title: Heparin-releasing scaffold for stem cells: a differentiating device for vascular aims.
abstract: OBJECTIVE
  Current limitations of tissue-engineered vascular grafts include timing for the scaffold preparation, cell type, cell differentiation and growth inside the construct, and thrombogenicity of the final device. To surmount these shortcomings, we developed a heparin-releasing poly-L-lactide (PLLA) scaffold using the electrospinning technique, to guide the differentiation of human mesenchymal stem cells towards the endothelial phenotype and to deliver a useful drug in the management of the postimplantation period.
  
  
  METHODS
  The heparin-releasing PLLA scaffold was produced by means of the electrospinning technique in a tubular shape. The scaffold was seeded with human mesenchymal stem cells and cultured for up to 1 week. Cell viability and cytotoxicity assays were performed, and cell differentiation was evaluated by immunofluorescence with confocal microscopy, cytofluorometry and western blotting. Heparin release was assayed by Azure A method and biological effectiveness of the drug was assessed by activated clotting time measurements.
  
  
  RESULTS
  The scaffold exhibited a morphology favorable to cell attachment. Heparin release showed an initial burst within the first 24 h, followed by a further sustained release profile. After 48 h of culturing, the construct demonstrated adequate engraftment and viability. Increased proliferation compared with the control scaffold in bare PLLA, suggested the induction of a favorable microenvironment. A shift towards CD31 positivity and modifications in cell morphology were observed in the heparin-releasing PLLA scaffold.
  
  
  CONCLUSIONS
  By exploiting the biological effects of heparin, we developed an ad hoc differentiating device towards the endothelial phenotype for autologous stem cell seeding and, at the same time, we were able to facilitate and optimize the management of the construct once in clinical settings.
authors.affiliation: Area of Cardiovascular Surgery, Center of Integrated Research, University Campus Bio-Medico of Rome, Italy.
authors.forename: Cristiano
authors.initials: C
authors.lastname: Spadaccio
authors.forename: Alberto
authors.initials: A
authors.lastname: Rainer
authors.forename: Matteo
authors.initials: M
authors.lastname: Centola
authors.forename: Marcella
authors.initials: M
authors.lastname: Trombetta
authors.forename: Massimo
authors.initials: M
authors.lastname: Chello
authors.forename: Mario
authors.initials: M
authors.lastname: Lusini
authors.forename: Elvio
authors.initials: E
authors.lastname: Covino
authors.forename: Yoshiya
authors.initials: Y
authors.lastname: Toyoda
authors.forename: Jorge A
authors.initials: JA
authors.lastname: Genovese
mesh_terms: D001672:Biocompatible Materials; D001807:Blood Vessel Prosthesis; D001808:Blood Vessels; D002454:Cell Differentiation; D049109:Cell Proliferation; D002478:Cells, Cultured; D016503:Drug Delivery Systems; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D006493:Heparin / Q000737:chemistry*; D006801:Humans; D059630:Mesenchymal Stem Cells / Q000187:drug effects / Q000378:metabolism; D011091:Polyesters / Q000737:chemistry*; D033581:Stem Cell Transplantation; D013234:Stem Cells / Q000166:cytology*; D023822:Tissue Engineering / Q000379:methods*; D054457:Tissue Scaffolds / Q000737:chemistry*
chemical_list: D001672:Biocompatible Materials; D011091:Polyesters; C033616:poly(lactide); D006493:Heparin