Here are three of our main interests/theories/discoveries, with published material to date, but we are also working on many more!
1) temporal adaptation of blood vessel branch spacing and 2) cell rearrangement dynamics and differential adhesion during angiogenesis both relate to our strong and ongoing interest in Notch dynamics and their impact on patterning and cell movement/decisions during angiogenesis.
3) 3D/4D imaging of mouse retinas using lightsheet microscopy is our first foray into advanced microscopy to improve our 3D view and understanding of cell movement and vessel morphology in the important mouse retina model of angiogenesis, which is largely imaged/analysed in 2D with confocal to date – which we show distorts and loses important morphological information.
Temporal adaption of blood vessel branch spacing
Though angiogenesis (the growth of new blood vessels from pre-existing ones) must carefully unfold over time to generate functional, well-adapted branching networks, we seldom hear about the time-based properties of angiogenesis, despite timing being central to other areas of biology.
We developed a novel, time-based formulation of endothelial cell behaviour during angiogenesis and through our collection of recent integrated in silico/in vivo studies we have demonstrate that various alterations to cell or tissue conditions act to locally adapt the timing of collective cell decisions and behaviours, impacting when certain cells decide to move, and generating a different spacing of vessel branches in the growing network. We are calling these ‘temporal regulators’ or ‘temporal adaptors’ of blood vessel branch spacing and they represent an exciting potential to externally modulate vessel branching under different conditions. As such we are now investigating them further and their potential as therapeutic targets to normalize vessel growth in disease.
The discovery of endothelial cell rearrangements and differential adhesion during angiogenesis
Previously endothelial cells were thought to remain in the same position relative to their neighbour cells as new blood vessels extend from pre-existing ones (angiogenesis). During my postdoctoral studies in Holger Gerhardt’s Laboratory at Cancer Research UK, I was part of the interdisciplinary team that discovered cells in fact rearrange their positions during sprouting: the migratory tip cells leading new sprouts can be overtaken (Jakobsson et. al. Nature Cell Biology 2010).
In order to explore and predict the mechanisms that underlie this competitive overtaking behaviour, I developed a computational model, focussing on how individual junctions may play a role (cell-cell junctions are the interface on which cells adhere to each other and communicate, they are known to be very dynamic and highly regulated, as vessels much stay adhered to prevent leaks, but loose enough to allow rearrangement of the cells). The model predicted that Notch signalling must regulate junctional adhesion and shape changes, as a differential adhesion pattern, driven by the alternating pattern of Notch activation in sprouts already present in growing sprouts, was required to creates an alternating pattern to match observed in vitro overtaking dynamics. We then tested this prediction and found it to be correct in vitro and in vivo using a range of experimental approaches.
One approach I utilised was to design a novel image analysis method, developed in Matlab with my collaborator Andy Philipiddes (Sussex University), to quantify endothelial junction shape changes in in vivo mouse retinal or in vitro images (this software is freely available on our tools tab – we are very happy to provide 1-1 training to use it and develop tailored extensions).
3D-4D imaging of mouse retinas using lightsheet microscopy
Eye diseases affect millions of people worldwide and can have devasting effects on people’s lives. To find new treatments, scientists need to understand more about how these diseases arise and how they progress. This is challenging and progress has been held back by limitations in current techniques for looking at the eye. Currently, the most commonly used method is called confocal imaging, which is slow and distorts the tissue. Distortion happens because confocal imaging requires that thin slices of eye tissue from mice used in experiments are flattened on slides; this makes it hard to accurately visualize three-dimensional structures in the eye.
We show that light-sheet fluorescent microscopy (or LSFM for short) can quickly produce highly detailed, three-dimensional images of mouse retinas, from the smallest parts of cells to the entire eye. The technique also identified new features in a well-studied model of retina damage caused by excessive oxygen exposure in young mice. Previous studies of this model suggested the disease caused blood vessels in the eye to balloon, hinting that drugs that shrink blood vessels would help. But using LSFM, we revealed that these blood vessels actually take on a twisted, knotted and swirled shape. This suggests that treatments that untangle the vessels rather than shrink them may be more effective - we are now actively investigating this further.