Notch signaling promotes intestinal crypt fission in the infant rat.
BACKGROUND
Growth of the small intestine in the infant rat is promoted by crypt fission and later by increased crypt cell proliferation. Notch signaling could promote crypt fission. Hes-1 is a Notch target gene.


OBJECTIVE
We assessed the effect of Notch signaling on intestinal crypt fission and on growth of the intestine in the infant rat.


METHODS
Hes-1 expression was determined in the small intestine of litters of Hooded Wistar rats aged between 3 and 72 days. Hes-1 RNA expression was measured by quantitative RT-PCR. Four groups of rats (n = 8 or 9) were injected daily, ip, either with vehicle or with the Notch inhibitor DAPT at doses of 3, 10, and 30 mg/kg, from days 9 to 13 of life, and killed on day 14. A microdissection technique was used to measure crypt fission, mitotic count, and apoptotic count. Data were analyzed by ANOVA and by use of Dunnett's F test.


RESULTS
Hes-1 expression and crypt fission peaked on day 14. DAPT reduced Hes-1 immunostaining in proportion to dose. DAPT reduced villous area to 72 % (p < 0.01), 53 % (p < 0.001), and 38 % (p < 0.001) of control values for 3, 10 and 30 mg/kg doses, respectively, and reduced crypt fission to 53 % (p < 0.001) and 38 % (p < 0.001) of control values, respectively, for 10 and 30 mg/kg doses. Crypt mitotic count was not affected by any DAPT dose. DAPT at 10 and 30 mg/kg significantly increased apoptosis in crypts, by 6.5 and 4.8-fold, respectively.


CONCLUSIONS
We conclude that Notch signaling promotes crypt fission and growth of the intestine by maintaining low apoptosis of crypt cells.
Department of Gastroenterology and Hepatology, The Queen Elizabeth Hospital, Woodville South, SA, 5011, Australia. cumthom@ozemail.com.au
Adrian G
AG
Cummins
Joshua A
JA
Woenig
Rino P
RP
Donato
Simon J
SJ
Proctor
Gordon S
GS
Howarth
Phulwinder K
PK
Grover
D000375:Aging; D000818:Animals; D017209:Apoptosis; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism; D018076:DNA, Complementary / Q000235:genetics / Q000378:metabolism; D004151:Dipeptides / Q000494:pharmacology; D005260:Female; D018507:Gene Expression Regulation, Developmental / Q000502:physiology; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D007421:Intestine, Small / Q000254:growth & development* / Q000378:metabolism*; D008297:Male; D012313:RNA / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D060888:Real-Time Polymerase Chain Reaction; D051880:Receptors, Notch / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D000072056:Transcription Factor HES-1
D051792:Basic Helix-Loop-Helix Proteins; D018076:DNA, Complementary; D004151:Dipeptides; D018398:Homeodomain Proteins; D012313:RNA; D051880:Receptors, Notch; D000072056:Transcription Factor HES-1; C489735:Hes1 protein, rat; C419410:N-(N-(3,5-difluorophenacetyl)alanyl)phenylglycine tert-butyl ester