Advanced Biomaterials VI

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Authors: H.Y. Yeung, J.Z. Liu, Ling Qin, Yun Yu Hu, Chang Wei Lu, K.M. Lee, Y.M. Chiu, Jack C.Y. Cheng
Abstract: Bone marrow mesenchymal stem cells (BMSCs) possess a high replicative capacity and have the capacity to differentiate into various connective tissue cell types. With the advance in cell culture technique, the BMSCs have been induced to differentiate to osteoblastics linage. To improve the situation of non-union in posterior spinal fusion (PSF), tissue engineering approach to combine BMSCs supported by the calcium phosphate ceramics was applied in PSF and its effect was investigated in the present study. Autologous BMSCs from 16-week-old rabbit tibiae were expanded and induced to differentiate into osteoblastic cells with defined medium and osteogenic supplement. Calcium phosphate ceramic (CPC) was used as the scaffold to deliver the cells to the standardized rabbit posterior spinal fusion model. The assessment of bone mineral and fusion mass volume was conducted at week 7 post-operation with quantitative computed tomography and micro-computed tomography. When compared with control, the composite of BMSCs with CPC enhanced the fusion mass volume by 40% (p<0.05) and bone mineral content in the CPC was 7% (p=0.05) higher. Our study showed that additional BMSCs at the fusion site of PSF did provide extra resource for new bone formation and enhanced the fusion rate.
Authors: Jin Liu, Xiao Feng Lu, Lin Wan, Bing Lu, Sheng Fu Li, Yang-zhi Zeng, Yan Rong Lu, Hong Bu, You Ping Li, Jing Qiu Cheng
Abstract: The aim of this experiment is to investigate whether MSCs from Banna Minipig Inbred Line (BMI) could be immortalized by introducing SV40 large T antigen gene. MSCs were isolated from BMI and transfected with pSV3neo plasmid. Normal BMI-MSCs would apoptosis and senescence during proliferation while its population doubling (PD) number exceeded 20. However, SV40-transfected cells were immortal. As same as that of normal BMI-MSCs, transfected MSCs were positive for stem cell markers and negative for differentiated osteoblast specific marker. After cultured in osteogenesis supplement media, cbfa1 and calcium deposit on stimulated cells were enhanced obviously. There were no data to prove the tumorigenicity potential of the immortalized cells. Furthermore, histological analysis demonstrated that bone formation was initiated in the pores of HA/TCP implants loaded immortalized BMI-MSCs 7 weeks postimplantation. BMI-MSCs were immortalized by introducing SV40 large T antigen into the cells and still kept the stem cell characters and might be used as seeding cells for tissue engineering as well as stable test cells for biocompatibility of bone biomaterials.
Authors: H.F. Hildebrand, N. Blanchemain, G. Mayer, Y.M. Zhang, O. Melnyk, M. Morcellet, B. Martel
Abstract: In order to improve the tissue integration and subsequently the long-term maintenance, the implant surface can be modified by mechanical, physical, chemical or biological functionalization. In this way, the surface becomes biologically active by further grafting of biomolecules. Two principal concepts are considered for materials functionalization. (i) The Drug Delivery Systems (DDS) where the bioactive molecules goes to the target. (ii) The grafting of the bioactive compounds on small strongly bound spacer molecules. In this system, the target goes to the bioactive molecules. These techniques provide promising outlooks for any polymeric or ceramic scaffold used in tissue engineering for the construction of whole artificial and functional organs.
Authors: A. Hokugo, K. Mushimoto, S. Morita, Yasuhiko Tabata
Abstract: Although clinically, grafting of vascularized autologous bone has been preferably performed, there are some disadvantages for this grafting therapy, such as the limited availability of donor site and the clinical difficulty to harvest the bone graft of desired shape and size. As one trial, we have designed a prefabricated vascularized bone graft by combining autologous vessels, particulate cancellous bone and marrow (PCBM), and β-tricalcium phosphate (β-TCP) with a biodegradable membrane. However, the volume of vascularized bone tissue newly formed was small and the density was low. In this study, the controlled system of basic fibroblast growth factor (bFGF) was combined with the conventional preparation method to improve the nature of vascularized bone graft. The femur vessels of rabbits were rolled with a membrane of L-lactide-ε-caploractone copolymer. Hydrogel microspheres of gelatin were prepared as the release carrier of bFGF. Autologous PCBM harvested from the beforehand tibia of rabbits was mixed with β-TCP granules with or without the microspheres incorporating bFGF and packed into the rolled membrane. When bone formation was assessed at different time intervals, additional mixing of bFGF significantly increased the volume of vascularized bone tissue compared to that without bFGF. It is concluded that combination of bFGF release system was a promising method to prefabricate the bone graft of large size with good blood circulation.
Authors: In Sup Noh
Abstract: Vascular Tissue engineering has drawn high interest due to its high demand in its vascular graft applications. We tissue-engineered a hybrid vascular graft consisting of tissues layers and non-biodegradable ePTFE by in vitro cell culture. Tissue formation was obtained by culturing vascular smooth muscle cells on the biodegradable polylactide scaffolds on the ePTFE surfaces. The fabricated hybrid ePTFE graft consisted of three layers, i.e. two biodegradable polylactide layers and a non-biodegradable ePTFE layer. The biodegradable layer was fabricated to have a porous structure with 30-60 µm pore sizes. Connection of biodegradable layers and ePTFE was obtained by filtering the polylactide solution through the porous ePTFE wall. For a better tissue formation coating of gelatin was performed on the luminal polylactide scaffolds. The generated tissues replaced the biodegradable layers on both inside and outside surfaces of the ePTFE.
Authors: Tetsuya Tateishi, Guo Ping Chen
Abstract: A new method for the preparation of biodegradable porous scaffolds has been developed by using preprepared ice particulates as porogen material. A novel kind of hybrid biodegradable porous scaffold has been developed by forming collagen microsponges in the pores or interstices of a synthetic polymer sponge or mesh. A hybrid sponge of synthetic polymer, collagen and hydroxyapatite has been developed for hard tissue engineering. Bovine articular cartilage-like tissue has been engineered by culturing chondrocytes in the PLGA-collagen scaffolds.
Authors: Lei Cui, Dong Li, Xiang Dong Liu, Fanfan Chen, Wei Liu, Yi Lin Cao
Abstract: Objective The purpose of this study is to explore the growth, differentiation and osteogeneration of bone marrow stromal cells (BMSCs) on partially demineralized bone matrix (pDBM) and to generate bone tissue by tissue engineering approach in vivo. Methods Demineralized bone was processed from femur head of Shanghai white swine. Calcium content, porosity and pore size was measured respectively. In vitro osteogenic differentiated human BMSCs of passage 3 were seeded in pDBM. Adhesive rate of cells to pDBM was calculated 24hours after seeding. Distribution, growth and proliferation of BMSCs on pDBM were observed with fluorescent DiI labeling. Matrix disposition was analyzed with SEM observation. Cell-material complex was implanted subcutaneously in nude mice. The implants were harvested at 8, 12 weeks post surgery and samples were observed by H&E staining. Results BMSCs adhered well on the material and the distribution of cells was uniform. The adhesive rate is 99.1%±1%. New bone formation was observed in implant of 8, 12 weeks respectively. The newly formed bone was generated on the surface of the residual material and a layer of cells with typical characteristic of osteoblast was observed to adhere on the surface of the new bone. Conclusion With good biocompatibility to hBMSCs, pDBM could serve as ideal scaffold for bone tissue engineering both in vitro and in vivo.
Authors: Lu Zhang, Lin Gang Wang, Ping Hu
Abstract: In this article, electrospinning of poly (ethylene oxide) (PEO) /egg white blend and that of poly (carbon dioxide-co-propylene oxide) were studied. Blend fibrous mats containing poly (carbon dioxide-co-propylene oxide) and PEO/egg white blend were obtained through multi-jet and component alternate eletrospinning, respectively. Component alternate electrospinning exhibits higher efficiency and produces better blended products than multi-jet electrospinning does because the inter-influence between different jets during multi-jet electrospinning greatly affects electrospinning process while component alternate electrospinning avoids such kind of influence.
Authors: Christopher M. Hill, Yuehuei H. An, Qian K. Kang, Marina V. Demcheva, S.William Whitson, John Vournakis
Abstract: Athymic nude mice were used as an animal model to evaluate the chondrogenic effects of bovine fetal chondrocytes seeded onto a new poly-N-acetyl glucosamine sponge. Results show excellent hyaline-like cartilage formation with high glycosaminoglycan concentration after 6 weeks. At 4 weeks there is less cartilage formation and more fibrous tissue infiltrate. Although further studies are needed, these initial data support the use of poly-N-acetyl glucosamine sponge as a scaffold for cartilage tissue engineering.
Authors: Quan Li Li, Zhi Qing Chen, Guo Min Ou, Laikui Liu, Hao Bin Jiang, Quan Zeng, Gang Li, G. He, An Chun Mo, Brian W. Darvell
Abstract: A novel three-dimensional scaffold of hydroxyapatite(HA)-polyelectrolyte complex (PEC) composite hydrogel was synthesized by a biomimetic method. PEC hydrogel was formed from equal volumes of 1% phosphorylated chitosan in water and 1% chitosan in 1% acetic acid solution. This PEC hydrogel was soaked in saturated Ca(OH)2 solution for 4 d and then in accelerated calcification solution (ACS) for 7 d, both at 37 oC. The PEC hydrogel was a nano-composite material with multiple levels of hierarchical porosity; hydroxyapatite (HA) crystals nucleated and grew on the fiber surfaces of the hydrogel; Rat osteoblasts were then seeded in this three-dimensional scaffold of HA-PEC composite hydrogel, the three-dimensional scaffold of HA-PEC hydrogel revealed excellent biocompatibility.

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