title: Gelatin hydrogel microspheres enable pinpoint delivery of basic fibroblast growth factor for the development of functional collateral vessels.
abstract: BACKGROUND
  Various growth factors promote collateral vessel development and are regarded as promising for the treatment of vascular occlusive diseases. However, an efficacious delivery system for them has yet to be established. We devised a strategy to augment functional collateral vessels by using acidic gelatin hydrogel microspheres (AGHMs) incorporating basic fibroblast growth factor (bFGF). The aim of the present study was to investigate the hypothesis that by intra-arterial (IA) administration of bFGF-impregnated AGHMs, bFGF could be delivered from AGHMs trapped in distal small-diameter vessels and thereby induce functional collateral vessels with an assured blood supply through the process of arteriogenesis.
  
  
  RESULTS
  Various sizes of AGHMs (3 mg) incorporating 125I-labeled bFGF were injected into the left internal iliac artery of a rabbit model of hindlimb ischemia. Less than 50% of radioactivity accumulated in the ischemic hindlimb after injection of AGHMs that were 10 mum in diameter, whereas approximately 80% of radioactivity was counted in the ischemic limb after administration of 29- or 59-microm-diameter AGHMs. Calf blood pressure ratio and the ratio of regional blood flow of the bilateral hindlimbs immediately before and after IA administration of 29-microm-diameter AGHMs showed no significant change. Then we evaluated the function of the developed collateral vessels 28 days after IA administration of bFGF-impregnated, 29-microm-diameter AGHMs. IA administration of bFGF-impregnated AGHMs induced marked collateral vessel improvement compared with IA administration of phosphate buffered saline-treated AGHMs and intramuscular administration of bFGF-impregnated AGHMs.
  
  
  CONCLUSIONS
  IA administration of bFGF-impregnated, 29-microm-diameter AGHMs strongly induced functional collateral vessels without worsening ischemia, indicating the possible therapeutic usefulness of this approach.
authors.affiliation: Department of Vascular Regeneration, Graduate School of Medicine, University of Tokyo, Tokyo, Japan.
authors.forename: Akihiro
authors.initials: A
authors.lastname: Hosaka
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Koyama
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Kushibiki
authors.forename: Yasuhiko
authors.initials: Y
authors.lastname: Tabata
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Nishiyama
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Miyata
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Shigematsu
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Takato
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Nagawa
mesh_terms: D000818:Animals; D003097:Collateral Circulation / Q000187:drug effects*; D004353:Drug Evaluation, Preclinical; D005263:Femoral Artery / Q000293:injuries; D016222:Fibroblast Growth Factor 2 / Q000008:administration & dosage* / Q000494:pharmacology; D005780:Gelatin; D006614:Hindlimb / Q000098:blood supply*; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D006863:Hydrogen-Ion Concentration; D007269:Injections, Intra-Arterial; D007511:Ischemia / Q000188:drug therapy* / Q000503:physiopathology; D008297:Male; D008863:Microspheres; D010316:Particle Size; D011817:Rabbits; D014018:Tissue Distribution
chemical_list: D016222:Fibroblast Growth Factor 2; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D005780:Gelatin