Cholangiocyte apoptosis is an early event during induced metamorphosis in the sea lamprey, Petromyzon marinus L.
BACKGROUND
Research in biliary atresia has been hindered by lack of a suitable animal model. Lampreys are primitive vertebrates with distinct larval and adult life cycle stages. During metamorphosis the biliary system of the larval lamprey disappears. Lamprey metamorphosis has been proposed as a model for biliary atresia. We have begun to explore cellular events during lamprey metamorphosis by assessing for cholangiocyte apoptosis.


METHODS
Sea lamprey larvae were housed under controlled environmental conditions. Premetamorphic larvae were induced to undergo metamorphosis by exposure to 0.01% KClO(4). Animals were photographed weekly, and the stage of metamorphosis was assigned based upon external features. Livers were harvested and processed for routine histology and immunohistochemistry. DNA fragmentation was detected using deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) assays and cholangiocytes were identified with antibodies to cytokeratin-19. Percent TUNEL+ cholangiocytes at different stages of metamorphosis was determined.


RESULTS
The percentage of TUNEL+ cholangiocytes was 10% in premetamorphic (stage 0) lamprey (n = 6), 51% at stage 1 (n = 6), 40% at stage 2 (n = 5), 18% at stage 3 (n = 5), and 9% stage 4 (n = 4). Routine hemotoxylin and eosin stained paraffin-embedded tissue sections revealed frequent apoptotic bodies at stages 3 and 4 of metamorphosis without histologic evidence of necrosis.


CONCLUSIONS
DNA fragmentation is identified at the earliest stages of metamorphosis during induced metamorphosis in lampreys. Additional studies are necessary to validate this potentially valuable animal model.
Boomer
Laura A
LA
Department of Surgery, University of Nevada School of Medicine, Las Vegas, NV 89102, USA.
Bellister
Seth A
SA
Stephenson
Linda L
LL
Hillyard
Stanley D
SD
Khoury
Joseph D
JD
Youson
John H
JH
Gosche
John R
JR
D000818:Animals; D013956:Antithyroid Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D001653:Bile Ducts, Intrahepatic / Q000166:cytology* / Q000502:physiology; D001656:Biliary Atresia / Q000473:pathology; D053938:DNA Fragmentation; D004195:Disease Models, Animal; D006801:Humans; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D007814:Larva / Q000187:drug effects / Q000502:physiology; D008018:Life Cycle Stages / Q000187:drug effects / Q000502:physiology; D008099:Liver / Q000033:anatomy & histology / Q000187:drug effects / Q000502:physiology; D008675:Metamorphosis, Biological / Q000187:drug effects / Q000502:physiology*; D048428:Petromyzon / Q000502:physiology*; D017680:Potassium Compounds / Q000494:pharmacology
D013956:Antithyroid Agents; D017680:Potassium Compounds