This work has been supported by grants from Ministerio de Econom&#237;a y Competitividad (RTC-2014-2626-1 to JE) and Instituto de Salud Carlos III (PI15/01458 to JE) of Spain. EC has been supported by the Atracci&#243;n de Talento Investigador grant 2017-T2/BMD-5766 (Comunidad de Madrid and UAM).

All mouse husbandry and experimental procedures must be conducted in compliance with local, national, international legislation and guidelines on animal experimentation.
1. Induction of hair growth, burn induction and identification of long-term BrdU LRCs in the tail skin epithelium wholemounts
NOTE: Use 10-day or 7-week old C57BL/6 mice, preferably littermates, for the experimental designs described below. In all the experimental procedures, animals will be anestheti...

<ol>
	<li>Bl&#225;zquez-Castro, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Direct+1O2+optical+excitation:+A+tool+for+redox+biology.">Direct 1O2 optical excitation: A tool for redox biology.</a> Redox Biology. 13, 39-59 (2017).</li><li>Valko, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Free+radicals+and+antioxidants+in+normal+physiological+functions+and+human+disease.">Free radicals and antioxidants in normal physiological functions and human disease.</a> The International Journal of Biochemistry &amp; Cell Biology. 39 (1), 44-84 (2007).</li><li>Sena, L. A., Chandel, N. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Physiological+Roles+of+Mitochondrial+Reactive+Oxygen+Species.">Physiological Roles of Mitochondrial Reactive Oxygen Species.</a> Molecular Cell. 48 (2), 158-167 (2012).</li><li>Bartosz, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reactive+oxygen+species:+Destroyers+or+messengers.">Reactive oxygen species: Destroyers or messengers.</a> Biochemical Pharmacology. 77 (8), 1303-1315 (2009).</li><li>Brieger, K., Schiavone, S., Miller, J., Krause, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reactive+oxygen+species:+from+health+to+disease.">Reactive oxygen species: from health to disease.</a> Swiss Medical Weekly. 142, 13659 (2012).</li><li>Speakman, J. R., Selman, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+free-radical+damage+theory:+Accumulating+evidence+against+a+simple+link+of+oxidative+stress+to+ageing+and+lifespan.">The free-radical damage theory: Accumulating evidence against a simple link of oxidative stress to ageing and lifespan.</a> BioEssays. 33 (4), 255-259 (2011).</li><li>Fernandez, V., Videla, L. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biochemical+aspects+of+cellular+antioxidant+systems.">Biochemical aspects of cellular antioxidant systems.</a> Biological Research. 29 (2), 177-182 (1996).</li><li>Mat&#233;s, J. M., S&#225;nchez-Jim&#233;nez, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Antioxidant+enzymes+and+their+implications+in+pathophysiologic+processes.">Antioxidant enzymes and their implications in pathophysiologic processes.</a> Frontiers in Bioscience. 4, 339-345 (1999).</li><li>Bedard, K., Krause, K. -. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+NOX+Family+of+ROS-Generating+NADPH+Oxidases:+Physiology+and+Pathophysiology.">The NOX Family of ROS-Generating NADPH Oxidases: Physiology and Pathophysiology.</a> Physiological Reviews. 87 (1), 245-313 (2007).</li><li>Leto, T. L., Morand, S., Hurt, D., Ueyama, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Targeting+and+Regulation+of+Reactive+Oxygen+Species+Generation+by+Nox+Family+NADPH+Oxidases.">Targeting and Regulation of Reactive Oxygen Species Generation by Nox Family NADPH Oxidases.</a> Antioxidants &amp; Redox Signaling. 11 (10), 2607-2619 (2009).</li><li>Hern&#225;ndez-Garc&#237;a, D., Wood, C. D., Castro-Obreg&#243;n, S., Covarrubias, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reactive+oxygen+species:+A+radical+role+in+development.">Reactive oxygen species: A radical role in development.</a> Free Radical Biology and Medicine. 49 (2), 130-143 (2010).</li><li>Covarrubias, L., Hern&#225;ndez-Garc&#237;a, D., Schnabel, D., Salas-Vidal, E., Castro-Obreg&#243;n, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Function+of+reactive+oxygen+species+during+animal+development:+Passive+or+active.">Function of reactive oxygen species during animal development: Passive or active.</a> Developmental Biology. 320 (1), 1-11 (2008).</li><li>Timme-Laragy, A. R., Hahn, M. E., Hansen, J. M., Rastogi, A., Roy, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Redox+stress+and+signaling+during+vertebrate+embryonic+development:+Regulation+and+responses.">Redox stress and signaling during vertebrate embryonic development: Regulation and responses.</a> Seminars in Cell &amp; Developmental Biology. 80, 17-28 (2018).</li><li>Owusu-Ansah, E., Banerjee, U. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reactive+oxygen+species+prime+Drosophila+haematopoietic+progenitors+for+differentiation.">Reactive oxygen species prime Drosophila haematopoietic progenitors for differentiation.</a> Nature. 461 (7263), 537-541 (2009).</li><li>Love, N. R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Amputation-induced+reactive+oxygen+species+are+required+for+successful+Xenopus+tadpole+tail+regeneration.">Amputation-induced reactive oxygen species are required for successful Xenopus tadpole tail regeneration.</a> Nature Cell Biology. 15 (2), 222-228 (2013).</li><li>Le Belle, J. E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Proliferative+Neural+Stem+Cells+Have+High+Endogenous+ROS+Levels+that+Regulate+Self-Renewal+and+Neurogenesis+in+a+PI3K/Akt-Dependant+Manner.">Proliferative Neural Stem Cells Have High Endogenous ROS Levels that Regulate Self-Renewal and Neurogenesis in a PI3K/Akt-Dependant Manner.</a> Cell Stem Cell. 8 (1), 59-71 (2011).</li><li>Myant, K. B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=production+and+NF-&#954;B+activation+triggered+by+RAC1+facilitate+WNT-driven+intestinal+stem+cell+proliferation+and+colorectal+cancer+initiation.">production and NF-&#954;B activation triggered by RAC1 facilitate WNT-driven intestinal stem cell proliferation and colorectal cancer initiation.</a> Cell Stem Cell. 12 (6), 761-773 (2013).</li><li>Hamanaka, R. B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mitochondrial+Reactive+Oxygen+Species+Promote+Epidermal+Differentiation+and+Hair+Follicle+Development.">Mitochondrial Reactive Oxygen Species Promote Epidermal Differentiation and Hair Follicle Development.</a> Science Signaling. 6 (261), 8 (2013).</li><li>Carrasco, E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Photoactivation+of+ROS+Production+in+situ+Transiently+Activates+Cell+Proliferation+in+Mouse+Skin+and+in+the+hair+Follicle+Stem+Cell+Niche+Promoting+Hair+Growth+and+Wound+Healing.">Photoactivation of ROS Production in situ Transiently Activates Cell Proliferation in Mouse Skin and in the hair Follicle Stem Cell Niche Promoting Hair Growth and Wound Healing.</a> Journal of Investigative Dermatology. 135 (11), 1-12 (2015).</li><li>Carrasco, E., Bl&#225;zquez-Castro, A., Calvo, M. I., Juarranz, &. #. 1. 9. 3. ;., Espada, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Switching+on+a+transient+endogenous+ROS+production+in+mammalian+cells+and+tissues.">Switching on a transient endogenous ROS production in mammalian cells and tissues.</a> Methods. , 109 (2016).</li><li>Braun, K. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Manipulation+of+stem+cell+proliferation+and+lineage+commitment:+visualisation+of+label-retaining+cells+in+wholemounts+of+mouse+epidermis.">Manipulation of stem cell proliferation and lineage commitment: visualisation of label-retaining cells in wholemounts of mouse epidermis.</a> Development. 130 (21), 5241-5255 (2003).</li><li>Hsu, Y. -. C., Li, L., Fuchs, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Emerging+interactions+between+skin+stem+cells+and+their+niches.">Emerging interactions between skin stem cells and their niches.</a> Nature Medicine. 20 (8), 847-856 (2014).</li><li>Plikus, M. V., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Epithelial+stem+cells+and+implications+for+wound+repair.">Epithelial stem cells and implications for wound repair.</a> Seminars in Cell &amp; Developmental Biology. 23 (9), 946-953 (2012).</li></ol>

All commercial applications of the procedures described in this work are protected by a CSIC-UAM patent (EP2932967A1) authored by EC, MIC and JE and licensed to Derma Innovate SL for commercial exploitation. JE and JJM have an advisory position in Derma Innovate SL.

Here, we present a methodology that allows a transient activation of endogenous ROS production in vivo in mouse skin with physiological effects. The methodology is based on a photodynamic procedure to induce a controlled and local stimulation of the endogenous photosensitizer PpIX (Figure 1B). This experimental approach is an interesting tool to study ROS biology in in vivo experimental systems constituting a significant advance over methodologies using external ROS sources (usually hydrogen...

Reactive oxygen species (ROS) are the result of the chemical reduction of molecular oxygen to form water, and include singlet oxygen, superoxide anion, hydrogen peroxide and the hydroxyl radical1,2,3. ROS have a very short lifespan due to their extremely chemical reactive nature. In aerobic organisms, ROS are incidentally formed inside the cells as a major leaky by-product of aerobic respiration (electron transport chain) in the mitochondria. Transient accumulation of high levels of ROS in the cell results in an oxidative stress condition that may provoke the irreversible inactivation of proteins, lipids and sugars and the introduction of mutations in the DNA molecule2,3,4,5. The gradual accumulation of oxidative damage in cells, tissues and whole organisms steadily increases with time and has been associated with the induction of cell death programs, several pathologies, and the ageing process2,3,4,6.
Aerobic organisms have steadily evolved efficient molecular mechanisms to tackle excess ROS accumulation in cells and tissues. These mechanisms include members of the superoxide dismutase (SOD) protein family, which catalyze superoxide radical dismutation into molecular oxygen and hydrogen peroxide, as well as different catalases and peroxidases which use the antioxidant pool (glutathione, NADPH, peroxiredoxin, thioredoxin7,8) to catalyze the subsequent conversion of hydrogen peroxide to water and molecular oxygen.
However, several reports support the role of ROS as key components of molecular circuits that regulate critical cell functions, including proliferation, differentiation and mobility2,3,4. This concept is further supported by the initial identification and characterization of dedicated ROS-producing mechanisms in aerobic organisms, including lipoxygenases cyclooxygenases and NADPH oxidases9,10. In this sense, ROS exhibit an active role during vertebrate embryo development11,12,13 and key roles for these molecules in the regulation of specific in vivo physiological functions have been reported in different experimental systems, including the differentiation program of hematopoietic progenitors in Drosophila14, healing induction in zebrafish, or tail regeneration in Xenopus tadpoles15. In mammals, ROS have been involved in the self-renewal/differentiation potential of neural stem cells in a neurosphere model16 and in the deregulation of intestinal stem cell function during colorectal cancer initiation17. In the skin, ROS signalling has been associated with epidermal differentiation and the regulation of the skin stem cell niche and the hair follicle growth cycle18,19.
In this perspective, a major experimental limitation to determine the physiological roles of ROS in biological systems, both in normal or pathological conditions, is the lack of adequate experimental tools to induce controlled production of these molecules in cells and tissues, accurately resembling their physiological production as second signalling messengers. At present, most experimental approaches involve the administration of exogenous ROS, mostly in the form of hydrogen peroxide. We have recently implemented an experimental approach to switch on a transient, nonlethal in vivo production of endogenous ROS in the mouse skin, based on the administration of precursors of the endogenous photosensitizer protoporphyrin IX (PpIX; e.g., aminolaevulinic acid or its methyl derivative methylaminolevulinate) and further irradiation of the sample with red light to induce the in situ formation of ROS from intracellular molecular oxygen (Figure 1). This photodynamic procedure may be efficiently used to stimulate resident stem cell niches, thus activating the regenerative programs of the tissue19,20 and opening the way for new therapeutic modalities in skin regenerative medicine. Here, we present a detailed description of the protocol, showing representative examples of stimulation of stem cell niches, measured as an increase in the number of long-term 5-bromo-2&#8217;-deoxyuridine (BrdU) label retaining cells (LRCs) in the bulge region of the hair follicle19,21, and subsequent activation of regeneration programs (acceleration of hair growth and burn healing processes) induced by transient, nonlethal ROS production in the skin of C57Bl6 mouse strain.

<table border="0" cellpadding="0" cellspacing="0" style="width:812px;" width="811">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:432px;">2&#8242;,7&#8242;-Dichlorofluorescin diacetate</td>
			<td style="width:104px;">Sigma Aldrich</td>
			<td style="width:115px;">D6883-50MG</td>
			<td style="width:161px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:432px;">5&#39;-bromo-2&#39;-deoxiuridine</td>
			<td style="width:104px;">Sigma Aldrich</td>
			<td style="width:115px;">B5002-500MG</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:432px;">Anti-Bromodeoxyuridine-Fluorescein</td>
			<td style="width:104px;">Roche</td>
			<td>11202693001</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Depilatory cream (e.g., Veet)</td>
			<td style="width:104px;">Veet</td>
			<td style="width:115px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:432px;">Dihydroethidium</td>
			<td style="width:104px;">Sigma Aldrich</td>
			<td>37291-25MG</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:432px;">In Vivo imaging system, e.g., IVIS Lumina 2</td>
			<td style="width:104px;">Perkin Elmer</td>
			<td style="width:115px;"></td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:432px;">mALA in the form of topical cream, e.g.,METVIX Crema 160 mg/g</td>
			<td style="width:104px;">Galderma</td>
			<td style="width:115px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:432px;">Power energy meter (e.g., ThorLabs Model PM100D)</td>
			<td style="width:104px;">ThorLabs</td>
			<td style="width:115px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:432px;">Red light source, e.g., 636 nm Aktilite LED lamp</td>
			<td style="width:104px;">Photocure ASA</td>
			<td style="width:115px;"></td>
			<td></td>
		</tr>
	</tbody>
</table>

stimulation of stem cell niches and tissue regeneration in mouse skin by switchable protoporphyrin ix-dependent photogeneration of reactive oxygen species in situ

Here, we describe a protocol to induce switchable in vivo photogeneration of endogenous reactive oxygen species (ROS) in mouse skin. This transient production of ROS in situ efficiently activates cell proliferation in stem cell niches and stimulates tissue regeneration as strongly manifested through the acceleration of burn healing and hair follicle growth processes. The protocol is based on a regulatable photodynamic treatment that treats the tissue with precursors of the endogenous photosensitizer protoporphyrin IX and further irradiates the tissue with red light under tightly controlled physicochemical parameters. Overall, this protocol constitutes an interesting experimental tool to analyze ROS biology.

The topical administration of the mALA precursor in the mouse back and tail skin results in a significant accumulation of PpIX in the whole tissue and, noticeably, in the hair follicle, as demonstrated by the reddish-pink fluorescence of this compound under blue light (407 nm) excitation (Figure 2A,C). Subsequent irradiation of treated tissue with red light (636 nm) at a fluence of 2.5&#8722;4 J/cm2 promotes transient production of ROS in the tissue, particularly ...

Watch this Scientific Journal Video about Stimulation of Stem Cell Niches and Tissue Regeneration in Mouse Skin by Switchable Protoporphyrin IX-Dependent Photogeneration of Reactive Oxygen Species In 

Stimulation of Stem Cell Niches and Tissue Regeneration in Mouse Skin by Switchable Protoporphyrin IX-Dependent Photogeneration of Reactive Oxygen Species In Situ

The aim of this protocol is to induce transient in vivo production of nonlethal levels of reactive oxygen species (ROS) in mouse skin, further promoting physiological responses in the tissue.

Here, we describe a protocol to induce switchable in vivo photogeneration of endogenous reactive oxygen species (ROS) in mouse skin. This transient ...

Our methodology is the first one to provide a reliable experimental tool to induce a transient activation of an endogenous reactive oxygen species or ROS production in a tissue in vivo. Our methodology provides a robust, user-friendly, and non-invasive procedure yielding a consistent production of physiological stimulating ROS levels in the skin basically using a red light source. As the physiological induction of ROS in the skin achieve the tissue stem needs, we have further applied our methodology for skin regeneration therapy including good healing and hair growth.ROS biology and signaling is currently a research hotpot. A major limitation to investigate ROS function in vivo is the lack of adequate tools to induce a controlled endogenous ROS production. OUR methodology is user-friendly and easy, but all devices, lamp, IV, IS, et cetera, need to be adequately calibrated.Critical chemical precursors must be fresh and all the steps or the protocol must be rigorously followed. To induce hair growth on the dorsal skin of mice in the second telogen phase, after confirming a lack of response to pedal reflex in about day 50 postnatal litter mate C57 black six mice, use a razor and depilatory cream to remove two independent side-by-side regions of skin from the back of each mouse. After a few minutes, remove the cream with PBS and record the hair follicle growth through the daily acquisition of high resolution images of the control and treated dorsal skin areas of each animal.To induce the generation of second degree burn lesions on the dorsal skin of mice in the second telogen phase, remove the hair from the back of the mouse. Preheat a one centimeter cross-section brass bar to 95 degrees Celsius in boiling water and apply the bar to the central region of the mouse skin for five seconds. Immediately after burn generation, intraperitoneally inject the animals with one milliliter of physiological solution to prevent dehydration and allow the mice to recover for 24 hours before proceeding to the treatment.For the generation of BrdU labeled retaining cells or LRCs, inject 10 or 14-day-old litter mates intraperitoneally once a day for four consecutive days with 50 milligrams per kilogram body weight of BrdU in PBS. After the labeling phase, allow mice to develop for 50 to 60 days before applying treatment. To induce the transient production of non-lethal reactive oxygen species or ROS levels in mouse skin for a hair growth analysis, after acquiring a baseline hair growth image, topically apply approximately 25 milligrams mALA cream on the right shaved skin region and place the animal in the dark for 2.5 hours.At the end of the photosensitizer treatment period, thoroughly remove any excess cream with PBS and confirm PP9 production in situ by red fluorescence expression under blue light excitation, then irradiate the whole back skin with an adequate red light source for a total dose of 2.5 to 4 joules per square centimeter. Then allow the mice to recover on an electric blanket with monitoring until full recumbency before returning the animals to their cages. To switch on transient ROS production for second degree burn healing, apply approximately 25 milligrams of mALA cream along the right burn surface and about four millimeters of adjacent tissue and place the animals in the dark for 2.5 hours as demonstrated.After removing the cream, irradiate the whole back skin and allow the mice to recover with monitoring as demonstrated. To induce transient ROS production in tail skin, apply approximately 25 milligrams of mALA cream all along the dorsal tissue area of the BrdU treated mice and irradiate the dorsal skin of the tail as demonstrated. After euthanizing the mice, harvest the tail skin for BrdU detection.Use a scalpel to harvest the tail from each animal, then make straight longitudinal incisions and peel the whole skin as a single piece from the backbone. Incubate the peeled skin pieces in five millimolar EDTA and PBS and five milliliter tubes for four hours at 37 degrees Celsius to allow the careful separation of intact sheets of epidermis from the dermis with forceps. Fix the separated tissues in 4%formaldehyde and PBS for at least 72 hours at room temperature.Then label the fixed tissues with the fluorescence conjugated antibodies of interest before visualizing the tissues by fluorescence confocal microscopy according to standard protocols to identify and quantify LRCs under each experimental condition. For the ex vivo evaluation of ROS production, after harvesting mouse tail skin pieces as demonstrated, incubate the control untreated tissues and five millimolar EDTA and PBS alone and the photodynamic treatment samples in EDTA supplemented with two millimolar mALA. Next, add hydroethidine to a 3.2 micromolar final concentration to each set of tissues and incubate all of the samples for one hour at room temperature in the dark.At the end of the incubation, use fingertips to stretch the tail skin samples over a glass surface and irradiate the treated tissues with 636 nanometers of red light at a 10 joules per square centimeter fluence. At the end of the treatment, immediately separate the epidermis from the dermis and fix the epidermal sheets in 4%formaldehyde and PBS for at least 72 hours at room temperature. At the end of the fixation, evaluate the red 2-hydroxyethidium emission by fluorescence microscopy using green exciting light to allow the acquisition of high-quality images.For in vivo detection of ROS production in the dorsal skin, just after red light irradiation, apply 100 microliters of one milligram per milliliter DH-FDA and 50%ethanol on all target control and treated skin areas. Topical administration of the mALA precursor onto the mouse back and tail skin results in a significant accumulation of protoporphyrin IX in the the whole tissue and noticeably in the hair follicle as demonstrated by the reddish pink fluorescence of this compound under blue light excitation. Subsequent irradiation of the treated tissue with red light promotes the transient production of ROS within the tissue particularly in the bulge region of the hair follicle.Switching on non-lethal ROS production in mouse skin in vivo promotes a significant increase in the number of LRCs in the bulge region of the hair follicle two days after photodynamic treatment. Notably, the increase in LRC numbers is transient, restoring to normal levels six days after treatment. Transient ROS production accelerates skin healing after a second degree burn.Quantification of the gradual reduction of the damaged skin demonstrates the robustness and statistical significance of the wound healing acceleration process tissue. Similarly, non-lethal ROS levels strongly promote hair growth after shaving during the second coordinated telogen, a phase during which the hair follicle is refractory to responding to growth stimuli. In addition, ROS production after photo treatments is also significantly reduced by the application of antioxidant compounds.PP IX production in situ by red fluorescent expression under blue light excitation must be carefully confirmed. To induce ROS production, the irradiance of the red light source must be correctly established. versus tissue and total light dose.After ROS induction, current biochemical and cell and molecular biology techniques may be used to analyze collected samples and evaluate the dynamic physiological response of the tissue. Our methodology provides a powerful tool to investigate the physiological effect of a transient production of endogenous ROS in a tissue in vivo. This is a new experimental approach that may be very useful for researchers in the field of ROS signaling.

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1.8K Görüntüleme.  Ramón y Cajal University Hospital. Our methodology is the first one to provide a reliable experimental tool to induce a transient activation of an endogenous reactive oxygen species or ROS production in a tissue in vivo. Our methodology provides a robust, user-friendly, and non-invasive procedure yielding a consistent production of physiological stimulating ROS levels in the skin basically using a red light source. As the physiological induction of ROS in the skin achieve the tissue stem needs, we have further applied our meth...

Video: Stimulation of Stem Cell Niches and Tissue Regeneration in Mouse Skin by Switchable Protoporphyrin IX-Dependent Photogeneration of Reactive Oxygen Species In Situ