Morphological and growth responses of vascular smooth muscle and endothelial cells cultured on immobilized heparin and dextran sulfate surfaces.

Heparin has shown promise as a component of various biomaterial formulations, but its variable properties and inhibitory effects on some cell types have raised interest in use of dextran sulfate as an alternative. In this study, we characterized the interactions of vascular smooth muscle (SMC) and endothelial cells (EC) with heparin and dextran sulfate immobilized onto chitosan-based films. Films were modified by blending chitosan with type I collagen and covalently attaching heparin or dextran sulfate at various levels. Cell-material interactions were evaluated by quantifying cell spreading, shape and proliferation rate. ECs proliferated well on chitosan, but the polymer was a mediocre substrate for SMC growth. Immobilizing heparin on chitosan further inhibited SMC proliferation. However, blending collagen reversed the heparin inhibition of SMC growth, resulting in a pro-proliferative effect of heparin immobilized on chitosan-collagen films. Dextran sulfate surfaces supported both SMC and EC proliferation with or without the presence of collagen. The results indicate that inhibitory effects of heparin on SMC are reversed by immobilization in the presence of collagen, and that dextran sulfate may be superior to heparin as a biomaterial additive for promoting vascular cell growth in chitosan-based scaffolds. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1725-1735, 2017.

The effects of 3D bioactive glass scaffolds and BMP-2 on bone formation in rat femoral critical size defects and adjacent bones.

Reconstruction of critical size defects in the load-bearing area has long been a challenge in orthopaedics. In the past, we have demonstrated the feasibility of using a biodegradable load-sharing scaffold fabricated from poly(propylene fumarate)/tricalcium phosphate (PPF/TCP) loaded with bone morphogenetic protein-2 (BMP-2) to successfully induce healing in those defects. However, there is limited osteoconduction observed with the PPF/TCP scaffold itself. For this reason, 13-93 bioactive glass scaffolds with local BMP-2 delivery were investigated in this study for inducing segmental defect repairs in a load-bearing region. Furthermore, a recent review on BMP-2 revealed greater risks in radiculitis, ectopic bone formation, osteolysis and poor global outcome in association with the use of BMP-2 for spinal fusion. We also evaluated the potential side effects of locally delivered BMP-2 on the structures of adjacent bones. Therefore, cylindrical 13-93 glass scaffolds were fabricated by indirect selective laser sintering with side holes on the cylinder filled with dicalcium phosphate dehydrate as a BMP-2 carrier. The scaffolds were implanted into critical size defects created in rat femurs with and without 10 µg of BMP-2. The x-ray and micro-CT results showed that a bridging callus was found as soon as three weeks and progressed gradually in the BMP group while minimal bone formation was observed in the control group. Degradation of the scaffolds was noted in both groups. Stiffness, peak load and energy to break of the BMP group were all higher than the control group. There was no statistical difference in bone mineral density, bone area and bone mineral content in the tibiae and contralateral femurs of the control and BMP groups. In conclusion, a 13-93 bioactive glass scaffold with local BMP-2 delivery has been demonstrated for its potential application in treating large bone defects.