Exposure of skin tissue to UV radiation has been shown to cause DNA photodamage. If this damaged DNA is allowed to
replicate, carcinogenesis may occur. DNA damage is prevented from being passed on to daughter cells by upregulation
of the protein p21. p21 halts the cells cycle allowing the cell to undergo apoptosis, or repair its DNA before replication.
Previous work suggested that milk phospholipids may possess protective properties against UV damage. In this study,
we observed cell morphology, cell apoptosis, and p21 expression in tissue engineered epidermis through the use of
Hematoxylin and Eosin staining, confocal microscopy, and western blot respectively. Tissues were divided into four
treatment groups including: a control group with no UV and no milk phospholipid treatment, a group exposed to UV
alone, a group incubated with milk phospholipids alone, and a group treated with milk phospholipids and UV. All
groups were incubated for twenty-four hours after treatment. Tissues were then fixed, processed, and embedded in
paraffin. Performing western blots resulted in visible p21 bands for the UV group only, implying that in every other
group, p21 expression was lesser. Numbers of apoptotic cells were determined by observing the tissues treated with
Hoechst dye under a confocal microscope, and counting the number of apoptotic and total cells to obtain a percentage of
apoptotic cells. We found a decrease in apoptotic cells in tissues treated with milk phospholipids and UV compared to
tissues exposed to UV alone. Collectively, these results suggest that milk phospholipids protect cell DNA from damage
incurred from UV light.
Current research on bioactive molecules in milk has documented health advantages of bovine milk and its components.
Milk Phospholipids, selected for this study, represent molecules with great potential benefit in human health and
nutrition. In this study we used confocal reflectance and multiphoton microscopy to monitor changes in skin
morphology upon skin exposure to ultraviolet light and evaluate the potential of milk phospholipids in preventing
photodamage to skin equivalent models. The results suggest that milk phospholipids act upon skin cells in a protective
manner against the effect of ultraviolet (UV) radiation. Similar results were obtained from MTT tissue viability assay