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Cleavage of hyaluronan is impaired in aged dermal wounds.

ABSTRACT: Changes in extracellular matrix (ECM) are one of many components that contribute to impaired wound healing in aging. This study examined the effect of age on the glycosaminoglycan hyaluronan (HA) in normal and wounded dermis from young (4-6 month-old) and aged (22-24 month-old) mice. HA content and size were similar in the normal dermis of young and aged mice. Dermal explants labeled with [(3)H]-glucosamine showed decreased generation of smaller forms of HA in aged explants relative to young explants. Aged mice exhibited delayed wound repair compared with young mice with the greatest differential at 5 days. Expression of hyaluronan synthase (HAS) 2 and 3, and hyaluronidase (HYAL) 1-3 mRNA in wounds of young and aged mice was similar. There was a trend toward a decreased HYAL protein expression in aged wound dermis, which was accompanied by changes in detectable HYAL activity. Total HA content was similar in young and aged wound dermis. There was significantly less HA in the lower MW range (~250 kDa and smaller) in 5-day wound dermis, but not in 9-day wound dermis, from aged mice relative to young mice. We propose that decreased cleavage of HA is an additional component of impaired dermal wound healing in aging.

SUBMITTER: Reed MJ

PROVIDER: S-EPMC3570623 | biostudies-literature | 2013 Jan

REPOSITORIES: biostudies-literature

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Cleavage of hyaluronan is impaired in aged dermal wounds.

Reed May J MJ Damodarasamy Mamatha M Chan Christina K CK Johnson Matthew N R MN Wight Thomas N TN Vernon Robert B RB

Matrix biology : journal of the International Society for Matrix Biology 20120927 1

Changes in extracellular matrix (ECM) are one of many components that contribute to impaired wound healing in aging. This study examined the effect of age on the glycosaminoglycan hyaluronan (HA) in normal and wounded dermis from young (4-6 month-old) and aged (22-24 month-old) mice. HA content and size were similar in the normal dermis of young and aged mice. Dermal explants labeled with [(3)H]-glucosamine showed decreased generation of smaller forms of HA in aged explants relative to young exp ...[more]

PMID: 23022999

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Project description:Extrinsic skin ageing converges on the dermis, a post-mitotic tissue compartment consisting of extracellular matrix and long-lived fibroblasts prone to damage accumulation and maladaptation. Aged human fibroblasts exhibit mitochondrial and nuclear dysfunctions, but it is unclear whether these are cause or consequence of ageing. We report on a systematic study of human dermal fibroblasts retrieved from female donors aged 20-67 years and analyzed in primary culture at low population doubling precluding replicative senescence. Genome-wide array analysis failed to detect significant (>2-fold) age-related expression changes for individual genes, but gene set enrichment analysis revealed down regulation of many genes involved in mitochondrial metabolism and respiratory electron transport, extracellular matrix maintenance, cell cycle progression and protein translation. Consistent with these changes, mitochondrial content, respiratory function and cell proliferation declined with donor age. This was associated with inadequate nuclear mito-biogenesis, hypo- phosphorylation of AMP-dependent protein kinase alpha and upregulation of the alpha2-isoform, suggesting that inadequate mito-nuclear signalling could be the leading event entailing decreased expression of mitochondrial genes and compensatory down regulation of proliferation and protein synthesis. The comparatively few genes exhibiting age-associated up regulation were associate with cholesterol metabolism, immune reactions and mRNA processing, possibly also reflecting adaptation to inadequate mitochondrial function. Donors: 15 human female donors included in the study were aged 20, 21, 23, 26, 26, 40, 41, 42, 43, 49, 60, 62, 63, 64 and 67 years, thus covering the age spectrum 20 – 67 years and providing five biological replicates for each of the age groups “young” (20-30 years), “middle” (40-50 years) and “old” (60-70 years). Human dermal fibroblasts were isolated from skin specimen removed in the course of cosmetic surgery from the bottom side of female breast. Isolation and primary culture of the cells followed published procedures (Tigges and others 2013). Cells were not expanded beyond 12 population doublings, while replicative cell cycle arrest was determined to not occur before 40 population doublings.

Project description:Communication of cells with their extracellular environment is crucial to fulfill their function in physiological and pathophysiological conditions. The literature data provide evidence that such a communication is also important in case of astrocytes. Mechanisms that contribute to the interaction between astrocytes and extracellular matrix (ECM) proteins are still poorly understood. Hyaluronan is the main component of ECM in the brain, where its major receptor protein CD44 is expressed by a subset of astrocytes. Considering the fact that functions of astrocytes are tightly coupled with changes in their morphology (e.g.: glutamate clearance in the synaptic cleft, migration, astrogliosis), we investigated the influence of hyaluronan cleavage by hyaluronidase, knockdown of CD44 by specific shRNA and CD44 overexpression on astrocyte morphology. Our results show that hyaluronidase treatment, as well as knockdown of CD44, in astrocytes result in a "stellate"-like morphology, whereas overexpression of CD44 causes an increase in cell body size and changes the shape of astrocytes into flattened cells. Moreover, as a dynamic reorganization of the actin cytoskeleton is supposed to be responsible for morphological changes of cells, and this reorganization is controlled by small GTPases of the Rho family, we hypothesized that GTPase Rac1 acts as a downstream effector for hyaluronan and CD44 in astrocytes. We used FRET-based biosensor and a dominant negative mutant of Rac1 to investigate the involvement of Rac1 activity in hyaluronidase- and CD44-dependent morphological changes of astrocytes. Both, hyaluronidase treatment and knockdown of CD44, enhances Rac1 activity while overexpression of CD44 reduces the activity state in astrocytes. Furthermore, morphological changes were blocked by specific inhibition of Rac1 activity. These findings indicate for the first time that regulation of Rac1 activity is responsible for hyaluronidase and CD44-driven morphological changes of astrocytes.

Dataset Information

Cleavage of hyaluronan is impaired in aged dermal wounds.

Publications

Cleavage of hyaluronan is impaired in aged dermal wounds.

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