Next Generation Sequencing Fascilitates Quantitative Analysis of Differential Gene Expression in Human Pericytes treated with PDGF-BB

PDGF-BB:PDGFRß signalling in brain pericytes is critical to the development, maintenance and function of a healthy blood-brain barrier (BBB). Furthermore, BBB impairment and pericyte loss in Alzheimer's disease (AD) is well documented. We used tissue microarrays from control and AD brains to determine if PDGF-BB:PDGFRß signalling components were altered in AD, and found that there was a reduction in vascular expression of PDGFB. We hypothesised that reduced PDGF-BB:PDGFRß signalling in pericytes may have an impact on functions related to the BBB. We therefore tested the effects of PDGF-BB on primary human brain pericytes in vitro to define important signalling pathways and outcomes related to BBB function. Pericytes demonstrate a biphasic response to PDGF-BB, predominantly dependent on Akt and ERK. We determined that the actions of PDGF-BB are on-target at PDGFRß, leading to internalisation and degradation of PDGFRß. Using pharmacological inhibitors, we dissected distinct aspects of the PDGF-BB response that are controlled by ERK and Akt pathways. PDGF-BB promotes the proliferation of pericytes and protection from toxic stimuli through ERK signalling. In contrast, PDGF-BB:PDGFRß signalling through Akt and NF-?B augments pericyte-derived inflammatory secretions. It may therefore be possible to supplement PDGF-BB or small molecule agonists to stabilise the cerebrovasculature in AD. Overall design: mRNA profiles of post-mortem human pericytes treated with PDGF-BB at 1hr and 24hr