Regeneration of Osteochondral Defects by Combined Delivery of Synovium-Derived Mesenchymal Stem Cells, TGF-ß1 and BMP-4 in Heparin-Conjugated Fibrin Hydrogel.

The regeneration of cartilage and osteochondral defects remains one of the most challenging clinical problems in orthopedic surgery. Currently, tissue-engineering techniques based on the delivery of appropriate growth factors and mesenchymal stem cells (MSCs) in hydrogel scaffolds are considered as the most promising therapeutic strategy for osteochondral defects regeneration. In this study, we fabricated a heparin-conjugated fibrin (HCF) hydrogel with synovium-derived mesenchymal stem cells (SDMSCs), transforming growth factor-ß1 (TGF-ß1) and bone morphogenetic protein-4 (BMP-4) to repair osteochondral defects in a rabbit model. An in vitro study showed that HCF hydrogel exhibited good biocompatibility, a slow degradation rate and sustained release of TGF-ß1 and BMP-4 over 4 weeks. Macroscopic and histological evaluations revealed that implantation of HCF hydrogel with SDMSCs, TGF-ß1 and BMP-4 significantly enhanced the regeneration of hyaline cartilage and the subchondral bone plate in osteochondral defects within 12 weeks compared to hydrogels with SDMSCs or growth factors alone. Thus, these data suggest that combined delivery of SDMSCs with TGF-ß1 and BMP-4 in HCF hydrogel may synergistically enhance the therapeutic efficacy of osteochondral defect repair of the knee joints.

Brillouin spectroscopy and radiography for assessment of viscoelastic and regenerative properties of mammalian bones.

Biomechanical properties of mammalian bones, such as strength, toughness, and plasticity, are essential for understanding how microscopic-scale mechanical features can link to macroscale bones' strength and fracture resistance. We employ Brillouin light scattering (BLS) microspectroscopy for local assessment of elastic properties of bones under compression and the efficacy of the tissue engineering approach based on heparin-conjugated fibrin (HCF) hydrogels, bone morphogenic proteins, and osteogenic stem cells in the regeneration of the bone tissues. BLS is noninvasive and label-free modality for probing viscoelastic properties of tissues that can give information on structure-function properties of normal and pathological tissues. Results showed that MCS and BPMs are critically important for regeneration of elastic and viscous properties, respectively, HCF gels containing combination of all factors had the best effect with complete defect regeneration at week nine after the implantation of bone grafts and that the bones with fully consolidated fractures have higher values of elastic moduli compared with defective bones.

Biomacromolecules as carriers in drug delivery and tissue engineering.

Natural biomacromolecules have attracted increased attention as carriers in biomedicine in recent years because of their inherent biochemical and biophysical properties including renewability, nontoxicity, biocompatibility, biodegradability, long blood circulation time and targeting ability. Recent advances in our understanding of the biological functions of natural-origin biomacromolecules and the progress in the study of biological drug carriers indicate that such carriers may have advantages over synthetic material-based carriers in terms of half-life, stability, safety and ease of manufacture. In this review, we give a brief introduction to the biochemical properties of the widely used biomacromolecule-based carriers such as albumin, lipoproteins and polysaccharides. Then examples from the clinic and in recent laboratory development are summarized. Finally the current challenges and future prospects of present biological carriers are discussed.

Optimal condition of heparin-conjugated fibrin with bone morphogenetic protein-2 for spinal fusion in a rabbit model.

BACKGROUND AIMS: Heparin-conjugated fibrin (HCF) is a carrier for long-term release of bone morphogenetic protein-2 (BMP-2) and has been shown to promote bone formation in animal models. We performed an experimental study to determine the optimal dose of BMP-2 with an HCF carrier that promotes bone formation comparable to that of autograft while minimizing complications in spinal fusion. METHODS: Twenty-four rabbits underwent posterolateral fusion of the L5-6 spinal segments. Different concentrations of HCF BMP-2 (1/10, 1/20, 1/30 or 1/40) were implanted in the spines of experimental rabbits, and autograft or INFUSE was implanted in the spines of control animals. Eight weeks after treatment, spinal fusion efficacy was evaluated by plain radiography, micro-computed tomography (micro-CT), mechanical testing and histomorphometry. RESULTS: Similar to autograft, the 1/40 HCF BMP-2 showed significant bone formation on micro-CT and histomorphometry with mechanical stability. However, the other HCF BMP-2 concentrations did not show significant bone formation compared with autograft. Although conventional BMP-2 (INFUSE) led to higher bone formation and stability, it also led to excessive ectopic bone and fibrous tissue formation. CONCLUSIONS: This study suggests the optimal concentration of BMP-2 using HCF for spinal fusion, which may decrease the complications of high-dose conventional BMP-2.

Long-term Angiogenesis Efficacy Using a Heparin-Conjugated Fibrin (HCF) Delivery System with HBM-MSCs

BACKGROUND AND OBJECTIVES: Heparin-conjugated fibrin (HCF) is suitable for the release and localization of bFGF. We analyzed the effects of a bFGF delivery system using HCF with human bone marrow-derived mesenchymal stem cells (HBM- MSCs) in a dog ischemic limb model. METHODS AND RESULTS: Animals were divided into HBM-MSCs, HBM-MSCs+HCF, bFGF-HCF, and HBM-MSCs+bFGF-HCF groups. A total of 1x10(7) HBM-MSCs were injected per animal, and the amount of bFGF was 1 mg per dog. Ischemic muscles were harvested at eight weeks and six months after injection of cells. The HBM-MSCs+bFGF-HCF group exhibited decreased proportions of capillaries and arterioles six months after transplantation. However, there were more cells positive for the angiogenic factors, VEGF and PDGF, in the eight-week specimens compared with those harvested six months after transplantation. CONCLUSIONS: Our results demonstrated that a single injection of HBM-MSCs did not have significant long-term angiogenic effects; however, a bFGF delivery system using HCF exerted prolonged angiogenic effects when combined with HBM-MSCs.

Long-term Angiogenesis Efficacy Using a Heparin-Conjugated Fibrin (HCF) Delivery System with HBM-MSCs.

BACKGROUND AND OBJECTIVES: Heparin-conjugated fibrin (HCF) is suitable for the release and localization of bFGF. We analyzed the effects of a bFGF delivery system using HCF with human bone marrow-derived mesenchymal stem cells (HBM- MSCs) in a dog ischemic limb model. METHODS AND RESULTS: Animals were divided into HBM-MSCs, HBM-MSCs＋HCF, bFGF-HCF, and HBM-MSCs＋ bFGF-HCF groups. A total of 1×10(7) HBM-MSCs were injected per animal, and the amount of bFGF was 1 mg per dog. Ischemic muscles were harvested at eight weeks and six months after injection of cells. The HBM-MSCs＋ bFGF-HCF group exhibited decreased proportions of capillaries and arterioles six months after transplantation. However, there were more cells positive for the angiogenic factors, VEGF and PDGF, in the eight-week specimens compared with those harvested six months after transplantation. CONCLUSIONS: Our results demonstrated that a single injection of HBM-MSCs did not have significant long-term angiogenic effects; however, a bFGF delivery system using HCF exerted prolonged angiogenic effects when combined with HBM-MSCs.