Multiple Roles for Elastic Fibers in the Skin

Comprehensive Evaluation of Injectability Attributes in OxiFree™ Dermal Fillers: MaiLi® Product Variants and Clinical Case Reports

Dermal filler injectability is a critical factor for commercial product adoption by medical aesthetic professionals and for successful clinical administration. We have previously reported (in vitro and ex vivo) cross-linked hyaluronic acid (HA)-based dermal filler benchmarking in terms of manual and automated injectability requirements. To further enhance the function-oriented product characterization workflows and the clinical relevance of dermal filler injectability assessments, the aim of this study was to perform in vivo evaluations. Therefore, several variants of the MaiLi® product range (OxiFree™ technology) were characterized in vitro and in vivo in terms of injectability attributes, with a focus on hydrogel system homogeneity and ease of injection. Firstly, standardized in vitro assays were performed in SimSkin® cutaneous equivalents, with variations of the clinical injector, injection site, and injection technique. Then, automated injections in SimSkin® cutaneous equivalents were comparatively performed in a texture analysis setup to obtain fine-granulometry injection force profile results. Finally, five female participants were recruited for the in vivo arm of the study (case reports), with variations of the clinical injector, injection site, and injection technique. Generally, the obtained quantitative force values and injection force profiles were critically appraised from a translational viewpoint, based on discussions around the OxiFree™ manufacturing technology and on in-use specialized clinician feedback. Overall, the present study outlined a notable level of homogeneity across the MaiLi® product range in terms of injectability attributes, as well as consistently high ease of administration by medical aesthetic clinicians.

Use of collagen and auricular cartilage in bioengineering: scaffolds for tissue regeneration

The aim of this study was the development of collagen and collagen/auricular cartilage scaffolds for application in dermal regeneration. Collagen was obtained from bovine tendon by a 72 h-long treatment, while bovine auricular cartilage was treated for 24 h and divided into two parts, external (perichondrium, E) and internal (elastic cartilage, I). The scaffolds were prepared by mixing collagen (C) with the internal part (CI) or the external part (CE) in a 3:1 ratio. Differential scanning calorimetry, scanning electron microscopy (SEM) analysis, microcomputed tomography imaging (micro-CT) and swelling degree were used to characterize the scaffolds. Cytotoxicity, cell adhesion, and cell proliferation assays were performed using the cell line NIH/3T3. All samples presented a similar denaturation temperature (Td) around 48 °C, while CE presented a second Td at 51.2 °C. SEM micrographs showed superficial pores in all scaffolds and micro-CT exhibited interconnected pore spaces with porosity above 60% (sizes between 47 and 149 µm). The order of swelling was CE < CI < C and the scaffolds did not present cytotoxicity, showing attachment rates above 75%-all samples showed a similar pattern of proliferation until 168 h, whereas CI tended to decrease after this time. The scaffolds were easily obtained, biocompatible and had adequate morphology for cell growth. All samples showed high adhesion, whereas collagen-only and collagen/external part scaffolds presented a better cell proliferation rate and would be indicated for possible use in dermal regeneration.

Contribution of intramuscular connective tissue and its structural components on meat tenderness-revisited: a review

The tenderness of meat influences consumers' perceptions of its quality. Meat tenderness is a key quality characteristic that influences consumer satisfaction, repeat purchases, and willingness to pay higher prices for meat. Muscle fibers, connective tissues, and adipocytes are the main structural components of meat that contribute to its tenderness and texture. In the present review, we have focused on the role of connective tissue and its components in meat tenderness, specifically perimysial intramuscular connective tissue (IMCT) and its concept as an immutable "background toughness." The collagen contribution to cooked meat toughness can be altered by animal diet, compensatory growth, slaughter age, aging, and cooking. As well, progressive thickening of the perimysium leads to a progressive increase in shear force values in beef, pork, chicken, and this may occur prior to adipocyte formation as cattle finish in feedlots. Conversely, adipocyte accumulation in the perimysium can decrease cooked meat shear force, suggesting that the contribution of IMCT to meat toughness is complex and driven by both collagen structure and content. This review provides a theoretical foundation of information to modify IMCT components to improve meat tenderness.

The Role of Extracellular Matrix in Wound Healing

BACKGROUND

Extracellular matrix communicates with surrounding cells to maintain skin homeostasis and modulate multiple cellular processes including wound healing.

OBJECTIVE

To elucidate the dynamic composition and potential roles of extracellular matrix in normal skin, wound healing process, and abnormal skin scarring.

MATERIALS AND METHODS

Literature review was performed to identify relevant publications pertaining to the extracellular matrix deposition in normal skin and wound healing process, as well as in abnormal scars.

RESULTS

A summary of the matrix components in normal skin is presented. Their primary roles in hemostasis, inflammation, proliferation, and remodeling phases of wound healing are briefly discussed. Identification of novel extracellular matrix in keloids is also provided.

CONCLUSION

Abnormal scarring remains a challenging condition with unmet satisfactory treatments. Illumination of extracellular matrix composition and functions in wound healing process will allow for the development of targeted therapies in the future.

Three-dimensional analysis of load-dependent changes in the orientation of dermal collagen fibers in human skin: A pilot study

The availability of quantitative structural data on the orientation of collagen fibers is of crucial importance for understanding the behavior of connective tissues. These fibers can be visualized using a variety of imaging techniques, including second harmonic generation (SHG) microscopy. However, characterization of the collagen network requires the accurate extraction of parameters from imaging data. To this end, several automated processes have been developed to identify the preferred orientation of collagen fibers. Common methods include fast Fourier transforms and curvelet transforms, but these tools are mostly used to infer a single preferred orientation. The purpose of this pilot study was to develop an easy procedure for comprehensively comparing multiple human skin samples with the goal of analyzing load-dependent changes via SHG microscopy. We created a 3D model based upon 2D image stacks that provide fiber orientation data perpendicular and parallel to the plane of the epidermis. The SHG images were analyzed by CurveAlign to obtain angle histogram plots containing information about the multiple fiber orientations in each single image. Subsequently, contour plots of the angle histogram intensities were created to provide a useful visual plotting method to clearly show the anomalies in the angle histograms in all samples. Our results provided additional details on how the collagen network carries a load. In fact, analysis of SHG images indicated that increased stretch was accompanied by an increase in the alignment of fibers in the loading direction. Moreover, these images demonstrated that more than one type of preferred orientation is present. In particular, the 3D network of fibers appears to have two preferred orientations in the planes both perpendicular and parallel to the plane of the epidermis.

The physiological study of emotional piloerection: A systematic review and guide for future research

This paper provides an accessible review of the biological and psychological evidence to guide new and experienced researchers in the study of emotional piloerection in humans. A limited number of studies have attempted to examine the physiological and emotional correlates of piloerection in humans. However, no review has attempted to collate this evidence to guide the field as it moves forward. We first discuss the mechanisms and function of non-emotional and emotional piloerection in humans and animals. We discuss the biological foundations of piloerection as a means to understand the similarities and differences between emotional and non-emotional piloerection. We then present a systematic qualitative review (k = 24) in which we examine the physiological correlates of emotional piloerection. The analysis revealed that indices of sympathetic activation are abundant, suggesting emotional piloerection occurs with increased (phasic) skin conductance and heart rate. Measures of parasympathetic activation are lacking and no definite conclusions can be drawn. Additionally, several studies examined self-reported emotional correlates, and these correlates are discussed in light of several possible theoretical explanations for emotional piloerection. Finally, we provide an overview of the methodological possibilities available for the study of piloerection and we highlight some pressing questions researchers may wish to answer in future studies.

Fascicular elastin within tendon contributes to the magnitude and modulus gradient of the elastic stress response across tendon type and species

Elastin, the main component of elastic fibers, has been demonstrated to significantly influence tendon mechanics using both elastin degradation studies and elastinopathic mouse models. However, it remains unclear how prior results differ between species and functionally distinct tendons and, in particular, how results translate to human tendon. Differences in function between fascicular and interfascicular elastin are also yet to be fully elucidated. Therefore, this study evaluated the quantity, structure, and mechanical contribution of elastin in functionally distinct tendons across species. Tendons with an energy-storing function had slightly more elastin content than tendons with a positional function, and human tendon had at least twice the elastin content of other species. While distinctions in the organization of elastic fibers between fascicles and the interfascicular matrix were observed, differences in structural arrangement of the elastin network between species and tendon type were limited. Mechanical testing paired with enzyme-induced elastin degradation was used to evaluate the contribution of elastin to tendon mechanics. Across all tendons, elastin degradation affected the elastic stress response by decreasing stress values while increasing the modulus gradient of the stress-strain curve. Only the contributions of elastin to viscoelastic properties varied between tendon type and species, with human tendon and energy-storing tendon being more affected. These data suggest that fascicular elastic fibers contribute to the tensile mechanical response of tendon, likely by regulating collagen engagement under load. Results add to prior findings and provide evidence for a more mechanistic understanding of the role of elastic fibers in tendon. STATEMENT OF SIGNIFICANCE: Elastin has previously been shown to influence the mechanical properties of tendon, and degraded or abnormal elastin networks caused by aging or disease may contribute to pain and an increased risk of injury. However, prior work has not fully determined how elastin contributes differently to tendons with varying functional demands, as well as within distinct regions of tendon. This study determined the effects of elastin degradation on the tensile elastic and viscoelastic responses of tendons with varying functional demands, hierarchical structures, and elastin content. Moreover, volumetric imaging and protein quantification were used to thoroughly characterize the elastin network in each distinct tendon. The results presented herein can inform tendon-specific strategies to maintain or restore native properties in elastin-degraded tissue.

Elastic Fibres in the subcutaneous tissue: Is there a difference between superficial and muscular fascia? A cadaver study

BACKGROUND

In last years the role of fascia in proprioception and pain has been confirmed in numerous papers, but the real structure of fasciae is not still entirely known. To date, many studies have evaluated the elastic fibres in arteries, ligaments, lungs, epidermis and dermis, but only two studies exist about the elastic fibres in the fasciae, and they did not distinguish between superficial (in the subcutaneous tissue) and deep/muscular fasciae. The aim of the study was to assess the percentage of elastic fibres between superficial and deep fascia.

MATERIALS AND METHODS

Three full thickness specimens (proximal, middle and distal respectively) were taken from each of four regions of the thigh of three non-embalmed cadavers: the anterior (Ant), the lateral (Lat), the posterior (Post) and the medial (Med) aspect. Thus, a total of 12 specimens were collected from each analysed thigh and histological Weigert Van Gieson stains was performed. Three sections per specimen were considered for the morphometric analysis.

RESULTS

In all the specimens the superficial and deep fasciae were clearly recognizable. The difference in percentage of elastic fibres between superficial and deep fasciae in same region for all four was highly significant (p < 0.001). They are abundant in the superficial fascia than deep fascia.

CONCLUSIONS

In the light of these findings is evident that the superficial (in the subcutaneous tissue) and deep fasciae have different elasticity. This difference may improve grading of fascial dysfunction in dermatological diseases as burns, scars and lymphedema to better plan treatments.

Preclinical models of diabetic wound healing: A critical review

The treatment of diabetic wounds (DWs) is always challenging for the medical community because of its multifaceted pathophysiology. Due to practical and ethical considerations, direct studies of therapeutic interventions on human subjects are limited. Thus, it is ideal for performing studies on animals having less genetic and biological variability. An ideal DW model should progress toward reproducibility, quantifiable interpretation, therapeutic significance, and effective translation into clinical use. In the last couple of decades, various animal models were developed to examine the complex cellular and biochemical process of skin restoration in DW healing. Also, these models were used to assess the potency of developed active pharmaceutical ingredients and formulations. However, many animal models lack studying mechanisms that can appropriately restate human DW, stay a huge translational challenge. This review discusses the available animal models with their significance in DW experiments and their limitations, focusing on levels of proof of effectiveness in selecting appropriate models to restate the human DW to improve clinical outcomes. Although numerous newer entities and combinatory formulations are very well appreciated preclinically for DW management, they fail in clinical trials, which may be due to improper selection of the appropriate model. The major future challenge could be developing a model that resembles the human DW environment, can potentiate translational research in DW care.

Release of the model drug SR101 from polyurethane nanocapsules in porcine hair follicles triggered by LED-derived low dose UVA light

Hair follicles (HFs) are important drug delivery targets for the therapy of miscellaneous skin diseases and for skin antisepsis. Furthermore, HFs significantly contribute to drug delivery of topically applied substances. Nanoparticulate systems are excellently suited for follicular drug delivery as they entail the opportunity of directed drug transport into HFs. Moreover, they involve the possibility of an intrafollicular drug release initiated by extrinsic or intrinsic trigger mechanisms. In this study, we present a novel preclinical model for an anatomically and temporally targeted intrafollicular drug release. In vitro release kinetics of the model drug sulforhodamine 101 (SR101) from newly synthesized ultraviolet A (UVA)-responsive polyurethane nanocapsules (NCs) were investigated by fluorescence spectroscopy. Low power density UVA radiation provided by a UVA light emitting diode (LED) induced a drug release of over 50% after 2 min. We further utilized confocal laser scanning microscopy (CLSM) to investigate follicular penetration as well as intrafollicular drug release on an ex vivo porcine ear skin model. UVA-responsive degradation of the NCs at a mean follicular penetration depth of 509 ± 104 µm ensured liberation of SR101 in the right place and at the right time. Thus, for the first time a UVA-triggered drug release from NCs within HFs was demonstrated in the present study. Cytotoxicity tests revealed that NCs synthesized with isophorone diisocyanate show sufficient biocompatibility after UVA-induced cleavage. A considerable and controllable release of various water-soluble therapeutics could be reached by means of the presented system without risking any radiation-related tissue damage. Therefore, the implementation of the presented system into clinical routine, e.g. for preoperative antisepsis of HFs, appears very promising.

Ameliorative Effects of Peptides from the Oyster (Crassostrea hongkongensis) Protein Hydrolysates against UVB-Induced Skin Photodamage in Mice

Chronic exposure to ultraviolet B (UVB) irradiation is a major cause for skin photoaging. UVB induces damage to skin mainly by oxidative stress, inflammation, and collagen degradation. This paper investigated the photo-protective effects of peptides from oyster (Crassostrea hongkongensis) protein hydrolysates (OPs) by topical application on the skin of UVB-irradiated mice. Results from mass spectrometry showed that OPs consisted of peptides with a molecular weight range of 302.17–2936.43 Da. In vivo study demonstrated that topical application of OPs on the skin significantly alleviated moisture loss, epidermal hyperplasia, as well as degradation of collagen and elastin fibers caused by chronic UVB irradiation. In this study, OPs treatment promoted antioxidant enzymes (SOD and GPH-Px) activities, while decreased malondialdehyde (MDA) level in the skin. In addition, OPs treatment significantly decreased inflammatory cytokines (IL-1β, IL-6, TNF-α) content, and inhibited inflammation related (iNOS, COX-2) protein expression in the skin. Via inhibiting metalloproteinase 1(MMP1) expression, OPs treatment markedly decreased the degradation of collagen and elastin fibers as well as recovered the altered arrangement of extracellular matrix network in the dermis of skin. Our study demonstrated for the first time that OPs protected against UVB induced skin photodamage by virtue of its antioxidative and anti-inflammatory properties, as well as regulating the abnormal expression of MMP-1. The possible molecular mechanism underlying OPs anti-photoaging is possibly related to downregulating of the MAPK/NF-κB signaling pathway, while promoting TGF-β production in the skin.

Topical Insulin Modulates Inflammatory and Proliferative Phases of Burn-Wound Healing in Diabetes-Induced Rats

The healing time of burn wounds depends on surface area and depth of the burn and associated comorbidities. Diabetes mellitus (DM) causes delays in the healing process by extending the inflammatory phase. Treatment with topical insulin can improve the inflammatory phase, restore metabolic dysregulation, and modulate impaired cellular signaling in burn wounds. The objective of this study was to evaluate markers of the inflammatory and proliferative phases of second-degree burns after topical insulin treatment in diabetic rats. Type I DM was induced with streptozotocin in male Wistar rats. The animals' backs were shaved and subjected to thermal burning. Rats were randomized into two groups: control diabetic (DC) and insulin diabetic (DI). At Days 7 and 14 postburn, rats were euthanized, and wound-tissue sections were evaluated by hematoxylin and eosin, Weigert, and Verhöeff staining, immunohistochemistry-paraffin, and enzyme-linked immunosorbent assay. A significant increase in reepithelialization was seen on Days 7 and 14 in DI versus DC rats. On Day 7, interleukin (IL)-1β, IL-6, monocyte chemotactic protein (MCP)-1, and F4/80 expression were increased in DI versus DC rats. On Day 14, MCP-1 expression was decreased and F4/80 increased in DI versus DC rats. On Days 7 and 14, Ki-67, transforming growth factor-β1, vascular endothelial growth factor expression, and formation of elastic fibers were increased in DI versus DC rats. Topical insulin modulates burn-wound healing in diabetic animals by balancing inflammation and promoting angiogenesis and formation of elastic fibers.

Ameliorative effects of snake (Deinagkistrodon acutus) oil and its main fatty acids against UVB-induced skin photodamage in mice

The effects of topically administered snake (Deinagkistrodon acutus) oil and its main fatty acid components on skin photodamage were explored. Epidermal thickness, mice body weight, antioxidant enzymes (superoxide dismutase, glutathione peroxidase, catalase), inflammatory cytokines (tumor necrosis factor alpha and interleukin-6), skin histology, collagen content, and metalloproteinase-1 indicators were analyzed. The results show that topical application of both snake oil and its main fatty acids recovered ultraviolet B (UVB) irradiation induced antioxidant enzymes depletion, prevented metalloproteinase-1. Snake oil and its main fatty acids suppressed dermal infiltration of inflammatory cells and reduced inflammatory cytokines levels. Notably, there was no significant difference in the antioxidant activity but a significant difference in the anti-inflammatory activity between fatty acids and snake oil under the same dose. Finally, snake oil and its main fatty acids inhibited UVB-induced histological damage such as epidermal thickening, collagen fiber and elastic fiber destruction. Our study demonstrated for the first time in KM mice that snake oil exhibited prominent photoprotection activity by protecting the activity of antioxidant enzymes and inhibiting inflammatory factors, as well as reducing the generation of MMP-1. What's more, the main fatty acids in snake oil play an important role in preventing photo-damage especially in protecting antioxidant enzyme activity.

Elastin-PLGA hybrid electrospun nanofiber scaffolds for salivary epithelial cell self-organization and polarization

Development of electrospun nanofibers that mimic the structural, mechanical and biochemical properties of natural extracellular matrices (ECMs) is a promising approach for tissue regeneration. Electrospun fibers of synthetic polymers partially mimic the topography of the ECM, however, their high stiffness, poor hydrophilicity and lack of in vivo-like biochemical cues is not optimal for epithelial cell self-organization and function. In search of a biomimetic scaffold for salivary gland tissue regeneration, we investigated the potential of elastin, an ECM protein, to generate elastin hybrid nanofibers that have favorable physical and biochemical properties for regeneration of the salivary glands. Elastin was introduced to our previously developed poly-lactic-co-glycolic acid (PLGA) nanofiber scaffolds by two methods, blend electrospinning (EP-blend) and covalent conjugation (EP-covalent). Both methods for elastin incorporation into the nanofibers improved the wettability of the scaffolds while only blend electrospinning of elastin-PLGA nanofibers and not surface conjugation of elastin to PLGA fibers, conferred increased elasticity to the nanofibers measured by Young's modulus. After two days, only the blend electrospun nanofiber scaffolds facilitated epithelial cell self-organization into cell clusters, assessed with nuclear area and nearest neighbor distance measurements, leading to the apicobasal polarization of salivary gland epithelial cells after six days, which is vital for cell function. This study suggests that elastin electrospun nanofiber scaffolds have potential application in regenerative therapies for salivary glands and other epithelial organs.

STATEMENT OF SIGNIFICANCE

Regenerating the salivary glands by mimicking the extracellular matrix (ECM) is a promising approach for long term treatment of salivary gland damage. Despite their topographic similarity to the ECM, electrospun fibers of synthetic polymers lack the biochemical complexity, elasticity and hydrophilicity of the ECM. Elastin is an ECM protein abundant in the salivary glands and responsible for tissue elasticity. Although it's widely used for tissue regeneration of other organs, little is known about its utility in regenerating the salivary tissue. This study describes the use of elastin to improve the elasticity, hydrophilicity and biochemical complexity of synthetic nanofibers and its potential in directing in vivo-like organization of epithelial salivary cells which helps the design of efficient salivary gland regeneration scaffolds.

The Role of Elastic Fibers in Scar Formation and Treatment

BACKGROUND

Laser therapy is a continuously evolving treatment option for scars, and the underlying therapeutic mechanisms continue to be elucidated.

OBJECTIVE

To comprehensively review the literature to summarize the role of elastin in the formation scars, as well as treatment via therapeutic lasers.

METHODS

Review of the PubMED/MEDLINE database for available studies pertaining to the role of elastic fibers in scar formation and after laser-based therapy.

RESULTS

The loss and disorganization of elastic fiber components plays a role in the development of atrophic, hypertrophic, and keloid scars. While the majority of histologic studies focus on the underlying changes in collagen, neoelastogenesis and reorganization of elastic fibers have also been demonstrated in studies using ablative, nonablative, and fractional laser devices for the treatment of scars.

CONCLUSION

Production of novel elastin and normalization of elastic fiber organization occur after a variety of resurfacing procedures to treat scarring. As the treatment modalities to manage scars continue to evolve, further characterization of the role of elastin in the skin and in scar formation is merited.

Subtle balance of tropoelastin molecular shape and flexibility regulates dynamics and hierarchical assembly

The assembly of the tropoelastin monomer into elastin is vital for conferring elasticity on blood vessels, skin, and lungs. Tropoelastin has dual needs for flexibility and structure in self-assembly. We explore the structure-dynamics-function interplay, consider the duality of molecular order and disorder, and identify equally significant functional contributions by local and global structures. To study these organizational stratifications, we perturb a key hinge region by expressing an exon that is universally spliced out in human tropoelastins. We find a herniated nanostructure with a displaced C terminus and explain by molecular modeling that flexible helices are replaced with substantial β sheets. We see atypical higher-order cross-linking and inefficient assembly into discontinuous, thick elastic fibers. We explain this dysfunction by correlating local and global structural effects with changes in the molecule's assembly dynamics. This work has general implications for our understanding of elastomeric proteins, which balance disordered regions with defined structural modules at multiple scales for functional assembly.

Characterisation of porcine dermis scaffolds decellularised using a novel non-enzymatic method for biomedical applications

Off-the-shelf availability of tissue-engineered skin constructs, tailored by different combinations of reagents to produce a highly preserved biological matrix is often the only means to help patients suffering skin damage. This study assessed the effect of five different decellularisation methods on porcine dermal scaffolds with regard to matrix composition, biomechanical strength, and cytotoxicity using an in vitro biocompatibility assay. Results demonstrated that four out of the five tested decellularisation protocols were efficient in producing acellular scaffolds. Nevertheless, decellularisation method using osmotic shock without enzymatic digestion showed to be efficient not only in removing cellular material and debris from dermal scaffolds but was also beneficial in the preservation of extracellular matrix components (glycosaminoglycans and collagen). Histological assessment revealed that the dermal architecture of coarse collagen bundles was preserved. Examinations by scanning electron microscopy and transmission electron microscopy showed that the arrangement and ultrastructure of collagen fibrils in the scaffolds were retained following non-enzymatic method of decellularisation and also after collagen crosslinking using genipin. Moreover, this decellularised scaffold was not only shown to be biologically compatible when co-cultured with bone marrow-derived mesenchymal stem cells and fibroblasts, but also stimulated the cells to release trophic factors essential for tissue regeneration.

Animal models for cutaneous vaccine delivery

Main challenges in skin vaccination are overcoming the stratum corneum (SC) barrier and targeting the antigen presenting cells (APC) in the epidermis and the dermis. For this purpose many delivery techniques are being developed. In vivo immunogenicity and safety studies in animals are mandatory before moving to clinical trials. However, the results obtained in animals may or may not be predictive for humans. Knowledge about differences and similarities in skin architecture and immunology within a species and between species is crucial. In this review, we discuss variables, including skin morphology, skin barrier function, mechanical properties, site of application and immunology, which should be taken into account when designing animal studies for vaccination via the skin in order to support the translation to clinical trial outcomes.

Cutis laxa with pulmonary emphysema, conjunctivochalasis, nasolacrimal duct obstruction, abnormal hair, and a novel FBLN5 mutation

We report on a 4-year-old girl with autosomal recessive cutis laxa, type IA, or pulmonary emphysema type (ARCL1A; OMIM #219100), with loose and wrinkled skin, mitral and tricuspid valve prolapse, conjunctivochalasis, obstructed nasolacrimal ducts, hypoplastic maxilla, and early childhood-onset pulmonary emphysema. Mutation analysis of FBLN5 showed a homozygous c.432C>G missense mutation, and heterozygosity in the parents. This is predicted to cause amino acid substitution p.Cys144Trp. Conjunctivochalasis or redundant folds of conjunctiva and obstructed nasolacrimal ducts have not been reported to be associated with FBLN5 mutations. Histopathological study of the conjunctival biopsy showed that most blood vessels had normal elastic fibers. The gingiva appeared normal, but histologically elastic fibers were defective. Scanning electron micrography of scalp hair demonstrated hypoplastic hair follicles. The cuticles appear intact underneath the filamentous meshwork.

The role of neprilysin in regulating the hair cycle

In most mammals, each hair follicle undergoes a cyclic process of growing, regressing and resting phases (anagen, catagen, telogen, respectively) called the hair cycle. Various biological factors have been reported to regulate or to synchronize with the hair cycle. Some factors involved in the extracellular matrix, which is a major component of skin tissue, are also thought to regulate the hair cycle. We have focused on an enzyme that degrades elastin, which is associated with skin elasticity. Since our previous study identified skin fibroblast elastase as neprilysin (NEP), we examined the fluctuation of NEP enzyme activity and its expression during the synchronized hair cycle of rats. NEP activity in the skin was elevated at early anagen, and decreased during catagen to telogen. The expression of NEP mRNA and protein levels was modulated similarly. Immunostaining showed changes in NEP localization throughout the hair cycle, from the follicular epithelium during early anagen to the dermal papilla during catagen. To determine whether NEP plays an important role in regulating the hair cycle, we used a specific inhibitor of NEP (NPLT). NPLT was applied topically daily to the dorsal skin of C3H mice, which had been depilated in advance. Mice treated with NPLT had significantly suppressed hair growth. These data suggest that NEP plays an important role in regulating the hair cycle by its increased expression and activity in the follicular epithelium during early anagen.

Oil components modulate the skin delivery of 5-aminolevulinic acid and its ester prodrug from oil-in-water and water-in-oil nanoemulsions

The study evaluated the potential of nanoemulsions for the topical delivery of 5-aminolevulinic acid (ALA) and methyl ALA (mALA). The drugs were incorporated in oil-in-water (O/W) and water-in-oil (W/O) formulations obtained by using soybean oil or squalene as the oil phase. The droplet size, zeta potential, and environmental polarity of the nanocarriers were assessed as physicochemical properties. The O/W and W/O emulsions showed diameters of 216-256 and 18-125 nm, which, respectively, were within the range of submicron- and nano-sized dispersions. In vitro diffusion experiments using Franz-type cells and porcine skin were performed. Nude mice were used, and skin fluorescence derived from protoporphyrin IX was documented by confocal laser scanning microscopy (CLSM). The loading of ALA or mALA into the emulsions resulted in slower release across cellulose membranes. The release rate and skin flux of topical drug application were adjusted by changing the type of nanocarrier, the soybean oil O/W systems showing the highest skin permeation. This formulation increased ALA flux via porcine skin to 180 nmol/cm(2)/h, which was 2.6-fold that of the aqueous control. The CLSM results showed that soybean oil systems promoted mALA permeation to deeper layers of the skin from ∼100 μm to ∼140 μm, which would be beneficial for treating subepidermal and subcutaneous lesions. Drug permeation from W/O systems did not surpass that from the aqueous solution. An in vivo dermal irritation test indicated that the emulsions were safe for topical administration of ALA and mALA.

Histomorphometric comparison after fixation with formaldehyde or glyoxal

Formaldehyde has long been the fixative of choice for histological examination of tissue. The use of alternatives to formaldehyde has grown, however, owing to the serious hazards associated with its use. Companies have striven to maintain the morphological characteristics of formaldehyde-fixed tissue when developing alternatives. Glyoxal-based fixatives now are among the most popular formaldehyde alternatives. Although there are many studies that compare staining quality and immunoreactivity, there have been no studies that quantify possible structural differences. Histomorphometric analysis commonly is used to evaluate diseased tissue. We compared fixation with formaldehyde and glyoxal with regard to the histomorphological properties of plantar foot tissue using a combination of stereological methods and quantitative morphology. We measured skin thickness, interdigitation index, elastic septa thickness, and adipocyte area and diameter. No significant differences were observed between formaldehyde and glyoxal fixation for any feature measured. The glyoxal-based fixative used therefore is a suitable fixative for structural evaluation of plantar soft tissue. Measurements obtained from the glyoxal-fixed tissue can be combined with data obtained from formalin-fixed for analysis.

In vivo molecular evaluation of guinea pig skin incisions healing after surgical suture and laser tissue welding using Raman spectroscopy

The healing process in guinea pig skin following surgical incisions was evaluated at the molecular level, in vivo, by the use of Raman spectroscopy. After the incisions were closed either by suturing or by laser tissue welding (LTW), differences in the respective Raman spectra were identified. The study determined that the ratio of the Raman peaks of the amide III (1247 cm(-1)) band to a peak at 1326 cm(-1) (the superposition of elastin and keratin bands) can be used to evaluate the progression of wound healing. Conformational changes in the amide I band (1633-1682 cm(-1)) and spectrum changes in the range of 1450-1520 cm(-1) were observed in LTW and sutured skin. The stages of the healing process of the guinea pig skin following LTW and suturing were evaluated by Raman spectroscopy, using histopathology as the gold standard. LTW skin demonstrated better healing than sutured skin, exhibiting minimal hyperkeratosis, minimal collagen deposition, near-normal surface contour, and minimal loss of dermal appendages. A wavelet decomposition-reconstruction baseline correction algorithm was employed to remove the fluorescence wing from the Raman spectra.

Analysis of dermal elastic fibers in the absence of fibulin-5 reveals potential roles for fibulin-5 in elastic fiber assembly

Fibulin-5 is a 66 kDa modular, extracellular matrix protein that localizes to elastic fibers. Although in vitro protein-protein binding studies have shown that fibulin-5 binds many proteins involved in elastic fiber formation, the specific role of fibulin-5 in elastogenesis remains unclear. To provide a more detailed analysis of elastic fiber assembly in the absence of fibulin-5, the dermis of wild-type and fibulin-5 gene knockout (Fbln5(-/-)) mice was examined with electron microscopy (EM). Although light microscopy showed apparently normal elastic fibers near the hair follicles and the absence of elastic fibers in the intervening dermis of the Fbln5(-/-) mouse, EM revealed the presence of aberrantly assembled elastic fibers in both locales. Instead of the elastin being incorporated into the microfibrillar scaffold, the elastin appeared as globules juxtaposed to the microfibrils. Desmosine analysis showed significantly lower levels of mature cross-linked elastin in the Fbln5(-/-) dermis, however, gene expression levels for tropoelastin and fibrillin-1, the major elastic fiber components, were unaffected. Based on these results, the nature of tropoelastin cross-linking was investigated using domain specific antibodies to lysyl oxidase like-1 (LOXL-1). Immunolocalization with an antibody to the N-terminal pro-peptide, which is cleaved to generate the active enzyme, revealed abundant staining in the Fbln5(-/-) dermis and no staining in the wild-type dermis. Overall, these results suggest two previously unrecognized functions for fibulin-5 in elastogenesis; first, to limit the extent of aggregation of tropoelastin monomers and/or coacervates and aid in the incorporation of elastin into the microfibril bundles, and second, to potentially assist in the activation of LOXL-1.

The effect of composition and microstructure on the viscoelastic properties of dermis

Dermis is a heterogeneous tissue in which extracellular matrix components change in relative amount and spatial assembly across the tissue thickness. The effect of the microstructural and compositional heterogeneities on the overall mechanical response of dermis is, however, largely ignored. In this work, we aimed at gaining a better insight into the effect of extracellular matrix microstructure and composition on the mechanical behaviour of different dermal strata by combining mechanical analysis and selective enzymatic digestion of extracellular matrix components. The dynamical-mechanical tests we performed on bovine dermal splits show that the upper dermal stratum, which is richer in papillary dermis, is characterized by higher mechanical properties than the lower one, which is almost composed of reticular dermis. Moreover, the depletion of interfibrillar proteins, proteoglycans and glycosamminoglycans decreases the dynamic moduli of dermis, especially at small frequencies. Of the two dermal layers tested, the upper dermal layer is more sensitive to the enzymatic treatment than the lower layer. Interestingly, the disruption of the elastic network greatly influenced the viscoelastic properties of upper dermis, inducing a dramatic decrease of both storage (G') and loss (G'') moduli, suggesting that the spatial assembly of the elastin and collagen networks as well as their mutual interactions dominate the dynamical mechanical response of the tissue.

Analysis of obstetric complications and uterine connective tissue in tenascin-X-deficient humans and mice

Tenascin-X (TNX) is a large, multi-domain, extracellular matrix glycoprotein. Complete deficiency of TNX in humans leads to a recessive form of Ehlers-Danlos syndrome (EDS), and TNX haploinsufficiency is a cause of hypermobility type EDS. EDS patients appear to have a higher risk of several complications during pregnancy, such as pelvic instability, premature rupture of membranes, and postpartum hemorrhage. Here, we present a study of genitourinary and obstetric complications in TNX-deficient women of reproductive age. We have found complications, such as uterus prolapses, that are in agreement with previous findings in other EDS types. In TNX knockout (KO) mice, we have observed mild pregnancy-related abnormalities. Morphological and immunohistological analysis of uterine tissues has not revealed obvious quantitative or spatial differences between TNX KO and wildtype mice with respect to collagen types I, III, V, and XII or elastic fibers. We conclude that TNX-deficient women are at risk of obstetric complications, but that TNX KO mice show only a mild phenotype. Furthermore, we show that TNX is involved in the stability of elastic fibers rather than in their initial deposition.

Increased degradation of extracellular matrix structures of lacrimal glands implicated in the pathogenesis of Sjögren's syndrome

Lacrimal glands (LGs) of male non-obese diabetic (NOD) mice display many features of human LGs in patients afflicted with the autoimmune disease Sjögren's syndrome (SS), including the loss of secretory functions and a lymphocytic infiltration into the glands by 4 months of age. So far, research has mainly focused on the intracellular events that are involved in initiating LG dysfunction; however, the impact of SS on extracellular matrix (ECM) structures of the diseased LGs has not yet been determined. In this study we identified and compared LG ECM formation and integrity of age-matched male healthy (BALB/c) and diseased (NOD) mice. LG tissues were examined using routine histological, biochemical, immunohistochemical and gene expression analysis. Multiphoton imaging and second-harmonic generation (SHG) microscopy permitted the non-invasive analysis of major LG ECM structures including collagen- and elastin-containing fibers. Biochemical testing demonstrated a significant loss of collagen, glycosaminoglycans and desmosine in NOD LGs when compared to healthy BALB/c LGs. Immunohistochemical staining and gene expression analysis confirmed this disease-related alteration of LG ECM structures. Furthermore, laser-induced autofluorescence and SHG microscopy revealed dramatic changes in the structural organization of most collagenous and elastic fibers of the diseased LG tissues that were more pronounced than those displayed by histological analysis. Our results clearly show an enhanced degradation of ECM proteins accompanied by the severe disorganization and deformation of ECM structures of diseased LG tissues. These new insights into the involvement of ECM degradation in SS may lead to novel therapies for patients suffering from dry eye disease.

Dietary iron deficiency compromises normal development of elastic fibers in the aorta and lungs of chicks

Elastic fibers play a key role in the structure and function of numerous organs that require elasticity. Elastogenesis is a complex process in which cells first produce a microfibrillar scaffold, composed of numerous structural proteins, upon which tropoelastin assembles to be cross-linked into polymeric elastin. Recently, it was demonstrated that low concentrations of free iron upregulate elastin gene expression in cultured fibroblasts. The present studies were conducted to assess whether low-iron diets would affect the deposition of elastic fibers in an in vivo model. One-day-old chicks were fed semipurified diets containing 1.3 (low), 12 (moderate), and 24 (control) mg/kg of iron. After 3 wk, chicks in the low-iron group were underweight and anemic. Their aortas were smaller with significantly thinner walls than control chicks, yet elastin or collagen content did not decrease relative to total protein. They also demonstrated a significantly lower stress-strain resistance than the controls. Electron microscopy demonstrated that aortic and lung smooth muscle cells were vacuolated and surrounded by loose extracellular matrix and disorganized elastic lamellae with diffuse and fragmented networks of elastic fibers and microfibrils. Immunohistology demonstrated that fibrillin-3 (FBN3) was disorganized and markedly reduced in amount in aortas of the low-iron chicks. Elastin messenger RNA levels were not downregulated in the tissues from the low-iron-fed chicks; however, there was a significant reduction in expression of the FBN1 and FBN3 genes compared with control chicks. The studies indicate that iron deficiency had a pronounced negative effect on elastic fiber development and suggests that fibrillin may have an important role in this pathology.

Optimized preservation of extracellular matrix in cardiac tissues: implications for long-term graft durability

BACKGROUND

Cryopreservation of human tissues, particularly heart valves, is widespread in clinical practice although the effects of this process on underlying tissue structures and its potential impact on valve durability have been poorly studied. Multiphoton imaging and second-harmonic generation (SHG) microscopy permit high-resolution, noninvasive analysis of living tissues at a subcellular level. In the present study we used these novel imaging modalities to compare the effects of vitreous and frozen cryopreservation on the extracellular matrix (ECM) of cardiac tissues.

METHODS

Conventional histology, electron microscopy, and multiphoton imaging to obtain autofluorescence and SHG images were performed on cardiac tissues to characterize the ECM in fresh, vitrified, and frozen cryopreserved tissues.

RESULTS

Autofluorescence and particularly SHG images revealed that conventional frozen cryopreservation of cardiac valves, when compared with fresh or vitrified tissues, leads to the loss of normal ECM structures in valve leaflets. Similar results were found in all other cardiac tissues suggesting that structural deterioration of the ECM is a common consequence of frozen cryopreservation.

CONCLUSIONS

Our results demonstrate that conventional cryopreservation, when compared with fresh or vitrified tissues, causes more destruction of normal ECM structure, which might contribute to eventual graft dysfunction. Whether vitrification preservation will translate into greater durability or less valve failure will need to be determined.

Wound healing in tenascin-X deficient mice suggests that tenascin-X is involved in matrix maturation rather than matrix deposition

Tenascin-X (TNX) is an extracellular matrix glycoprotein whose absence in humans leads to a recessive form of Ehlers-Danlos Syndrome (EDS). TNX deficient patients have hypermobile joints and fragile skin, but unlike the classical type of EDS, no atrophic scars were observed. Anecdotal evidence suggested that wound healing in TNX deficient patients is abnormal, but no detailed study has been performed so far. To address the role of TNX in wound healing, we analyzed skin wound morphology and mechanical properties of scars in TNX knockout (KO) mice. Breaking strength of unwounded skin of KO mice is significantly lower (<50%) than that of wild-type (WT) mice. In the early stage of wound healing when TNX is hardly expressed in WT wounds (day 7), WT and KO skin are of similar strength. After 14 days, when TNX starts to be expressed at moderate levels in wounds of WT mice, the WT scars gain a further increase in breaking strength, whereas KO scars do not progress beyond the mechanical strength of uninjured KO skin. No obvious differences between KO and WT mice were noted in the rate of wound closure, or in expression of fibrillar collagens during wound healing. We conclude that TNX is unlikely to be involved in matrix deposition in the early phase of wound healing, but it is required in the later phase when remodeling and maturation of the matrix establishes and improves its biomechanical properties.

Late Deposition of Elastin to Vertical Microfibrillar Fibers in the Presumptive Dermis of the Chick Embryonic Tarsometatarsus

Fibrillin microfibrils are integral components of elastic fibers and serve as a scaffold for elastin deposition. However, microfibrillar fibers (MFs) are not necessarily committed to develop into so-called elastic fibers. In dermis, elastin-free oxytalan MFs originating from the dermoepidermal junction are continuous to elaunin-type MFs (with a small amount of elastin) in the deeper papillary dermis, whereas the reticular dermis contains elastic fibers, or MFs embedded largely in elastin. In this study, we have investigated temporospatial patterns of elastin deposition on the MFs in tarsometatarsal presumptive dermis. While the earliest expression of elastin was demonstrated immunohistochemically as early as embryonic day 4 (ED4) in the wall of cardiac outflow and pharyngeal arch arteries, its deposition in the tarsometatarsus was first detected at ED6 in the deeper mesenchyme and at ED13 in the subectodermal mesenchyme. In the latter tissue, MFs had been organized perpendicularly to the covering ectoderm by ED4, well before an overt accumulation of collagenous matrix. Elastin deposition was observed initially in a punctate manner at ED13 and afterward became continuous along MFs. However, a characteristic spaced array of subectodermal vertical MFs was disorganized by ED17. These findings suggest that elastin deposition in the subectodermal MFs is not deployed by continuous, orderly propagation from elastic fibers in the deeper mesenchyme but occurs de novo in multiple foci along vertical MFs. Moreover, the present chronology of elastin deposition indicates that subectodermal, elastin-free MFs function as a transient, but primary fibrous structure in the presumptive dermis before the accumulation of collagenous matrix.

Healing Slack Skin

A non-lethal, murine knockout of fibulin-5 with features of autosomal recessive cutis laxa and marked defects in elastic fiber formation amplifies previous observations on the minimal role of the elastic component in acute, cutaneous wound healing. More demanding wound models or long-term studies may yet reveal how fibulin-5 and elastin impact the quality of repair.

Dermal connective tissue development in mice: an essential role for tenascin-X

Deficiency of the extracellular matrix protein tenascin-X (TNX) causes a recessive form of Ehlers-Danlos syndrome (EDS) characterized by hyperextensible skin and hypermobile joints. It is not known whether the observed alterations of dermal collagen fibrils and elastic fibers in these patients are caused by disturbed assembly and deposition or by altered stability and turnover. We used biophysical measurements and immunofluorescence to study connective tissue properties in TNX knockout and wild-type mice. We found that TNX knockout mice, even at a young age, have greatly disturbed biomechanical properties of the skin. No joint abnormalities were noted at any age. The spatio-temporal expression of TNX during normal mouse skin development, during embryonic days 13-19 (E13-E19), was distinct from tropoelastin and the dermal fibrillar collagens type I, III, and V. Our data show that TNX is not involved in the earliest phase (E10-E14) of the deposition of collagen fibrils and elastic fibers during fetal development. From E15 to E19, TNX starts partially to colocalize with the dermal collagens and elastin, and in adult mice, TNX is present in the entire dermis. In adult TNX knockout mice, we observed an apparent increase of elastin. We conclude that TNX knockout mice only partially recapitulate the phenotype of TNX-deficient EDS patients, and that TNX could potentially be involved in maturation and/or maintenance of the dermal collagen and elastin network.