth germs), and using clinical-epidemiological approach. The main target is to contribute to the knowledge about the normal and abnormal development, pathogenesis of inborn defects and possibilities of their prevention

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Laboratory of Embryogenesis

Assoc. Prof. Miroslav Peterka, MD, DSc | Head of Laboratory
Phone: +420 241 062 604

Laboratory of Odontogenesis

Renata Peterková, MD, PhD | Head of Laboratory
Phone: +420 241 062 232
Miroslav Peterka, MD, DSc | Research Scientist
Zuzana Pavlíková, MSc | PhD Student
Klára Steklíková | Undergraduate Student
Petra Herlová, MSc | Technician
Simona Vojtěchová, MSc | Technician
Šárka Dvořáková | Technician
 

Renata Peterková, MD, PhD | Research Scientist
Mária Hovořáková, MSc, PhD | Research Scientist
Oldřich Zahradníček, MSc, PhD | Research Scientist
Svatava Churavá-Lagronová, MSc, PhD | Research Scientist

Kateřina Lochovská, MSc | PhD Student

Lucie Smrčková, MSc | PhD Student
Ivana Koppová | Technician
Zdena Lisá | Technician
Lenka Jandová | Technician

 

 

Laboratory of Embryogenesis

 

Research topics
The incidence of the oro-facial clefts in Czech population is longitudinally followed in the clinical-epidemiological studies. Their causes are detected from anamnestic data. The possible suspected factors, especially medicaments used during pregnancy, are tested experimentally in the chick embryo model using the method CHEST (Chick Embryotoxicity Screening Test). The results are evaluated on the basis of embryo-lethal effect, growth retardation and occurrence of developmental malformations. 

 

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Experimental model – developing chick embryo.
(A) The injection of a test substance into the amniotic sac of a day 3 chick embryo in ovo. (B) Unilateral cleft beak in a day 9 chick embryo induced by the intra-amniotic injection of hydrocortisone on day 4 of incubation.

 

 

Harmful external factors and a genetic predisposition are sought in clinical/epidemiological studies of developmental defects. Suspected external factors are tested experimentally in an animal model – chick embryogenesis.


Previous investigations in the Department have detected significant differences in the incidence of orofacial clefts between Czech districts during the last 30 years. The analysis of natality data from the Czech Republic has revealed that the number of newborn boys was higher than that of girls in each month from 1950 to 2005. The only exception was November 1986, when the number of newborn boys was significantly reduced. This has been explained by a selective negative impact of the Chernobyl accident in April 1986 on male fetuses during the 3rd month of their prenatal development. The correlation between the numbers of missing boys with the radioactivity levels has suggested that I-131 probably played the most important role, being taken-up by the fetal thyroid gland during saturation by iodine at the onset of its function in the 3rd month of human prenatal development. 

 

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Orofacial clefts in man.
(A) The mean incidence of orofacial clefts in the districts of the Czech Republic during 1983–1997. (B) Basic types of orofacial clefts in man. CL – cleft lip and jaw unilateral, CLP – cleft lip and palate unilateral, CP – isolated cleft palate. The CL and CLP can also affect both the right and left side - CL bilateral and CLP bilateral, respectively.

 

 

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The percentage of boys among infants born in the Czech Republic in each November during 1950–2005.
Note the only exception – the percentage of newborn boys was less than 50% in November 1986, indicating that fewer boys were born than girls.

 

 

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Schematic maps of the Czech Republic showing the situation after the Chernobyl accident.
(A) Country regions are delineated: CB – Central Bohemia; EB - East Bohemia; NB - North Bohemia; NM - North Moravia; P - Prague; SB - South Bohemia; SM - South Moravia; WB - West Bohemia. The black arrows show the passage of the first radioactive cloud over the country on April 30, 1986. The colors indicate the intensity of the rainfall measured from 07: 00 hours on April 30 until 07: 00 hours on May 1.
(B) Distribution and levels of radiation represented by Cs-137; note that the highest radiation levels were in North and South Moravia, which reflects the areas of rainfall at the time the radioactive cloud passed over the country. The lowest radiation levels were recorded in the areas outside the passage of the radioactive cloud - in North and West Bohemia, where rain was absent or minimal.
(C) The percentage of missing boys in each region during November 1986.

 

   

Experimental testing (see Fig. 1) of embryotoxic factors on the developing chick embryo) has determined the embryotoxicity ranges of more than 150 chemical substances and allowed for the estimation of embryotoxicity ranges for humans. We have shown that the upper second incisor originates from the fusion of two components in human embryos. These two components presumably do not fuse in patients with a jaw cleft; consequently, their upper lateral incisor can be duplicated, hypoplastic or missing.

 

Present studies
  • Testing of harmful chemical and physical factors and estimation of their minimum embryotoxic doses using a chick embryotoxicity screening test;
  • mechanism of development of the cleft beak in chick embryos and its possible prevention and reparation;
  • clinical/epidemiological studies searching for the causes underlying the origin of orofacial clefts in humans, based on a critical analysis of case- and family-history data;
  • monitoring of the newborn sex ratio as a tool for detecting ecological accidents.
 
The studies bring new data about the ethiopathogenesis of developmental defects that help in the prevention of inborn anomalies in humans.
 

Laboratory of Odontogenesis

 
Research topics
The laboratory of odontogenesis is focused on the studies on tooth development under normal, pathological and experimental conditions. We found that rudimentary structures are involved significantly during odontogenesis. Although the rudiments stop their growth and/or regress under normal conditions, their abnormal development can be implicated in the formation of inborn defects of the dentition. The knowledge of the development and of the role of rudimentary structures during odontogenesis can contribute not only to elucidating the evolution of dentitions but also to understanding pathogenesis of distinct dental anomalies. If the rudiments continue developing instead regression, they can give rise to supernumerary teeth. From this point of view, the regressing/revitalizing rudiments are the natural model for studying of inhibition/stimulation mechanisms of tooth development and for testing possibilities of tooth regeneration.
 
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Sequential development of the rudimentary tooth and functional incisor in mice.
 
Our study brought new insight into the development of the mouse incisor and introduced a new interpretation of the molecular data published in the literature. We focused on the early stages of tooth development in the upper and lower prospective incisor areas in wild type mice using morphology (3D reconstructions) and Sonic hedgehog (Shh) expression (whole mount in situ hybridization) as a marker of odontogenesis. Two antero-posteriorly localized Shh expression domains were found in the area of the prospective upper and lower incisors in mice. The anterior and more superficial Shh expression domain (orange) appeared at embryonic day (ED) 12.5 in each of upper and lower jaw quadrants. This domain is generally attributed to the functional incisor. In fact, we have shown that it co-localizes with a generation of rudimentary (prelacteal) teeth detectable on frontal histological sections at more advanced stages of the tooth development as a minute tooth germ localized anteriorly to the functional incisor anlage. The posterior and deeper Shhexpression domain (blue) appeared in the developmentally more advanced specimens at ED13.5 in both upper and lower jaws. This domain was located in the center of the developing germ of the prospective functional incisor. Bar is 100um.
 

 

 
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Origin of the double upper lateral incisor in humans.
(A) Scheme of the embryonic human face with a unilateral left-sided cleft of the lip and jaw (green arrow). The medial nasal (mn) and the maxillary (mx) facial processes are fused on the right and not fused on the left side. ln – lateral nasal process, md – mandibular process.
(B) Scheme of the human upper jaw arch viewed from the oral cavity. On the right site, the mn (red) and mx (yellow) fuse. At the fusion site, the lateral deciduous incisor (i2) develops (dotted line), containing material from both facial processes. On the left side, non-fusion of the mn and mx results in a jaw cleft and the non-fusion of the dental epithelia, which leads to the formation of two i2.
(C) Double deciduous lateral incisors i2 (arrow) in a patient with a left-sided alveolar cleft after surgical treatment (from the archive of the Clinic of Plastic Surgery, Prague). The midline is shaded. i1 – deciduous central incisor; c – deciduous canine.

 

 
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Schematic of the tooth pattern of adult and embryonic mice.
(A) Adult mice have one incisor and three molars separated by a toothless diastema in each jaw quadrant.
(B) A schematic comparison of the tooth pattern in a jaw quadrant of adult and embryonic mice. In contrast to adult mice, we found that mouse embryos have rudimentary tooth primordia in the prospective diastema (green). In the anterior part of the diastema (light green), either rudimentary small placodes/buds (D1-D5) or an epithelial thickening (dashed line) develop in the maxilla or mandible, respectively. In the posterior part of diastema (dark green), two rudimentary buds are the most prominent primordia in the cheek region at early stages. Later on, D1-D5 disappear, R1, R2 and MS regress, while R2 is incorporated into the first molar (M1). I - incisor; M2 and M3 – the second and third molars, respectively.

 

   

Present studies

Odontogenesis in wild type mice – model of the normal development of mammalian dentition;

  • comparative odontogenesis studies;
  • development of tooth anomalies in mice with genetic alterations;
  • experimental odontogenesis studies – role of growth activating or inhibiting factors in primordial tooth organ cultures in vitro;
  • Developmental dynamics of tooth development. Fluorescence transgenic mouse embryos and time lapse microscopy are used to study morphological and molecular events during tooth development in real time. 

 

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Tentative explanation of the supernumerary tooth in mouse mutants as an atavistic premolar.
The posterior part of the mouth cavity is at the top of each picture. 3D reconstructions show a similar antero-posterior length of the dental epithelium in wild type (A) and Tabby homo/hemizygous embryos (B) at ED 15. 5. However, the segmentation of the dental epithelium along the antero-posterior axis is different. At the level of one cap of the first molar (M1) in the wild type embryo, we found two small caps (T1, T2) in the mutant. T1 gives rise to the so-called supernumerary tooth (S), which thus corresponds to the anterior part of the M1 in wild type mice. (C) We have suggested a developmental relationship between (a) the last premolar (P4) of non-muroid rodents, (b) the anterior part of the adult M1, (c) the embryonic diastemal vestigial bud (PV) in normal mice, and (d) the supernumerary tooth (S) in mutants. The S in mutants can be considered as an atavism – the revitalization of a premolar suppressed during evolution.

 

 

These studies are made in collaboration with H. Lesot (INSERM U-595, Strasbourg, France) and O. D. Klein (Departments of Orofacial Sciences and Pediatrics, UC, San Francisco, USA).
The results can help to elucidate the origin of tooth anomalies and to develop methods of tooth regeneration and engineering.

 

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Schemes of the pattern of the dental and vestibular epithelium in human embryos and in the teeth of fishes.
(A) A textbook concept presenting two parallel U-shaped ridges in human embryos (e. g. Bhaskar, 1980): DL – dental lamina (giving rise to teeth) and VL – vestibular lamina or labio-gingival band (where the oral vestibule will form). (B) Our 3D reconstructions have documented that no continuous vestibular lamina exists, but rather a set of discontinuous epithelial structures (ridges and bulges) transiently occurs externally to the dental lamina. Red – dental epithelium; blue – vestibular epithelium. c, m1 and m2 – the deciduous canine, first and second molars. The yellow spot indicates the site of fusion between the dental lamina and the vestibular ridges. (For further explanations, see Hovorakova et al., 2005). (C) The schematic pattern of tooth rows (“Zahnreihen”) in fish (according to data by Edmund, 1960). The empty rings and black spots indicate the older and younger teeth, respectively. New teeth are formed at the posterior end of each tooth row.

 

 

Important result in 2013

 

The Reinterpretation of the data on Shh signaling during the early development of the mouse dentition
The tooth development in mice is one of the most often used models to study regulation mechanisms of organogenesis. Since recently, this model started to be used to develop methods of tooth engineering and regeneration. Correct interpretation of the morphological and molecular data is an essential prerequisite of the reliable conclusions of developmental studies on the mouse model of odontogenesis.
We have shown in our study that the firstly appearing structures and its corresponding Shh expression in the upper incisor region in mice (Fig. 1) are not related to two functional incisors but to the tooth rudiments suppressed during evolution (Hovorakova et al., 2013).
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Fig. 1. The early development in the prospective incisor region in the mouse.
(A) Two generations of the Shh expression domains (green and yellow, respectively) and their sequential development are documented on the hybridized upper jaws (B–D), and corresponding 3D reconstructions of the dental and adjacent oral epithelium with visualized Shh expression domains (red), (E–G). Two generations of Shh expression domains correspond to two generations of tooth primordia. The first generation (green arrow) appears anteriorly and it corresponds to the rudimentary primordium. The second generation (yellow arrow) appears posteriorly and it corresponds to the signaling center of the functional incisor.

 

 

The upper mouse incisor development study has finished our systematic revision of classical data on mouse model of tooth development published in the most recent paper by Peterkova et al. (2014). We have shown in both the incisor and cheek region of a jaw that the development until ED13 corresponds to the rudimentary tooth primordia suppressed during evolution. This is in contrast to the classical view assuming their correspondence to the functional teeth. However, the primordia of functional teeth appear later (Fig. 2).

The developing dentition of mice contains primordia, with progressive or regressive development. The studies on their development allow determination of regulation factors involved in growth stimulation or growth retardation. Such information can be very important for regenerative medicine. 

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Fig. 2. Correlation between Shh signaling centers and developing teeth in the mandible of WT mice.
Insert: Shh in situ hybridization of the whole mandible at embryonic day 12.5. Rectangles – functional teeth; round and oval shapes – Shh expression domains of developing teeth. Classical view: According to the literature, Shh expression is present in two signaling centers in each mandible half. The anterior one corresponds to the incisor primordium (I), the posterior one corresponds to the first molar (M1) until embryonic day 14. New view: According to the summary of our recent results, the Shh expression appears in several domains along the antero-posterior jaw axes of the lower jaw. The earlier-appearing domains correspond to the rudimentary tooth primordia in the incisor (pt-green) and cheek (MS-blue; R2-red) regions. Later, the primordia of functional teeth with their signaling centers appear: incisor (I-yellow), first molar (M1-yellow). The signaling centers MS, R2 and M1 appear successively in the posterior direction. In adults, the functional M1 takes its origin with the contribution of R2 rudiment (red rectangle). A minor contribution of MS rudiment cannot be excluded (blue rectangle).

 

 

References

Hovorakova M, Smrckova L, Lesot H, Lochovska K, Peterka M, Peterkova R. Sequential Shh expression in the development of the mouse upper functional incisor. J Exp Zool B Mol Dev Evol. 320B: 455–464, 2013. IF 2,123

Peterkova R, Hovorakova M, Peterka M, Lesot H. Three-dimensional analysis of the early development of the dentition. Aust Dent J. 59:(1 Suppl): 1–26, 2014 Feb 4. doi: 10.1111/adj.12130. [Epub ahead of print] IF 1,371