Understanding Solar Skin Elastosis-Cause and Treatment.

Photoageing, also called actinic ageing, is the main cause of prematurely aged skin. Our expertise in elastic fibers has led us to discover a process triggered in response to ultraviolet (UV) light and which upsets the balance of elastin fibers: there is too much elastin and insufficient lysyl oxidase (LOXL1) enzyme to form functional elastic fibers. This imbalance then leads to an accumulation of nonfunctional elastin, which forms aggregates. In addition to this imbalance, UV rays also induce elafin synthesis by fibroblasts. Known to be a marker of elastotic aggregates, elafin crystallizes the elastin fibers and stimulates the formation of aggregates that cannot be naturally eliminated by the skin. We developed a Hamamelis virginiana leaf extract that was able to restore both the balance between elastin and LOXL1 and to decrease the elafin synthesis to fight and correct the damage. This specific Hamamelis virginiana extract increased LOXL1 expression by twofold and decreased elafin synthesis. As a consequence, elastic fibers became functional and aggregates of unfunctional fibers decreased. The specific Hamamelis extract activity was confirmed in vivo with decreasing wrinkles and improving skin firmness.

Treatment of pseudoxanthoma elasticum-like papillary dermal elastolysis with nonablative fractional resurfacing laser resulting in clinical and histologic improvement in elastin and collagen.

OBJECTIVE: Pseudoxanthoma elasticum-like papillary dermal elastolysis (PXE-PDE) is a rare skin condition seen predominantly in elderly females. These asymptomatic lesions are brought to the dermatologist's attention due to patient's displeasure in their appearance. We report a case of a 28-year-old female with PXE-PDE on the right neck treated with nonablative fractional resurfacing (NAFR). CASE: The patient on examination had yellow-to-skin-colored papules that coalesced into a cobblestone-appearing plaque on her lateral neck. The area was treated with NAFR to improve texture and cosmesis. After three treatments, the patient noted at least a 50% improvement of appearance and texture in the affected skin. Adverse effects were mild without development of serious side effects, such as scarring and/or permanent dyspigmenation. CONCLUSION: Established therapies for elastin disorders like PXE-PDE have yielded unsatisfactory results by patient and clinician standards. Positive results with NAFR, illustrated in our PXE-PDE case, further provides a role for NAFR in elastin disorders.

Lower energy and pulse stacking. A safer alternative for skin tightening using fractional CO2 laser.

PURPOSE: To evaluate the effect of different energies and stacking in skin shrinkage. METHODS: Three decreasing settings of a fractional CO2 laser were applied to the abdomen of Twenty five Wistar rats divided into three groups. Group I (n=5) was histologically evaluated for microthermal zones dimensions. Groups II and III (n=10 each) were macroscopic evaluated with freeware ImageJ for area contraction immediately and after 30 and 60 days. RESULTS: No statistical significance was found within microthermal zone histological dimensions (Group I) in all settings studied. (Ablation depth: 76.90 to 97.18µm; Coagulation depth: 186.01 to 219.84 µm). In Group II, macroscopic evaluation showed that all settings cause significant immediate skin contraction. The highest setting cause significant more intense tightening effect initially, contracting skin area from 258.65 to 179.09 mm2. The same pattern was observed in Group III. At 30 and 60 days, the lowest setting significantly sustained contraction. CONCLUSION: Lower fractional CO2 laser energies associated to pulse stacking could cause consistent and long lasting tissue contraction in rats.

Study of 1550-nm Erbium glass laser fractional non-ablative treatment of photoaging: Comparative clinical effects, histopathology, electron microscopy, and immunohistochemistry.

BACKGROUND: Non-ablative fractional lasers have been effectively used in skin rejuvenation. OBJECTIVES: This study evaluates the efficacy of 1550-nm Erbium glass laser for facial rejuvenation through the correlation of clinical evaluation and histopathology, immunohistochemistry, and electron microscopy analysis. METHODS: Fifteen subjects (average age: 56.4 years, skin types: I-III) with mild-to-moderate photodamage were submitted to biopsies and 3 facial treatments. Data from the photo assessments and the clinical improvement were analyzed 4 months after the treatments. The biopsy skins were fixed in neutral buffered formalin before being embedded in paraffin, and stained with hematoxylin and eosin. The histomorphometric quantification of collagen and elastic fibers; intercellular adhesion molecule 1 expression by immunohistochemistry; and analysis of cell cycle phases, the electrical potential of the mitochondrial, and interleukin (IL)-1, CD34, transforming growth factor (TGF)-ß, and caspase-3 expression by flow cytometry were analyzed. RESULTS: After 4 months of treatment, collagen fibers had increased by 6.68%, and intercellular adhesion molecule 1 (ICAM-1) had increased by 4.47% in vessel area. Significantly enhanced IL-1 and TGF-ß receptor expressions were identified after treatment. Proliferative responses and non-apoptosis-dependent caspase-3 activity were both observed in the cell after dermal treatment. CONCLUSION: The histopathology, immunohistochemistry, and electron microscopy showed an improvement compatible to the clinical effectiveness after 4 months.

Lower energy and pulse stacking. A safer alternative for skin tightening using fractional CO2 laser

PURPOSE : To evaluate the effect of different energies and stacking in skin shrinkage. METHODS : Three decreasing settings of a fractional CO2 laser were applied to the abdomen of Twenty five Wistar rats divided into three groups. Group I (n=5) was histologically evaluated for microthermal zones dimensions. Groups II and III (n=10 each) were macroscopic evaluated with freeware ImageJ for area contraction immediately and after 30 and 60 days. RESULTS : No statistical significance was found within microthermal zone histological dimensions (Group I) in all settings studied. (Ablation depth: 76.90 to 97.18µm; Coagulation depth: 186.01 to 219.84 µm). In Group II, macroscopic evaluation showed that all settings cause significant immediate skin contraction. The highest setting cause significant more intense tightening effect initially, contracting skin area from 258.65 to 179.09 mm2. The same pattern was observed in Group III. At 30 and 60 days, the lowest setting significantly sustained contraction. CONCLUSION : Lower fractional CO2 laser energies associated to pulse stacking could cause consistent and long lasting tissue contraction in rats.

Conditioned medium from human bone marrow-derived mesenchymal stem cells promotes skin moisturization and effacement of wrinkles in UVB-irradiated SKH-1 hairless mice.

BACKGROUND: Mesenchymal stem cells (MSCs) are promising therapeutic agents for various diseases. AIMS: To investigate the effects of conditioned medium from human bone marrow-derived mesenchymal stem cells (MSC-CdM) on pro-collagen production and wrinkle formation, we performed in vitro and in vivo experiments. METHODS: We assessed the effects of MSC-CdM on proliferation and photo-aging in human dermal fibroblasts after UVB exposure using enzyme activity assays for collagen type I secretion and MMP-1. To determine the effect of topically applied MSC-CdM on wrinkle formation, MSC-CdM (1% and 10%) and vehicle (propylene glycol: ethanol, 7 : 3) were applied to the dorsal skin of UVB-irradiated hairless mice for 8 weeks. We examined the effects on wrinkle formation by assessing visual skin grading, replica, tape stripping, transepidermal water loss (TEWL), and skin hydration measurement. We also examined histology of the lesions using hematoxylin-eosin, Masson's trichrome, and immunohistochemical staining. RESULTS: MSC-CdM markedly reduced UV-induced matrix metalloproteinase-1 expression and increased pro-collagen synthesis in a dose-dependent manner. Our findings suggest that MSC-CdM induces repair of dermal damage and effacement of wrinkles on UVB-irradiated hairless mice through protective effect of hydration. CONCLUSION: These results support an anti-wrinkle effect of MSC-CdM that involves increased collagen synthesis and suggest that MSC-CdM might be a potential candidate for preventing UV-induced skin damage.

Fractional Erbium laser in the treatment of photoaging: randomized comparative, clinical and histopathological study of ablative (2940nm) vs. non-ablative (1540nm) methods after 3 months.

BACKGROUND: Fractional non-ablative lasers keep the epidermis intact, while fractional ablative lasers remove it, making them theoretically more effective. OBJECTIVES: To evaluate the clinical and histological alterations induced by fractional photothermolysis for treating photoaging, comparing the possible equivalence of multiple sessions of 1540nm Erbium, to one session of 2940nm Erbium. METHODS: Eighteen patients (mean age 55.9) completed the treatment with three sessions of 1540nm fractional Erbium laser on one side of the face (50 mJ/mB, 15ms, 2 passes), and one session of 2940nm on the other side (5mJ/mB, 0.25ms, 2 passes). Biopsies were performed before and 3 months after treatment. Clinical, histological and morphometric evaluations were carried out. RESULTS: All patients presented clinical improvement with no statistically significant difference (p> 0.05) between the treated sides. Histopathology revealed a new organization of collagen and elastic fibers, accompanied by edema, which was more evident with the 2940nm laser. This finding was confirmed by morphometry, which showed a decrease in collagen density for both treatments, with a statistical significance for the 2940nm laser (p > 0.001). CONCLUSIONS: Three 1540nm sessions were clinically equivalent to one 2940nm session. The edema probably contributed to the positive results after three months, togheter with the new collagen and elastic fibers organization. The greater edema after the 2940nm session indicates that dermal remodeling takes longer than with 1540nm. It is possible that this histological superiority relates to a more prolonged effect, but a cohort longer than three months is needed to confirm that supposition.

Fractional Erbium laser in the treatment of photoaging: randomized comparative, clinical and histopathological study of ablative (2940nm) vs. non-ablative (1540nm) methods after 3 months

BACKGROUND: Fractional non-ablative lasers keep the epidermis intact, while fractional ablative lasers remove it, making them theoretically more effective. OBJECTIVES: To evaluate the clinical and histological alterations induced by fractional photothermolysis for treating photoaging, comparing the possible equivalence of multiple sessions of 1540nm Erbium, to one session of 2940nm Erbium. METHODS: Eighteen patients (mean age 55.9) completed the treatment with three sessions of 1540nm fractional Erbium laser on one side of the face (50 mJ/mB, 15ms, 2 passes), and one session of 2940nm on the other side (5mJ/mB, 0.25ms, 2 passes). Biopsies were performed before and 3 months after treatment. Clinical, histological and morphometric evaluations were carried out. RESULTS: All patients presented clinical improvement with no statistically significant difference (p> 0.05) between the treated sides. Histopathology revealed a new organization of collagen and elastic fibers, accompanied by edema, which was more evident with the 2940nm laser. This finding was confirmed by morphometry, which showed a decrease in collagen density for both treatments, with a statistical significance for the 2940nm laser (p > 0.001). CONCLUSIONS: Three 1540nm sessions were clinically equivalent to one 2940nm session. The edema probably contributed to the positive results after three months, togheter with the new collagen and elastic fibers organization. The greater edema after the 2940nm session indicates that dermal remodeling takes longer than with 1540nm. It is possible that this histological superiority relates to a more prolonged effect, but a cohort longer than three months is needed to confirm that supposition. .

Evaluación de los efectos del LED en el tejido dérmico de ratones / The effect of application of red LED on the dermis of rats

Diodos Emisores de la Luz- Light Emitting Diodes (LED) son fuentes de luz que están siendo introducidos en los tratamientos del envejecimiento. El objetivo del estudio fue evaluar los efectos del LED rojo en la dermis de ratones wistar. Se trata de un estudio experimental controlado y randomizado, fueron utilizados 20 ratones wistar divididos en cinco grupos. Los grupos fueron: G1 en donde se aplicó 10 sesiones de diez minutos de fototerapia por LED. El G2 con 20 sesiones de 10minutos, el G3 con 10 sesiones de 20 minutos, el G4 con 20 sesiones de 20 minutos y el G5 fue el grupo control. Después de las aplicaciones se recolectó el material biológico de la zona, siendo realizado el análisis histológico de las áreas que recibieron las aplicaciones, sometiéndolas a las coloraciones de HE, tricómico de Masson y Verhoeef. Fue observada la presencia de micro vasos dérmicos con resultados significativos entre el G2 y el G5. Con relación a la presencia de mastocitos hubo resultados significativos entre el G1 y el G3. El análisis de las fibras elásticas presentó resultados significativos en los grupos G1, G2, G3, G4 en comparación al grupo control (G5). La evaluación de los efectos del LED en las fibras colágenos, los grupos tratados comparados al grupo control no presentaron ninguna diferencia significativa.

The Light-Emitting Diodes Light Emitting Diodes (LED) are a source of light wich are being introduced into the treatment of aging process. This study evaluate the effect of application of red LED on the dermis of Wistar rats. Twenty Wistar rats were used in this randomized controlled experimental study. Those rats were divided randomly into five groups. The G1 group underwent ten sessions of phototherapy by LED lasting ten minutes each. The G-2, 20 sessions of 10 minutes, the G-3, 20 minutes, the fourth group, 20 sessions of 20 minutes and the G-5 group was the control group. After the application, the biological material was collected and the histological analysis of the areas that suffered application were done, being subjected to HE staining, and Masson trichrome & Verhoeff. It was observed the presence of dermal microvascular, with significant results among G2 and G5 groups. Regarding the presence of mast cells, significant results were observed among G1 and G3 groups, however, that was not the case with the G5. By analyzing the elastic fibers, significant results were observed among G1, G2, G3, G4 groups, but the same results weren’t observed in the fifth group. Regarding the assessment of the effects of LED on the collagen fibers, the treated groups, when compared to the control group, showed no significant difference.

Morphological study of the relationship between solar elastosis and the development of wrinkles on the forehead and lateral canthus.

OBJECTIVE: To identify whether there is a relationship between solar elastosis and the development of wrinkles in human skin. DESIGN: Wrinkle depth was measured on the forehead and lateral canthus of human cadavers using image analysis. The thickness of the dermis was measured in skin sections obtained around wrinkles and stained with Elastica-van Gieson. SETTING: Gross Anatomy Section, Kagoshima University Graduate School of Medical and Dental Sciences, Kagoshima, Japan. SUBJECTS: Fifty-eight male and female cadavers (age range at death, 29-93 years). MAIN OUTCOME MEASURES: The ratio of solar elastosis dermal thickness to full dermal thickness (elastosis ratio) was calculated and compared between the deepest point of a wrinkle (wrinkle point) and a point within 1 mm where no wrinkle existed (nonwrinkle point). The relationship between elastosis ratios and wrinkle depths was investigated. RESULTS: Advanced solar elastosis was present at nonwrinkle points but was present a little bit at wrinkle points. On the forehead, a positive correlation between elastosis ratios and wrinkle depths was observed at nonwrinkle points but not at wrinkle points. On the lateral canthus, a positive correlation between elastosis ratios and wrinkle depths was observed at nonwrinkle points, as well as at wrinkle points until the wrinkle became deeper than one-half of the original dermal thickness (0.6 mm). Solar elastosis on the lateral canthus ceased developing at this point, but the wrinkle developed further. CONCLUSIONS: Solar elastosis tends to commence with the development of a wrinkle until the wrinkle becomes deeper than 0.6 mm. This tendency is less evident at wrinkle points than at nonwrinkle points.

Luz intensa pulsada no fotoenvelhecimento: avaliação clínica, histopatológica e imuno-histoquímica / Intense pulsed light in photoaging: a clinical, histopathological and immunohistochemical evaluation

FUNDAMENTOS: A luz intensa pulsada tem sido muito utilizada no tratamento do fotoenvelhecimento sem completo conhecimento de seu mecanismo de ação. OBJETIVO: Estudar a ação da luz intensa pulsada no fotoenvelhecimento e na resposta imunológica cutânea por meio de estudo clínico, histopatológico, avaliando células de Langerhans (CD1), expressão da molécula de adesão intercelular, de linfócitos CD4 e CD8 e quantificação de colágeno e fibras elásticas. MÉTODOS: Um total de 26 pacientes, com idades entre 40 e 65 anos, com fototipos II a III de Fitzpatrick, foram tratadas do fotoenvelhecimento usando LIP, em 5 sessões, com intervalo mensal, durante o ano de 2006. Todas as pacientes foram submetidas à avaliação histológica e imuno-histoquímica 6 meses após o tratamento. RESULTADOS: Ao término do tratamento, houve melhora clínica em 76,92 por cento dos casos, estando relacionada ao aumento significante de fibras colágenas (51,33 por cento) e elásticas (44,13 por cento). O tratamento com luz intensa pulsada promoveu redução de linfócitos CD4 e não alterou a intensidade de linfócitos CD8. Além disso, promoveu aumento significante de pequenos vasos sanguíneos, não ectásicos, molécula de adesão intercelular positivos. CONCLUSÃO: O tratamento facial com luz intensa pulsada promoveu intensa melhora clínica que foi comprovada pelo estudo histopatológico da pele, constituindo boa opção de tratamento para o fotoenvelhecimento cutâneo, por ser técnica não- ablativa, segura e eficaz.

BACKGROUND: Intense pulsed light has been used in the treatment of photoaging without a full understanding of its mechanism of action. OBJECTIVE: To study the effect of intense pulsed light on photoaging and on the skin immune response by means of a clinical and histopathological study, evaluating Langerhans cells (CD1), expression of intercellular adhesion molecule, of CD4 and CD8 lymphocytes and quantification of collagen and elastic fibers. METHODS: In 2006 a total of 26 patients, aged 40 to 65 years, with phototypes II to III (Fitzpatrick scale), were treated for photoaging using intense pulsed light in five sessions with a monthly interval. All the patients were subjected to histological and immunohistochemical evaluation 6 months after treatment. RESULTS: At the end of the treatment clinical improvement was observed in 76.92 percent of cases. This improvement was associated to a significant increase of collagen (51.33 percent) and elastic (44.13 percent) fibers. Intense pulsed light treatment led to a reduction of CD4 lymphocytes and did not alter the amount of CD8 lymphocytes. It also led to a significant increase of small, nonectatic blood vessels, positive intercellular adhesion molecule. CONCLUSION: Facial treatment with intense pulsed light promoted major clinical improvement that was confirmed by histological examination of the skin. This technique is a good treatment option for skin photoaging because it is non-ablative, safe and effective.

Expression of vitamin D receptor decreases during progression of pigmented skin lesions.

1,25-dihydroxyvitamin D3 affects proliferation, differentiation, and apoptosis and protects DNA against oxidative damage with a net tumorostatic and anticarcinogenic effect. It acts through a specific nuclear receptor that is widely distributed through the body. Although a beneficial role of vitamin D in melanoma patients has been suggested, there is lack of information on the changes in the expression pattern of vitamin D receptor during progression of pigmented lesions. Using immunohistochemistry, we analyzed the expression of vitamin D receptor in 140 samples obtained form 82 patients, including 25 benign nevi, 70 primary cutaneous melanomas, 35 metastases, 5 re-excisions, and 5 normal skin biopsies. The strongest expression was observed in normal skin that significantly decreased in melanocytic proliferations with the following order of expression: normal skin > melanocytic nevi > melanomas = metastases. The vitamin D receptor expression in skin surrounding nevi and melanoma was also significantly reduced as compared to normal skin. Tumor-infiltrating and lymph node lymphocytes retained high levels of vitamin D receptor. There was negative correlation between tumor progression and vitamin D receptor expression with a remarkable decrease of the immunoreactivity in nuclei of melanoma cells at vertical versus radial growth phases and with metastatic melanomas showing the lowest cytoplasmic receptor staining. Furthermore, lack of the receptor expression in primary melanomas and metastases was related to shorter overall patients' survival. In addition, the receptor expression decreased in melanized melanoma cells in comparison to amelanotic or poorly pigmented cells. Therefore, we propose that reduction or absence of vitamin D receptor is linked to progression of melanocytic lesions, that its lack affects survival of melanoma patients, and that melanogenesis can attenuate receptor expression. In conclusion, changes in vitamin D receptor expression pattern can serve as important variables for diagnosis, predicting clinical outcome of the disease, and/or as a guidance for novel therapy of melanomas based on use of vitamin D or its derivatives.

Intense pulsed light in photoaging: a clinical, histopathological and immunohistochemical evaluation.

BACKGROUND: Intense pulsed light has been used in the treatment of photoaging without a full understanding of its mechanism of action. OBJECTIVE: To study the effect of intense pulsed light on photoaging and on the skin immune response by means of a clinical and histopathological study, evaluating Langerhans cells (CD1), expression of intercellular adhesion molecule, of CD4 and CD8 lymphocytes and quantification of collagen and elastic fibers. METHODS: In 2006 a total of 26 patients, aged 40 to 65 years, with phototypes II to III (Fitzpatrick scale), were treated for photoaging using intense pulsed light in five sessions with a monthly interval. All the patients were subjected to histological and immunohistochemical evaluation 6 months after treatment. RESULTS: At the end of the treatment clinical improvement was observed in 76.92% of cases. This improvement was associated to a significant increase of collagen (51.33%) and elastic (44.13%) fibers. Intense pulsed light treatment led to a reduction of CD4 lymphocytes and did not alter the amount of CD8 lymphocytes. It also led to a significant increase of small, nonectatic blood vessels, positive intercellular adhesion molecule. CONCLUSION: Facial treatment with intense pulsed light promoted major clinical improvement that was confirmed by histological examination of the skin. This technique is a good treatment option for skin photoaging because it is non-ablative, safe and effective.

Solar elastotic material in dermal lymphatics and lymph nodes.

The movement of material via passive mechanical transport through lymphatic channels (also known as benign mechanical transport) is a physiologic mechanism invoked to explain the occasional presence of benign heterotopic tissues within lymph nodes. However, historically, the concept of benign mechanical transport has provoked controversy. The proof of this concept is of fundamental importance to the claim that foreign cells or cellular aggregates found within a sentinel lymph node do not necessarily represent clinically relevant metastatic disease. Herein we present the previously undescribed finding of solar elastotic material within the dermal lymphatics, and/or capsules, subcapsular sinuses, and parenchyma of lymph nodes of 9 patients. Eight of the patients were treated and/or staged for cutaneous melanoma; one had Merkel cell carcinoma. Solar elastotic material was found in lymph nodes in association with metastatic melanoma, nodal melanocytic nevi, and in otherwise unremarkable lymph nodes lacking extrinsic cells. These findings support the concept of the mechanical transport of both benign and malignant tissues through lymphatics and document that passively transported material can appear in any compartment of the lymph node; an important concept to give evidence for, as it offers a sound explanation for the presence of some cellular deposits within lymphoid tissue and supports the assertion that some of these deposits are benign.

Associations of cumulative sun exposure and phenotypic characteristics with histologic solar elastosis.

BACKGROUND: Solar elastosis adjacent to melanomas in histologic sections is regarded as an indicator of sun exposure, although the associations of UV exposure and phenotype with solar elastosis are yet to be fully explored. METHODS: The study included 2,589 incident primary melanoma patients with assessment of histologic solar elastosis in the population-based Genes, Environment, and Melanoma study. Ambient erythemal UV (UVE) at places of residence and sun exposure hours, including body site-specific exposure, were collected. We examined the association of cumulative site-specific and non-site-specific sun exposure hours and ambient UVE with solar elastosis in multivariable models adjusted for age, sex, center, pigmentary characteristics, nevi, and, where relevant, body site. RESULTS: Solar elastosis was associated most strongly with site-specific UVE [odds ratio (OR) for top exposure quartile, 5.20; 95% confidence interval (95% CI), 3.40-7.96; P for trend <0.001] and also with site-specific sun exposure (OR for top quartile, 5.12; 95% CI, 3.35-7.83; P for trend <0.001). Older age (OR at >70 years, 7.69; 95% CI, 5.14-11.52; P for trend < 0.001) and having more than 10 back nevi (OR, 0.77; 95% CI, 0.61-0.97; P = 0.03) were independently associated with solar elastosis. CONCLUSION: Solar elastosis had a strong association with higher site-specific UVE dose, older age, and fewer nevi. IMPACT: Solar elastosis could be a useful biomarker of lifetime site-specific UV. Future research is needed to explore whether age represents more than simple accumulation of sun exposure and to determine why people with more nevi may be less prone to solar elastosis.

The 308-nm excimer laser in the darkening of the white lines of striae alba.

OBJECTIVE: To evaluate the true efficacy of the 308-nm excimer laser for darkening striae alba using a modified approach. METHODS: Ten subjects were treated using the excimer laser on the white lines of striae, while the normal skin near to and between the lines was covered with zinc oxide cream. Assessment of efficacy was performed by colorimetric scores based on mexameter measurement and also digital photographs showing before-after laser therapy, which were compared by two independent dermatologists. RESULTS: The mexameter-based data analysis showed that the excimer laser was weakly effective in the repigmentation of the lines of striae. The analysis using before-after photographs showed that 80% of patients had a poor or moderate result. CONCLUSIONS: The results of this study showed the weakly positive effect of the 308-nm excimer laser in the repigmentation of striae alba; the splaying of pigment was a major side effect.

Low-dose ultraviolet radiation selectively degrades chromophore-rich extracellular matrix components.

Photoageing of human skin due to chronic exposure to ultraviolet radiation (UVR) is characterized histologically by extensive remodelling of the dermal elastic fibre system. Whilst enzymatic pathways are thought to play a major role in mediating extracellular matrix (ECM) degeneration in UV-exposed skin, the substrate specificity of UVR-up-regulated and activated matrix metalloproteinases (MMPs) is low. It is unclear, therefore, how such cell-mediated mechanisms alone could be responsible for the reported selective degradation of elastic fibre components such as fibrillin-1 and fibulin-5 during the early stages of photoageing. Here we use atomic force microscopy (AFM) and scanning transmission electron microscopy (STEM) to demonstrate that physiologically attainable doses (20-100 mJ/cm(2)) of direct UV-B radiation can induce profound, dose-dependent, changes in the structure of, and mass distribution within, isolated fibrillin microfibrils. Furthermore, using reducing and native PAGE in combination with AFM, we show that, whilst exposure to low-dose UV-B radiation significantly alters the macromolecular and quaternary structures of both UV chromophore (Cys, His, Phe, Trp and Tyr)-rich fibrillin microfibrils (fibrillin-1, 21.0%) and fibronectin dimers (fibronectin, 12.9%), similar doses have no detectable effect on UV chromophore-poor type I collagen monomers (2.2%). Analysis of the published primary amino acid sequences of 49 dermal ECM components demonstrates that most elastic fibre-associated proteins, but crucially neither elastin nor members of the collagen family, are rich in UV chromophores. We suggest, therefore, that the amino acid composition of elastic fibre-associated proteins [including the fibrillins, fibulins, latent TGFbeta binding proteins (LTBPs) and the lysyl oxidase family of enzymes (LOK/LOXLs)] may predispose them to direct degradation by UVR. As a consequence, this selective acellular photochemical pathway may play an important role in initiating and/or exacerbating cell-mediated ECM remodelling in UVR-exposed skin.

Mechanism of UVB-induced wrinkling of the skin: paracrine cytokine linkage between keratinocytes and fibroblasts leading to the stimulation of elastase.

In clinical studies, the formation of facial wrinkles has been closely linked to the loss of elastic properties of the skin. Repetitive irradiation of animal skin with UVB radiation at suberythemal doses significantly reduces its elastic properties, resulting in the formation of wrinkles. Repetitive UVB irradiation elicits a marked alteration in the three-dimensional structure of elastic fibers, which is closely associated with a subsequent reduction in the elastic properties of the skin. Although UVB irradiation stimulates the activity of fibroblast elastases in the dermis, a synthetic inhibitor specific for fibroblast elastases prevents wrinkle formation. The close interrelationships among wrinkle formation, elastic properties, and elastic fiber linearity are revealed by the effects of different concentrations of the elastase inhibitor (R(2)>0.9), suggesting that enhanced elastase activity by dermal fibroblasts plays a pivotal role in the UVB wrinkling mechanism. In in vitro studies we identified a paracrine linkage between keratinocytes and fibroblasts that leads to wrinkle formation through the upregulation of fibroblast elastases. These studies support our hypothesis for a mechanism of wrinkle formation by which cytokine expression is activated in epidermal keratinocytes by UVB radiation and triggers dermal fibroblasts to increase their expression of elastase.Journal of Investigative Dermatology Symposium Proceedings (2009) 14, 36-43; doi:10.1038/jidsymp.2009.11.