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EMBRYONIC PALATAL RESPONSES TO TERATOGENS IN SERUM-FREE ORGAN CULTURE
Citation:
Abbott, B. AND A. Buckalew. EMBRYONIC PALATAL RESPONSES TO TERATOGENS IN SERUM-FREE ORGAN CULTURE. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/J-92/190 (NTIS PB92188960), 1992.
Description:
This study examines development of rat, mouse and human embryonic palates in submerged, serum-free organ culture. he concentration-response profiles for retinoic acid (RA), triamcinolone (TRI), hydrocortisone (HC), dexamethasone (DEX), and 2,3,7,11- tetrachlorodibenzo-p-dioxin (TCDD) were examined and the mechanisms of clefting in vitro were compared to observed in vivo responses. Craniofacial regions were dissected on GD 12 for mice and GD 14 for rat, and cultured for 3-4 days in Bigger'd BGJb medium in flasks flushed with 50% 02, 45% N2, 5% C02. Growth and fusion of secondary palate: as scored under a dissecting microscope. In serum-free control medium, mouse and rat: palatal fusion occurred within the f day culture period. Supplementing with FBS in excess of 1:% interfered with growth and fusion in control medium. A significantly inhibited fusion of mouse and rat palates at 5x10-9 M and 1x10-10 M, respectively, with RA-induced clefting related to abnormal proliferation and differentiation of medial epithelia. In contrast, glucocorticoid-induced clefting was due to concentration dependent inhibition of shelf growth. TRI significantly inhibited fusion at 4 x 10-5 M, and 1 x 10-4 M DEX or HC, inhibited fusion of 19% and 42% of shelves, respectively. The response rate for DEX in the presence of 1% FBS was increased (42% unfused. CDD clefting was due to altered medial epithelial differentiation and 1 x 1O-8 M TCDD affected 36% of CD-1 mouse, 23% of C57BL/6N mouse, and 47% of F344 rat palates. When the medium was supplemented with 1% FBS, selenium, transferrin, and additional glutamine, the response for C46BL/6N embryos increased to 75%. This rate is similar to that reported for Trowell's-type cultures with IMEM:F12 medium and 1% FBS. The increased responsiveness to DEX or TCDD in presence of serum suggests that an unknown factor in serum maybe required for full activity. Three human embryonic palatal explants (GD 52 or 53) were cultured for 3-6 days and fused during culture. The present study demonstrates that serum-free organ culture supports development of mouse, rat, and human palatal explants. The present study demonstrates the capacity of this organ culture system to model palatogenesis for several species, and to distinguish between various mechanisms fo clefting as presented through selected model compounds. This model should be useful for exploring mechanisms of activity at a cellular and molecular level.