Thanks, James! I agree that these are very difficult experiments, but perhaps they could be carried out using an in vitro system like yours, where cell volume and osmolarity could be controlled 'pharmacologically'...

A few years ago, we introduced a new theoretical framework that treats tissues as biphasic poroelastic media. Through simulations, we demonstrated that the effective diffusion coefficient of morphogens essentially depends on:

i- The size and geometry of extracellular space; ii- Interactions of morphogens with cells through binding-unbinding or endo-/exocytosis; iii- Mechano-osmotic effects associated with cell volume regulation and intercellular fluid flows.