Increased expression of insulin-like growth factor in intestinal lengthening by mechanical force in rats.
BACKGROUND
A segment of the jejunum could double its length by the application of an axial mechanical force. We hypothesize that this growth is correlated with an increased expression of insulin-like growth factor (IGF-I) in the jejunum.


METHODS
Adult Sprague-Dawley rats underwent the isolation of a 1.5-cm segment of the jejunum. The isolated jejunal segment was either lengthened using mechanical force or left alone for 3 weeks. The jejunal segments were analyzed by quantitative polymerase chain reaction and immunofluorescence for the expression of IGF-I.


RESULTS
Whereas jejunal segments that underwent isolation alone did not change their length, isolated jejunal segments that were stretched by applying a gradual mechanical force doubled their initial length. Both groups increased their muscular thickness 5 folds as compared to the normal jejunum. The mRNA level of IGF-I in the lengthened jejunum was 6 folds higher than that in the normal jejunum, but the IGF-I mRNA level in the isolated jejunum without mechanical lengthening was unchanged. By immunofluorescence, the increased IGF-I expression in the lengthened jejunum was localized to the intestinal smooth muscle cells.


CONCLUSIONS
Insulin-like growth factor I may be an important signal induced by the applied axial force that mediates longitudinal intestinal growth.
Dunn
James C Y
JC
Division of Pediatric Surgery, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA. jdunn@mednet.ucla.edu
Lam
Mandy M
MM
Lee
Edward
E
D000818:Animals; D005260:Female; D005455:Fluorescent Antibody Technique; D007583:Jejunum / Q000254:growth & development* / Q000473:pathology / Q000601:surgery; D023421:Models, Animal; D009130:Muscle, Smooth / Q000254:growth & development / Q000473:pathology; D009929:Organ Size; D011336:Probability; D012333:RNA, Messenger / Q000032:analysis; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D012680:Sensitivity and Specificity; D013002:Somatomedins / Q000032:analysis*; D013314:Stress, Mechanical; D015626:Tissue Expansion / Q000379:methods*
D012333:RNA, Messenger; D013002:Somatomedins