Effects of Tretinoin on Overall Chicken Embryo and Ocular Development
Effects of Tretinoin on Overall Chicken Embryo and Ocular Development
Dhruvi Patel, Jenisa Gandhi, and Rishi Patel
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Vitamin A is an essential, fat-soluble molecule that is stored in the liver as a retinyl ester (Tantibanchachai, 2014). Retinyl ester can be converted into different derivatives of Vitamin A and shuttled throughout the body to play a role in many physiological processes. Vitamin A is important for ocular and skeletal development in both adults and fetuses; specifically, it plays a critical role in the eyes' formation, shape, and function (Bastos, 2019). There are many different forms of Vitamin A, but retinol, retinal, and retinoic acid are the most commonly used derivatives in medicine, skincare, and pharmaceuticals (Thirunavukarasu, 2022). One form of retinoic acid, tretinoin, is commonly taken orally and topically by women of all ages for acne treatment.
Topical tretinoin is prescribed by many doctors to women without testing for pregnancy, and it is highly accessible because it is also offered over the counter in lower concentrations at almost all pharmacies. Pregnant women should not use tretinoin or take any other topical and oral Vitamin A treatments because excessive levels of Vitamin A can cause teratogenic effects and malformations in the growing fetus's eyes, limbs, and central nervous system (Tantibanchachai, 2014). This causes severe abnormalities of the fetal skeleton as well as spontaneous abortion of the fetus (Bastos, 2019). Tretinoin and other forms of Vitamin A are important topics to study because of their widespread use amongst women, and if taken during pregnancy, it can affect the growth of their fetuses.
While there are many studies showing the effects of excessive Vitamin A on the body and skeletal growth of adult animals such as chickens and hens, there is a literary gap on the effects of Vitamin A on the ocular development of embryos. This study aims to determine the effects of topical tretinoin on the ocular and overall body development of chicken embryos. Three different concentrations of trans-tretinoin (0.025 %, 0.05 %, 0.01%) were applied topically to the chicken eggshells, which were incubated for one week, and then cut open to test for any abnormalities or malformations in the embryos. Chicken embryos serve as an efficient animal model for this research as they are accessible, economical, and anatomically similar to human embryos (Vergara & Canto-Soler, 2012).
Control chicken embryo on day 7.
Chicken embryo on day 7 after application of 0.025% tretinoin cream.
Chicken embryo on day 7 after application of 0.050% tretinoin cream.
Chicken embryo on day 7 after application of 0.100% tretinoin cream.
The results show that the 0.025% tretinoin caused the greatest decrease in both eyeball diameter and body length, with a smaller decrease from the 0.050% and the smallest decrease from the 0.100%. Although the eggs that received the 0.100% tretinoin had longer eyeball diameters and longer body lengths than 0.0250% and 0.050% on average, all the tretinoin treatments eggs still had shorter eyeball diameters and shorter body lengths compared to the control eggs. This shows that all-trans retinoic acid plays a significant role in ocular and overall body development of chicken embryos. Body length was found to be significantly different between groups (p<0.05). Ocular diameter between groups was also found to be significant (p<0.05).
The effects of increasing tretinoin concentrations on the average eyeball diameters of the chicken embryos. Chicken embryo average eyeball diameter (mm) versus tretinoin concentrations (%). Sample sizes: control, n=22; 0.025%, n=21; 0.050%, n=26; 0.100%, n=23. The error bars represent 95% confidence intervals.
The effects of increasing tretinoin concentrations on the average body lengths of chicken embryos. Chicken embryo average body length (mm) versus tretinoin concentrations (%). Sample sizes: control, n=22; 0.025%, n=21; 0.050%, n=26; 0.100%, n=23. The error bars represent 95% confidence intervals.
Similar Studies
Similar Studies
In other studies, all-trans retinoic acid has been found to regulate germ layer formation and body axis formation along with neurogenesis and cardiogenesis. Furthermore, eye development has also been linked to all-trans retinoic acid (Kin et al. 2012). In this study, the highest concentration of tretinoin was found to increase overall body length and eyeball length, which suggests the all-trans retinoic acid potentially aided the embryonic development in higher concentrations. Furthermore, another study concluded high levels of all-trans retinoic acid promote neuroretinal development in retinal organoids and aid the posterior and anterior axis formation of the eye in humans (Isla-Magrané et al. 2022). After administration of the 0.1% tretinoin, the average eyeball diameter was larger compared to 0.025% and 0.05% administrations of tretinoin, but all three were lower than the control. Although higher all-trans retinoic acid concentrations may have impacted ocular development indicated by longer eyeball diameters with increased concentrations, tretinoin still lowered ocular development overall compared to control groups.
Limitations and Future Direction
Limitations and Future Direction
One limitation in this study is that while chicken embryos show similar growth and morphology as human embryos, they are not exactly the same. Also, the embryos were grown in an incubator and not a womb that can contain different conditions. In a womb, there are more confounding factors that could prevent tretinoin from fully absorbing in the embryo, whereas in this experiment, the tretinoin was applied directly to the eggshell so it would reach the embryo. Additionally, extracting the embryos from the eggs may have altered their natural embryonic position, so they had to manually be placed into embryonic position before being measured; this may have led to some differences in measurements between embryos. Between trials, a few embryos from each of the conditions displayed signs of severe inhibition of growth. For example, a few embryos were missing eyes, did not have clear differentiation of appendages, and did not have proper vasculature. Although the embryos were present, it would raise further questions on whether they were viable. Further studies can research viability after administration of tretinoin by opening eggs in further stages of development to determine other factors such as presence and sustenance of a heart rate and advanced development.
Please feel free to contact us if you have further questions about our study.
Please feel free to contact us if you have further questions about our study.
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