title: Quantitative assessment of islet cell products: estimating the accuracy of the existing protocol and accounting for islet size distribution.
abstract: The ability to consistently and reliably assess the total number and the size distribution of isolated pancreatic islet cells from a small sample is of crucial relevance for the adequate characterization of islet cell preparations used for research or transplantation purposes. Here, data from a large number of isolations were used to establish a continuous probability density function describing the size distribution of human pancreatic islets. This function was then used to generate a polymeric microsphere mixture with a composition resembling those of isolated islets, which, in turn, was used to quantitatively assess the accuracy, reliability, and operator-dependent variability of the currently utilized manual standard procedure of quantification of islet cell preparation. Furthermore, on the basis of the best fit probability density function, which corresponds to a Weibull distribution, a slightly modified scale of islet equivalent number (IEQ) conversion factors is proposed that incorporates the size distribution of islets and accounts for the decreasing probability of finding larger islets within each size group. Compared to the current calculation method, these factors introduce a 4-8% downward correction of the total IEQ estimate, but they reflect a statistically more accurate contribution of differently sized islets.
authors.affiliation: Diabetes Research Institute, University of Miami Leonard M. Miller School of Medicine, Miami, FL 33136, USA. pbuchwald@med.miami.edu
authors.forename: Peter
authors.initials: P
authors.lastname: Buchwald
authors.forename: Xiaojing
authors.initials: X
authors.lastname: Wang
authors.forename: Aisha
authors.initials: A
authors.lastname: Khan
authors.forename: Andres
authors.initials: A
authors.lastname: Bernal
authors.forename: Chris
authors.initials: C
authors.lastname: Fraker
authors.forename: Luca
authors.initials: L
authors.lastname: Inverardi
authors.forename: Camillo
authors.initials: C
authors.lastname: Ricordi
mesh_terms: D002469:Cell Separation / Q000379:methods*; D048429:Cell Size; D005434:Flow Cytometry; D006801:Humans; D007515:Islets of Langerhans / Q000166:cytology*; D016381:Islets of Langerhans Transplantation; D015203:Reproducibility of Results