Editors’ Picks from Experimental Dermatology (June issue)

“Frozen leukocytes“: To roll or not to roll

Phenotypic or functional analysis of peripheral blood mononuclear cells (PBMC) is a valuable tool for both basic and clinical research. However, at the time of specimen collection, analysis is not always possible. Hence, several preservation strategies (mostly freezing) have been developed to allow phenotypic characterization of PBMC. Yet, little is known regarding the effect of freezing on PBMC functions. Migration of PBMC in and out of tissues is a key function of PBMC, and it had so far been unclear if freeze/thaw affects that important functional feature.

Lockmann and Schön (2013) have addressed this issue in a new study. In a flow chamber system, they demonstrate that PBMC isolated from healthy donors show similar rolling and adhesion behavior on resting and activated HUVEC cells before and after freeze/thaw. This nicely illustrates that cryopreserved PBMC can indeed be used to investigate dynamic interactions with endothelial cells. These findings are a milestone that fully justifies detailed functional analyses of cryopreserved  PMBCs (and subsets) from patients with inflammatory diseases.

Lockmann A and Schön MP, Phenotypic and functional traits of PBMC preserved by controlled cryoconservation: Implications for reliable sequential studies of dynamic interactions with endothelial cells. Exp Dermatol. 2013 May;22(5):358-9. doi: 10.1111/exd.12123.

Selected by Ralf J. Ludwig, Lübeck, Germany

 

The sound of silence: autosomal recessive congenital ichthyosis caused by a synonymous mutation in ABCA12 

Autosomal recessive congenital ichthyosis (ARCI) is a rare congenital keratinisation disorder with multiple phenotypes of varying severity. These include harlequin ichthyosis (HI), congenital ichthyosiform erythroderma (CIE), and lamellar ichthyosis (LI). Mutations in a number of genes have been identified as being linked with ARCI, amongst the most rare of which are abnormalities in the ABCA12 gene. This gene encodes for an epidermal lipid transporter (ATP-binding cassette A12). Impaired activity of the ABCA12 protein reduces granular layer lipid transport, resulting in malformation or complete absence of lamellar granules.

Although “silent” synonymous sequence alterations are now recognised in a number of human pathologies, Goldsmith et al. (2013) have, for the first time, identified such a mutation in a severe case of CIE in an 18 year old female. The ABCA12 mutation identified results in aberrant splicing and may impact both on transmembrane and ATP-binding domains of the protein. Interestingly, both aberrant and wild-type splice variants were produced, resulting in a less severe phenotype than is associated with null-mutations.

In providing evidence of a novel synonymous sequence alteration resulting in ARCI, this study adds to the growing body of evidence suggesting the importance of such mutations in human disease. In addition, the authors highlight the potential development of future treatment therapies for ARCI aimed at manipulating splicing mechanisms.

Goldsmith T, Fuchs-Telem D, Israeli S, Sarig O, Padalon-Brauch G, Bergman R, Indelman M, Sprecher E, Nousbeck J. The sound of silence: autosomal recessive congenital ichthyosis caused by a synonymous mutation in ABCA12. Exp Dermatol. 2013 Apr;22(4):251-4. doi: 10.1111/exd.12110

Selected by Iain Haslam, Manchester, UK

 

Visualization of dermal innervations in an ex vivo human skin model

Re-innervation processes are key cutaneous regenerative events following skin injuries. Yet, the exact mechanisms (especially in human skin) are poorly understood, mostly due to lack of proper visualization techniques. In a new METHODS LETTER, Sevrain et al. (2013)  introduce the two-photon excitation fluorescence (TPEF) microscopy method as an appropriate technique to monitor the processes of how afferent neurons re-innervate human skin.

The authors established co-cultures of murine sensory neurons (labeled with a vital, fluorescence dye [FM1-43] with high affinity to neurons) and human full-thickness skin explants, which were long-term (10 days) cultured at the air-liquid interface in defined media. Re-innervated skin explants were then fixed in paraformaldehyde and were subjected to TPEF in combination with the assessment of endogenous second-harmonic generation (SHG) signals from the collagen-rich dermis. The authors present convincing evidence of detecting the sprouting of neurites in the dermis (as identified by co-visualizing the SHG signals of collagen fibers of the dermal extracellular matrix) and, moreover, in the close vicinity of the basal layers of the epidermis. Importantly, the presented technique allows a significant (cca. 300 μm) in-depth analysis of the 3D tissue which is at least twice the depth limitations of the standard confocal microscopy method.

The technique mastered by the investigators allows the detailed in-depth investigation of cutaneous re-innervation processes in intact (i.e. unsectioned and hence undistorted) 3D ex vivo models of human skin. Moreover, when combined with time-lapse microscopy, this technology may be used to evaluate the growth and sprouting of cutaneous sensory afferents in “real-time”.

Sevrain D, Le Grand Y, Buhé V, Jeanmaire C, Pauly G, Carré JL, Misery L, Lebonvallet  N. Two-photon microscopy of dermal innervations in a human re-innervated model of skin. Exp Dermatol. 2013 Apr;22(4):290-1. doi: 10.1111/exd.12108. Epub 2013 Feb 28.

Selected by Tamas Bíró, Debrecen, Hungary

 

Mesenchymal stem cell therapy in wound healing

Over the past decade, significant progress has been made in understanding stem cell biology in the skin and its translation into new therapies for patients.  Mesenchymal stem cells (MSCs) have been used in a wide range of conditions including systemic inflammatory and autoimmune disorders that affect the skin, as well as in certain inherited skin fragility disorders. Khosrotehrani (2013) now provides a comprehensive overview of MSC properties and current clinical applications in physiologic and pathologic skin conditions, with particular emphasis on cutaneous wound healing.

Because engraftment of MSCs in skin wounds is inconsistent, Khosrotehrani suggests that MSCs are inappropriate for cell replacement therapies in a wound healing context.  The author also hypothesizes that a replete niche and competition with resident mesenchymal populations in the dermis cause the insufficient engraftment of newly delivered MSCs.  However, the author also suggests that paracrine effects of exogenous MSCs may provide a therapeutic benefit for wound healing:  MSCs and their culture supernatants (MSC ‘juice’) can modulate tissue repair and host immune responses, suggesting a broader role for MSCs in dermatological therapy.  Taken together, along with concise but comprehensive up-to-date information on MSC applications in in vitro models, pre-clinical animal models and clinical studies,  the author offers a consistent and logical analysis of the challenges one faces with MSCs therapy..

Khosrotehrani K.  Mesenchymal stem cell therapy in skin: why and what for? Exp Dermatol. 2013 May;22(5):307-10. doi: 10.1111/exd.12141.

Selected by Takashi Hashimoto, Kurume, Fukuoka, Japan

 

Oxytocin modulates proliferation and stress responses of human skin cells: implications for atopic dermatitis

Since the initial proposition that skin acts as a neuroendocrine organ (Endocr Rev 21, 457-481, 2000), a flurry of data from different laboratories have substantiated the concept of neuroendocrinology of the skin (Adv Anat Embryol Cell Biol 212, 1-15, 2012). Most recently, Deing et al. (2013) have enriched the cutaneous neuroendocrinology theater with another player,  oxytocin (OXT). Specifically, they provide evidence that a functionally active oxytocin regulatory system is expressed in the human skin.

The authors have detected OXT receptors (OXTR) in epidermal keratinocytes and dermal fibroblasts. Ligand activation of these receptors led to increases in Ca+2 and inhibition of cell proliferation. Furthermore, silencing of the OXTR gene induced oxidative stress and enhanced proinflammatory activity of skin cells. Additional analyses showed decreased production of oxytocin and decreased expression of OXTR in skin affected by atopic dermatitis. The authors conclude that oxytocin signaling can play a role in the regulation of skin immune functions and that defects in this system are detectable in atopic dermatitis.

These important findings offer new insights into the role of the OXT/OXTR-mediated signaling in the regulation of epidermal barrier formation and anti-oxidative responses as well as in the attenuation of proinflammatory activities. This adds an intriguing and important new frontier to the rapidly developing field of cutaneous neuroendocrinology..

Deing V, Roggenkamp D, Kühnl J, Gruschka A, Stäb F, Wenck H, Bürkle A, Neufang G. Oxytocin modulates proliferation and stress responses of human skin cells: implications for atopic dermatitis. ExpDermatol 2013: 22: 399-405. doi: 10.1111/exd.12155

Selected by Andrzej Slominski, Memphis, USA

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