Cell and Tissue Journal

Abstract Introduction: Paxlovid, an investigational oral therapeutic combining the antiviral Nirmatrelvir and the pharmacokinetic enhancer Ritonavir, is being developed to treat SARS-CoV-2 infection, aiming to reduce severe disease progression, hospitalization, and mortality. While its efficacy has been shown in Phase 2/3 trials for non-hospitalized patients, its safety, particularly regarding fetal development, remains under investigation. Coronaviruses have long posed significant challenges to global public health, with their potential to cause severe respiratory infections in humans. Over the past two decades, two novel coronaviruses—Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV) and Middle East Respiratory Syndrome Coronavirus (MERS-CoV)—have emerged, leading to widespread morbidity and mortality. The SARS - CoV outbreak, which occurred in the early 2000s, infected over 8,000 individuals worldwide and resulted in nearly 800 deaths, representing a mortality rate of approximately 10 %. Similarly, MERS - CoV, identified in 2012, caused 857 confirmed infections and 3 34 deaths, with a strikingly high mortality rate of around 35 %. These outbreaks underscored the persistent threat posed by coronaviruses to human health.
Aims: Pregnant women represent a particularly vulnerable population during infectious disease outbreaks, and the potential teratogenic effects of new therapeutics must be carefully evaluated. Previous studies on Nirmatrelvir have explored its effects on skeletal morphogenesis, but comprehensive data on Paxlovid's impact on fetal development remain limited. This study aims to address this gap by investigating the effects of Paxlovid on the reproduction and skeletal morphogenesis of rat embryos, providing critical insights into its safety profile during pregnancy. By elucidating the potential risks associated with Paxlovid, this research contributes to the broader effort to ensure the safe use of antiviral therapies in vulnerable populations. This study assessed the potential embryotoxic effects of Paxlovid on rat fetal skeletal morphogenesis, following ICH guidelines.
Materials and methods: Pregnant rats were divided into four groups, receiving doses of 0, 100/60, 300/200, or 1000 mg/kg/day of Paxlovid. Maternal clinical symptoms and weight were monitored, and fetal outcomes, including weight, crown-rump length (CRL), and abdominal circumference (AC), were evaluated on gestational day 21. Histological analysis of fetal skeletal tissue was conducted using hematoxylin-eosin and Alizarin Red S staining to detect structural abnormalities.
Results: Results showed reduced maternal weight gain in Paxlovid-treated groups compared to controls. Fetuses in treated groups also exhibited lower weight, CRL, and AC. However, histological analysis revealed no structural abnormalities in skeletal tissue. These findings suggest that while Paxlovid may transiently affect fetal growth metrics, it does not induce teratogenic effects on skeletal development.
Discussion: The findings of this study revealed no histological abnormalities in the skeletal system of fetuses exposed to Paxlovid. The observed effects were limited to reductions in fetal weight, crown-rump length (CRL), and abdominal circumference (AC). Collectively, the data from this investigation, along with existing evidence, suggest a low risk of fetal harm associated with Paxlovid, which comprises Nirmatrelvir (NMV), a potent and selective inhibitor of the SARS-CoV-2 main protease, and Ritonavir, a pharmacokinetic enhancer. Nonetheless, the use of Paxlovid during pregnancy should be carefully evaluated, with a thorough discussion of potential risks and benefits conducted in consultation with a healthcare professional.
Conclusion: The study concludes that Paxlovid does not compromise the histological integrity of fetal skeletal tissue, supporting its potential safety during pregnancy. However, further research is needed to understand the mechanisms behind the observed growth effects and to confirm these findings in human populations. Overall, the results indicate a low risk of fetal harm, reinforcing Paxlovid's safety profile for use in pregnant individuals

Abstract Introduction: Titanium dioxide nanoparticles (TiO₂ NPs) are widely used in industry, medicine, food, and cosmetics. TiO₂ NPs are harmful to the environment and human health. Changes in the environment may especially affect the growing neurological system. Therefore, it is impossible to overlook their impact on the development of the embryo and reproductive success. A sensitive and widely used model for evaluating the teratogenic potential and developmental toxicity of different nanoparticles is the chicken embryo. At the outset of embryogenesis, the application of TiO₂ NPs enables the penetration into various tissues, such as brain precursor cells and structures. Furthermore, the organs are unable to remove the nanoparticles from the egg due to their isolation and enclosure from the mother and the environment. Consequently, the embryos are perpetually exposed to TiO₂ NPs during the 20-day embryogenesis period. In recent years, a growing number of studies have been conducted to examine the possible harmful effects of TiO₂ NPs due to worries about inadvertent exposure of NPs on humans.
Aim: In this study, the embryonic toxicity of various dosages of TiO₂ NPs was investigated in the chicken embryo's brain cortex.
Materials and Methods: In this study, 90 fertilized eggs were divided into five groups: control group (untreated group), four treatment groups that received 0 (sham), 12.5, 25, and 50 μg/mL of TiO₂ nanoparticles. The embryos' morphology, weight, and Crown-rump length (CRL) were assessed after 7, 9, and 13 days.   Tissue samples were collected from the cerebrum and cerebellum of the chick embryos. The specimens were immediately fixed in a 10% neutral buffered formalin solution for 48 hours. Subsequently, they were dehydrated through a series of ascending ethanol concentrations (70%, 80%, 90%, and 100%), with each step lasting two hours. The samples were then cleared in xylene for one hour, embedded in paraffin wax, and sectioned at a thickness of 5μm using a microtome. The sections were then mounted on glass slides.  Finally, all tissue sections were stained with hematoxylin and eosin, and the effects of TiO₂ NPs were examined on the histology, pathology, and histomorphometry of the chick embryo cerebrum and cerebellum tissues.
Results: The findings showed that TiO₂ NPs cause embryo death in all days at 25 and 50 μg/mL. In morphological studies, the weight and length of 13-day-old embryos treated with 50 μg/mL of TiO₂ NPs decreased. Counting of cells (neurons and glial cells) in the cerebral cortex of a 13-day-old chick embryo displayed a significant decrease in the experimental group of 50 μg/ml compared to the control and sham groups. The evaluations showed a decrease in the number of Purkinje cells of the cerebellum cortex in 13-day-old embryos treated with 50 μg/ml of TiO₂ NPs.   The group of 13-day-old embryos treated with 50 µg/ml had a considerable capillary hyperemia in the cerebellar cortex.
Conclusion: It was concluded that the in-ovo-administered TiO₂ NPs given immediately before incubation have adverse effects on the developing cerebellum and cerebrum. So that the increase of damage happened in older embryos, and the highest damage occurred on day 13 of incubation.