Origin of the dental lamina in the regenerating salamander jaw

Abstract

The origin of the dental lamina (DL) in the regenerating lower jaws of seven species of larval and adult urodeles was examined by various transverse amputation procedures. Collectively the results indicate that jaw and DL regeneration following experimental amputation is a widespread phenomenon in urodeles. In 1/4 and 1/2 amputated jaws of larvae (DL present in the stump), the dental epithelium was replaced from both the anterior and posterior ends of the regenerate area, while in adults it was replaced from the posterior stump tissues only. In 1/4 and 1/2 jaw removals (no DL present in the stump), larval forms exhibited a posterior regrowth of the DL, while in adults DL accumulated at the edge of the regenerate area, resulting in 1/4 and 1/2 edentulous jaws. Removal of all DL in both stumps in larval and adult forms resulted in completely edentulous jaws. The DL does not arise de novo during regeneration, nor is it a direct outgrowth of the DL in the stump. Serial sections made in various planes of the area of the regenerating tip of the DL indicated that DL formation in the regenerate is an epithelio‐mesenchymal interaction caused by the inductive influence of remnant DL in the stump on the adjacent regenerating oral epithelium, resulting in a chain of proliferating and invading cells developing serially and sequentially through time. The mechanism involved in the inductive event remains undetermined.

Comparison of molecular and cellular events during lower jaw regeneration of newt (Cynops pyrrhogaster) and West African clawed frog (Xenopus tropicalis)

“…It has been reported that dentary bone regenerates and fuses at the center of the mandible in newts 6 months after amputation, as demonstrated using 2-dimensional X-ray analysis (Graver, 1974). We detected the regenerated dentary bone fused at the center of the mandible and also regenerating teeth in more detail using 3-dimensional analysis (Fig.…”

Evolution of patterns and processes in teeth and tooth‐related tissues in non‐mammalian vertebrates

“…In aquatic o teichthyan , tooth germs can derive directly from the oral or pharyngeal epithelium without an intervening dental lamina ( 114,170,(253)(254)(255). It is well po sible that the fir t tooth germs to develop in a dentition are always derived directly from the superficial epithelium, rather than indirectly from a dental lamina, as ha been reported for tel o ts ( 46,152,169,240), larval urodeles ( 256) and embryonic crocodile ( 1 19, 121, 171 ). Thi po ibly reflect the ance tral condition as in odontode development (p. 448).…”

Amphibians as research models for regenerative medicine

“…Both larval Ambystoma maculatum and adult newt mandibles regenerated alveolar cartilage and bone across the gap after removal of one-quarter or one-half of the mandible, 77 suggesting that there is no CSD for regeneration in the urodele mandible. In A. maculatum larvae, the dental lamina containing the toothforming epithelium regenerated in both anterior and posterior directions over the regenerated bone, but the adult newt dental lamina exhibited polarity of regeneration, being regenerated only in a posterior direction.…”

“…75,[77][78][79][80] Jaw regeneration takes longer than limb regeneration, about 24 weeks compared to only 4-6 weeks for the limb. Only the tooth bearing skeletal element, the dentary of the maxilla and mandible, is ossified 5 months after amputation.…”