Deacetylation via SIRT2 prevents keratin-mutation-associated injury and keratin aggregation

Keratin (K) and other intermediate filament (IF) protein mutations at conserved arginines disrupt keratin filaments into aggregates and cause human epidermolysis bullosa simplex (EBS; K14-R125C) or predispose to mouse liver injury (K18-R90C). The challenge for more than 70 IF-associated diseases is the lack of clinically utilized IF-targeted therapies. We used high-throughput drug screening to identify compounds that normalized mutation-triggered keratin filament disruption. Parthenolide, a plant sesquiterpene lactone, dramatically reversed keratin filament disruption and protected cells and mice expressing K18-R90C from apoptosis. K18-R90C became hyperacetylated compared with K18-WT and treatment with parthenolide normalized K18 acetylation. Parthenolide upregulated the NAD-dependent SIRT2, and increased SIRT2-keratin association. SIRT2 knockdown or pharmacologic inhibition blocked the parthenolide effect, while site-specific Lys-to-Arg mutation of keratin acetylation sites normalized K18-R90C filaments. Treatment of K18-R90C-expressing cells and mice with nicotinamide mononucleotide had a parthenolide-like protective effect. In 2 human K18 variants that associate with human fatal drug-induced liver injury, parthenolide protected K18-D89H- but not K8-K393R-induced filament disruption and cell death. Importantly, parthenolide normalized K14-R125C-mediated filament disruption in keratinocytes and inhibited dispase-triggered keratinocyte sheet fragmentation and Fas-mediated apoptosis. Therefore, keratin acetylation may provide a novel therapeutic target for some keratin-associated diseases.

Short Time to Market and Forward Planning Will Enable Cell Therapies to Deliver R&D Pipeline Value

There is considerable industry excitement about the curative potential of cell and gene therapies, but significant challenges remain in designing cost-effective treatments that are accessible globally. We have taken a modeling-based approach to define the cost and value drivers for cell therapy assets during pharmaceutical drug development. We have created a model development program for a lentiviral modified ex vivo autologous T cell therapy for Oncology indications. Using internal and external benchmarks, we have estimated the total out-of-pocket cost of development for an Oncology cell therapy asset from target identification to filing of marketing application to be $500-600 million. Our model indicates that both clinical and Chemistry Manufacturing and Controls (CMC) cost of development for cell therapies are higher due to unique considerations of ex vivo autologous cell therapies. We have computed a threshold revenue-generating patient number for our model asset that enables selection of assets that can address high unmet medical need and generate pipeline value. Using statistical approaches, we identified that short time to market (<5 years) and reduced commercial cost of goods (<$65,000 per dose) will be essential in developing competitive assets and we propose solutions to reduce both. We emphasize that teams must proactively plan alternate development scenarios with clear articulation of path to value generation and greater patient access. We recommend using a modeling-based approach to enable data driven go/no-go decisions during multigenerational cell therapy development.

The Landscape of Early Clinical Gene Therapies outside of Oncology

The field of cell and gene therapy (GT) is expanding rapidly and there is undoubtedly a wave of enthusiasm and anticipation for what these treatments could achieve next. Here we assessed the worldwide landscape of GT assets currently in early clinical development (clinical trial phase 1/2 or about to enter clinical trial). We included all gene therapies, i.e., strategies that modify an individual's protein make-up by introducing exogenous nucleic acid or nucleic acid modifiers, regardless of delivery. Unmodified cell therapies, oncology therapies (reviewed elsewhere), and vaccine programs (distinct therapeutic strategy) were not included. Using a December 31, 2018 cutoff date, we identified 336 gene therapies being developed for 138 different indications covering 165 genetic targets. In all, we found that the early clinical GT landscape comprises a very disparate group of drug candidates in terms of indications, organizations, and delivery methods. We also highlight interesting trends, revealing the evolution of the field toward in vivo therapies and adeno-associated virus vector-based delivery systems. It will be interesting to witness what proportion of this current list effectively translates into new medicines.

Oxygen and Conformation Dependent Protein Oxidation and Aggregation by Porphyrins in Hepatocytes and Light-Exposed Cells

BACKGROUND & AIMS

Porphyrias are caused by porphyrin accumulation resulting from defects in the heme biosynthetic pathway that typically lead to photosensitivity and possible end-stage liver disease with an increased risk of hepatocellular carcinoma. Our aims were to study the mechanism of porphyrin-induced cell damage and protein aggregation, including liver injury, where light exposure is absent.

METHODS

Porphyria was induced in vivo in mice using 3,5-diethoxycarbonyl-1,4-dihydrocollidine or in vitro by exposing human liver Huh7 cells and keratinocytes, or their lysates, to protoporphyrin-IX, other porphyrins, or to δ-aminolevulinic acid plus deferoxamine. The livers, cultured cells, or porphyrin exposed purified proteins were analyzed for protein aggregation and oxidation using immunoblotting, mass spectrometry, and electron paramagnetic resonance spectroscopy. Consequences on cell-cycle progression were assessed.

RESULTS

Porphyrin-mediated protein aggregation required porphyrin-photosensitized singlet oxygen and porphyrin carboxylate side-chain deprotonation, and occurred with site-selective native protein methionine oxidation. Noncovalent interaction of protoporphyrin-IX with oxidized proteins led to protein aggregation that was reversed by incubation with acidified n-butanol or high-salt buffer. Phototoxicity and the ensuing proteotoxicity, mimicking porphyria photosensitivity conditions, were validated in cultured keratinocytes. Protoporphyrin-IX inhibited proteasome function by aggregating several proteasomal subunits, and caused cell growth arrest and aggregation of key cell proliferation proteins. Light-independent synergy of protein aggregation was observed when porphyrin was applied together with glucose oxidase as a secondary peroxide source.

CONCLUSIONS

Photo-excitable porphyrins with deprotonated carboxylates mediate protein aggregation. Porphyrin-mediated proteotoxicity in the absence of light, as in the liver, requires porphyrin accumulation coupled with a second tissue oxidative injury. These findings provide a potential mechanism for internal organ damage and photosensitivity in porphyrias.

Restoration of the basement membrane after wounding: a hallmark of young human skin altered with aging

In skin, the basement membrane at the dermal-epidermal junction (DEJ-BM) is an important structure that tightly binds the epidermis to the dermis, and acts as a permeability barrier that controls exchange of macromolecules. Repair of the DEJ-BM during wound healing is important for restoration of skin functional properties after wounding. Here, we used a CO₂ laser to perform partial thickness wounds in human volunteers, and directly compared wound repair in healthy young and aged individuals, focusing on the DEJ-BM. Our results show that the DEJ-BM is restored within four weeks after partial thickness wounds in young adults. We identified laminin-γ2 as preferred substrate for keratinocytes during reepithelialization of partial thickness human wounds. Laminin-γ2 is expressed continuously by migrating keratinocytes during reepithelialization, whereas collagen IV and collagen VII are deposited after wound closure. In contrast, our study shows that the DEJ-BM restoration following wounding is deficient in elderly individuals. Specifically, COL7A2 was barely increased during wound repair in aged skin and, as a result, the DEJ-BM in elderly skin was not restored and showed abnormal structure. Our data suggest that ameliorating the quality of the DEJ-BM restoration is a promising therapeutic approach to improve the quality of repaired skin in the elderly.

Abstract 2080: Polycomb-mediated disruption of an AR-feedback loop drives castration-resistant prostate cancer

Androgen receptor (AR) is an androgen-stimulated transcription factor that critically promotes prostate cancer development and progression. In addition to its conventional role in transcriptional activation, AR also acts as a transcriptional repressor to directly inhibit target gene expression. Through meta-analysis of androgen-regulated expression microarray data, we nominated CCN3/NOV, a CCN family protein, as one of the top AR-repressed genes in prostate cancer, implicating that CCN3 may play a tumor suppressive role in prostate cancer development. Therefore, we sought to investigate the molecular functions of CCN3 and its roles in prostate cancer progression especially in castration-resistant prostate cancer (CRPC). We first showed that CCN3 protein physically interacts with AR. The CCN3 interaction domain was mapped in the N-terminal domain of AR which is also present in constitutively active AR variants. Using immunofluorescence microscopy as well as subcellular fractionation technique, we demonstrated that CCN3 sequesters AR or AR variants into the cytoplasm to inhibit AR nuclear translocation, which in turn suppresses AR chromatin targeting and transcriptional activation. However, this negative feedback loop between AR and AR-repressed gene CCN3is disrupted in CRPC through CCN3 persistent epigenetic silencing by the Polycomb group protein EZH2, rendering AR transcriptional activation and CRPC progression. Taking advantage of this repressive mechanism, we restored CCN3 in CRPC cell model, either through ectopic overexpression or treatment with EZH2 inhibitor, which results in strong suppression of CRPC cell proliferation and anchorage-independent cell growth. Consistently, application of EZH2 inhibitor remarkably reduced tumor size in a castrated mice model. Taken together, our data highlight CCN3 as a novel regulator of AR signaling and support the promise of EZH2-targeting agents in treating CRPC.

Citation Format: Ka-Wing Fong, Jonathan Zhao, Jung Kim, Shangze Li, Angela Yang, Bing Song, Laure Rittié, Ming Hu, Ximing Yang, Bernard Perbal, Jindan Yu. Polycomb-mediated disruption of an AR-feedback loop drives castration-resistant prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2080. doi:10.1158/1538-7445.AM2017-2080

Report of the 13th Annual International Pachyonychia Congenita Consortium Symposium

The International Pachyonychia Congenita Consortium (IPCC) is a group of physicians and scientists from around the world dedicated to developing therapies for pachyonychia congenita, a rare autosomal dominant skin disorder. The research presented at the 13th Annual Research Symposium of the IPCC, held on 10-11 May 2016, in Scottsdale, AZ, U.S.A., is reported here.

Type I Collagen Purification from Rat Tail Tendons

Type I collagen, or collagen I, is the most abundant protein in the human body and provides strength and resiliency to tissues such as bone, tendons, ligaments, and skin. Collagen I forms macromolecular networks in which resident mesenchymal cells are embedded. Cell-extracellular matrix interactions are critical not only for maintenance of tissue properties but also for guiding and orienting the phenotype of resident cells. Cues from the extracellular matrix have been shown to be critical in pathophysiologies such as fibrosis, aging, and cancer. Hence, the details of these interactions are being scrutinized to better understand the mechanisms of such diseases and conditions. Many in vitro assays, such as cell-embedded collagen lattices, preparation of hydrogels, adhesion assays, etc., have been developed to study various aspects of cell-extracellular matrix interactions. All these in vitro models rely on utilizing high-quality purified collagen I. Here, we provide state-of-the-art collagen I extraction protocol and useful tips to produce high-quality purified collagen I solutions. We also provide a detailed protocol for pepsin digestion of collagen I, for a highly reliable collagen concentration assay, and guidelines for conducting quality controls to validate purified collagen solutions. Collagen I prepared with these procedures is highly suitable for many in vitro applications.

Mouse Models of Corneal Scarring

Corneal scarring is an obligatory consequence of stroma corneal injury and is a major cause of decreased visual quality and vision loss worldwide. There are currently no satisfactory intervention therapies for corneal fibrosis. In this chapter, we describe well-established in vivo corneal wound models to allow researchers to investigate epithelial and stromal responses to corneal injury.

Method for Picrosirius Red-Polarization Detection of Collagen Fibers in Tissue Sections

The extracellular matrix is critical in guiding cell behavior in normal and pathologic tissues, particularly in cancers and fibrosis. Highlighting the organization (or disorganization) of a collagen-containing matrix can be very useful for understanding or grading pathophysiological conditions. The picrosirius red stain (also called "Sirius red" stain) is one of the best understood histochemical techniques able to selectively highlight collagen networks. Relatively inexpensive, the technique relies on the birefringent properties of collagen molecules. While the picrosirius red stain alone does not selectively bind collagen network, it becomes more specific than the other common collagen stains when combined with polarized light detection. This is why the selective histochemical procedure for collagen detection should be called the picrosirius-polarization method. In this chapter, we will provide essential explanation and detailed protocols and tips to allow collagen researchers not only to better understand how this staining technique works but also to easily apply this technique to their collagen-related research.

Reduced cell cohesiveness of outgrowths from eccrine sweat glands delays wound closure in elderly skin

Human skin heals more slowly in aged vs. young adults, but the mechanism for this delay is unclear. In humans, eccrine sweat glands (ESGs) and hair follicles underlying wounds generate cohesive keratinocyte outgrowths that expand to form the new epidermis. Here, we compared the re‐epithelialization of partial‐thickness wounds created on the forearm of healthy young (< 40 yo) and aged (> 70 yo) adults. Our results confirm that the outgrowth of cells from ESGs is a major feature of repair in young skin. Strikingly, in aged skin, although ESG density is unaltered, less than 50% of the ESGs generate epithelial outgrowths during repair (vs. 100% in young). Surprisingly, aging does not alter the wound‐induced proliferation response in hair follicles or ESGs. Instead, there is an overall reduced cohesiveness of keratinocytes in aged skin. Reduced cell–cell cohesiveness was most obvious in ESG‐derived outgrowths that, when present, were surrounded by unconnected cells in the scab overlaying aged wounds. Reduced cell–cell contact persisted during the repair process, with increased intercellular spacing and reduced number of desmosomes. Together, reduced outgrowths of ESG (i) reduce the initial number of cells participating in epidermal repair, (ii) delay wound closure, and (iii) lead to a thinner repaired epidermis in aged vs. young skin. Failure to form cohesive ESG outgrowths may reflect impaired interactions of keratinocytes with the damaged ECM in aged skin. Our findings provide a framework to better understand the mediators of delayed re‐epithelialization in aging and further support the importance of ESGs for the repair of human wounds.

Comparative biology of decellularized lung matrix: Implications of species mismatch in regenerative medicine

Lung engineering is a promising technology, relying on re-seeding of either human or xenographic decellularized matrices with patient-derived pulmonary cells. Little is known about the species-specificity of decellularization in various models of lung regeneration, or if species dependent cell-matrix interactions exist within these systems. Therefore decellularized scaffolds were produced from rat, pig, primate and human lungs, and assessed by measuring residual DNA, mechanical properties, and key matrix proteins (collagen, elastin, glycosaminoglycans). To study intrinsic matrix biologic cues, human endothelial cells were seeded onto acellular slices and analyzed for markers of cell health and inflammation. Despite similar levels of collagen after decellularization, human and primate lungs were stiffer, contained more elastin, and retained fewer glycosaminoglycans than pig or rat lung scaffolds. Human endothelial cells seeded onto human and primate lung tissue demonstrated less expression of vascular cell adhesion molecule and activation of nuclear factor-κB compared to those seeded onto rodent or porcine tissue. Adhesion of endothelial cells was markedly enhanced on human and primate tissues. Our work suggests that species-dependent biologic cues intrinsic to lung extracellular matrix could have profound effects on attempts at lung regeneration.

Sebaceous Gland Atrophy in Psoriasis: An Explanation for Psoriatic Alopecia?

In a transcriptome study of lesional psoriatic skin (PP) versus normal skin, we found a coexpressed gene module (N5) enriched 11.5-fold for lipid biosynthetic genes. We also observed fewer visible hairs in PP skin, compared with uninvolved nonlesional psoriatic skin or normal skin (P < 0.0001). To ask whether these findings might be due to abnormalities of the pilosebaceous unit, we carried out three-dimensional morphometric analysis of paired PP and nonlesional psoriatic skin biopsies. Sebaceous glands were markedly atrophic in PP versus nonlesional psoriatic skin (91% average reduction in volume, P = 0.031). Module N5 genes were strongly downregulated in PP versus normal skin (fold change < 0.25, 44.4-fold) and strongly upregulated in sebaceous hyperplasia (fold change > 4, 54.1-fold). The intersection of PP-downregulated and sebaceous hyperplasia-upregulated gene lists generated a gene expression signature consisting solely of module N5 genes, whose expression in PP versus normal skin was inversely correlated with the signature of IL17-stimulated keratinocytes. Despite loss of visible hairs, morphometry identified elongated follicles in PP versus nonlesional psoriatic skin (average 1.7 vs. 1.2 μm, P = 0.020). These results document sebaceous gland atrophy in nonscalp psoriasis, identify a cytokine-regulated set of sebaceous gland signature genes, and suggest that loss of visible hair in PP skin may result from abnormal sebaceous gland function.

Membrane-Tethered Intracellular Domain of Amphiregulin Promotes Keratinocyte Proliferation

The epidermal growth factor receptor (EGFR) and its ligands are essential regulators of epithelial biology, which are often amplified in cancer cells. We have previously shown that shRNA-mediated silencing of one of these ligands, amphiregulin (AREG), results in keratinocyte growth arrest that cannot be rescued by soluble extracellular EGFR ligands. To further explore the functional importance of specific AREG domains, we stably transduced keratinocytes expressing tetracycline-inducible AREG-targeted shRNA with lentiviruses expressing silencing-proof, membrane-tethered AREG cytoplasmic and extracellular domains (AREG-CTD and AREG-ECD), as well as full-length AREG precursor (proAREG). Here we show that growth arrest of AREG-silenced keratinocytes occurs in G2/M and is significantly restored by proAREG and AREG-CTD but not by AREG-ECD. Moreover, the AREG-CTD was sufficient to normalize cell cycle distribution profiles and expression of mitosis-related genes. Our findings uncover an important role of the AREG-CTD in regulating cell division, which may be relevant to tumor resistance to EGFR-directed therapies.

Cellular mechanisms of skin repair in humans and other mammals

The increased incidence of non-healing skin wounds in developed societies has prompted tremendous research efforts on the complex process known as "wound healing". Unfortunately, the weak relevance of modern wound healing research to human health continues to be a matter of concern. This review summarizes the current knowledge of the cellular mechanisms that mediate wound closure in the skin of humans and laboratory animals. The author highlights the anatomical singularities of human skin vs. the skin of other mammals commonly used for wound healing research (i.e. as mice, rats, rabbits, and pigs), and discusses the roles of stem cells, myofibroblasts, and the matrix environment in the repair process. The majority of this review focuses on reepithelialization and wound closure. Other aspects of wound healing (e.g. inflammation, fibrous healing) are referred to when relevant to the main topic. This review aims at providing the reader with a clear understanding of the similarities and differences that have been reported over the past 100 years between the healing of human wounds and that of other mammals.

Matricellular protein CCN3 mitigates abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is a major cause of morbidity and mortality; however, the mechanisms that are involved in disease initiation and progression are incompletely understood. Extracellular matrix proteins play an integral role in modulating vascular homeostasis in health and disease. Here, we determined that the expression of the matricellular protein CCN3 is strongly reduced in rodent AAA models, including angiotensin II-induced AAA and elastase perfusion-stimulated AAA. CCN3 levels were also reduced in human AAA biopsies compared with those in controls. In murine models of induced AAA, germline deletion of Ccn3 resulted in severe phenotypes characterized by elastin fragmentation, vessel dilation, vascular inflammation, dissection, heightened ROS generation, and smooth muscle cell loss. Conversely, overexpression of CCN3 mitigated both elastase- and angiotensin II-induced AAA formation in mice. BM transplantation experiments suggested that the AAA phenotype of CCN3-deficient mice is intrinsic to the vasculature, as AAA was not exacerbated in WT animals that received CCN3-deficient BM and WT BM did not reduce AAA severity in CCN3-deficient mice. Genetic and pharmacological approaches implicated the ERK1/2 pathway as a critical regulator of CCN3-dependent AAA development. Together, these results demonstrate that CCN3 is a nodal regulator in AAA biology and identify CCN3 as a potential therapeutic target for vascular disease.

Transgenic expression of human amphiregulin in mouse skin: inflammatory epidermal hyperplasia and enlarged sebaceous glands

To explore the role of amphiregulin in inflammatory epidermal hyperplasia, we overexpressed human AREG (hAREG) in FVB/N mice using a bovine K5 promoter. A construct containing AREG coding sequences flanked by 5' and 3' untranslated region sequences (AREG-UTR) led to a >10-fold increase in hAREG expression compared to an otherwise-identical construct containing only the coding region (AREG-CDR). AREG-UTR mice developed tousled, greasy fur as well as elongated nails and thickened, erythematous tail skin. No such phenotype was evident in AREG-CDR mice. Histologically, AREG-UTR mice presented with marked epidermal hyperplasia of tail skin (2.1-fold increase in epidermal thickness with a 9.5-fold increase in Ki-67(+) cells) accompanied by significantly increased CD4+ T-cell infiltration. Dorsal skin of AREG-UTR mice manifested lesser but still significant increases in epidermal thickness and keratinocyte hyperplasia. AREG-UTR mice also developed marked and significant sebaceous gland enlargement, with corresponding increases in Ki-67(+) cells. To determine the response of AREG-UTR animals to a pro-inflammatory skin challenge, topical imiquimod (IMQ) or vehicle cream was applied to dorsal and tail skin. IMQ increased dorsal skin thickness similarly in both AREG-UTR and wild type mice (1.7- and 2.2-fold vs vehicle, P < 0.001 each), but had no such effect on tail skin. These results confirm that keratinocyte expression of hAREG elicits inflammatory epidermal hyperplasia, and are consistent with prior reports of tail epidermal hyperplasia and increased sebaceous gland size in mice expressing human epigen.

Pachyonychia congenita cornered: report on the 11th Annual International Pachyonychia Congenita Consortium Meeting

This is a report of the research presented at the 11th Annual Meeting of the International Pachyonychia Congenita Consortium, held on 6 May 2014 in Albuquerque, NM, U.S.A. This year's meeting was divided into five corners concerning pachyonychia congenita (PC) research: (i) 'PC Pathogenesis Cornered', an overview of recent keratin research, for PC and other skin disorders; (ii) 'From All Corners of …', an outline of other genetic disorders that we can learn from; (iii) 'Fighting For Our Corner', an outline of National Institutes of Health/National Institute of Arthritis and Musculoskeletal and Skin Diseases programmes and U.S. funding opportunities applicable to rare skin disorders; (iv) 'The PC Corner', focusing on recent clinical studies related to PC; and (v) 'Clinical Corners: Turning the Corner?', an update on ongoing PC clinical trials.

Hypo-collagenesis in photoaged skin predicts response to anti-aging cosmeceuticals

BACKGROUND

Chronic sun exposure causes photoaging, the appearance of prematurely aged skin. This phenomenon is characterized by progressive alteration of the dermal extracellular matrix, including elastin and collagen fibers. While many cosmeceuticals claim to improve the appearance of photoaged skin, data are lacking regarding their ability to induce molecular responses associated with wrinkle effacement, particularly increased collagen production.

AIMS

To conduct a meta-analysis to determine whether there was a factor(s) that could predict response to various cosmeceuticals.

PATIENTS/METHODS

Hundred subjects enrolled in five separate studies of cosmeceuticals containing: L-ascorbic acid, pentapeptide, α-lipoic acid, yeast extract, or 1% idebenone. Five groups consisting of 16-20 volunteers applied one cosmeceutical to their photodamaged forearms for several weeks. Punch biopsies were obtained pretreatment and post-treatment and analyzed for type I procollagen by ELISA.

RESULTS

Analysis of basal collagenesis reinforced the notion that hypo-collagenesis is associated with photoaging severity, independent of age or gender. Treatment outcome varied greatly among subjects, ranging from no improvement to a 7-fold increase in collagenesis. Retrospective statistical meta-analysis was conducted to determine whether age, gender, type of cosmeceutical, or evidence of hypo-collagenesis in untreated skin could predict responsiveness to cosmeceuticals. Our analysis revealed that subjects with hypo-collagenesis responded 6.4 times more often than subjects with normo-collagenesis.

DISCUSSION

Hypo-collagenesis was the only factor that influenced treatment outcome. This study therefore identifies hypo-collagenesis as the unique parameter predicting anti-aging cosmeceutical treatment outcome. These findings provide a basis for future cosmetic testing and the potential development of custom formula skin care.

Transforming growth factor β controls CCN3 expression in nucleus pulposus cells of the intervertebral disc

OBJECTIVE

To investigate transforming growth factor β (TGFβ) regulation of CCN3 expression in cells of the nucleus pulposus.

METHODS

Real-time reverse transcription-polymerase chain reaction and Western blot analyses were used to measure CCN3 expression in the nucleus pulposus. Transfections were used to measure the effect of Smad3, MAPKs, and activator protein 1 (AP-1) on TGFβ-mediated CCN3 promoter activity. Lentiviral knockdown of Smad3 was performed to assess the role of Smad3 in CCN3 expression.

RESULTS

CCN3 was expressed in embryonic and adult intervertebral discs. TGFβ decreased the expression of CCN3 and suppressed its promoter activity in nucleus pulposus cells. DN-Smad3, Smad3 small interfering RNA, or DN-AP-1 had little effect on TGFβ suppression of CCN3 promoter activity. However, p38 and ERK inhibitors blocked suppression of CCN3 by TGFβ, suggesting involvement of these signaling pathways in the regulation of CCN3. Interestingly, overexpression of Smad3 in the absence of TGFβ increased CCN3 promoter activity. We validated the role of Smad3 in controlling CCN3 expression in Smad3-null mice and in nucleus pulposus cells transduced with lentiviral short hairpin Smad3. In terms of function, treatment with recombinant CCN3 showed a dose-dependent decrease in the proliferation of nucleus pulposus cells. Moreover, CCN3-treated cells showed a decrease in aggrecan, versican, CCN2, and type I collagen expression.

CONCLUSION

The opposing effect of TGFβ on CCN2 and CCN3 expression and the suppression of CCN2 by CCN3 in nucleus pulposus cells further the paradigm that these CCN proteins form an interacting triad, which is possibly important in maintaining extracellular matrix homeostasis and cell numbers.

Eccrine sweat glands are major contributors to reepithelialization of human wounds

Eccrine sweat glands are skin-associated epithelial structures (appendages) that are unique to some primates including humans and are absent in the skin of most laboratory animals including rodents, rabbits, and pigs. On the basis of the known importance of other skin appendages (hair follicles, apocrine glands, and sebaceous glands) for wound repair in model animals, the present study was designed to assess the role of eccrine glands in the repair of wounded human skin. Partial-thickness wounds were generated on healthy human forearms, and epidermal repair was studied in skin biopsy samples obtained at precise times during the first week after wounding. Wound reepithelialization was assessed using immunohistochemistry and computer-assisted 3-dimensional reconstruction of in vivo wounded skin samples. Our data demonstrate a key role for eccrine sweat glands in reconstituting the epidermis after wounding in humans. More specifically, (i) eccrine sweat glands generate keratinocyte outgrowths that ultimately form new epidermis; (ii) eccrine sweat glands are the most abundant appendages in human skin, outnumbering hair follicles by a factor close to 3; and (iii) the rate of expansion of keratinocyte outgrowths from eccrine sweat glands parallels the rate of reepithelialization. This novel appreciation of the unique importance of eccrine sweat glands for epidermal repair may be exploited to improve our approaches to understanding and treating human wounds.

Enhancing structural support of the dermal microenvironment activates fibroblasts, endothelial cells, and keratinocytes in aged human skin in vivo

The dermal extracellular matrix (ECM) provides strength and resiliency to skin. The ECM consists mostly of type I collagen fibrils, which are produced by fibroblasts. Binding of fibroblasts to collagen fibrils generates mechanical forces, which regulate cellular morphology and function. With aging, collagen fragmentation reduces fibroblast-ECM binding and mechanical forces, resulting in fibroblast shrinkage and reduced function, including collagen production. Here, we report that these age-related alterations are largely reversed by enhancing the structural support of the ECM. Injection of dermal filler, cross-linked hyaluronic acid, into the skin of individuals over 70 years of age stimulates fibroblasts to produce type I collagen. This stimulation is associated with localized increase in mechanical forces, indicated by fibroblast elongation/spreading, and mediated by upregulation of type II TGF-β receptor and connective tissue growth factor. Interestingly, enhanced mechanical support of the ECM also stimulates fibroblast proliferation, expands vasculature, and increases epidermal thickness. Consistent with our observations in human skin, injection of filler into dermal equivalent cultures causes elongation of fibroblasts, coupled with type I collagen synthesis, which is dependent on the TGF-β signaling pathway. Thus, fibroblasts in aged human skin retain their capacity for functional activation, which is restored by enhancing structural support of the ECM.

Molecular mechanisms of nonablative fractionated laser resurfacing

BACKGROUND

Nonablative fractionated laser resurfacing improves the texture of treated skin, but little is known about the molecular mechanisms that underlie clinical improvements.

OBJECTIVES

We sought to examine and quantify the time course and magnitude of dermal matrix changes that occur in response to nonablative fractionated laser resurfacing, with the dual goals of better understanding the molecular mechanisms that underlie clinical improvements and of gaining knowledge that will enable evidence-based treatment parameter optimization.

METHODS

Twenty patients (mean age 58 years) with photodamaged skin were focally treated on dorsal forearms with a nonablative fractionated laser. Serial skin samples were obtained at baseline and at various times after treatment. Biopsies were examined with real-time polymerase chain reaction technology and immunohistochemical techniques.

RESULTS

Laser treatment resulted in an initial inflammatory response as indicated by statistically significant induction of proinflammatory cytokines (interleukin-1β and tumour necrosis factor-α). This was followed by substantial increases in levels of several matrix metalloproteinases and later by significant induction of type I collagen. Dermal remodelling was noted with both low and high microbeam energy treatment parameters.

CONCLUSIONS

Nonablative fractionated laser resurfacing induces a well-organized wound-healing response that leads to substantial dermal remodelling and collagen induction. Surprisingly, only minimal differences were observed between lower and higher microbeam energy settings. These data suggest that lower microbeam energy/higher microbeam density treatment parameters, which are generally better tolerated by patients, may yield dermal changes similar to those that result from higher microbeam energy/lower microbeam density treatment parameters.

Intraepidermal erbium:YAG laser resurfacing: impact on the dermal matrix

BACKGROUND

Various minimally invasive treatments enhance the skin's appearance. Little is known about the molecular mechanisms whereby treatments working at the epidermal level might alter the dermis.

OBJECTIVE

We sought to quantify the molecular changes that result from erbium:yttrium-aluminium-garnet (Er:YAG) laser microablative resurfacing.

METHODS

We performed biochemical analyses after intraepidermal Er:YAG laser resurfacing of 10 patients. Immunohistochemical analysis and polymerase chain reaction technology were utilized to measure key biomarkers.

RESULTS

The basement membrane remained intact after intraepidermal microablation, as demonstrated by laminin γ2 immunostaining. Epidermal injury was demonstrated with acute up-regulation of keratin 16. An inflammatory response ensued as indicated by increases in cytokines interleukin 1 beta (IL-1β) and IL-8 as well as a substantial neutrophil infiltrate. Levels of cJun and JunB proteins, components of the transcription factor AP-1 complex, were also elevated. Up-regulation of extracellular matrix degrading proteinases matrix metalloproteinase 1 (MMP-1), MMP-3, and MMP-9 was noted. A transient increase in keratinocyte proliferation, as indicated by staining for Ki67, was observed. Increased expression of type I and type III procollagen was demonstrated.

LIMITATIONS

The data presented are those that resulted from a single treatment session.

CONCLUSIONS

Although microablation was confined to the uppermost epidermis, marked changes in epidermal and dermal structure and function were demonstrated after Er:YAG laser microablative resurfacing. We demonstrated substantial dermal matrix remodeling, including a degree of collagen production that compares favorably with some more invasive interventions. Dermal remodeling and stimulation of collagen production are associated with wrinkle reduction. Thus these results suggest that the skin's appearance may be enhanced by creating dermal changes through the use of superficially acting treatments.

Spatial-temporal modulation of CCN proteins during wound healing in human skin in vivo

CCN proteins are important modulators of development and function of adult organs. In this study, we examined the localization and expression of the six CCN family members in normal adult human skin and during wound healing in vivo. Transcript and protein expression were studied by laser-capture microdissection-coupled real-time PCR and immunohistochemistry, respectively. Our results demonstrate that CCN1, CCN4, and CCN6 are expressed at relatively low levels in normal human skin. CCN2, CCN3, and CCN5 are the most highly expressed transcripts in the epidermis. CCN3 and CCN5 proteins are prominent in epidermal keratinocytes, whereas CCN2 is primarily expressed in melanocytes. Differential expression within epidermal layers suggests that CCN3 and CCN5 are linked with keratinocyte differentiation. CCN2, CCN3 and CCN5, are the three most highly expressed transcripts in the dermis. Their respective proteins are produced to various extents by dermal fibroblasts, blood vessels, eccrine sweat glands and hair follicles. We find that most CCN family members are temporally and specifically regulated during different phases (inflammation, proliferation, and remodeling) of partial thickness wound repair. By highlighting spatial-temporal regulations of CCN family member expression in relation to cell proliferation and differentiation, our results suggest a diverse range of functions for CCN proteins in both epidermal and dermal cells, and provides a solid reference for interpretation of future studies aimed at understanding the role of CCN proteins in human skin physiology and diseases.

A novel role of CCN3 in regulating endothelial inflammation

The vascular endothelium plays a fundamental role in the health and disease of the cardiovascular system. The molecular mechanisms regulating endothelial homeostasis, however, remain incompletely understood. CCN3, a member of the CCN (Cyr61, Ctgf, Nov) family of cell growth and differentiation regulators, has been shown to play an important role in numerous cell types. The function of CCN3 in endothelial cells has yet to be elucidated. Immunohistochemical analysis of CCN3 expression in mouse tissues revealed robust immunoreactivity in the endothelium of large arteries, small resistance vessels, and veins. We found that CCN3 expression in human umbilical vein endothelial cells (HUVECs) is transcriptionally induced by laminar shear stress (LSS) and HMG CoA-reductase inhibitors (statins). Promoter analyses identified the transcription factor Kruppel-like factor 2 (KLF2) as a direct regulator of CCN3 expression. In contrast to LSS, proinflammatory cytokines reduced CCN3 expression. Adenoviral overexpression of CCN3 in HUVEC markedly inhibited the cytokine-mediated induction of vascular adhesion molecule-1 (VCAM-1). Consistent with this observation, CCN3 significantly reduced monocyte adhesion. Conversely, CCN3 knockdown in HUVECs resulted in enhancement of cytokine-induced VCAM-1 expression. Concordant effects were observed on monocyte adhesion. Gain and loss-of-function mechanistic studies demonstrated that CCN3 negatively regulates nuclear factor kappaB (NF-κB) activity by reducing its translocation into the nucleus and subsequent binding to the VCAM-1 promoter, suggesting that CCN3's anti-inflammatory effects occur secondary to inhibition of NF-κB nuclear accumulation. This study identifies CCN3 as a novel regulator of endothelial proinflammatory activation.

Amphiregulin carboxy-terminal domain is required for autocrine keratinocyte growth

The EGFR ligand amphiregulin (AREG) has been implicated as an important autocrine growth factor in several epithelial malignancies and in psoriasis, a hyperproliferative skin disorder. To characterize the mechanisms by which AREG regulates autocrine epithelial cell growth, we transduced human keratinocytes (KCs) with lentiviral constructs expressing tetracycline (TET)-inducible small hairpin RNA (shRNA). TET-induced expression of AREG shRNA markedly reduced autocrine extracellular signal-regulated kinase phosphorylation, strongly inhibited autocrine KC growth with an efficiency similar to metalloproteinase and EGFR inhibitors, and induced several markers of KC differentiation, including keratins 1 and 10. Addition of various concentrations of exogenous EGFR ligands to KC cultures reversed the growth inhibition in response to AREG-blocking antibodies but not to shRNA-mediated AREG knockdown. Lentivirus-mediated expression of the full-length AREG transmembrane (TM) precursor, but not of the AREG extracellular domain, markedly reversed the shRNA-mediated growth inhibition and morphological changes, and strongly reduced the induction of multiple markers of KC differentiation. Taken together, our data show that autocrine human KC growth is highly dependent on the AREG TM precursor protein and strongly suggest a previously unreported function of the metalloproteinase-processed carboxy (C)-terminal domain of AREG.

Metalloproteinase-mediated, context-dependent function of amphiregulin and HB-EGF in human keratinocytes and skin

Human keratinocytes (KCs) express multiple EGF receptor (EGFR) ligands; however, their functions in specific cellular contexts remain largely undefined. To address this issue, first we measured mRNA and protein levels for multiple EGFR ligands in KCs and skin. Amphiregulin (AREG) was by far the most abundant EGFR ligand in cultured KCs, with >19 times more mRNA and >7.5 times more shed protein than any other family member. EGFR ligand expression in normal skin was low (<8 per thousand of RPLP0/36B4); however, HB-EGF and AREG mRNAs were strongly induced in human skin organ culture. KC migration in scratch wound assays was highly metalloproteinase (MP)- and EGFR dependent, and was markedly inhibited by EGFR ligand antibodies. However, lentivirus-mediated expression of soluble HB-EGF, but not soluble AREG, strongly enhanced KC migration, even in the presence of MP inhibitors. Lysophosphatidic acid (LPA)-induced ERK phosphorylation was also strongly EGFR and MP dependent and markedly inhibited by neutralization of HB-EGF. In contrast, autocrine KC proliferation and ERK phosphorylation were selectively blocked by neutralization of AREG. These data show that distinct EGFR ligands stimulate KC behavior in different cellular contexts, and in an MP-dependent fashion.

Hedgehog signaling maintains hair follicle stem cell phenotype in young and aged human skin

Skin hair follicles (HF) contain bulge stem cells (SC) that regenerate HFs during hair cycles, and repair skin epithelia following injury. As natural aging is associated with decreased skin repair capacity in humans, we have investigated the impact of age on human scalp HF bulge cell number and function. Here, we isolated human bulge cells, characterized as CD200+/KRT15+/KRT19+ cells of the HF, by dissection-combined CD200 selection in young and aged human skin. Targeted transcriptional profiling indicates that KRT15, KRT19, Dkk3, Dkk4, Tcf3, S100A4, Gas1, EGFR and CTGF/CCN2 are also preferentially expressed by human bulge cells, compared to differentiated HF keratinocytes (KC). Our results demonstrate that aging does not alter expression or localization of these HF SC markers. In addition, we could not detect significant differences in HF density or bulge cell number between young and aged human scalp skin. Interestingly, hedgehog (Hh) signaling is activated in human bulge cells in vivo, and down-regulated in differentiated HF KCs, both in young and aged skin. In addition, activation of Hh signaling by lentivirus-mediated overexpression of transcription factor Gli1 induces transcription of HF SC markers KRT15, KRT19, and Gas1, in cultured KCs. Together with previously reported knock-out mouse results, these data suggest a role for Hh signaling in maintaining bulge cell phenotype in young and aged human skin.

Molecular analysis of aggressive microdermabrasion in photoaged skin

OBJECTIVE

To investigate dermal remodeling effects of crystal-free microdermabrasion on photodamaged skin.

DESIGN

Biochemical analyses of human skin biopsy specimens following microdermabrasion treatment in vivo.

SETTING

Academic referral center.

PARTICIPANTS

Volunteer sample of 40 adults, aged 50 to 83 years, with clinically photodamaged forearms. Intervention Focal microdermabrasion treatment with diamond-studded handpieces of varying abrasiveness on photodamaged forearms and serial biopsies at baseline and various times after treatment.

MAIN OUTCOME MEASURES

Quantitative polymerase chain reaction, immunohistochemistry, and enzyme-linked immunosorbent assay were used to quantify changes in inflammatory, proliferative, and remodeling effectors of normal wound healing. Type I and type III procollagen served as the main outcome marker of dermal remodeling.

RESULTS

Coarse-grit microdermabrasion induces a wound healing response characterized by rapid increase in induction of cytokeratin 16 and activation of the AP-1 transcription factor in the epidermis. Early inflammation was demonstrated by induction of inflammatory cytokines, antimicrobial peptides, and neutrophil infiltration in the dermis. AP-1 activation was followed by matrix metalloproteinase-mediated degradation of extracellular matrix. Consistent with this wound-healing response, we observed significant remodeling of the dermal component of the skin, highlighted by induction of type I and type III procollagen and by induction of collagen production enhancers heat shock protein 47 and prolyl 4-hydroxylase. Dermal remodeling was not achieved when microdermabrasion was performed using a medium-grit handpiece.

CONCLUSIONS

Microdermabrasion using a coarse diamond-studded handpiece induces a dermal remodeling cascade similar to that seen in incisional wound healing. Optimization of these molecular effects is likely the result of more aggressive treatment with a more abrasive handpiece.

Enzymes used in molecular biology: a useful guide

Since molecular cloning has become routine laboratory technique, manufacturers offer countless sources of enzymes to generate and manipulate nucleic acids. Thus, selecting the appropriate enzyme for a specific task may seem difficult to the novice. This review aims at providing the readers with some cues for understanding the function and specificities of the different sources of polymerases, ligases, nucleases, phosphatases, methylases, and topoisomerases used for molecular cloning. We provide a description of the most commonly used enzymes of each group, and explain their properties and mechanism of action. By pointing out key requirements for each enzymatic activity and clarifying their limitations, we aim at guiding the reader in selecting appropriate enzymatic source and optimal experimental conditions for molecular cloning experiments.

Differential ErbB1 signaling in squamous cell versus basal cell carcinoma of the skin

In this study, we examined ErbB1 signaling in human basal and squamous cell carcinomas (BCC and SCC) of the skin in vivo. We used enzyme-linked immunosorbent assay, laser capture microdissection-coupled real-time reverse transcriptase-polymerase chain reaction, and immunohistochemistry to assess expression and activation levels of ErbB1 protein, ligands, and potential downstream effectors, in BCC and SCC tumors, stroma, and adjacent epidermis. Although total ErbB1 protein and mRNA were similar in cancerous and normal skin, we found that ErbB1 activation (phospho-Tyr(1068)) was greater in bulk SCC versus BCC or normal skin. In addition, three ErbB1 ligand transcripts (amphiregulin, heparin-binding epidermal growth factor-like growth factor, and transforming growth factor-alpha) were up-regulated in tumor cells of SCC but not BCC. Expression of these ligands was also increased in asymptomatic epidermis adjacent to both SCC and BCC, relative to normal skin. Interestingly, betacellulin transcript levels were inversely regulated compared with the other ligands. Consistently, downstream ErbB1 effectors (Erk1/2 and Akt) were activated in tumor cells of SCC but not of BCC and in adjacent epidermis of both BCC and SCC. These results demonstrate that ErbB1 signaling is hyperactive in tumor cells of SCC but not of BCC and in nearby asymptomatic epidermis of both tumor types. Our results suggest that targeting ErbB1 signaling might be of benefit in the treatment of SCC.

Retinoid-induced epidermal hyperplasia is mediated by epidermal growth factor receptor activation via specific induction of its ligands heparin-binding EGF and amphiregulin in human skin in vivo

Retinoids are widely used in the treatment of photoaging to stimulate dermal repair. However, retinoids also induce epidermal hyperplasia, which can lead to excessive scaling. Scaling is the major deterrent to topical retinoid therapy. Keratinocyte growth is strongly stimulated via ligand activation of EGFR. We examined regulation of EGFR ligands by retinoids and the role of EGFR in retinoid-induced hyperplasia in human skin in vivo. Topical treatment of human skin with all-trans retinoic acid (tRA) induces EGFR ligands heparin-binding (HB)-EGF and amphiregulin (AR), and reduces betacellulin mRNA levels. Laser capture microdissection-coupled real-time reverse transcription-PCR reveals that tRA increases HB-EGF mRNA throughout the epidermis, whereas AR induction is limited to basal keratinocytes. Topical tRA activates extracellular signal-regulated kinase 1/2 (Erk1/2) downstream EGFR effectors in human skin in vivo. tRA increases the soluble forms of AR and HB-EGF proteins, and induces epidermal hyperplasia, in human skin organ culture. Neutralization of HB-EGF or AR with specific antibodies strongly reduces tRA-induced epidermal hyperplasia. Finally, inhibition of EGFR activation by genistein reduces epidermal hyperplasia caused by topical retinoid treatment. These data demonstrate the central role of EGFR activation in retinoid-induced epidermal hyperplasia, and suggest that EGFR inhibitors can mitigate retinoid-induced scaling.

Isolation and culture of skin fibroblasts

Dermal fibroblasts synthesize and organize skin connective tissue (dermis). Fibroblast cultures provide a powerful tool for investigating both the molecular mechanisms that regulate skin connective tissue production and the pathophysiology of fibrotic skin diseases. In this chapter, we describe detailed procedures for establishing and maintaining primary cultures of adult human fibroblasts. We also provide protocols for constructing three-dimensional dermal and skin equivalent culture models.

UV-light-induced signal cascades and skin aging

UV irradiation acts as a broad activator of cell surface growth factor and cytokine receptors. This ligand-independent receptor activation induces multiple downstream signaling pathways that regulate expression of multiple genes. These signaling pathways converge to stimulate transcription factor AP-1. Among genes whose expression is regulated by AP-1 are several matrix-metalloproteinase (MMP) family members and type I procollagen. UV-enhanced matrix degradation is accompanied with decreased collagen production mediated not only by activation of AP-1, but also by inhibition of transforming growth factor (TGF)-beta signaling. Several alterations to skin connective tissue that occur during aging are mediated by mechanisms that are similar to those that occur in response to UV irradiation. Thus, skin aging is associated with increased AP-1 activity, increased MMP expression, impaired TGF-beta signaling, enhanced collagen degradation, and decreased collagen synthesis. Knowledge gained from examining molecular responses of human skin to UV irradiation provides not only a framework for understanding mechanisms involved in skin aging, but also may help in development of new clinical strategies to impede chronological and UV-induced skin aging.

Malondialdehyde binding to proteins dramatically alters fibroblast functions

The regulation of cell metabolism by the surrounding environment is deeply altered by the posttranslational nonenzymatic modifications of extracellular proteins that occur throughout lifespan in vivo and modify their structural and functional properties. Among them are protein adducts formed by components generated from oxidative processes, such as malondialdehyde (MDA). We have investigated here the effects of MDA-binding to proteins on cultured fibroblast functions. Type I collagen and/or serum proteins were incubated with 0-100 mM MDA for 3 h before use in fibroblast cultures. In tridimensional lattice cultures, MDA-treated collagen inhibited the contracting activity of fibroblasts. A similar inhibition of lattice contraction was reproduced by the addition of MDA-treated serum to the culture medium. In monolayer cultures, the addition of MDA-modified serum proteins completely inhibited fibroblast multiplication without effect on initial adhesion steps. MDA-modified proteins decreased the proliferative capacities of cells, strongly altered cell cycle progression by blocking passage to G2/M phases, and induced apoptotic features in fibroblasts. Our results show, for the first time, that MDA-modified proteins are potentially as deleterious as free MDA, and could be involved in aging as well as in degenerative complications of diseases with increased oxidative stress such as diabetes mellitus or atherosclerosis.

Human blood monocytes interact with type I collagen through alpha x beta 2 integrin (CD11c-CD18, gp150-95)

Human blood monocytes are attracted into connective tissues during early steps of inflammation and wound healing, and locally interact with resident cells and extracellular matrix proteins. We studied the effects of type I collagen on monocyte adhesion and superoxide anion production, using human monocytes elutriated from peripheral blood and type I collagen obtained from rat tail tendon. Both acid-soluble and pepsin-digested type I collagens promoted the adhesion of monocytes, whereas only acid-soluble collagen with intact telopeptides induced the production of superoxide. Adhesion and activation of monocytes on acid-soluble type I collagen depended on the presence of divalent cations. mAbs directed against integrin subunits CD11c and CD18 specifically inhibited adhesion and activation of monocytes on type I collagen. Protein membrane extracts obtained from monocytes were submitted to affinity chromatography on collagen I-Sepharose 4B, and analyzed by Western blotting using specific anti-integrin subunit Abs. In the case of both acid-soluble and pepsin-digested collagens, two bands were revealed with mAbs against CD11c and CD18 integrin subunits. Our results demonstrate that monocytes interact with type I collagen through CD11c-CD18 (alpha x beta 2) integrins, which promote their adhesion and activation. For monocyte activation, specific domains of the type I collagen telopeptides are necessary. Interactions between monocytes and collagen are most likely involved in the cascade of events that characterize the initial phases of inflammation.

Decreased contraction of glycated collagen lattices coincides with impaired matrix metalloproteinase production

Nonenzymatic glycation of extracellular matrix (ECM) proteins is increased in diabetes mellitus and aging and triggers cellular events leading to an imbalance in ECM homeostasis. We studied the influence of collagen glycation on matrix metalloproteinase production by dermal fibroblasts using the model of lattice cultures. Contraction of glycated collagen lattices was strongly reduced when compared to controls. Meanwhile, fibroblasts synthesized lower amounts of interstitial collagenase (MMP-1). Gelatinase A (MMP-2) production was not modified, but its activation was strongly inhibited. These effects were independent from the intensity of lattice contraction and from any simultaneous modification of tissue inhibitors of metalloproteinase (TIMP-1 and 2) production. These results demonstrate that the impaired ability of fibroblasts to remodel and contract a glycated extracellular matrix coincides with a decrease in MMP production.