Vitamin A administration in lizards during tail regeneration determines epithelial mucogenesis and delays muscle and cartilage differentiation

Abstract

Regenerating epidermis and spinal cord is essential to maintain tail regeneration in lizards. The effects of vitamin A, an inhibitor of epithelial cornification, have been studied in lizards during tail regeneration. The injection of high doses of vitamin A induces regeneration of a thinner tail with gummy consistency and suppression of the formation of a normal cartilaginous axial skeleton. Microscopic analysis reveals that all epithelia increase the secretion of glycoprotein‐mucus. During the analyzed period the epidermis does not form scales and keratinocytes limit or stop the production of bundles of intermediate filament keratins and packets of corneous beta‐proteins (β‐keratins). Differentiation of oberhautchen and β‐layers is much reduced or inhibited while α‐keratinization and the formation of a corneous layer are affected as well. The effects of vitamin A are dramatic also on mesoderm cells since the treatment stimulates an invasion of blood cells likely due to the disruption of the wall of blood vessels, mesenchymal cell death (pycnosis), and diffuse phagocytosis by immune cells. A delay of cartilage differentiation and cartilage degradation due to an increase of lysosomes in these cells or released by white blood cells explains the lack of stiffness of the regenerating tail after vitamin A treatment. Regenerating muscles are variably affected, ranging from a variable necrotic effect with partial degradation of internal organelles and myofilaments to a massive or complete loss of myofibrils that do not organize in sarcomeres. In general hypervitaminosis A appears to delay epithelial but also mesodermal cell differentiation and maintains the regenerating tail in an immature condition.

Exploring the Effects of Varying Retinol Vitamin A Concentrations on Tissue Regeneration in the Species Asterina coronata

“…In his 2019 study, Lorenzo Alibardi administered vitamin A in four adult wall lizards (Podarcis muralis) during tail regeneration. Regenerating epithelial tissues (apical epidermis and ependyma) simulated tail regeneration [13]. However, Alibardi decided to inject high doses of vitamin A to see whether high concentrations cause epithelial mucogenesis and muscle differentiation delay [13].…”

“…Regenerating epithelial tissues (apical epidermis and ependyma) simulated tail regeneration [13]. However, Alibardi decided to inject high doses of vitamin A to see whether high concentrations cause epithelial mucogenesis and muscle differentiation delay [13]. During the observational period, the epidermis did not form scales, and the differentiation of oberhautchen and β-layers was reduced [13].…”

“…However, Alibardi decided to inject high doses of vitamin A to see whether high concentrations cause epithelial mucogenesis and muscle differentiation delay [13]. During the observational period, the epidermis did not form scales, and the differentiation of oberhautchen and β-layers was reduced [13]. Overall, the injection of high doses of vitamin A caused the degeneration of multiple tissues such as muscle and cartilage during tail regeneration, leading to soft tails rather than the stiffness in the original.…”

“…Overall, the injection of high doses of vitamin A caused the degeneration of multiple tissues such as muscle and cartilage during tail regeneration, leading to soft tails rather than the stiffness in the original. Using these ISSN: 2167-1907 www.JSR.org 2 results, Alibardi determined that the high dosage of vitamin A caused upregulation of a few genes that are involved in retinol metabolisms, such as retinoic acid-binding proteins and retinoic acid receptor gamma protein [13].…”

“…The revelation that vitamin A may instead hinder the developmental process and reverse tissue regeneration in high doses [5,13,17] is expanded upon in Zinder et al's paper. On a cellular level, retinol vitamin A binds to protein receptors such as RBP within the plasma membrane [14].…”