Papers by Author: Yi Lin Cao

Abstract: Tendon is an important supportive tissue of human body responsible for normal physical activity. However, tendon damage and defect remain an important factor for causing disability. The rise of tissue engineering technology provides an effective means of tendon reconstruction and repair, which will bring promise for functional recovery. In our center, tendon engineering is one of major research areas. We have performed the in vivo study by using tenocytes and polyglycolic acid fibers to reconstruct and repair tendon defect in hen and porcine models. The results demonstrated the successful regeneration and repair of tendon defects created in different models. In addition, tendon function was also well recovered by generated autologous tendon tissue that possesses strong biomechanical property. Recently, we have also successfully generated tendon tissue in vitro by using static strain device and bioreactors, which could be potentially transplanted as the tendon graft for tendon defect repair.

Abstract: Organ engineering remains a challenge to researchers. We tried to reconstruct kidney-like tissue using tissue engineering technique. Kidney fragments were isolated from rat E16 embryonic kidneys and seeded on either ECM gel or on polyglycolic acid (PGA) fibers, then implanted in vivo into the subcutaneous tissue of nude mice for 2 and 3 weeks, respectively. As a negative control, ECM alone was implanted. Results showed that kidney like tissue could be formed in ECMfragment constructs after 2 or 3 weeks of implantation, including the formation of glomeruli, tubules and collecting ducts. In addition, these structures seemed more mature in 3 weeks specimens than that of 2 weeks. Further development of this model may lay a solid foundation for kidney tissue engineering.

Abstract: Chitin/Chitosan membrane has been used as wound dressing materials to facilitate clinical wound healing for many years. However, there are fewer articles studying the cell-biomaterial interaction in vitro or in vivo. In this study, the biological characteristics of human keratinocytes cultured on chitosan membrane that was mixed with gelatin in different ratio were investigated in vitro. Chitosan-gelatin membrane (CGM) in different ratio were prepared with N, N-(3 dimethylaminopropyl)-N'-ethyl carbodiimide (EDC). CGMs were divided into four groups: pure chitosan membrane, 7:3 (chitosan: gelatin), 5:5 and 3:7 groups. Human keratinocytes were isolated from foreskin by Dispase/Trypsin-EDTA digestion. Keratinocytes of passage3 were then seeded on the surface of CGM. Cloning forming efficiency (CFE) and migration distance of cultured keratinocytes on CGM were measured. The CFE of keratinocytes cultured on the surface of pure chitosan membrane was 9.8±2.08%; cultured on 7:3 CGM was 14.33±1.53%, 5:5 CGM was 19.17±1.26%, 3:7 CGM was 18.33±2.08%. The migration distance of cultured keratinocytes on pure chitosan membrane was 61.47±2.70µm, 7:3 CGM was 66.22±9.39µm, 5:5 CGM was 120.31±15.82µm, 3:7 CGM was 225.38±10.48µm. This sutdy demonstrated that increasing contents of gelatin in CGM could promote keratinocyte proliferation and migration. The results also suggested the membrane prepared from chitosan and gelatin can be utilized as a good keratinocyte delivery system.

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.

Abstract: Objective: To compare biocompatibility, degradation, and mechanical properties of polyglycolic acid (PGA) unwoven and woven fibers as scaffolding materials for tendon engineering in vitro. Methods: Three kinds of PGA fibers were included in this study. PGA raw material (Purac Co, Holland) was spun into single PGA filaments that were further twisted into woven fibers (PGA- 1). PGA filaments (Nantong Holycon, China) were twisted into woven fibers (PGA-2) as well. PGA-1 and PGA-2 served as experimental groups 1 and 2, while unwoven PGA fibers (Albany Co, USA) served as control group. Three types of PGA fibers were made into cord-like scaffolds that mimic tendon shape and compared with each other for biocompatibility, degradation and biomechanical properties. Avian tenocytes were isolated from digital flexor tendon and expanded in vitro. Cells of the second passage were seeded onto the PGA scaffolds. In the first 2 weeks, the cell- PGA constructs were in vitro cultured without tension and observed for cell adhesion and matrix production. The constructs were then cultured under dynamic loading in a bioreactor for another 2 weeks followed by gross and histological examinations. Results: PGA unwoven fibers have the median diameter of 10µm, while PGA-1 and PGA-2 fibers have the median diameters of 200µm and 60µm, respectively. Microscopy showed that tenocytes adhered well to all three types of PGA fibers in the first 10 days and produced abundant matrices. However, cells showed poor viability on PGA-2 fibers after 10 days, yet good viability on the other two PGA fibers over 2 weeks of observation period. H&E staining showed that there were viable cells and abundant matrices in the control and PGA-1 groups, but not in PGA-2 group after 4 weeks of in vitro culture. Additionally, PGA unwoven fibers degraded faster than woven fibers (PGA-1 and -2). Interestingly, the PGAtenocyte constructs formed tendon-like tissue after 4 weeks of in vitro culture grossly and histologically. Furthermore, mechanical test demonstrated that both PGA woven fibers had much higher tensile strength than unwoven fibers. Conclusion: Different PGA fibers have different biocompatibility with seeded tenocytes. PGA woven fibers could bear more intense mechanical loading and degrade slower than unwoven fibers, which is essential for in vitro generation of tendon tissue. Thus PGA woven fibers might serve as a proper form of scaffolding material for in vitro tendon engineering in a bioreactor.

Abstract: Bone Marrow Stromal Cells (BMSCs) have chondrogenesis potential if chondrogenic environments or factors are provided. This study tests the hypothesis that chondrocytes can promote BMSC chondrogenesis at non-chondrogensis site. Porcine BMSCs and auricular chondrocytes were mixed at different ratios and 2.5×107 mixed cells were resuspended in 0.5 ml 30％ Pluronic, and then the mixture was injected into nude mice subcutaneously as experimental groups. Chondrocytes or BMSCs at the same cell number were mixed with 0.5 ml Pluronic and injected respectively as controls. 2.5×107 chondrocytes were mixed and injected as low concentration chondrocyte control. 8 weeks later, all specimens in experimental groups and chondrocyte group formed mature cartilage with abundant collagen II expression. Mature lacuna structures and metachromatic matrices were also observed in these specimens with the same level of GAG contents. Average wet weight of specimens in experimental groups was over 70% of that in chondrocyte group. In contrast, specimens in BMSC group showed mainly fibrous tissue. Only a small amount of cartilage was formed in specimens of low concentration chondrocyte group and the average wet weight was below 30% of that in chondrocyte group. These results demonstrate that chondrocytes can provide chondrogenic microenvironment and thus promote in vivo chondrogenesis of BMSCs at non-chondrogenesis sites. It also indicates that Pluronic is an ideal injectable biomaterial for cartilage tissue engineering.