Heparin-regulated release of growth factors in vitro and angiogenic response in vivo to implanted hyaluronan hydrogels containing VEGF and bFGF.
Controlled release of human vascular endothelial growth factor (VEGF) or basic fibroblast growth factor (bFGF) from hydrogels composed of chemically modified hyaluronan (HA) and gelatin (Gtn) was evaluated both in vitro and in vivo. We hypothesized that inclusion of small quantities of heparin (Hp) in these gels would regulate growth factor (GF) release over an extended period, while still maintaining the in vivo bioactivity of released GFs. To test this hypothesis, HA, Gtn, and Hp (15 kDa) were modified with thiol groups, then co-crosslinked with poly (ethylene glycol) diacrylate (PEGDA). Either VEGF or bFGF was incorporated into the gels before crosslinking with PEGDA. Release of these GFs in vitro could be sustained over 42 days by less than 1% Hp content, and was found to decrease monotonically with increasing Hp concentration. As little as 0.03% Hp in the gels reduced the released VEGF fraction from 30% to 21%, while 3% Hp reduced it to 19%. Since the minimum Hp concentration capable of effective controlled GF release in vitro was found to be 0.3% (w/w), this concentration was selected for subsequent in vivo experiments. To evaluate the bioactivity of released GFs in vivo, gel samples were implanted into the ear pinnas of Balb/c mice and the resulting neovascularization response measured. In the presence of Hp, vascularization was sustained over 28 days. GF release was more rapid in vitro from gels containing Gtn than from gels lacking Gtn, though unexpectedly, the in vivo neovascularization response to Gtn-containing gels was decreased. Nevertheless significant numbers of neovessels were generated. The ability to stimulate localized microvessel growth at controlled rates for extended times through the release of GFs from covalently linked, Hp-supplemented hydrogels will ultimately provide a powerful therapeutic tool.
Pike
Daniel B
DB
Department of Chemical Engineering, Oregon State University, 102 Gleeson Hall, Corvallis, OR 97331, USA. piked@onid.orst.edu <piked@onid.orst.edu>
Cai
Shenshen
S
Pomraning
Kyle R
KR
Firpo
Matthew A
MA
Fisher
Robert J
RJ
Shu
Xiao Zheng
XZ
Prestwich
Glenn D
GD
Peattie
Robert A
RA
D043925:Angiogenesis Inducing Agents / Q000008:administration & dosage* / Q000737:chemistry / Q000378:metabolism; D000818:Animals; D002196:Capillaries / Q000187:drug effects / Q000254:growth & development; D004343:Drug Implants / Q000737:chemistry* / Q000378:metabolism; D004423:Ear / Q000098:blood supply; D016222:Fibroblast Growth Factor 2 / Q000008:administration & dosage* / Q000737:chemistry / Q000378:metabolism; D006493:Heparin / Q000737:chemistry*; D006801:Humans; D006820:Hyaluronic Acid / Q000737:chemistry; D020100:Hydrogels / Q000008:administration & dosage / Q000737:chemistry*; D051379:Mice; D008807:Mice, Inbred BALB C; D018919:Neovascularization, Physiologic / Q000187:drug effects; D011092:Polyethylene Glycols / Q000737:chemistry; D042461:Vascular Endothelial Growth Factor A / Q000008:administration & dosage* / Q000737:chemistry / Q000378:metabolism
D043925:Angiogenesis Inducing Agents; D004343:Drug Implants; D020100:Hydrogels; D042461:Vascular Endothelial Growth Factor A; C437167:poly(ethylene glycol)diacrylate; D016222:Fibroblast Growth Factor 2; D011092:Polyethylene Glycols; D006820:Hyaluronic Acid; D006493:Heparin