Cellular organization of the human epidermal basal layer: clues sustaining a hierarchical model

Effectiveness and Tolerability of Natural Herbal Formulations in the Prevention of Radiation-Induced Skin Toxicity in Patients Undergoing Radiotherapy

The aim of this study is to investigate the preventive role of 3 herbal formulation products on reducing the incidence of radiation-induced dermatitis in patients undergoing radiotherapy for either breast or head and neck cancer. A total of 59 patients participated in the study. The novel herbal products, a combination of beeswax, olive oil, Calendula and Hypericum oils and Aloe gel, were daily and regularly being used by the patients during radiotherapy and 2 weeks after treatment end. Acute skin toxicity was scored weekly during radiotherapy and after treatment for a further 4-week follow-up period. Demographic data were analyzed by descriptive statistics. Statistical analyses of the study objectives were based on an intent-to-treat principle. Most of the patients presented with grade I (RTOG/EORTC) toxicity in the first weeks of radiotherapy, progressed to grade II but reverted to grade I toxicity up until the study end. A total of 94.9% of the patients had Dermatology Life Quality Index up to 1, and 66.1% remained in this scale. The application of the novel natural product combinations proved to be statistically significantly effective in reducing the intensity of radiation dermatitis, positively affecting the quality of life of the patients.

Epidermal Keratinocyte Depletion during Five Weeks of Radiotherapy is Associated with DNA Double-Strand Break Foci, Cell Growth Arrest and Apoptosis: Evidence of Increasing Radioresponsiveness and Lack of Repopulation; the Number of Melanocytes Remains Unchanged

During fractionated radiotherapy, epithelial cell populations are thought to decrease initially, followed by accelerated repopulation to compensate cell loss. However, previous findings in skin with daily 1.1 Gy dose fractions indicate continued and increasing cell depletion. Here we investigated epidermal keratinocyte response with daily 2 Gy fractions as well as accelerated and hypofractionation. Epidermal interfollicular melanocytes were also assessed. Skin-punch biopsies were collected from breast cancer patients before, during and after mastectomy radiotherapy to the thoracic wall with daily 2 Gy fractions for 5 weeks. In addition, 2.4 Gy radiotherapy four times per week and 4 Gy fractions twice per week for 5 weeks, and two times 2 Gy daily for 2.5 weeks, were used. Basal keratinocyte density of the interfollicular epidermis was determined and immunostainings of keratinocytes for DNA double-strand break (DSB) foci, growth arrest, apoptosis and mitosis were quantified. In addition, interfollicular melanocytes were counted. Initially minimal keratinocyte loss was observed followed by pronounced depletion during the second half of treatment and full recovery at 2 weeks post treatment. DSB foci per cell peaked towards the end of treatment. p21-stained cell counts increased during radiotherapy, especially the second half. Apoptotic frequency was low throughout radiotherapy but increased at treatment end. Mitotic cell count was significantly suppressed throughout radiotherapy and did not recover during weekend treatment gaps, but increased more than threefold compared to unexposed skin 2 weeks post-radiotherapy. The number of melanocytes remained constant over the study period. Germinal keratinocyte loss rate increased gradually during daily 2 Gy fractions for 5 weeks, and similarly for hypofractionation. DSB foci number after 2 Gy irradiation revealed an initial radioresistance followed by increasing radiosensitivity. Growth arrest mediated by p21 strongly suggests that cells within or recruited into the cell cycle during treatment are at high risk of loss and do not contribute significantly to repopulation. It is possible that quiescent (G₀) cells at treatment completion accounted for the accelerated post-treatment repopulation. Recent knowledge of epidermal tissue regeneration and cell cycle progression during genotoxic and mitogen stress allows for a credible explanation of the current finding. Melanocytes were radioresistant regarding cell depletion.