title: Mechanisms of adhesion and subsequent actions of a haematopoietic stem cell line, HPC-7, in the injured murine intestinal microcirculation in vivo.
abstract: OBJECTIVE
  Although haematopoietic stem cells (HSCs) migrate to injured gut, therapeutic success clinically remains poor. This has been partially attributed to limited local HSC recruitment following systemic injection. Identifying site specific adhesive mechanisms underpinning HSC-endothelial interactions may provide important information on how to enhance their recruitment and thus potentially improve therapeutic efficacy. This study determined (i) the integrins and inflammatory cyto/chemokines governing HSC adhesion to injured gut and muscle (ii) whether pre-treating HSCs with these cyto/chemokines enhanced their adhesion and (iii) whether the degree of HSC adhesion influenced their ability to modulate leukocyte recruitment.
  
  
  METHODS
  Adhesion of HPC-7, a murine HSC line, to ischaemia-reperfused (IR) injured mouse gut or cremaster muscle was monitored intravitally. Critical adhesion molecules were identified by pre-treating HPC-7 with blocking antibodies to CD18 and CD49d. To identify cyto/chemokines capable of recruiting HPC-7, adhesion was monitored following tissue exposure to TNF-α, IL-1β or CXCL12. The effects of pre-treating HPC-7 with these cyto/chemokines on surface integrin expression/clustering, adhesion to ICAM-1/VCAM-1 and recruitment in vivo was also investigated. Endogenous leukocyte adhesion following HPC-7 injection was again determined intravitally.
  
  
  RESULTS
  IR injury increased HPC-7 adhesion in vivo, with intestinal adhesion dependent upon CD18 and muscle adhesion predominantly relying on CD49d. Only CXCL12 pre-treatment enhanced HPC-7 adhesion within injured gut, likely by increasing CD18 binding to ICAM-1 and/or CD18 surface clustering on HPC-7. Leukocyte adhesion was reduced at 4 hours post-reperfusion, but only when local HPC-7 adhesion was enhanced using CXCL12.
  
  
  CONCLUSIONS
  This data provides evidence that site-specific molecular mechanisms govern HPC-7 adhesion to injured tissue. Importantly, we show that HPC-7 adhesion is a modulatable event in IR injury and further demonstrate that adhesion instigated by injury alone is not sufficient for mediating anti-inflammatory effects. Enhancing local HSC presence may therefore be essential to realising their clinical potential.
authors.affiliation: Centre for Cardiovascular Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, United Kingdom.
authors.forename: Dean P J
authors.initials: DP
authors.lastname: Kavanagh
authors.forename: Adrian I
authors.initials: AI
authors.lastname: Yemm
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhao
authors.forename: Jon
authors.initials: J
authors.lastname: Frampton
authors.forename: Neena
authors.initials: N
authors.lastname: Kalia
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000235:genetics / Q000276:immunology; D002448:Cell Adhesion / Q000276:immunology; D002460:Cell Line; D054377:Chemokine CXCL12 / Q000494:pharmacology; D002633:Chemotaxis / Q000187:drug effects / Q000276:immunology; D004730:Endothelium, Vascular / Q000276:immunology / Q000473:pathology*; D015870:Gene Expression; D018380:Hematopoietic Stem Cell Transplantation; D006412:Hematopoietic Stem Cells / Q000166:cytology* / Q000187:drug effects / Q000276:immunology; D016023:Integrins / Q000235:genetics / Q000276:immunology; D018799:Intercellular Adhesion Molecule-1 / Q000235:genetics / Q000276:immunology; D053583:Interleukin-1beta / Q000494:pharmacology; D007422:Intestines / Q000098:blood supply* / Q000276:immunology / Q000293:injuries; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008833:Microcirculation; D015427:Reperfusion Injury / Q000276:immunology / Q000473:pathology*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D019010:Vascular Cell Adhesion Molecule-1 / Q000235:genetics / Q000276:immunology
chemical_list: D015703:Antigens, CD; D054377:Chemokine CXCL12; C515256:Cxcl12 protein, mouse; D016023:Integrins; D053583:Interleukin-1beta; D014409:Tumor Necrosis Factor-alpha; D019010:Vascular Cell Adhesion Molecule-1; D018799:Intercellular Adhesion Molecule-1
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