Impaired migration and delayed differentiation of pancreatic islet cells in mice lacking EGF-receptors.
Pancreatic acini and islets are believed to differentiate from common ductal precursors through a process requiring various growth factors. Epidermal growth factor receptor (EGF-R) is expressed throughout the developing pancreas. We have analyzed here the pancreatic phenotype of EGF-R deficient (-/-) mice, which generally die from epithelial immaturity within the first postnatal week. The pancreata appeared macroscopically normal. The most striking feature of the EGF-R (-/-) islets was that instead of forming circular clusters, the islet cells were mainly located in streak-like structures directly associated with pancreatic ducts. Based on BrdU-labelling, proliferation of the neonatal EGF-R (-/-) beta-cells was significantly reduced (2.6+/-0.4 versus 5.8+/-0.9%, P<0.01) and the difference persisted even at 7-11 days of age. Analysis of embryonic pancreata revealed impaired branching morphogenesis and delayed islet cell differentiation in the EGF-R (-/-) mice. Islet development was analyzed further in organ cultures of E12.5 pancreata. The proportion of insulin-positive cells was significantly lower in the EGF-R (-/-) explants (27+/-6 versus 48+/-8%, P<0.01), indicating delayed differentiation of the beta cells. Branching of the epithelium into ducts was also impaired. Matrix metalloproteinase (MMP-2 and MMP-9) activity was reduced 20% in EGF-R (-/-) late-gestation pancreata, as measured by gelatinase assays. Furthermore, the levels of secreted plasminogen activator inhibitor-1 (PAI-1) were markedly higher, while no apparent differences were seen in the levels of active uPA and tPa between EGF-R (-/-) and wild-type pancreata. Our findings suggest that the perturbation of EGF-R-mediated signalling can lead to a generalized proliferation defect of the pancreatic epithelia associated with a delay in beta cell development and disturbed migration of the developing islet cells as they differentiate from their precursors. Upregulated PAI-1 production and decreased gelatinolytic activity correlated to this migration defect. An intact EGF-R pathway appears to be a prerequisite for normal pancreatic development.
Miettinen
P J
PJ
Department of Pathology and Transplantation Laboratory, The Haartman Institute, and Hospital for Children and Adolescents, University of Helsinki, Helsinki, Finland. paivi.miettinen@helsinki.fi
Huotari
M
M
Koivisto
T
T
Ustinov
J
J
Palgi
J
J
Rasilainen
S
S
Lehtonen
E
E
Keski-Oja
J
J
Otonkoski
T
T
D000818:Animals; D017209:Apoptosis; D001786:Blood Glucose / Q000378:metabolism; D002454:Cell Differentiation; D002465:Cell Movement; D005314:Embryonic and Fetal Development; D066246:ErbB Receptors / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D005865:Gestational Age; D007515:Islets of Langerhans / Q000166:cytology / Q000196:embryology*; D020778:Matrix Metalloproteinase 2 / Q000378:metabolism; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D009024:Morphogenesis; D010179:Pancreas / Q000166:cytology / Q000196:embryology; D010641:Phenotype
D001786:Blood Glucose; D066246:ErbB Receptors; D020778:Matrix Metalloproteinase 2; D020780:Matrix Metalloproteinase 9