BACKGROUND:The 49-year history of the Teratology Society is reviewed. An abbreviated history is outlined in table form, with listings of the Warkany Lectures, the Continuing Education Courses, and officers of the society. The original article was updated to include the years 2000 to 2010.METHODS:A year-by-year description of the events is given, including the scientific and social content of the annual meetings and changes in the business of the society, in many cases using comments from the past presidents. The valuable and unique diversity of the members is discussed and illustrated, presenting the disciplines and main research areas of the presidents. The number of submitted abstracts and the various categories are tabulated, averaging the number and type over successive periods. A significant increase in the number of abstracts dealing with epidemiology and developmental biology is evident. The society's development is compared to that of a human, and the question was asked by Shephard et al. (2000): Have we reached the maturational stage of old age or senescence, or is the society still maturing gracefully? This question needs further discussion by all the members. By 2010, many positive changes are happening to revitalize the society.RESULTS:During the past 50 years, we have developed the scientific basis to prevent birth defects caused by rubella, alcoholism, and folate deficiency, as well as other prenatal exposures. We are now taking advantage of advances in many fields to begin shaping the Teratology Society of the 21st century.CONCLUSIONS:We must now engage in political battles to obtain the resources needed to conduct further research and to implement prevention programs, as well as to provide care and rehabilitation for persons with birth defects.

TeratologyVolume 63, Issue 6 p. 211-241 ProgramFree Access The Teratology Society 41st Annual Meeting June 23 – 28, 2001: Program and abstracts First published: 17 May 2001 https://doi.org/10.1002/tera.1036AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Volume63, Issue6June 2001Pages 211-241 RelatedInformation

Multiple fetal anomalies occur in vitamin A deficient animals as well as in retinoic acid receptor gene 'knockout' mice, indicating that retinoic acid (an active metabolite of vitamin A) performs some essential functions in normal development. Additional approaches are needed to probe directly the stages and sites in the embryo where a presence of endogenous retinoic acid is indispensable. We have employed a new strategy for this purpose which involved an intervention in retinoic acid receptor (RAR)-dependent functions at specific developmental stages by means of a highly effective RAR antagonist, AGN 193109. We report that in an in vitro cell differentiation bioassay, AGN 193109 completely reversed the inhibitory action of a potent RAR agonist, AGN 190121. In pregnant mice, a single oral 1 mg/kg dose of the antagonist given on 8 day post coitum (dpc) produced a severe craniofacial anomaly (median cleft face or frontonasal dysplasia) and eye malformations in virtually all exposed fetuses. On the other hand, treatment on 11 dpc, a time in development when RARs are strategically expressed in the limb bud primordium, no limb anomalies could be induced by the antagonist. Even after a high dose of 100 mg/kg, limb development progressed normally in spite of the fact that measurable concentrations of the antagonist were present. Because retinoids are long known to influence skin morphology, we next monitored the effects of the antagonist on skin development. When given late in gestation, on 14 dpc, we found that the antagonist delayed differentiation and maturation of the fetal skin and hair follicles. We conclude that this model provides a convenient and pertinent system which enables us to seek and clarify true functions of retinoic acid and its cognate receptors in embryogenesis and in adult animals.

Tretinoin has been thoroughly evaluated for its potential as an embryofetal developmental toxicant. Oral tretinoin produces developmental anomalies in animal models; the minimal teratogenic dose is consistently 2.5 to 10 mg/kg. In contrast, topical application does not induce developmental malformations in laboratory animals. A structurally related compound, isotretinoin, is a potent toxicant in humans and animals; the lowest systemic dose that induces fetal anomalies varies more than 100-fold depending on the model. Oral isotretinoin is a more potent developmental toxicant than oral tretinoin in monkeys. Between-drug differences in the metabolism and transplacental transfer of the two retinoids account for the differences in toxicant potency. Pharmacokinetic studies reveal that absorption of tretinoin from the skin is poor and yields maternal plasma concentrations below the developmentally toxic threshold established after oral administration. Analysis of outcomes of developmental toxicology and pharmacokinetic studies suggests that the human risk of fetal anomalies is negligible after therapeutic application of topical tretinoin.

An excess of retinoic acid (RA) in the mouse embryo in utero produces hypochondrogenesis and severe limb bone deformities. Since one of the RA receptors--RAR-beta 2, is specifically induced in the limb bud cells upon treatment of embryos with teratogenic doses of RA, we investigated if this receptor played a role in teratogenesis by regulating the process of chondrogenesis. In micromass cultures of mouse limb bud mesenchymal cells, we found that a downregulation of RAR-beta 2 as well as several other RAR isoforms by supplementation of the culture medium with specific oligodeoxynucleotides stimulated chondrogenesis: cartilage nodule number, sulfated proteoglycans, and synthesis of collagen type IIB were all enhanced in a dose-dependent manner. However, only the antisense RAR-beta 2 probe efficiently prevented the strong inhibitory effects of exogenous RA on chondrogenesis in these cells. The data suggest that the RAR-RA complexes play a role in position-dependent patterning of the limb skeleton in normal development and that, in particular, RAR-beta 2 serves to prevent the mesenchymal cells from expressing their chondrogenic bias. Our results further strengthen the argument that RA-dependent elevation in RAR-beta 2 levels plays a unique role in RA-induced teratogenesis.

Retinoic acid (RA) plays an important role during normal embryogenesis, however high doses of RA are teratogenic. Retinoic acid receptor-beta 2 (RAR-beta 2) mRNA and protein levels were previously demonstrated to undergo rapid elevation in susceptible tissues after treatment with teratogenic doses of RA. In this report we compared the effects of a number of retinoids, which represent a wide variety of chemical structures and which differ in their teratogenic potencies, on RAR-beta 2 mRNA levels in mouse embryos 6 hr after treatment. Retinoid treatments which result in a high incidence of limb defects elevated RAR-beta 2 mRNA levels similarly (10-14 fold in the limb buds, 4-8 fold in the head, and 2-4 fold in the remainder of the body). On the other hand, retinoid treatments which cause a low or no incidence of limb defects resulted in minor changes in RAR-beta 2 mRNA levels in each embryonic region. Therefore, a strong positive correlation was found between the elevation of RAR-beta 2 mRNA levels and the retinoids which produce limb defects. This provides further evidence that an elevation of RAR-beta 2 mRNA levels, and subsequently protein levels, is an important event involved in mediating the effects of RA during dysmorphogenesis.

Vitamin A and its analogs (retinoids) have acquired particular significance in embryonic development since the discovery that retinoic acid (RA) possesses properties of an endogenous morphogen and that embryonic tissues contain specific nuclear receptors for RA. Since the mammalian embryo does not synthesize RA de novo but rather must acquire it directly or in a precursor form from the maternal circulation, we sought to establish the relationship between levels of RA, retinol, and retinyl esters in the maternal system and their acquisition by the embryo, particularly during organogenesis in the mouse. Results indicate profound changes in maternal vitamin A levels during pregnancy in the mouse. These changes were characterized by a large, transient decrease in plasma retinol levels coincident with the period of organogenesis (e.g. gestational Days 9-14), and an apparent increase in mobilization from hepatic stores to the conceptus. During organogenesis, the embryo exhibited a steady increase in retinol levels with little increase in retinyl esters and virtually no change in RA. Analysis of retinoid accumulation patterns in the embryonic liver indicate that functional onset of vitamin A storage occurs by mid-organogenesis. In contrast, placental levels of these retinoids remained unchanged throughout organogenesis. Analysis of the conceptus as a developmental unit revealed that during early organogenesis the majority of retinoids are contained in the placenta (8-fold more than in the embryo). However, by mid-organogenesis the retinoid content of the embryo exceeds that of the placenta. Together, these results provide evidence that pregnancy in the mouse is accompanied by pronounced alterations in maternal retinoid homeostasis that occur coincident with the period of high embryonic sensitivity to exogenous retinoids.

It has been reported that fractionated doses of 13-cis-retinoic acid are disproportionately more embryotoxic in pregnant mice than is the same dose given in a single bolus. Here, we examined limited pharmacokinetic profiles of a single (100 mg/kg dose given to NMRI mice on day 11 of gestation) versus multiple (3 x 100 mg/kg, 4 h apart) doses in an effort to assess the relative contribution to teratogenicity made by the drug and/or its metabolites. The major plasma metabolite of 13-cis-retinoic acid in the mouse was 13-cis-retinoyl-beta-glucuronide, followed by the 4-oxo metabolites and all-trans-retinoic acid. Transfer to the mouse embryo was very efficient for all-trans-retinoic acid, whereas, it was tenfold less efficient for 13-cis-retinoic acid and 100-fold less efficient for 13-cis-retinoyl-beta-glucuronide. The isomer all-trans-retinoic acid was found in the placenta at concentrations two- to three-fold higher than in the plasma, suggesting placental accumulation as well as placental cis/trans isomerization. Since 13-cis-retinoyl-beta-glucuronide and 13-cis- and all-trans-retinoic acid were detected in the embryo after this multiple dosing schedule, any of the three or their combinations may have been involved in the induction of malformations, but all-trans-retinoic acid, a well-known potent teratogen detected at concentrations of between 590 and 80 ng/g for 10 critical hours during gestation, could have been the major component.

TeratologyVolume 39, Issue 6 p. 615-616 Letter Response to Kalter D. M. Kochhar, D. M. Kochhar Thomas Jefferson University, Philadelphia, PA 19107Search for more papers by this author D. M. Kochhar, D. M. Kochhar Thomas Jefferson University, Philadelphia, PA 19107Search for more papers by this author First published: June 1989 https://doi.org/10.1002/tera.1420390613Citations: 1AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Literature Cited Anonymous (1987) Teratology Society position paper: recommendations for vitamin A use during pregnancy. Teratology, 35: 269–275. Creech Kraft, J., D. M. Kochhar, W. J. Scott, and H. Nau (1987) Low teratatogenicity of 13-cis retinoic acid (isotretinoin) in the mouse corresponds to low embryo concentrations during organogenesis: Comparison to the all-trans isomer. Toxicol. Appl. Pharmacol., 87: 474–482. Giguere, V., E. S. Ong, P. Segui, and R. M. Evans (1987) Identification of a receptor for the morphogen retinoic acid. Nature, 330: 624–629. Kochhar, D. M., J. D. Penner, and M. A. Satre (1988) Derivation of retinoic acid and metabolites from a teratogenic dose of retinol (vitamin A) in mice. Toxicol. Appl. Pharmacol., 96: 429–441. Napoli, J. L., and K. R. Race (1987) The biosynthesis of retinoic acid from retinol by rat tissues in vitro. Arch. Biochem Biophys., 255: 95–101. Petkovich, M., N. J. Brand, A. Krust, and P. Chambon (1987) A human retinoic acid receptor belongs to the family of nuclear receptors. Nature, 330: 444–450. Thaller, C., and G. Eichele (1987) 625–628. Willhite, C. C. (1989) Molecular correlates in retinoid pharmacology and toxicology. In: Chemistry and Biology of Synthetic Retinoids. M. I. Dawson and W. H. Okamura, eds. CRC Press, Inc., Boca Raton, FL. In press. Williams, J. B., and J. L. Napoli (1985) Metabolism of retinoic acid and retinol during differentiation of F9 embryonal carcinoma cells. Proc. Natl. Acad. Sci. USA, 82: 4658–4662. Citing Literature Volume39, Issue6June 1989Pages 615-616 ReferencesRelatedInformation

The transplacental pharmacokinetics of single teratogenic doses of etretinate and motretinide were compared with particular emphasis on distribution and concentrations in the exposed embryos of the free acid metabolite, etretin. The three aromatic retinoids were also tested for their direct inhibitory effect on chon-drogenesis in the limb bud mesenchymal cell “micromass” culture assay. After a standard dose of 100 nig/kg administered on day 11 of gestation in nmri mice, all three compounds were teratogenic, but they differed from each other in potency. Etretinate was most active as a teratogen, equalling the potency of our standard all-trans-retinoic acid; every exposed fetus was deformed with severe shortening of all limb bones as well as cleft palate. Etretin was less potent than etretinate, and motretinide was considerably less active as a teratogen than the other two. In the in vitro assay, only etretin suppressed chondrogenesis and this activity was equivalent to that of all-trans-retinoic acid (ic50 of 12 ng/ml). Both etretinate and motretinide (which contain an ethyl ester and ethylamide terminal group, respectively) were essentially inactive in vitro, demonstrating the fact that a free carboxylic group may be a requirement for the in vitro suppression of chondrogenesis. These differences between the results obtained in vivo and in vitro could be resolved by pharmacokinetic investigations using hplc methods. Both etretinate and motretinide were metabolized in vivo to etretin, their likely common teratogenic metabolite. The high teratogenic potency of etretinate was probably the result of high concentrations as well as AUC values of its metabolite etretin in the embryo. On the other hand, the comparatively low teratogenicity of motretinide could be related to approximately 5 × lower embryonic peak levels as well as AUC values of etretin. A comparison of these results with those previously obtained for all-trans- and 13-cis-retinoic acids confirms the correlation between embryonic exposure and teratogenic potency in the mouse. Our results indicate that pharmacokinetic studies are essential for the interpretation of relative teratogenic potencies of retinoids as well as apparent differences between in vivo and in vitro teratogenesis. A free carboxyl group at the terminal end of the tetraene chain was necessary for high activity of the retinoids studied.

As a teratogenic agent retinoic acid (RA) produces severe limb reduction defects if administered at a certain stage of embryonic development. In vitro, RA is able to prevent chondrogenesis and this inhibitory effect is accompanied by the absence of cartilage specific proteoglycans in treated cultures. Such an effect is ruled out as a direct causative factor in teratogenesis for two reasons. First, the limbs of treated embryos show extensive chondrogenesis and this cartilage is normal as far as the expression of biochemical markers of differentiation are concerned. Second, the morphogenetic effects of a mutant gene, cmd, where there is a functional deficit of the proteoglycan core protein are very different from those associated with RA-induced teratogenesis. The differences between the two are not wholly reconciled by the fact that the effects of the mutant gene are cumulative and progressive while those of the RA insult are transitory. There are a number of developmental events which are, however, altered by RA in the mesenchymal cells of the early limb bud such as cell proliferation, cell death, and hyaluronic acid metabolism. Not only any one or more of these factors may secondarily inhibit chondrogenesis but, more importantly, may also have a number of other consequences in the developing embryo. Since a number of cell types besides mesenchymal cells respond to RA by altering their pattern of differentiation, it is conceivable that some fundamental molecular step in the process of differentiation provides a target for its action. In a recent review, Sporn and Roberts (1983) have suggested that to be compatible with the wide ranging effects of retinoids documented so far, any hypothesis put forward for its molecular mechanism of action must include a role in gene expression. No experimental work has yet directly addressed how retinoids might modify gene expression. We believe that along with teratocarcinoma stem cell lines, the use of retinoids as selective teratogens may open up another avenue in search of molecular mechanisms of cell differentiation.

The cmd mutation is associated with a systemic defect in all parts of the cartilaginous skeleton. Since limb buds isolated from the embryos and cultured in vitro develop the defect, the gene expression is independent of the humoral factors in the maternal/placental/embryonic environment. The limb development in the mutant progresses normally through early events in morphogenesis including the formation of mesenchymal cell condensations preparatory to chondrogenesis. The deviation first becomes apparent as soon as the chondrogenic cells begin the process of accumulation of extracellular matrix; cmd/cmd chondrogenic cells remain close to each other and lack the abundant extracellular matrix which accumulates between normal cells. Quantitatively normal levels of chondroitin sulfate proteoglycans are synthesized by the mutant limbs during precartilaginous stages. Subsequently, however, the mutant fails to attain the normally high levels of chondroitin sulfate synthesis. Its growth rate also slows down, as judged by the lowered protein synthesis in the mutant cultured limb buds. The lack of at least one species of protein molecules, ie, proteoglycan core-protein, is already known from previous studies on this mutation; an abnormal or a deficient core-protein was shown to lead to a virtually complete shut off of the biosynthesis of cartilage-specific proteoglycans in another mutation in the chick embryo [Goetinck, 1982]. It may be important to note that the cmd mutation does not seem to interfere with the process of determination of cartilage even though it interrupts virtually completely one important biosynthetic aspect of the chondrogenic cell differentiation pathway. The mutant chondrocytes, embedded as they are in an abnormal and proteoglycan-deficient matrix, begin to degenerate prematurely without first undergoing hypertrophy. Also, the process of ossification begins precociously in the shortened cartilage models of the mutant, hence resulting in overall shortening of the limbs. As assessed from the HA:s-GAG ratios during early embryonic limb development, some of the phenotypically normal embryos could be distinguished as recessive carriers of the mutation. Even though these carriers have an intermediate level of chondroitin sulfate proteoglycan synthesis, this does not interfere with their normal development during prenatal stages. It will be of practical importance to follow these carriers through subsequent postnatal stages and adult life to assess any long-term effects.

The Consensus Workshop on In Vitro Teratogenesis Testing recommended that test validation be facilitated by a listing of agents with defined teratogenicity; subsequently, a panel was convened to review and select such agents. This communication established a list of 47 compounds or conditions which demonstrate a wide range of teratogenicity in vivo. The agents were chosen primarily on the strength of the literature base denoting their in vivo effects. The tables note a number of general biological and toxicological characteristics for each agent, and the details of representative in vivo teratology studies are summarized and referenced. This list is intended to serve as a base for in vitro teratogenesis test validation and should prove useful in developing and identifying those systems which will contribute to a more effective testing program.

It is not my purpose to review the field of experimental embryology that deals with tissue culture of mammalian embryonic organs (Wessells 1967). A number of embryonic organs and tissues are known to undergo morphogenesis and attain functional maturation upon explanation in vitro, and their capabilities have been exploited to a variable degree in investigations on developmental mechanisms and the processes of cell differentiation (Saxén and Kohonen 1969). Some examples are: kidney (Grobstein 1956; Saxén et al. 1968), sex organs (Odor and Blandau 1971; Haffen 1976), pancreas (Sarras et al. 1981; Maylde-Pfenninger and Jamieson 1981; Grobstein 1953), skin (Sugimoto and Endo 1969), tooth (Thesleff 1976; Thesleff et al. 1981), palate (Moriarty et al. 1963; Lahti et al. 1972; Newall and Edwards 1976, 1981; Greene and Pratt 1977), other craniofacial tissues (Johnston and Listgarten 1972; Johnston et al. 1977; Greenberg and Schrier 1977), and limbs (Agnish and Kochhar 1977; Kochhar et al. 1976). Any of these or other developing organs are suitable subjects for the development of a teratologic screening system. This chapter, however, is limited to just one example, i.e., limb bud, that may suffice to bring out feasibility, advantages, and shortcomings of organ culture system in general for short-term teratologic screening purposes.

The limb bud organ culture system offers a variety of endpoints which may be monitored in the screening process. These are: cell proliferation, differential growth, morphogenetic cell death, size and shape of limb parts, chondrogenesis, collagen or proteoglycan biosynthesis, etc. Essentials of the system including various parameters of normal limb bud development in vitro are described. These parameters serve to gauge the effects of test chemicals with unknown hazard potential. Validation has been carried out only to a limited extent. Further, it needs to be combined with an efficient drug metabolizing preparation before it can achieve its full potential as a short-term screening system.

The need for efficient methods to screen new chemicals, drugs, and environmental pollutants for their teratogenic activity is obvious. The method currently available, ie, pregnant-animal testing, is of considerable value but there are certain drawbacks which prevent reliance on this method alone as the predictive device. Nutritional state of the dam, variability in the developmental age of embryos from litter to litter and even within the same litter, metabolic differences between species, placental function, and a host of other factors must be taken into account before data obtained from animal testing can be logically extrapolated to human situation. Many of these variables are either eliminated altogether or at least can be controlled by the use of tissue culture techniques. After surveying a variety of in vitro systems, it is our opinion that organ culture, whole embryo culture, and a combination of the two offer at present the best potential for screening of suspected teratogens. These culture techniques provide a much better simulation of in vivo situations than isolated cells grown as monolayers. Among other advantages, these procedures allow one to exercise control over the effective concentration of the suspected teratogen to which an embryo is exposed and also the duration of this exposure. Since maternal metabolism or modification of the drug is routinely eliminated in these experiments, there is a need for exploring the use of drug-metabolizing preparations as additives to the culture medium. The choice of limb bud in the screening system is promising since during its development, the limb progresses through a succession of embryonic processes that are generally relevant to other organ systems as well. Hence, such a screening system may not only predict teratogenicity but also provide insight into the mechanisms by which a test chemical is teratogenic.

Maternal administration of a single dose of retinoic acid (vitamin A acid, 100 mg/kg) on either the 11 th, 11 1/2, 12th, 12 1/2, 13th or 13 1/2 day of gestation produced phocomelia or partial phocomelia in ICR/DUB fetuses. The results depended upon the time of treatment and two gradients of effect were produced: 1) cranio-caudal gradient, since forelimb defects resulted from treatment between days 11 and 13, while similar hindlimb abnormalities were produced by administration of retinoic acid 12 to 24 hours later: 2) proximo-distal gradient, due to the heterogenous sensitivity among individual bones of the limb. In the forelimb, early treatment (11th day) produced humero-ulnar defects and later treatment (12th day) ulnoradial defects. A similar proximo-distal gradient was observed in the hindlimb. The use of teratological studies as a tool to assist morphogenetic investigation is discussed.