Epithelial-mesenchymal interaction mechanisms leading to the over-expression of neprilysin are involved in the UVB-induced formation of wrinkles in the skin.

In clinical studies, the formation of facial wrinkles has been closely linked to the loss of elastic properties of the skin. Repetitive UVB irradiation of animal skin at suberythemal doses significantly reduces its elastic properties, resulting in the formation of wrinkles. That also elicits a marked alteration in the three-dimensional structure of elastic fibres, which is closely associated with a subsequent reduction in the elastic properties of the skin. While UVB irradiation stimulates the activity of skin fibroblast-derived elastase in the dermis, a synthetic inhibitor specific for skin fibroblast-derived elastase as well as an extract of Zingiber officinale (L.) Rose capable of inhibiting skin fibroblast-derived elastase, but not neutrophil elastase, prevented wrinkle formation in our studies of animal and human facial skin, respectively. The close interrelationship among wrinkle formation, elastic properties and elastic fibre linearity is revealed by the effects of different concentrations of the elastase inhibitor, which indicates that enhanced elastase activity by dermal fibroblasts plays a pivotal role in the UVB wrinkling mechanism. Fortunately, we were able to identify human skin fibroblast-derived elastase as the previously known enzyme neprilysin/neutral endopeptidase. Using both a UVB-conditioned medium assay and a co-culture system, we characterized the epithelial-mesenchymal interaction between keratinocytes and fibroblasts which leads to increased expression of neprilysin at the transcriptional, translational and enzymatic levels. Our results demonstrate that interleukin-1α and granulocyte-macrophage colony-stimulating factor are intrinsic cytokines secreted by UVB-exposed keratinocytes that stimulate the expression of neprilysin by skin fibroblasts.

Microfibrils provide non-linear elastic behaviour in the abdominal artery of the lobster Homarus americanus.

1. Microfibrils are becoming increasingly recognized as an important component of the extra-cellular matrix. However, almost nothing is known about their mechanical role in the diversity of tissues in which they are found. 2. Microfibrils form the principal structural component in the wall of the abdominal artery of the lobster Homarus americanus. We have used previous estimates of the mechanical properties of these microfibrils, estimates of the fraction of the aorta wall volume occupied by the microfibrils, and their angular distribution as a function of strain in a numerical model that predicts the macroscopic mechanical properties of the whole tissue. 3. Microfibrils alone, when their reorientation and deformation are accounted for, characterize the stress-strain behaviour of the vessel. Evidence of the evolutionary conservation of fibrillin between medusans, echinoderms and vertebrates implies that the mechanical properties of lobster microfibrils may apply to microfibrillar function in other taxa. This will have profound implications on the perceived roles of microfibrils in development, physiology and disease.

The reliability and accuracy of a standard method of tissue compliance assessment.

OBJECTIVE: To assess the reliability and the accuracy of a common method of tissue compliance measurement using a series of non-biological test surfaces (foam). Currently, tissue compliance measurement is most commonly obtained with a hand-held instrument known as a tissue compliance meter (TCM). DESIGN: Descriptive study. SETTING: Human Performance Laboratory, University of Calgary. INTERVENTION: A TCM was tested on four surfaces (three test and one control) with five different input forces resulting in 20 unique surface/force combinations. For each combination of surface/force, ten trials were obtained in a random order by each of five examiners, yielding a total of 1000 separate measurements of surface compliance. MAIN OUTCOME MEASURE: Millimeters of surface displacement per Newtons of input force. RESULTS: Intraclass correlation coefficients were calculated for each of the 20 surface/force combinations to judge interexaminer reliability. The median of these 20 coefficients was 0.005: the greatest single value tending toward complete reliability was 0.22. Trials obtained from the control surface (assumed to be incompressible), demonstrated a range of displacements from 0.00 to 2.00 mm. CONCLUSIONS: Within the design of this experiment, the reliability and accuracy of the hand-held tissue compliance meter was poor. We would suggest that the adequacy of this instrument in clinical practice or scientific work must be seriously questioned. Although the assessment of tissue compliance may be useful in the characterization of the musculoskeletal system and particularly in the assessment of treatment outcome, we surmise that a more reliable and accurate instrument is needed for the quantification of tissue compliance.