Name: Astaras Stelios
Title: The anatomical site, the developmental stage and the differentiation state direct the vulnerability of human mesenchymal cells to UVB radiation.
Supervisor: Dr. Dimitris Kletsas, Research Director
Date: May 8, 2026
Ώρα: 11:00
Place: https://upatras-gr.zoom.us/j/92702932162?pwd=oo2u933CgpbJ8SdUGVXkhyXLuLRGfj.1
ABSTRACT
Skin is the largest organ in humans and because of its location it is characterized as the first defense against biological, environmental and physicochemical insults. Skin is categorized into three layers, the epidermis that is the outermost part of the organ, the dermis that is the main part of the organ and the hypodermis. Fibroblasts are the major cellular components of the dermis and the main extracellular matrix
(ECM) producers. Due to its outermost anatomical location skin is continuously exposed to solar ultraviolet (UV) radiation. The more energetic UVB wavelength (280–315 nm) is mainly absorbed by the epidermis; however, a ~5–10% of its photons reach and affect the upper part of the dermis. On the other hand, UVB radiation is considered as the main effector of premature skin ageing (the so-called photoaging), characterized among others, by skin fibroblasts’ death and premature senescence.
In a previous work of our laboratory it was shown that physiologically relevant UVB radiation doses are cytotoxic and provoke apoptosis to human skin fibroblasts, while the cells possess an arsenal of synergistically acting protective signaling pathways, with JNKs/ATM-p53 activation and interplay being indispensable for the cellular resistance towards UVB radiation and the maintenance of cell viability (Mavrogonatou et al., 2022). Aim of the present work was to explore if the different anatomical sites experiencing a different exposure to UVB radiation play a role in the vulnerability of UVB-treated fibroblasts and what are the molecular mechanisms underlying the resistance of fibroblasts to UVB-induced apoptosis.
Our results show that fibroblasts derived from the face are more resistant to UVB radiation compared to those derived from the arm or the lung. Interestingly, skin and lung fibroblasts from human fetuses are much more vulnerable to UVB radiation, compared to their counterparts from adult donors. Even more intriguingly, human adult adipose-derived mesenchymal stem cells have similar LD50 values with fetal fibroblasts.
Interestingly, JNKs/ATM-p53 axis does not seem to play a photoprotective role in all other cell types. Finally, in all cases an activation of the apoptotic machinery is occurring, as shown by the intense down-regulation of the anti-apoptotic gene BCL-2.
To conclude, these data indicate that the anatomical position, the developmental stage and the level of differentiation direct the vulnerability to UVB radiation, which adds to the well know heterogeneity of human mesenchymal cells. Moreover, the variance in the anti-oxidant capacity, the response to DNA damage and the activation of the apoptotic machinery are involved in the above-mentioned differences and the clarification of the underlying mechanisms may lead to novel photoprotective approaches.
Three-membered inquiry Committee
1. Dimitris Kletsas, Research Director (Supervisor)
Laboratory of Cell Proliferation and Ageing, Institute of Biosciences and Applications, NCSR “Demokritos”
2. Nikos Karamanos, Professor
Biochemistry, Biochemical Analysis & Matrix Pathobiology Research Group, Laboratory of Biochemistry, Department of Chemistry, University of Patras
3. Eleni Mavrogonatou, Senior Researcher
Laboratory of Cell Proliferation and Ageing, Institute of Biosciences and Applications, NCSR “Demokritos”
MSc Presentation - Astaras Stelios