Long-term sun exposure alters the collagen of the papillary dermis. Comparison of sun-protected and photoaged skin by northern analysis, immunohistochemical staining, and confocal laser scanning microscopy

Differential levels of elastin fibers and TGF-β signaling in the skin of Caucasians and African Americans

BACKGROUND

While skin color is the most notable difference among ethnic skins the current knowledge on skin physiological and aging properties are based mainly on Caucasian skin studies.

OBJECTIVE

To evaluate histological differences in elastin fiber network and differential responsiveness to TGF-β in skin of Caucasians and African Americans.

METHODS

These studies were undertaken using human skin biopsies, primary dermal fibroblasts, Western blot analyses, immunofluorescence microscopy, cDNA array and quantitative real-time PCR.

RESULTS

In Caucasian subjects, tropoelastin expression and elastin fibers in photoprotected skin was substantially less than in age-matched African American skin. Expression of tropoelastin in photoexposed skin of African American was similar to their photoprotected skin, suggesting that photoexposure did not affect elastin fibers in African American skin to the same extent as Caucasian skin. An elevated level of TGF-β1 present in media from dermal fibroblasts derived from African American skins correlated well with the higher levels of TGF-β mRNA in African American skins analyzed by cDNA array. Treatment with TGF-β1 resulted in a considerably higher induction of elastin mRNA in dermal fibroblasts from African Americans than from Caucasian fibroblasts, indicative of enhanced TGF-β signaling in African American skins. Furthermore, UVA exposure decreased levels of elastin mRNA in Caucasian fibroblasts compared to African Americans fibroblasts.

CONCLUSION

These results suggest that there are ethnic differences in the elastin fiber network and in TGF-β signaling in African American and Caucasian skin, and that African American have less UV dependent loss of elastin than Caucasian which may contribute to the different perceived aging phenotypes.

Breast cancer cell-derived matrix supports vascular morphogenesis

The extracellular matrix (ECM), important for maintaining tissue homeostasis, is abnormally expressed in mammary tumors and additionally plays a crucial role in angiogenesis. We hypothesize that breast cancer cells (BCCs) deposit ECM that supports unique patterns of vascular morphogenesis of endothelial cells (ECs). Evaluation of ECM expression revealed that a nontumorigenic cell line (MCF10A), a tumorigenic cell line (MCF7), and a metastatic cell line (MDA-MB-231) express collagens I and IV, fibronectin, and laminin, with tenascin-C limited to MCF10A and MCF7. The amount of ECM deposited by BCCs was found to be higher in MCF10A compared with MCF7 and MDA231, with all ECM differing in their gross structure but similar in mean fiber diameter. Nonetheless, deposition of ECM from BCC lines was overall difficult to detect and insufficient to support capillary-like structure (CLS) formation of ECs. Therefore, a coculture approach was undertaken in which individual BCC lines were cocultured with fibroblasts. Variation in abundance of deposited ECM, deposition of ECM proteins, such as absent collagen I deposition from MDA231-fibroblast cocultures, and fibril organization was found. Deposited ECM from fibroblasts and each coculture supported rapid CLS formation of ECs. Evaluation of capillary properties revealed that CLS grown on ECM deposited from MDA231-fibroblast cocultures possessed significantly larger lumen diameters, occupied the greatest percentage of area, expressed the highest levels of von Willebrand factor, and expressed the greatest amount of E-selectin, which was upregulated independent of exposure to TNF-α. To our knowledge, this is the first study to report tumor cell ECM-mediated differences in vascular capillary features, and thus offers the framework for future investigations interrogating the role of the tumor ECM in supporting vascular morphogenesis.

Can Platelet-rich Plasma Be Used for Skin Rejuvenation? Evaluation of Effects of Platelet-rich Plasma on Human Dermal Fibroblast

Background

Autologous platelet-rich plasma has attracted attention in various medical fields recently, including orthopedic, plastic, and dental surgeries and dermatology for its wound healing ability. Further, it has been used clinically in mesotherapy for skin rejuvenation.

Objective

In this study, the effects of activated platelet-rich plasma (aPRP) and activated platelet-poor plasma (aPPP) have been investigated on the remodelling of the extracellular matrix, a process that requires activation of dermal fibroblasts, which is essential for rejuvenation of aged skin.

Methods

Platelet-rich plasma (PRP) and platelet-poor plasma (PPP) were prepared using a double-spin method and then activated with thrombin and calcium chloride. The proliferative effects of aPRP and aPPP were measured by [³H]thymidine incorporation assay, and their effects on matrix protein synthesis were assessed by quantifying levels of procollagen type I carboxy-terminal peptide (PIP) by enzyme-linked immunosorbent assay (ELISA). The production of collagen and matrix metalloproteinases (MMP) was studied by Western blotting and reverse transcriptase-polymerase chain reaction.

Results

Platelet numbers in PRP increased to 9.4-fold over baseline values. aPRP and aPPP both stimulated cell proliferation, with peak proliferation occurring in cells grown in 5% aPRP. Levels of PIP were highest in cells grown in the presence of 5% aPRP. Additionally, aPRP and aPPP increased the expression of type I collagen, MMP-1 protein, and mRNA in human dermal fibroblasts.

Conclusion

aPRP and aPPP promote tissue remodelling in aged skin and may be used as adjuvant treatment to lasers for skin rejuvenation in cosmetic dermatology.

Cell-based cytokine therapy for skin rejuvenation

The interaction between stem cells from human exfoliated deciduous teeth (SHEDs)-derived growth factors and human dermal fibroblast (HDF) has been investigated for the first time, as the application of SHEDs for dermal wound healing remains speculative. Stem cells from human exfoliated deciduous teeth have effects on HDFs by increasing collagen synthesis and by activating proliferation and migration activity of HDFs, suggesting that SHEDs or SHED-derived conditioned medium (SH-CM) can be used for the treatment of photoaging. Our results suggest that SHEDs and SH-CM should be constitutionally suited for photoaging treatment. Mainly with secreted growth factors or extracellular matrix proteins, SHEDs contribute to enhanced wound-healing potential of HDFs. Further mechanism studies using neutralizing antibodies against each growth factor may clarify the role of soluble factors of SHEDs in wound-healing process.

Reflectance confocal microscopy criteria of lichen planus-like keratosis

BACKGROUND

Lichen planus-like keratosis (LPLK) may be difficult to differentiate from melanoma and other skin cancers on sun-damaged skin based on clinical and dermoscopic examination. Reflectance confocal microscopy (RCM) allows evaluation of skin lesions at high resolution.

OBJECTIVES

The aim of this study was to identify criteria for specific diagnosis of LPLK using in vivo RCM.

METHODS

Lesions included in the study were derived from patients presenting for skin examination at a private dermatology practice specializing in skin cancer. We retrospectively analysed RCM features of 28 biopsy-proven LPLK and compared them to RCM findings in skin cancers on sun-damaged skin, including five in situ squamous cell carcinomas, six actinic keratoses, seven superficial basal cell carcinomas and eight melanomas.

RESULTS

The main RCM features of LPLK and their relative frequencies were: (i) typical honeycomb pattern of the spinous layer (78.6%); (ii) elongated cords and/or bulbous projections at the dermal-epidermal junction (75%); and (iii) numerous plump-bright cells and/or bright stellate spots in the superficial dermis (92.9%). These RCM features correlated with the following histopathological findings respectively: (i) spinous-granular layers without significant atypia of keratinocytes; (ii) elongated, bulbous rete ridges; and (iii) dense infiltration of melanophages and lymphocytes in superficial dermis. We propose diagnostic criteria that classify correctly 71.4% of LPLK, while avoiding misclassification of any of the skin cancers in the present series as LPLK.

CONCLUSIONS

We identified RCM criteria for diagnosis of LPLK that correlate well with histopathological findings and that allow differentiation of LPLK from skin cancer.

Plasma membrane factor XIIIA transglutaminase activity regulates osteoblast matrix secretion and deposition by affecting microtubule dynamics

Transglutaminase activity, arising potentially from transglutaminase 2 (TG2) and Factor XIIIA (FXIIIA), has been linked to osteoblast differentiation where it is required for type I collagen and fibronectin matrix deposition. In this study we have used an irreversible TG-inhibitor to ‘block –and-track’ enzyme(s) targeted during osteoblast differentiation. We show that the irreversible TG-inhibitor is highly potent in inhibiting osteoblast differentiation and mineralization and reduces secretion of both fibronectin and type I collagen and their release from the cell surface. Tracking of the dansyl probe by Western blotting and immunofluorescence microscopy demonstrated that the inhibitor targets plasma membrane-associated FXIIIA. TG2 appears not to contribute to crosslinking activity on the osteoblast surface. Inhibition of FXIIIA with NC9 resulted in defective secretory vesicle delivery to the plasma membrane which was attributable to a disorganized microtubule network and decreased microtubule association with the plasma membrane. NC9 inhibition of FXIIIA resulted in destabilization of microtubules as assessed by cellular Glu-tubulin levels. Furthermore, NC9 blocked modification of Glu-tubulin into 150 kDa high-molecular weight Glu-tubulin form which was specifically localized to the plasma membrane. FXIIIA enzyme and its crosslinking activity were colocalized with plasma membrane-associated tubulin, and thus, it appears that FXIIIA crosslinking activity is directed towards stabilizing the interaction of microtubules with the plasma membrane. Our work provides the first mechanistic cues as to how transglutaminase activity could affect protein secretion and matrix deposition in osteoblasts and suggests a novel function for plasma membrane FXIIIA in microtubule dynamics.

Age-related changes in material behavior of porcine mitral and aortic valves and correlation to matrix composition

Recent studies showing significant changes in valvular matrix composition with age offer design criteria for age-specific tissue-engineered heart valves. However, knowledge regarding aging-related changes in valvular material properties is limited. Therefore, 6-week, 6-month, and 6-year-old porcine aortic valves (AV) and mitral valves (MV) were subjected to uniaxial tensile testing. In addition to standard material parameters, the radius of transition curvature (RTC) was measured to assess the acuteness of the transition region of the tension-strain curve. Radially, the MV had greater stiffness and a smaller RTC compared with the AV. Circumferentially, the center of the MV anterior leaflet (MVAC) had the highest stiffness (MVAC > AV > MV free edge [MVF]), greater stress relaxation (MVAC > MVF/AV), lowest extensibility (MVAC < AV < MVF), and smaller RTC compared with MVF (AV < MVAC < MVF). AV and MV radial strips had a larger RTC compared with circumferential strips. Aging elevated stiffness for MV and AV radial and circumferential strips, elevated stress relaxation in AV and MVF circumferential strips, and increased RTC for MV radial and MVF circumferential strips. In conclusion, there are significant age-related differences in the material properties of heart valves, which parallel differences in tissue composition and structure, likely impact valve function, and highlight the need for age-specific design goals for tissue-engineered heart valves.

Lack of host SPARC enhances vascular function and tumor spread in an orthotopic murine model of pancreatic carcinoma

Utilizing subcutaneous tumor models, we previously validated SPARC (secreted protein acidic and rich in cysteine) as a key component of the stromal response, where it regulated tumor size, angiogenesis and extracellular matrix deposition. In the present study, we demonstrate that pancreatic tumors grown orthotopically in Sparc-null (Sparc(-/-)) mice are more metastatic than tumors grown in wild-type (Sparc(+/+)) littermates. Tumors grown in Sparc(-/-) mice display reduced deposition of fibrillar collagens I and III, basement membrane collagen IV and the collagen-associated proteoglycan decorin. In addition, microvessel density and pericyte recruitment are reduced in tumors grown in the absence of host SPARC. However, tumors from Sparc(-/-) mice display increased permeability and perfusion, and a subsequent decrease in hypoxia. Finally, we found that tumors grown in the absence of host SPARC exhibit an increase in alternatively activated macrophages. These results suggest that increased tumor burden in the absence of host SPARC is a consequence of reduced collagen deposition, a disrupted vascular basement membrane, enhanced vascular function and an immune-tolerant, pro-metastatic microenvironment.

Evaluation of procollagen I deposition after intense pulsed light treatments at varying parameters in a porcine model

Several lasers and light sources have been reported to induce dermal collagen remodeling without damaging the epidermis. The intense pulsed light (IPL) system, which emits polychromatic light of wavelengths between 560 and 1200 nm belongs to this group of increasingly popular non-ablative skin rejuvenation devices. Various IPL treatment parameters can be adjusted to achieve optimal dermal remodeling and clinical improvement. The aim of this study was to evaluate variations in IPL treatment parameters and the effect on procollagen I deposition. Marked areas of a live Yorkshire pig's flank skin were irradiated with a single or double pass of an IPL source using a fluence of 30 or 40 J/cm2 and a cut-off wavelength filter of 590 nm. Skin biopsies were performed on postoperative days 1, 7, 14, 21, and 42. A statistically significant increase in procollagen I in treated versus untreated sites was found on postoperative days 21 and 42, but not earlier. There was a uniformly significant increase in procollagen I on day 42 using the 590 nm filter at both 30 and 40 J/cm2 with either a single or double pass. The increase in procollagen was greater with a fluence of 40 J/cm2 compared with 30 J/cm2.

Relationship between dermal birefringence and the skin surface roughness of photoaged human skin

The dermal degeneration accompanying photoaging is considered to promote skin roughness features such as wrinkles. Our previous study demonstrated that polarization-sensitive spectral domain optical coherence tomography (PS-SD-OCT) enabled noninvasive three-dimensional evaluation of the dermal degeneration of photoaged skin as a change in dermal birefringence, mainly due to collagenous structures. Our purpose is to examine the relationship between dermal birefringence and elasticity and the skin morphology in the eye corner area using PS-SD-OCT. Nineteen healthy male subjects in their seventees were recruited as subjects. A transverse dermal birefringence map, automatically produced by the algorithm, did not show localized changes in the dermal birefringence in the part of the main horizontal wrinkle. The averaged upper dermal birefringence, however, showed depth-dependent correlation with the parameters of skin roughness significantly, suggesting that solar elastosis is a major factor for the progress of wrinkles. Age-dependent parameters of skin elasticity measured with Cutometer did not correlate with the parameters. These results suggest that the analysis of dermal birefringence using PS-SD-OCT enables the evaluation of photoaging-dependent upper dermal degeneration related to the change of skin roughness.

ER stress-mediated apoptosis in a new mouse model of osteogenesis imperfecta

Osteogenesis imperfecta is an inherited disorder characterized by increased bone fragility, fractures, and osteoporosis, and most cases are caused by mutations affecting the type I collagen genes. Here, we describe a new mouse model for Osteogenesis imperfecta termed Aga2 (abnormal gait 2) that was isolated from the Munich N-ethyl-N-nitrosourea mutagenesis program and exhibited phenotypic variability, including reduced bone mass, multiple fractures, and early lethality. The causal gene was mapped to Chromosome 11 by linkage analysis, and a C-terminal frameshift mutation was identified in the Col1a1 (procollagen type I, alpha 1) gene as the cause of the disorder. Aga2 heterozygous animals had markedly increased bone turnover and a disrupted native collagen network. Further studies showed that abnormal proα1(I) chains accumulated intracellularly in Aga2/+ dermal fibroblasts and were poorly secreted extracellularly. This was associated with the induction of an endoplasmic reticulum stress-specific unfolded protein response involving upregulation of BiP, Hsp47, and Gadd153 with caspases-12 and −3 activation and apoptosis of osteoblasts both in vitro and in vivo. These studies resulted in the identification of a new model for Osteogenesis imperfecta, and identified a role for intracellular modulation of the endoplasmic reticulum stress-associated unfolded protein response machinery toward osteoblast apoptosis during the pathogenesis of disease.

Osteogenesis imperfecta (OI) is a heterogeneous collection of connective tissue disorders typically caused by mutations in the COL1A1/2 genes that encode the chains of type I collagen, the principle structural protein of bone. Phenotypic expression in OI depends on the nature of the mutation, causing a clinical heterogeneity ranging from a mild risk of fractures to perinatal lethality. Here, we describe a new OI mouse model with a dominant mutation in the terminal C-propeptide domain of Col1a1 generated using the N-ethyl-N-nitrosourea (ENU) mutagenesis strategy. Heterozygous animals developed severe-to-lethal phenotypes that were associated with endoplasmic reticulum stress, and caspases-12 and −3 activation within calvarial osteoblasts. We provide evidence for endoplasmic reticulum stress–associated apoptosis as a key component in the pathogenesis of disease.

Forced expression of MMP9 rescues the loss of angiogenesis and abrogates metastasis of pancreatic tumors triggered by the absence of host SPARC

Pancreatic adenocarcinoma is characterized by desmoplasia, local invasion, and metastasis. These features are regulated in part by MMP9 and SPARC. To explore the interaction of SPARC and MMP9 in cancer, we first established orthotopic pancreatic tumors in SPARC-null and wild-type mice with the murine pancreatic adenocarcinoma cell line, PAN02. MMP9 expression was higher in tumors from wild-type compared to SPARC-null mice. Coincident with lower MMP9 expression, tumors grown in SPARC-null mice were significantly larger, had decreased ECM deposition and reduced microvessel density compared to wild-type controls. In addition, metastasis was enhanced in the absence of host SPARC. Therefore, we next analyzed the orthotopic tumor growth of PAN02 cells transduced with MMP9 or a control empty vector. Forced expression of MMP9 by the PAN02 cells resulted in larger tumors in both wild-type and SPARC-null animals compared to empty vector controls and further diminished ECM deposition. Importantly, forced expression of MMP9 within the tumor reversed the decrease in angiogenesis and abrogated the metastatic potential displayed by control tumors grown in SPARC-null mice. Finally, contrary to the in vivo results, MMP9 increased cell migration in vitro, which was blocked by the addition of SPARC. These results suggest that SPARC and MMP9 interact to regulate many stages of tumor progression including ECM deposition, angiogenesis and metastasis.

Cellulite and skin ageing: is there any interaction?

OBJECTIVE

This study aimed to identify the characteristics of cellulite in women of different age and to appreciate whether cellulite could interfere with skin ageing or not.

METHODS

94 Healthy females, divided into three age groups (21-30yrs; 31-40yrs; 51-60yrs) and two grade groups of cellulite (grade 2; grade 0 or control group), were investigated using non invasive techniques. The "orange peel appearance" was quantified by measuring the shadowed surfaces under low angle light. The biomechanichal properties were measured (extensibility-retractability-elasticity). The thicknesses of the skin structures were also evaluated using ultrasound. Echogenicity of the dermis was recorded and dermis density determined in two bands (superficial and low dermis).

RESULTS

In grade 2, the shadowed surfaces are significantly different according to age; i.e. smaller and more numerous after age of 30; the total skin thickness including hypodermis is increased of about 30% irrespective to age, compared to control group. The biomechanical properties of the skin are significantly modified as age increases without any grade effect. In grade 2, retractability and elasticity parameters are altered from age 30 whilst only from age 50 in the control group. Echogenicities of the superficial and deep dermis also decrease from age 30 and become significantly lower than the ones of grade 0.

CONCLUSION

Population with cellulite presents earlier skin ageing characteristics than the control population. Two sub-populations may exist: the under 30 age with large dimpled surfaces, normal biomechanical and density properties; and the over 30 age with smaller and numerous dimpled surfaces and already altered dermis properties. This premature skin ageing should be prevented accordingly.

Aesthetic Analysis of Asian Skin

Attention to restoring healthy and more youthful facial skin complements facial plastic surgery, optimizing cosmetic results. Asian skin has structural and physiologic differences from white skin. These distinctions account for variations in response to ultraviolet light exposure and alternate clinical manifestations of photoaging. The response to cosmetic treatment modalities also differs in patients of darker skin pigmentation, and this needs to be recognized by the cosmetic and laser surgeon. This article reviews the biology of Asian skin and discusses a clinical approach to aesthetic analysis of Asian skin.

Assessment and management of chronic pressure ulcers in the elderly

Pressure ulcers remain a complex and costly problem to the health care system. As the population ages, a greater number of individuals will be at high risk for developing pressure ulcers. An understanding of the physiologic changes that occur with aging skin is important in preventing and treating chronic wounds. Risk factor assessment and modification, when possible, can help to reduce the development of pressure ulcerations. Although the goal continues to be prevention, once a pressure ulcer does occur, a systematic and comprehensive approach to assessment and treatment is necessary to reduce healing times.

Age-specific hormonal decline is accompanied by transcriptional changes in human sebocytes in vitro

The importance of hormones in endogenous aging has been displayed by recent studies performed on animal models and humans. To decipher the molecular mechanisms involved in aging we maintained human sebocytes at defined hormone-substituted conditions that corresponded to average serum levels of females from 20 (f20) to 60 (f60) years of age. The corresponding hormone receptor expression was demonstrated by reverse transcription-polymerase chain reaction (RT-PCR), Western blotting and immunocytochemistry. Cells at f60 produced significantly lower lipids than at f20. Increased mRNA and protein levels of c-Myc and increased protein levels of FN1, which have been associated with aging, were detected in SZ95 sebocytes at f60 compared to those detected at f20 after 5 days of treatment. Expression profiling employing a cDNA microarray composed of 15 529 cDNAs identified 899 genes with altered expression levels at f20 vs. f60. Confirmation of gene regulation was performed by real-time RT-PCR. The functional annotation of these genes according to the Gene Ontology identified pathways related to mitochondrial function, oxidative stress, ubiquitin-mediated proteolysis, cell cycle, immune responses, steroid biosynthesis and phospholipid degradation - all hallmarks of aging. Twenty-five genes in common with those identified in aging kidneys and several genes involved in neurodegenerative diseases were also detected. This is the first report describing the transcriptome of human sebocytes and its modification by a cocktail of hormones administered in age-specific levels and provides an in vitro model system, which approximates some of the hormone-dependent changes in gene transcription that occur during aging in humans.

Exposure of mouse preosteoblasts to pulsed electromagnetic fields reduces the amount of mature, type I collagen in the extracellular matrix

We tested the hypothesis that exposure of a mouse preosteoblast cell line to pulsed electromagnetic fields (PEMF) would affect components of the extracellular matrix. We report that exposure of MC3T3-E1 cells to a single PEMF waveform significantly reduced the amount of mature, alpha1(I) collagen in the extracellular matrix (ECM) and the conditioned medium, without affecting the amount of total ECM protein. This decrease was not due to changes in the steady-state level of Col1A1 mRNA or to degradation of mature collagen. We then tested the effect of three distinct PEMF waveforms, two orthogonal coil orientations, and two waveform amplitude levels on the amount of alpha1(I) collagen in the conditioned medium. A sequence of factorial ANOVAs and stepwise regression modeling revealed that the period (duration) of the individual pulses accounted for a significant proportion of the variance associated with the amount of alpha1(I) collagen in the conditioned medium. The total variance accounted for, however, was small (R(2)=0.155, p<0.001 and R(2)=0.172, p<0.001, in the horizontal and vertical orientations, respectively). The positive and negative regression coefficients for the coil orientations revealed that the influence of pulse period was significantly different for the orthogonal coil orientations (p<0.001). The findings imply that the dominant influence of PEMF on the amount of mature, alpha1(I) collagen in the ECM is related to variables other than those expressed in the time-amplitude domain. The results provide objective direction toward identifying waveform characteristics that contribute to the observed between-waveform differences with regard to collagen. Advances in this area may lead toward improving waveforms and waveform delivery protocols.

Long-term efficacy and safety of tretinoin emollient cream 0.05% in the treatment of photodamaged facial skin: a two-year, randomized, placebo-controlled trial

BACKGROUND

Long-term (>1 year) placebo-controlled studies of tretinoin in the treatment of photodamaged skin have not been conducted. Recently, we conducted a 2-year placebo-controlled study of tretinoin emollient cream 0.05%, including histopathologic assessment of safety and analysis of markers of collagen deposition.

OBJECTIVE

The objective of the study was to determine the long-term safety and efficacy of tretinoin emollient cream 0.05% in the treatment of moderate to severe facial photodamage.

METHODS

A total of 204 subjects were treated with tretinoin or placebo (vehicle emollient cream) applied to the entire face once a day for up to 2 years. Clinical and histologic effects were assessed at regularly scheduled clinic visits.

RESULTS

Treatment with tretinoin resulted in significantly greater improvement relative to placebo in clinical signs of photodamage (fine and coarse wrinkling, mottled hyperpigmentation, lentigines, and sallowness), overall photodamage severity, and investigator's global assessment of clinical response (p<0.05). Histologic evaluation showed no increase in keratinocytic or melanocytic atypia, dermal elastosis, or untoward effects on stratum corneum following treatment with tretinoin compared with placebo. Immunohistochemistry studies, conducted at three study centers, showed a significant increase relative to placebo in facial procollagen 1C terminal, a marker for procollagen synthesis, at month 12 (p=0.0074).

CONCLUSION

Long-term treatment with tretinoin emollient cream 0.05% is safe and effective in subjects with moderate to severe facial photodamage.

Ultrasonic backscatter and attenuation (11-27 MHz) variation with collagen fiber distribution in ex vivo human dermis

This ex vivo study explores the relationship of ultrasonic attenuation and backscatter to dermal microarchitecture by comparing ultrasonic measurements of these parameters (11-27 MHz) to a microscopic analysis of three parameters describing the collagen distribution (mean thickness and spacing of collagen bundles along the insonification direction and the percent area occupied by collagen). Skin samples (N= 31) were obtained from patients undergoing breast or abdominal reduction surgery. Radio-frequency (rf) signals were acquired in a B-scan format using an ultrasound system developed for skin imaging (Ultrasons Technologies, Tours, France). Ultrasonic data were analyzed to calculate average integrated backscatter (IBS in dB) and frequency dependence of backscatter (n, dimensionless) of each specimen at depths centered approximately 370,620 and 880 microm beneath the skin surface. Average integrated attenuation coefficient (IA in dB.cm(-1)) and frequency dependence of attenuation coefficient (beta in dB.cm(-1).MHz(-1)) were estimated across the depth between 240 and 1,000 microm. The three collagen distribution parameters were estimated using digitized microcopic fields from matched regions of histological sections stained with hematoxylin-eosin-saffron. No significant correlation was identified between collagen distribution parameters and IA or beta. For the most superficial depth studied in abdominal skin, n was inversely correlated to collagen bundle thickness (r = -0.67,p = 0.002) and percent area (r = -0.65,p = 0.003). At the same depth, IBS was inversely correlated to percent area of collagen (r = -0.51,p = 0.03). The rather high collagen packing (48 to 82% area) measured in histological sections and the inverse relationship observed between IBS and percent area of collagen suggest that a packing factor should be included in models relating skin collagen distribution to ultrasound spectral parameters. A better understanding of the relationship between ultrasound parameters and the microarchitecture of the dermis should help to interpret changes in ultrasonic parameters observed during in vivo ultrasonic skin examinations.

Nonablative skin rejuvenation

Laser resurfacing of photodamaged or scarred skin has traditionally involved the use of ablative lasers with their associated limitations and side effects. Nonablative skin rejuvenation is a relatively new concept in facial rejuvenation, which aims to induce dermal remodeling without visible epidermal disruption. A number of laser devices and light sources, emitting at various wavelengths, have been shown to effectively enhance the appearance of facial skin through nonablative mechanisms. Among the conditions that can be treated with this novel modality are erythema, telangiectasia, pigmentation, lentigines, and textural imperfections ranging from fine and moderate rhytides to other surface irregularities such as acne scarring. A major attraction of nonablative laser therapy is the very limited downtime after each treatment, making it an ideal method for patients seeking a minimally invasive procedure with an excellent safety profile.

Epidermal growth factor receptor signaling is partially responsible for the increased matrix metalloproteinase-1 expression in ocular epithelial cells after UVB radiation

Pterygia are inflammatory, invasive, and proliferative lesions of the human ocular surface in which the matrix metalloproteinase (MMP) collagenase-1 (MMP-1) is highly expressed. Pterygia development may involve MMP-1 activity against interstitial fibrillar collagen, an abundant extracellular matrix component of the cornea, and its induction by ultraviolet light (UVB). We examined the pathways responsible for enhanced expression of MMP-1 in pterygium epithelial cells after UVB exposure and/or treatment with chemical inhibitors of mitogen-activated protein kinases or epidermal growth factor receptor. The induction of MMP-1 by UVB was comparable to that mediated by heparin-binding epidermal growth factor-like growth factor and epidermal growth factor. The epidermal growth factor receptor inhibitor PD153035 partially blocked the UVB-mediated induction of MMP-1 and totally abrogated its production after stimulation with either heparin-binding epidermal growth factor-like growth factor or epidermal growth factor. UVB exposure enhanced the phosphorylated form of ERK1/2 in a time-dependent manner whereas the ERK1/2 inhibitor PD98059 decreased this induction by at least fivefold. Transcripts for c-jun and c-fos were detected as early as 2 hours after UVB exposure and were suppressed by PD98059. The identification of a specific intracellular signaling pathway responsible for the enhanced production of a key enzyme that denatures intact fibrillar collagen has important implications for understanding the pathophysiology and future therapy for pterygia.

Intracellular collagen degradation mediated by uPARAP/Endo180 is a major pathway of extracellular matrix turnover during malignancy

We recently reported that uPARAP/Endo180 can mediate the cellular uptake and lysosomal degradation of collagen by cultured fibroblasts. Here, we show that uPARAP/Endo180 has a key role in the degradation of collagen during mammary carcinoma progression. In the normal murine mammary gland, uPARAP/Endo180 is widely expressed in periductal fibroblast-like mesenchymal cells that line mammary epithelial cells. This pattern of uPARAP/Endo180 expression is preserved during polyomavirus middle T-induced mammary carcinogenesis, with strong uPARAP/Endo180 expression by mesenchymal cells embedded within the collagenous stroma surrounding nests of uPARAP/Endo180-negative tumor cells. Genetic ablation of uPARAP/Endo180 impaired collagen turnover that is critical to tumor expansion, as evidenced by the abrogation of cellular collagen uptake, tumor fibrosis, and blunted tumor growth. These studies identify uPARAP/Endo180 as a key mediator of collagen turnover in a pathophysiological context.

Nonablative laser and light therapies for skin rejuvenation

BACKGROUND

Multiple modalities have been described for skin rejuvenation, including ablative and nonablative therapies. Because of the prolonged recovery period associated with ablative procedures that injure the epidermis, nonablative skin treatments have grown increasingly popular. Various laser- and light-based systems have been designed or applied for promoting skin remodeling without damage to the epidermis.

METHODS

Studies investigating the use of nonablative procedures for facial rhytids or acne scarring with clinical, histological, and objective quantitative measurements are systematically reviewed.

RESULTS

Nonablative treatments are associated with clinical and objective improvements for the treatment of facial rhytids and acne scarring. Dermal remodeling seems to occur as a result of thermal injury, leading to dermal fibrosis without epidermal disruption.

CONCLUSIONS

Although results are not as impressive as those of ablative treatments, nonablative procedures are effective in the treatment of photoaging and acne scarring. As technology in nonablative therapies continues to evolve, future laser and light sources may yield even more favorable results.

Calcified Matrix Production by SAOS-2 Cells Inside a Polyurethane Porous Scaffold, Using a Perfusion Bioreactor

The repair and regeneration of damaged or resected bone are problematic. Bone autografts show optimal skeletal incorporation, but often bring about complications. Hence, there is increasing interest in designing new biomaterials that could potentially be used in the form of scaffolds as bone substitutes. In this study we used a hydrophobic cross-linked polyurethane in a typical tissue-engineering approach, that is, the seeding and in vitro culturing of cells within a porous scaffold. The polyurethane porous scaffold had an average pore diameter of 624 microm. Using a perfusion bioreactor, we investigated the effect of shear stress on SAOS-2 human osteoblast proliferation and calcified matrix production. The physical, morphological, and compressive properties of the polyurethane foam were characterized. At a scaffold perfusion rate of 3 mL/min, in comparison with static conditions without perfusion, we observed 33% higher cell proliferation; higher secretion of osteopontin, osteocalcin, decorin, and type I collagen (9.16-fold, 71.9-fold, 30.6-fold, and 18.12-fold, respectively); and 10-fold increased calcium deposition. The design of the bioreactor and the design of the polyurethane foam aimed at obtaining cell colonization and calcified matrix deposition. This cultured biomaterial could be used, in clinical applications, as an osteoinductive implant for bone repair.

Skin aging and natural photoprotection

Aging of skin is a continuous process that may be enhanced by sun exposure. Photoaging may provoke changes different from aging. Epidermal changes involve thinning of stratum spinosum and flattening of the dermo-epidermal junction. The senescent keratinocytes becomes resistant to apoptosis and may survive for a long time giving time for DNA and protein damage to accumulate with possible implication for carcinogenesis. The numbers of melanocytes decrease with age with dysregulation of melanocyte density resulting in freckles, guttate hypo-melanosis, lentigines and nevi. The number of dendritic Langerhans cells also decreases with age and the cells get less dendrites and have reduced antigen-trapping capacity. Aging involves dermal changes such as damage to elastic and collagen fibers giving thickened, tangled, and degraded non-functional fibers. Collagen intermolecular cross-links are stable and essential for stability and tensile strength. Cross-links increase with age converting divalent cross-links into mature trivalent cross-links of, e.g. histidinohydroxylysinonorleucine. Two mechanisms are involved; an enzyme-controlled process of maturation and a non-enzymatic glycosylation, the Maillard reaction leading to cross-links in proteins such as in collagen between arginine and lysine. Such may be seen with age and in diabetes mellitus. However, autofluorescence studies have shown that UVR reduces collagen cross-links. Natural photoprotection involves thickening of stratum corneum by sunlight and increased pigmentation. This leads to a factor 2 increase in photoprotection from spring until after-summer. The constitutive pigmentation is independent of age and thickness of stratum corneum is likewise independent of age. The minimal erythema dose is thus the same through life, when corrected for pigmentation or measured in areas with constitutive pigmentation.

Changes in Matrix Gene and Protein Expressions After Single or Repeated Exposure to One Minimal Erythemal Dose of Solar-simulated Radiation in Human Skin In Vivo

Damage to the skin extracellular matrix (ECM) is the hallmark of long-term exposure to solar UV radiation. The aim of our study was to investigate the changes induced in unexposed human skin in vivo after single or repeated (five times a week for 6 weeks) exposure to 1 minimal erythemal dose (MED) of UV solar-simulated radiation. Morphological and biochemical analyses were used to evaluate the structural ECM components and the balance between the degrading enzymes and their physiologic inhibitors. A three-fold increase in matrix metalloproteinase 2 messenger RNA (mRNA) (P < 0.02, unexposed versus exposed) was observed after both single and repeated exposures. Fibrillin 1 mRNA level was increased by chronic exposure (P < 0.02) and unaltered by a single MED. On the contrary, a single MED significantly enhanced mRNA levels of interleukin-1alpha (IL-1alpha), IL-1beta (P < 0.02) and plasminogen activator inhibitor-1 (P < 0.05). Immunohistochemistry demonstrated a significant decrease in Type-I procollagen localized just below the dermal-epidermal junction in both types of exposed sites. At the same location, the immunodetected tenascin was significantly enhanced, whereas a slight increase in Type-III procollagen deposits was also observed in chronically exposed areas. Although we were unable to observe any change in elastic fibers in chronically exposed buttock skin, a significant increase in lysozyme and alpha-1 antitrypsin deposits on these fibers was observed. These results demonstrate the existence of a differential regulation, after chronic exposure compared with an acute one, of some ECM components and inflammatory mediators.

Nonablative laser and light treatments: histology and tissue effects--a review

BACKGROUND AND OBJECTIVES

Nonablative laser and light treatments have largely replaced ablative laser therapy in clinical use for the improvement of the visible signs of cutaneous photoaging, including rhytides, vascular lesions, and pigmentation. However, the mechanisms underlying the reported clinical efficacy of nonablative treatments are not well-understood. The purpose of this analysis is to critically evaluate what is known about histologic and tissue effects of nonablative laser therapy and suggest future directions for research.

STUDY DESIGN/MATERIALS AND METHODS

This is a review of the English language literature pertaining to nonablative laser and light treatments available through MEDline (1995-2002), and unpublished reports presented at major national meetings. Only studies that included harvesting and analysis of tissue samples are included.

RESULTS AND CONCLUSIONS

(a) Thermal injury to the dermis in association with epidermal cooling most likely affects the dermal vasculature, which initiates a cascade of inflammatory events that includes fibroblastic proliferation and apparent up-regulation of collagen expression; (b) There is no indication that nonablative treatments are harmful or able to induce skin cancer; (c) It is possible that the horizontally distributed collagen reported after nonablative treatments is a "microscar," an enlarged Grenz sone associated with repetitive photo-induced trauma; (d) Further research is needed to elucidate the biophysical mechanisms underlying nonablative treatment, as well as to distinguish the utility of different wavelengths on epidermal and dermal improvement.

Microresurfacing using the variable-pulse erbium:YAG laser: a comparison of the 0.5- and 4-ms pulse durations

BACKGROUND

Laser resurfacing has become less popular because of its long recovery time, significant discomfort, and potential risks. Microsurfacing employs the use of single-pass erbium:YAG (Er:YAG) "mini peels," which may be performed serially.

OBJECTIVE

The purpose of this study was to evaluate the efficacy and patient acceptance of microresurfacing Er:YAG peels in treating facial photodamage. The variable-pulse Er:YAG system was used and was allowed a comparison of the 0.5- and 4-ms pulse widths.

METHODS

Six female patients underwent eight microresurfacing peels in a split-face fashion using the 0.5- and 4.0-ms pulse durations of a variable-pulse Er:YAG laser. Patients returned at postoperative Days 3 to 4 and 7 for clinical evaluation and Mexameter measurements.

RESULTS

There were no significant differences in healing or postoperative erythema between the 0.5- and 4-ms pulse durations on postoperative Day 7. The average time to reepithelialization was 3.6 days. In a 1-year postoperative interview, four of six patients said that they would undergo the peel again periodically, and five of six stated they had maintained some level of improvement.

CONCLUSION

Microresurfacing is an effective and well-tolerated procedure. Benefits include its tolerability under topical anesthesia, limited down time, and high patient satisfaction.

Transforming growth factor-beta induces secretion of activated ADAMTS-2. A procollagen III N-proteinase

The metalloproteinase ADAMTS-2 has procollagen I N-proteinase activity capable of cleaving procollagens I and II N-propeptides in vitro, whereas mutations in the ADAMTS-2 gene in dermatosparaxis and Ehlers-Danlos syndrome VIIC show this enzyme to be responsible in vivo for most biosynthetic processing of procollagen I N-propeptides in skin. Yet despite its important role in the regulation of collagen deposition, information regarding regulation and substrate specificity of ADAMTS-2 has remained sparse. Here we demonstrate that ADAMTS-2 can, like the procollagen C-proteinases, be regulated by transforming growth factor-beta 1 (TGF-beta 1), with implications for mechanisms whereby this growth factor effects net increases in formation of extracellular matrix. TGF-beta 1 induced ADAMTS-2 mRNA approximately 8-fold in MG-63 osteosarcoma cells in a dose- and time-dependent, cycloheximide-inhibitable manner, which appeared to operate at the transcriptional level. Secreted ADAMTS-2 protein induced by TGF-beta 1 was 132 kDa and was identical in size to the fully processed, active form of the protease. Biosynthetic processing of ADAMTS-2 to yield the 132-kDa form is shown to be a two-step process involving sequential cleavage by furin-like convertases at two sites. Surprisingly, purified recombinant ADAMTS-2 is shown to cleave procollagen III N-propeptides as effectively as those of procollagens I and II, whereas processing of procollagen III is shown to be decreased in Ehlers-Danlos VIIC. Thus, the dogma that procollagen I and procollagen III N-proteinase activities are provided by separate enzymes appears to be false, whereas the phenotypes of dermatosparaxis and Ehlers-Danlos VIIC may arise from defects in both type I and type III collagen biosynthesis.