MedicalResearch.com Interview with:
David Granville, BSc, PhD, FAHA
Professor, University of British Columbia
Scholar of the Royal Society of Canada
Director, GEM Facility, Centre for Heart Lung Innovation, St. Paul's Hospital Founder and CSO, viDA Therapeutics, Inc.
Vancouver, BC, Canada
Medical Research: What is the background for this study? What are the main findings?
Dr. Granville: My background is in cardiovascular research. In particular, how age affects blood vessels and how age affects mechanisms of blood vessel and heart injury and repair. We became interested in skin aging during a study in which we were studying the role of a protein degrading enzyme known as Granzyme B in atherosclerosis (hardening of the arteries) and aging. In these studies, we were using a genetic mouse model that is prone to accelerated aging, and knocked out Granzyme B. Although we were initially focused on the blood vessels, we also found that Granzyme B-deficient mice exhibited younger-looking skin. As we started to look into this, we became aware that UV light can induce the skin cells to produce Granzyme B. As sunlight is believed to be responsible for 80-90% of preventable skin aging, we generated a solar-simulated light box (with the similar ratios of
UVA/UVB to sunlight) to assess whether Granzyme B played a role in UV-induced skin aging (aka photoaging). We exposed the mice to repetitive, low dose UV three times per week for 20 weeks. After 20 weeks we observed that Granzyme B deficient mice exhibited fewer wrinkles. We then wanted to look histologically and biochemically into how Granzyme B was affecting skin morphology. Granzyme B deficient mice exhibited greater collagen density compared to mice that possessed Granzyme B. As we looked into the mechanism in more detail, we determined that Granzyme B was cleaving a protein known as decorin. Decorin is responsible for collagen fibrillogenesis and assembling collagen into tight bundles. Loss of decorin is associated with a loss of collagen tensile strength. Interestingly, decorin also protects collagen from destruction by a protein-degrading enzyme known as MMP1. We showed in the study that by breaking down decorin, Granzyme B renders collagen susceptible to MMP1-mediated degradation. In addition, we showed that Granzyme B-fragmentation of another protein, fibronectin, led to the upregulation of MMP1 in skin fibroblasts. In summary, the paper showed that UV induced Granzyme B expression in the skin and showed that this enzyme contributes to the breakdown of extracellular matrix proteins and formation of wrinkles.
A link to the Aging Cell publication: http://onlinelibrary.wiley.com/doi/10.1111/acel.12298/pdf
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