• Does blue light restore human epidermal barrier function via activation of Opsin during cutaneous wound healing?

      Castellano-Pellicena, Irene; Uzunbajakava, N.E.; Mignon, Charles; Raafs, B.; Botchkarev, Vladimir A.; Thornton, M. Julie (2019-04)
      Background and Objective Visible light has beneficial effects on cutaneous wound healing, but the role of potential photoreceptors in human skin is unknown. In addition, inconsistency in the parameters of blue and red light‐based therapies for skin conditions makes interpretation difficult. Red light can activate cytochrome c oxidase and has been proposed as a wound healing therapy. UV‐blue light can activate Opsin 1‐SW, Opsin 2, Opsin 3, Opsin 4, and Opsin 5 receptors, triggering biological responses, but their role in human skin physiology is unclear. Materials and Methods Localization of Opsins was analyzed in situ in human skin derived from face and abdomen by immunohistochemistry. An ex vivo human skin wound healing model was established and expression of Opsins confirmed by immunohistochemistry. The rate of wound closure was quantitated after irradiation with blue and red light and mRNA was extracted from the regenerating epithelial tongue by laser micro‐dissection to detect changes in Opsin 3 (OPN3) expression. Retention of the expression of Opsins in primary cultures of human epidermal keratinocytes and dermal fibroblasts was confirmed by qRT‐PCR and immunocytochemistry. Modulation of metabolic activity by visible light was studied. Furthermore, migration in a scratch‐wound assay, DNA synthesis and differentiation of epidermal keratinocytes was established following irradiation with blue light. A role for OPN3 in keratinocytes was investigated by gene silencing. Results Opsin receptors (OPN1‐SW, 3 and 5) were similarly localized in the epidermis of human facial and abdominal skin in situ. Corresponding expression was confirmed in the regenerating epithelial tongue of ex vivo wounds after 2 days in culture, and irradiation with blue light stimulated wound closure, with a corresponding increase in OPN3 expression. Expression of Opsins was retained in primary cultures of epidermal keratinocytes and dermal fibroblasts. Both blue and red light stimulated the metabolic activity of cultured keratinocytes. Low levels of blue light reduced DNA synthesis and stimulated differentiation of keratinocytes. While low levels of blue light did not alter keratinocyte migration in a scratch wound assay, higher levels inhibited migration. Gene silencing of OPN3 in keratinocytes was effective (87% reduction). The rate of DNA synthesis in OPN3 knockdown keratinocytes did not change following irradiation with blue light, however, the level of differentiation was decreased. Conclusions Opsins are expressed in the epidermis and dermis of human skin and in the newly regenerating epidermis following wounding. An increase in OPN3 expression in the epithelial tongue may be a potential mechanism for the stimulation of wound closure by blue light. Since keratinocytes and fibroblasts retain their expression of Opsins in culture, they provide a good model to investigate the mechanism of blue light in wound healing responses. Knockdown of OPN3 led to a reduction in early differentiation of keratinocytes following irradiation with blue light, suggesting OPN3 is required for restoration of the barrier function. Understanding the function and relationship of different photoreceptors and their response to specific light parameters will lead to the development of reliable light‐based therapies for cutaneous wound healing.
    • A new path in defining light parameters for hair growth: discovery and modulation of photoreceptors in human hair follicle

      Buscone, S.; Mardaryev, Andrei N.; Raafs, B.; Bikker, J.W.; Sticht, C.; Gretz, N.; Farjo, N.P.; Uzunbajakava, N.E.; Botchkareva, Natalia V. (2017-09)
      Background and Objective: Though devices for hair growth based on low levels of light have shown encouraging results, further improvements of their efficacy is impeded by a lack of knowledge on the exact molecular targets that mediate physiological response in skin and hair follicle. The aim of this study was to investigate the expression of selected light-sensitive receptors in the human hair follicle and to study the impact of UV-free blue light on hair growth ex vivo. Material and Methods: The expression of Opsin receptors in human skin and hair follicles has been characterised using RT-qPCR and immunofluorescence approaches. The functional significance of Opsin 3 was assessed by silencing its expression in the hair follicle cells followed by a transcriptomic profiling. Proprietary LED-based devices emitting two discrete visible wavelengths were used to access the effects of selected optical parameters on hair growth ex vivo and outer root sheath cells in vitro. Results: The expression of OPN2 (Rhodopsin) and OPN3 (Panopsin, Encephalopsin) was detected in the distinct compartments of skin and anagen hair follicle. Treatment with 3.2 J/cm2 of blue light with 453 nm central wavelength significantly prolonged anagen phase in hair follicles ex vivo that was correlated with sustained proliferation in the light-treated samples. In contrast, hair follicle treatment with 3.2 J/cm2 of 689 nm light (red light) did not significantly affect hair growth ex vivo. Silencing of OPN3 in the hair follicle outer root sheath cells resulted in the altered expression of genes involved in the control of proliferation and apoptosis, and abrogated stimulatory effects of blue light (3.2 J/cm2; 453 nm) on proliferation in the outer root sheath cells. Conclusions: We provide the first evidence that 1) OPN2 and OPN3 are expressed in human hair follicle, and 2) 453 nm blue light at low radiant exposure exerts a positive effect on hair growth ex vivo, potentially via interaction with OPN3.
    • Photobiomodulation devices for hair regrowth and wound healing: a therapy full of promise but a literature full of confusion.

      Mignon, Charles; Botchkareva, Natalia V.; Uzunbajakava, N.E.; Tobin, Desmond J. (2016)
      Photobiomodulation is reported to positively influence hair regrowth, wound healing, skin rejuvenation, and psoriasis. Despite rapid translation of this science to commercial therapeutic solutions, significant gaps in our understanding of the underlying processes remain. The aim of this review was to seek greater clarity and rationality specifically for the selection of optical parameters for studies on hair regrowth and wound healing. Our investigation of 90 reports published between 1985-2015 revealed major inconsistencies in optical parameters selected for clinical applications. Moreover, poorly understood photoreceptors expressed in skin such as cytochrome c oxidase, cryptochromes, opsins, may trigger different molecular mechanisms. All this could explain the plethora of reported physiological effects of light. To derive parameters for optimal clinical efficacy of photobiomodulation, we recommend a more rational approach, underpinning clinical studies with research of molecular targets and pathways using well-defined biological model systems enabling easy translation of optical parameters from in vitro to in vivo. Furthermore, special attention needs to be paid when conducting studies for hair regrowth, aiming for double-blind, placebo-controlled randomized clinical trials as the gold standard for quantifying hair growth.
    • Photobiomodulation of human dermal fibroblasts in vitro: decisive role of cell culture conditions and treatment protocols on experimental outcome

      Mignon, Charles; Uzunbajakava, N.E.; Raafs, B.; Botchkareva, Natalia V.; Tobin, Desmond J. (2017-06-05)
      Photobiomodulation-based (LLLT) therapies show tantalizing promise for treatment of skin diseases. Confidence in this approach is blighted however by lamentable inconsistency in published experimental designs, and so complicates interpretation. Here we interrogate the appropriateness of a range of previously-reported treatment parameters, including light wavelength, irradiance and radiant exposure, as well as cell culture conditions (e.g., serum concentration, cell confluency, medium refreshment, direct/indirect treatment, oxygen concentration, etc.), in primary cultures of normal human dermal fibroblasts exposed to visible and near infra-red (NIR) light. Apart from irradiance, all study parameters impacted significantly on fibroblast metabolic activity. Moreover, when cells were grown at atmospheric O2 levels (i.e. 20%) short wavelength light inhibited cell metabolism, while negligible effects were seen with long visible and NIR wavelength. By contrast, NIR stimulated cells when exposed to dermal tissue oxygen levels (approx. 2%). The impact of culture conditions was further seen when inhibitory effects of short wavelength light were reduced with increasing serum concentration and cell confluency. We conclude that a significant source of problematic interpretations in photobiomodulation reports derives from poor optimization of study design. Further development of this field using in vitro/ex vivo models should embrace significant standardization of study design, ideally within a design-of-experiment setting.
    • Shedding light on the variability of optical skin properties: finding a path towards more accurate prediction of light propagation in human cutaneous compartments

      Mignon, Charles; Tobin, Desmond J.; Zeitouny, M.; Uzunbajakava, N.E. (2018-01)
      Finding a path towards a more accurate prediction of light propagation in human skin remains an aspiration of biomedical scientists working on cutaneous applications both for diagnostic and therapeutic reasons. The objective of this study was to investigate variability of the optical properties of human skin compartments reported in literature, to explore the underlying rational of this variability and to propose a dataset of values, to better represent an in vivo case and recommend a solution towards a more accurate prediction of light propagation through cutaneous compartments. To achieve this, we undertook a novel, logical yet simple approach. We first reviewed scientific articles published between 1981 and 2013 that reported on skin optical properties, to reveal the spread in the reported quantitative values. We found variations of up to 100-fold. Then we extracted the most trust-worthy datasets guided by a rule that the spectral properties should reflect the specific biochemical composition of each of the skin layers. This resulted in the narrowing of the spread in the calculated photon densities to 6-fold. We conclude with a recommendation to use the identified most robust datasets when estimating light propagation in human skin using Monte Carlo simulations. Alternatively, otherwise follow our proposed strategy to screen any new datasets to determine their biological relevance.