title: Allometric scaling of the active hematopoietic stem cell pool across mammals.
abstract: BACKGROUND
  Many biological processes are characterized by allometric relations of the type Y = Y(0)M(b) between an observable Y and body mass M, which pervade at multiple levels of organization. In what regards the hematopoietic stem cell pool, there is experimental evidence that the size of the hematopoietic stem cell pool is conserved in mammals. However, demands for blood cell formation vary across mammals and thus the size of the active stem cell compartment could vary across species.
  
  
  RESULTS
  Here we investigate the allometric scaling of the hematopoietic system in a large group of mammalian species using reticulocyte counts as a marker of the active stem cell pool. Our model predicts that the total number of active stem cells, in an adult mammal, scales with body mass with the exponent 3/4.
  
  
  CONCLUSIONS
  The scaling predicted here provides an intuitive justification of the Hayflick hypothesis and supports the current view of a small active stem cell pool supported by a large, quiescent reserve. The present scaling shows excellent agreement with the available (indirect) data for smaller mammals. The small size of the active stem cell pool enhances the role of stochastic effects in the overall dynamics of the hematopoietic system.
authors.affiliation: Division of Hematology, Mayo Clinic College of Medicine, Rochester, Minnesota, United States of America. dingli@fas.harvard.edu
authors.forename: David
authors.initials: D
authors.lastname: Dingli
authors.forename: Jorge M
authors.initials: JM
authors.lastname: Pacheco
mesh_terms: D000328:Adult; D000818:Animals; D049628:Body Size; D002452:Cell Count; D004920:Erythropoiesis; D006410:Hematopoiesis; D006412:Hematopoietic Stem Cells / Q000166:cytology*; D006801:Humans; D008322:Mammals / Q000033:anatomy & histology* / Q000097:blood*; D008954:Models, Biological; D017701:Reticulocyte Count; D013045:Species Specificity; D013269:Stochastic Processes