Reproducibility of scratch assays is affected by the initial degree of confluence: experiments, modelling and model selection

Wang Jin, Esha T. Shah, Catherine J. Penington, Scott W. McCue, Lisa K. Chopin, Matthew J. Simpson*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

45 Citations (Scopus)


Scratch assays are difficult to reproduce. Here we identify a previously overlooked source of variability which could partially explain this difficulty. We analyse a suite of scratch assays in which we vary the initial degree of confluence (initial cell density). Our results indicate that the rate of re-colonisation is very sensitive to the initial density. To quantify the relative roles of cell migration and proliferation, we calibrate the solution of the Fisher-Kolmogorov model to cell density profiles to provide estimates of the cell diffusivity, D, and the cell proliferation rate, λ. This procedure indicates that the estimates of D and λ are very sensitive to the initial density. This dependence suggests that the Fisher-Kolmogorov model does not accurately represent the details of the collective cell spreading process, since this model assumes that D and λ are constants that ought to be independent of the initial density. Since higher initial cell density leads to enhanced spreading, we also calibrate the solution of the Porous-Fisher model to the data as this model assumes that the cell flux is an increasing function of the cell density. Estimates of D and λ associated with the Porous-Fisher model are less sensitive to the initial density, suggesting that the Porous-Fisher model provides a better description of the experiments.

Original languageEnglish
Pages (from-to)136-145
Number of pages10
JournalJournal of Theoretical Biology
Publication statusPublished - 7 Feb 2016
Externally publishedYes


  • Scratch assay
  • Reproducibility
  • Cell diffusivity
  • Cell proliferationrate
  • Cell proliferation rate

Cite this