Ensemble heterogeneity mimics ageing for endosomal dynamics within eukaryotic cells

Transport processes of many structures inside living cells display anomalous diffusion, such as endosomes in eukaryotic cells. They are also heterogeneous in space and time. Large ensembles of single particle trajectories allow the heterogeneities to be quantified in detail and provide insights for mathematical modelling. The development of accurate mathematical models for heterogeneous dynamics has the potential to enable the design and optimization of various technological applications, for example, the design of effective drug delivery systems. Central questions in the analysis of anomalous dynamics are ergodicity and statistical ageing which allow for selecting the proper model for the description. It is believed that non-ergodicity and ageing occur concurrently. However, we found that the anomalous dynamics of endosomes is paradoxical since it is ergodic but shows ageing. We show that this behaviour is caused by ensemble heterogeneity that, in addition to space-time heterogeneity within a single trajectory, is an inherent property of endosomal motion. Our work introduces novel approaches for the analysis and modelling of heterogeneous dynamics.

Automated summary

Transport processes of structures in living cells display anomalous diffusion and heterogeneity in space and time. Quantification of heterogeneities using single particle trajectories can lead to accurate mathematical models, enabling the design of applications such as drug delivery systems. The analysis of anomalous dynamics involves ergodicity and statistical ageing, and it is believed that non-ergodicity and ageing occur concurrently. However, the anomalous dynamics of endosomes are paradoxical as they are ergodic but show ageing. This paradoxical behavior is caused by ensemble heterogeneity, which is an inherent property of endosomal motion.