The matricellular protein periostin contributes to proper collagen function and is downregulated during skin aging.
BACKGROUND
Periostin is a secreted 90kDa matricellular protein, which is predominantly expressed in collagen-rich tissues. Collagen is the most abundant protein in mammals and has great tensile strength. Recent investigations have shown that periostin influences collagen fibrillogenesis and biomechanical properties of murine connective tissues.


OBJECTIVE
We investigated the function of periostin concerning collagen homeostasis during intrinsic and extrinsic skin aging. For this purpose, human skin samples of young and old donors as well as samples of photoaged and sun-protected skin areas were analyzed for periostin expression. Using in vitro models, we determined the cell types responsible for periostin expression and performed functional analyses with periostin knockdown cells.


METHODS
TaqMan Real-Time PCR, UV irradiation, knockdown experiments, immunostaining, electron microscopy, collagen degradation assay, collagen crosslink analysis.


RESULTS
Periostin expression is highest in the papillary dermis and downregulated during skin aging. Fibroblasts and non-follicular skin derived precursors were identified as main source for periostin expression in human skin. Periostin knockdown in fibroblasts has no effect on collagen expression, but results in an increased fibril diameter and aberrant collagen structure. This leads to an increased susceptibility of collagen toward proteases, whereas recombinant periostin protects collagen fibrils from degradation.


CONCLUSION
Our data show that periostin plays an important role for proper collagen assembly and homeostasis. During skin aging periostin expression decreases and contributes to the phenotype of aged skin.
['Egbert|M|M|', 'Ruetze|M|M|', 'Sattler|M|M|', 'Wenck|H|H|', 'Gallinat|S|S|', 'Lucius|R|R|', 'Weise|J M|JM|']
D000328:Adult D000367:Age Factors D000368:Aged D000369:Aged, 80 and over D000375:Aging D015815:Cell Adhesion Molecules D002478:Cells, Cultured D024042:Collagen Type I D015536:Down-Regulation D005260:Female D005347:Fibroblasts D006706:Homeostasis D006801:Humans D008297:Male D008875:Middle Aged D034622:RNA Interference D012867:Skin D015595:Skin Aging D013472:Sunlight D013997:Time Factors D014162:Transfection D053773:Transforming Growth Factor beta1 D055815:Young Adult
Matricellular protein Periostin Collagen Skin aging UV skin derived precursor AA2P BAPN Ct DHLNL ECM HDF HHMD HLNL HP HPLC LOX MMP SKP SSR TEM cycle threshold dihydroxylysinonorleucine extracellular matrix high performance liquid chromatography histidinohydroxymerodesmosine human dermal fibroblasts hydroxylysinonorleucine hydroxylysylpyridinoline l-ascorbic acid 2-phosphate sesquimagnesium salt hydrate lysyloxidase matrix metalloproteinase qRT-PCR quantitative real-time polymerase chain reaction recombinant human rh solar simulated radiation transmission electron microscopy ultraviolet β-aminopropionitrile-fumarate