Hyaluronan-based heparin-incorporated hydrogels for generation of axially vascularized bioartificial bone tissues: in vitro and in vivo evaluation in a PLDLLA–TCP–PCL-composite system
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Smart matrices are required in bone tissue-engineered grafts that provide an optimal environment for cells and retain osteo-inductive factors for sustained biological activity. We hypothesized that a slow-degrading heparin-incorporated hyaluronan (HA) hydrogel can preserve BMP-2; while an arterio–venous (A–V) loop can support axial vascularization to provide nutrition for a bio-artificial bone graft. HA was evaluated for osteoblast growth and BMP-2 release. Porous PLDLLA–TCP–PCL scaffolds were produced by rapid prototyping technology and applied in vivo along with HA-hydrogel, loaded with either primary osteoblasts or BMP-2. A microsurgically created A–V loop was placed around the scaffold, encased in an isolation chamber in Lewis rats. HA-hydrogel supported growth of osteoblasts over 8 weeks and allowed sustained release of BMP-2 over 35 days. The A–V loop provided an angiogenic stimulus with the formation of vascularized tissue in the scaffolds. Bone-specific genes were detected by real time RT-PCR after 8 weeks. However, no significant amount of bone was observed histologically. The heterotopic isolation chamber in combination with absent biomechanical stimulation might explain the insufficient bone formation despite adequate expression of bone-related genes. Optimization of the interplay of osteogenic cells and osteo-inductive factors might eventually generate sufficient amounts of axially vascularized bone grafts for reconstructive surgery.
Hyaluronic acid/hyaluronan hydrogel
Bone morphogenetic protein
This study was supported by research grants from the Deutsche Forschungsgemeinschaft (DFG) (KN 578/2-1) and the Xue Hong and Hans Georg Geis Foundation. The authors thank Dr. Andreas Hess, Institute of Experimental and Clinical Pharmacology and Toxicology for helping in micro-CT scanning and Prof. Peter Greil and Mr. Peter Reinhard for production of the Teflon chambers.
- 1.Pneumaticos SG, Triantafyllopoulos GK, Basdra EK, Papavassiliou AG. Segmental bone defects: from cellular and molecular pathways to the development of novel biological treatments. J Cell Mol Med. 2010. doi: 10.1111/j.1582-4934.2010.01062.x.
- 2.Scheufler O, Schaefer DJ, Jaquiery C, Braccini A, Wendt DJ, Gasser JA, et al. Spatial and temporal patterns of bone formation in ectopically pre-fabricated, autologous cell-based engineered bone flaps in rabbits. J Cell Mol Med. 2008;12(4):1238–49. doi: 10.1111/j.1582-4934.2008.00137.x.CrossRefGoogle Scholar
- 3.Arkudas A, Tjiawi J, Bleiziffer O, Grabinger L, Polykandriotis E, Beier JP, et al. Fibrin gel-immobilized VEGF and bFGF efficiently stimulate angiogenesis in the AV loop model. Mol Med. 2007;13(9–10):480–7.Google Scholar
- 4.Reddi A. Bone morphogenetic proteins: from basic science to clinical applications. J Bone Joint Surg J. 2001;83(Suppl 1, Part 1):S1.Google Scholar
- 10.Eyckmans J, Roberts SJ, Schrooten J, Luyten FP. A clinically relevant model of osteoinduction: a process requiring calcium phosphate and BMP/Wnt signaling. J Cell Mol Med. 2009. doi: 10.1111/j.1582-4934.2009.00807.x.
- 18.Pike DB, Cai S, Pomraning KR, Firpo MA, Fisher RJ, Shu XZ, et al. Heparin-regulated release of growth factors in vitro and angiogenic response in vivo to implanted hyaluronan hydrogels containing VEGF and bFGF. Biomaterials. 2006;27(30):5242–51. doi: 10.1016/j.biomaterials.2006.05.018.CrossRefGoogle Scholar
- 37.Lamoureux F, Baud’huin M, Duplomb L, Heymann D, Redini F. Proteoglycans: key partners in bone cell biology. BioEssays. 2007;29(8).Google Scholar