Origin of the dental lamina in the regenerating salamander jaw.

Abstract

AbstractThe 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.