title: Integrin αv mediates contractility whereas integrin α4 regulates proliferation of human bladder smooth muscle cells via FAK pathway under physiological stretch.
abstract: OBJECTIVE
  The requirement of integrins for mechanotransduction has been recognized for some time. We investigated the role of integrin subunits and their pathway in the physiological stretch induced contractility and proliferation of human bladder smooth muscle cells.
  
  
  METHODS
  Human bladder smooth muscle cells were seeded on silicone membrane and subjected to stretch, simulating bladder cycles of various stretches and times, as controlled by customized software on a modified BioDynamic bioreactor. Cell proliferation, viability and cycle were determined by BrdU incorporation assay, the Cell Counting Kit-8 (Beyotime Institute of Biotechnology, Haimen, People's Republic of China) and flow cytometry, respectively. Cell contractility was determined using a collagen gel contraction assay.
  
  
  RESULTS
  Physiological stretch increased cell contractility, proliferation and viability. Knockdown of integrin αv but not α4 in the cells disrupted the enhanced contractility induced by stretch. Under physiological stretch conditions, the integrin αv level and phospho-FAK/FAK ratio correlated positively with cell stretch induced enhanced contractility. Further examination revealed that contractile marker expression was associated with integrin αv activation through the FAK pathway. At the same time integrin α4 but not integrin αv mediated stretch induced cell proliferation and viability.
  
  
  CONCLUSIONS
  These data revealed that different integrins have different roles in the contractility and proliferation of human bladder smooth muscle cells under physiological stretch. This suggests that different integrins may become specific therapeutic targets in patients with voiding dysfunction. They may also be used to design a specific microenvironment for optimal bladder tissue regeneration.
authors.affiliation: Department of Urology, West China Hospital, Sichuan University, Chengdu, Sichuan, People's Republic of China.
authors.forename: De-Yi
authors.initials: DY
authors.lastname: Luo
authors.forename: Romel
authors.initials: R
authors.lastname: Wazir
authors.forename: Ye
authors.initials: Y
authors.lastname: Tian
authors.forename: Xuan
authors.initials: X
authors.lastname: Yue
authors.forename: Tang-Qiang
authors.initials: TQ
authors.lastname: Wei
authors.forename: Kun-Jie
authors.initials: KJ
authors.lastname: Wang
mesh_terms: D001696:Biomechanical Phenomena; D049109:Cell Proliferation; D002478:Cells, Cultured; D051417:Focal Adhesion Kinase 1 / Q000502:physiology*; D006801:Humans; D039441:Integrin alpha4 / Q000502:physiology*; D039564:Integrin alphaV / Q000502:physiology*; D040542:Mechanotransduction, Cellular / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology*; D032389:Myocytes, Smooth Muscle / Q000166:cytology*; D001743:Urinary Bladder / Q000166:cytology*
chemical_list: D039564:Integrin alphaV; D039441:Integrin alpha4; D051417:Focal Adhesion Kinase 1; C496050:PTK2 protein, human
keywords: 5-bromo-2′-deoxyuridine; BSMC; BrdU; DMEM; Dulbecco's modified Eagle's medium; FAK; GAPDH; HBSMC; PBS; PCR; RNA interference; RNAi; SM; bladder SM cell; cellular; focal adhesion kinase; glyceraldehyde-3-dehydrogenase; human BSMC; integrins; mechanotransduction; muscle; muscle contraction; p-FAK; phosphate buffered saline; phospho-FAK; polymerase chain reaction; siRNA; small interfering RNA; smooth; smooth muscle; urinary bladder