title: Mechanical stretch modulates TGF-beta1 and alpha1(I) collagen expression in fetal human intestinal smooth muscle cells.
abstract: Intestinal muscle undergoes stretch intermittently during peristalsis and persistently proximal to obstruction. The influence of this pervasive biomechanical force on developing smooth muscle cell function remains unknown. We adapted a novel in vitro system to study whether stretch modulates transforming growth factor-beta1 (TGF-beta1) and type I collagen protein and component alpha1 chain [alpha1(I) collagen] expression in fetal human intestinal smooth muscle cells. Primary confluent cells at 20-wk gestation, cultured on flexible silicone membranes, were subjected to two brief stretches or to 18 h tonic stretch. Nonstretched cultures served as controls. TGF-beta1 protein was measured by ELISA and type I collagen protein was assayed by Western blot. TGF-beta1 and alpha1(I) collagen mRNA abundance was determined by Northern blot analysis, quantitated by phosphorimaging, and normalized to 18S rRNA. Transcription was examined by nuclear run-on assay. Tonic stretch increased TGF-beta1 protein 40%, type I collagen protein 100%, TGF-beta1 mRNA content 2.16-fold, and alpha1(I) collagen mRNA 3.80-fold and enhanced transcription of TGF-beta1 and alpha1(I) collagen by 3.1- and 4.25-fold, respectively. Brief stretch stimulated a 50% increase in TGF-beta1 mRNA content but no change in alpha1(I) collagen. Neutralizing anti-TGF-beta1 ablated stretch-mediated effects on alpha1(I) collagen. Therefore, stretch upregulates transcription for TGF-beta1, which stimulates alpha1(I) collagen gene expression in smooth muscle from developing gut.
authors.affiliation: Department of Pediatrics, University of California, San Francisco, San Francisco, California 94143, USA.
authors.forename: J A
authors.initials: JA
authors.lastname: Gutierrez
authors.forename: H A
authors.initials: HA
authors.lastname: Perr
mesh_terms: D000906:Antibodies; D003094:Collagen / Q000032:analysis / Q000235:genetics*; D005333:Fetus / Q000166:cytology; D018507:Gene Expression Regulation, Developmental; D006801:Humans; D007422:Intestines / Q000737:chemistry / Q000196:embryology* / Q000502:physiology*; D009130:Muscle, Smooth / Q000737:chemistry / Q000196:embryology* / Q000502:physiology*; D009500:Neutralization Tests; D010528:Peristalsis / Q000502:physiology; D012333:RNA, Messenger / Q000032:analysis; D012337:RNA, Ribosomal, 18S / Q000032:analysis; D013314:Stress, Mechanical; D014158:Transcription, Genetic / Q000502:physiology; D016212:Transforming Growth Factor beta / Q000032:analysis / Q000235:genetics* / Q000276:immunology
chemical_list: D000906:Antibodies; D012333:RNA, Messenger; D012337:RNA, Ribosomal, 18S; D016212:Transforming Growth Factor beta; D003094:Collagen