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Lifespan Differences in Hematopoietic Stem Cells are Due to Imperfect Repair and Unstable Mean-Reversion

Figure 5

Hurst Exponents of the Failure Rate Kinetics of Long-term Repopulating HSCs.

Plotted are the Hurst exponents (plot symbol: blue triangles; values vertical axis) of the failure rate kinetics of HSCs with lifespans and months (horizontal axis). Calculations were performed using Algorithm 0 (compare Table S1 in Text S1). All exponents are , thus falling into the region of anti-persistent behavior (defined by Hurst values (light-yellow region)) and not into the region of persistent behavior (defined by (light-pink region (only displayed up to 0.7 to enhance visibility of the data))). Our previous results [8] that past values of an HSC's repopulation kinetic predict future values, had suggested the hypothesis that Hurst exponents of the failure rates would either be greater, or less, than . The value is traditionally interpreted as “no memory” of past behavior in future behavior (horizontal line marked “no memory”). The data shown then suggest that, mechanistically, anti-persistence plays a role in controlling clonal growth. The values obtained from our experimental data were fitted to the line as a function of lifespan (gray solid line through the data). Goodness-of-Fit was determined using the Akaike Information Criterion (). The parameter estimates were highly significant (intercept estimate, standard error, p-value; slope estimate, standard error, p-value). The extension of the fitted line to include lifespans only serves visualization purposes, since we only considered HSCs with lifespans months. The negative slope of the linear fit predicts that anti-persistent behavior in the failure rate kinetics is more pronounced for longer-lived long-term repopulating HSCs than for shorter-lived long-term repopulating HSCs.

doi: https://doi.org/10.1371/journal.pcbi.1003006.g005