title: Fractionated external beam radiotherapy as a suitable preparative regimen for hepatocyte transplantation after partial hepatectomy.
abstract: OBJECTIVE
  Hepatocyte transplantation is strongly considered to be a promising option to correct chronic liver failure through repopulation of the diseased organ. We already reported on extensive liver repopulation by hepatocytes transplanted into rats preconditioned with 25-Gy single dose selective external beam irradiation (IR). Herein, we tested lower radiation doses and fractionated protocols, which would be applicable in clinical use.
  
  
  METHODS
  Livers of dipeptidylpeptidase IV (DPPIV)-deficient rats were preconditioned with partial liver external beam single dose IR at 25 Gy, 8 Gy, or 5 Gy, or fractionated IR at 5 × 5 Gy or 5 × 2 Gy. Four days after completion of IR, a partial hepatectomy (PH) was performed to resect the untreated liver section. Subsequently, 12 million wild-type (DPPIV(+)) hepatocytes were transplanted via the spleen into the recipient livers. The degree of donor cell integration and liver repopulation was studied 16 weeks after transplantation by means of immunofluorescence and DPPIV-luminescence assay.
  
  
  RESULTS
  Donor hepatocyte integration and liver repopulation were more effective in the irradiated livers following pretreatment with the IR doses 1 × 25 Gy and 5 × 5 Gy (formation of large DPPIV-positive cell clusters) than single-dose irradiation at 8 Gy or 5 Gy (DPPIV-positive clusters noticeably smaller and less frequent). Quantitative analysis of extracted DPPIV revealed signals exceeding the control level in all transplanted animals treated with IR and PH. Compared with the standard treatment of 1 × 25 Gy, fractionation with 5 × 5 Gy was equally efficacious, the Mann-Whitney U test disclosing no statistically significant difference (p = 0.146). The lower doses of 1 × 5 Gy, 1 × 8 Gy, and 5 × 2 Gy were significantly less effective with p < 0.05.
  
  
  CONCLUSIONS
  This study suggests that fractionated radiotherapy in combination with PH is a conceivable pretreatment approach to prime the host liver for hepatocyte transplantation, thus bringing the experimental model a step closer to clinical application.
authors.affiliation: Department of General and Visceral Surgery, University Medical Centre Goettingen, Goettingen, Germany.
authors.forename: Petra
authors.initials: P
authors.lastname: Krause
authors.forename: Hendrik A
authors.initials: HA
authors.lastname: Wolff
authors.forename: Margret
authors.initials: M
authors.lastname: Rave-Frank
authors.forename: Heinz
authors.initials: H
authors.lastname: Schmidberger
authors.forename: Heinz
authors.initials: H
authors.lastname: Becker
authors.forename: Clemens Friedrich
authors.initials: CF
authors.lastname: Hess
authors.forename: Hans
authors.initials: H
authors.lastname: Christiansen
authors.forename: Sarah
authors.initials: S
authors.lastname: Koenig
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000032:analysis; D018819:Dipeptidyl Peptidase 4 / Q000032:analysis / Q000172:deficiency; D019583:Dose Fractionation, Radiation; D006498:Hepatectomy / Q000379:methods*; D022781:Hepatocytes / Q000166:cytology / Q000637:transplantation*; D008099:Liver / Q000528:radiation effects*; D051381:Rats; D019172:Transplantation Conditioning / Q000379:methods*
chemical_list: D015415:Biomarkers; D018819:Dipeptidyl Peptidase 4