Temperature Is a Key Factor Governing the Toxic Impact of Ultra-Violet Radiation-Emitting Nail Dryers When Used on Human Skin Cells.

The skin is the largest organ in the body and the only one to come into contact with solar UV radiation (UVR). UVA (320-400 nm) is a significant contributor to UV-related skin damage. The UVA spectrum makes up over 95% of solar-UV energy reaching the earth's surface causing the majority of the visible signs of skin photoaging. Many consumer products also emit UVA, including nail dryers. There have been sporadic reports suggesting that these units may be contributing to skin cancer incidence. This notion was recently bolstered by a finding that nail dryer-irradiated mammalian skin cells develop a mutational signature consistent with UVA exposure. This report was surprising considering the comparatively low level of UVA to which the skin is exposed during nail treatments. In this research, we investigated how UVA-emitting devices caused cytotoxic/genotoxic impact after only low levels of UVA exposure. Our data showed that levels of UVA in the unit are highly variable and location dependent. We confirm previous reports that using prolonged exposure protocols could induce significant levels of DNA damage. It was also determined that UV-induced DNA damage only partially correlated with the level of UVA fluency. On investigation, we found that the unit had a rapid increase in internal temperature when in use. Exposing human cells to these elevated temperatures acted synergistically with UVA to magnify the cytotoxic and genotoxic impact of UV irradiation.

A Nude Mouse Model of Xenografted Hypertrophic Scar Cells to Test Therapeutics in the Skin.

BACKGROUND: Existing animal models for testing therapeutics in the skin are limited. Mouse and rat models lack similarity to human skin in structure and wound healing mechanism. Pigs are regarded as the best model with regards to similarity to human skin; however, these studies are expensive, time-consuming, and only small numbers of biologic replicates can be obtained. In addition, local-regional effects of treating wounds that are closely adjacent to one-another with different treatments make assessment of treatment effectiveness difficult in pig models. Therefore, here, a novel nude mouse model of xenografted porcine hypertrophic scar (HTS) cells was developed. This model system was developed to test if supplying hypo-pigmented cells with exogenous alpha melanocyte stimulating hormone (α-MSH) will reverse pigment loss in vivo. METHODS: Dyschromic HTSs were created in red Duroc pigs. Epidermal scar cells (keratinocytes and melanocytes) were derived from regions of hyper-, hypo-, or normally pigmented scar or skin and were cryopreserved. Dermal fibroblasts (DFs) were isolated separately. Excisional wounds were created on nude mice and a grafting dome was placed. DFs were seeded on day 0 and formed a dermis. On day 3, epidermal cells were seeded onto the dermis. The grafting dome was removed on day 7 and hypo-pigmented xenografts were treated with synthetic α-MSH delivered with microneedling. On day 10, the xenografts were excised and saved. Sections were stained using hematoxylin and eosin hematoxylin and eosin (H&E) to assess xenograft structure. RNA was isolated and quantitative real-time polymerase chain reaction (qRT-PCR) was performed for melanogenesis-related genes TYR, TYRP1, and DCT. RESULTS: The seeding of HTSDFs formed a dermis that is similar in structure and cellularity to HTS dermis from the porcine model. When hyper-, hypo-, and normally-pigmented epidermal cells were seeded, a fully stratified epithelium was formed by day 14. H&E staining and measurement of the epidermis showed the average thickness to be 0.11 ± 0.07 µm vs. 0.06 ± 0.03 µm in normal pig skin. Hypo-pigmented xenografts that were treated with synthetic α-MSH showed increases in pigmentation and had increased gene expression of TYR, TYRP1, and DCT compared to untreated controls (TYR: 2.7 ± 1.1 vs. 0.3 ± 1.1; TYRP1: 2.6 ± 0.6 vs. 0.3 ± 0.7; DCT 0.7 ± 0.9 vs. 0.3 ± 1-fold change from control; n = 3). CONCLUSIONS: The developed nude mouse skin xenograft model can be used to study treatments for the skin. The cells that can be xenografted can be derived from patient samples or from pig samples and form a robust dual-skin layer containing epidermis and dermis that is responsive to treatment. Specifically, we found that hypo-pigmented regions of scar can be stimulated to make melanin by synthetic α-MSH in vivo.

CD133 Stimulates Cell Proliferation via the Upregulation of Amphiregulin in Melanoma.

CD133, a cancer stem cell (CSC) marker in tumors, including melanoma, is associated with tumor recurrence, chemoresistance, and metastasis. Patient-derived melanoma cell lines were transduced with a Tet-on vector expressing CD133, generating doxycycline (Dox)-inducible cell lines. Cells were exposed to Dox for 24 h to induce CD133 expression, followed by RNA-seq and bioinformatic analyses, revealing genes and pathways that are significantly up- or downregulated by CD133. The most significantly upregulated gene after CD133 was amphiregulin (AREG), validated by qRT-PCR and immunoblot analyses. Induced CD133 expression significantly increased cell growth, percentage of cells in S-phase, BrdU incorporation into nascent DNA, and PCNA levels, indicating that CD133 stimulates cell proliferation. CD133 induction also activated EGFR and the MAPK pathway. Potential mechanisms highlighting the role(s) of CD133 and AREG in melanoma CSC were further delineated using AREG/EGFR inhibitors or siRNA knockdown of AREG mRNA. Treatment with the EGFR inhibitor gefitinib blocked CD133-induced cell growth increase and MAPK pathway activation. Importantly, siRNA knockdown of AREG reversed the stimulatory effects of CD133 on cell growth, indicating that AREG mediates the effects of CD133 on cell proliferation, thus serving as an attractive target for novel combinatorial therapeutics in melanoma and cancers with overexpression of both CD133 and AREG.

TFEB drives mTORC1 hyperactivation and kidney disease in Tuberous Sclerosis Complex.

Tuberous Sclerosis Complex (TSC) is caused by TSC1 or TSC2 mutations, leading to hyperactivation of mechanistic target of rapamycin complex 1 (mTORC1) and lesions  in multiple organs including lung (lymphangioleiomyomatosis) and kidney (angiomyolipoma and renal cell carcinoma). Previously, we found that TFEB is constitutively active in TSC. Here, we generated two mouse models of TSC in which kidney pathology is the primary phenotype. Knockout of TFEB rescues kidney pathology and overall survival, indicating that TFEB is the primary driver of renal disease in TSC. Importantly, increased mTORC1 activity in the TSC2 knockout kidneys is normalized by TFEB knockout. In TSC2-deficient cells, Rheb knockdown or Rapamycin treatment paradoxically increases TFEB phosphorylation at the mTORC1-sites and relocalizes TFEB from nucleus to cytoplasm. In mice, Rapamycin treatment normalizes lysosomal gene expression, similar to TFEB knockout, suggesting that Rapamycin's benefit in TSC is TFEB-dependent. These results change the view of the mechanisms of mTORC1 hyperactivation in TSC and may lead to therapeutic avenues.