The in vivo failure of implantable glucose sensors is thought to be largely the result of inflammation and fibrosis-induced vessel regression at sites of sensor implantation.
These data are consistent with vascular normalisation [24], although the extensive vessel regression observed in our model would be expected to be associated with decreased rather than increased perfusion.
However, with time, the tumor endothelial cells die and the blood vessel regression is achieved (reviewed in [36]), which would lead to a decreased retention of (R -[11C]PAQ.
In summary, this study provides insight into the relationship between neurodegeneration, glial activation and vessel regression.
At low levels of VEGF-A, high Ang-2 levels may lead to vessel regression and a better prognosis.
To this end, we established a clear temporal relationship between neuronal degeneration, glial activation and vessel regression and found a predominance of neurotrophic factor activation.
As we determined gene expression before and after vessel regression, the involvement of specific tyrosine kinases in relation to vasoregression is not surprising.
In this line, vessel abnormalities like vessel regression, hypoperfusion, endothelial degeneration, abnormal vessel growth, size and shape and microangiopathy are found in neurological disorders and are often associated with neuronal loss [61].
In contrast, the increased CBV and decreased MBV observed over time for control mice would be consistent with an increasingly avascular tumor with vessel regression in the tumor core and fewer, but larger, blood vessels.
However, the role of microglia in the destruction of retinal vessels is suggestive given the evidence, e.g. from the RCS rat and other models in which photoreceptor degeneration, microglia activation, and vessel regression have been demonstrated [6], [23], [24].
These results can be explained by the functional role of Ang-2, as it is known to destabilize the endothelium, and the plastic state triggered by Ang-2 can lead to new vessel growth or vessel regression, depending on the presence of factors such as VEGF-A [4], [28].
