Systematic comparison of biologically active foreign ions-codoped calcium phosphate microparticles on osteogenic differentiation in rat osteoporotic and normal mesenchymal stem cells.

Osteoporosis is a disease characterized by structural deterioration of bone tissue, leading to skeletal fragility with increased fracture risk. Calcium phosphates (CaPs) are widely used in bone tissue engineering strategies as they have similarities to bone apatite except for the absence of trace elements (TEs) in the CaPs. Bioactive glasses (BGs) have also been used successfully in clinic for craniomaxillofacial and dental applications during the last two decades due to their excellent potential for bonding with bone and inducing osteoblastic differentiation. In this study, we evaluated the osteogenic effects of the ionic dissolution products of the quaternary Si-Sr-Zn-Mg-codoped CaP (TEs-CaP) or 45S5 Bioglass® (45S5 BG), both as mixtures and separately, on rat bone marrow-derived mesenchymal stem cells (rOMSCs & rMSCs) from osteoporotic and normal animals, using an MTT test and Alizarin Red S staining. The materials enhanced cell proliferation and osteogenic differentiation, especially the combination of the BG and TEs-CaP. Analysis by quantitative PCR and ELISA indicated that the expression of osteogenic-specific genes and proteins were elevated. These investigations suggest that the TEs-CaP and 45S5 BG operate synergistically to create an extracellular environment that promotes proliferation and terminal osteogenic differentiation of both osteoporotic and normal rMSCs.

Application of collagen-chitosan/fibrin glue asymmetric scaffolds in skin tissue engineering.

To create a scaffold that is suitable for the construction of tissue-engineered skin, a novel asymmetric porous scaffold with different pore sizes on either side was prepared by combining a collagen-chitosan porous membrane with fibrin glue. Tissue-engineered skin was fabricated using this asymmetric scaffold, fibroblasts, and a human keratinocyte line (HaCaT). Epidermal cells could be seen growing easily and achieved confluence on the fibrin glue on the upper surface of the scaffold. Scanning electron microscopy showed typical shuttle-like fibroblasts adhering to the wall of the scaffold and fluorescence microscopy showed them growing in the dermal layer of the scaffold. The constructed composite skin substitute had a histological structure similar to that of normal skin tissue after three weeks of culture. The results of our study suggest that the asymmetric scaffold is a promising biologically functional material for skin tissue engineering, with prospects for clinical applications.

[Mechanisms and effects of biosynthesis and apoptosis in repair of full-thickness skin defect with collagen-chitosan dermal stent].

OBJECTIVE: To investigate biosynthetic and apoptotic mechanisms in repair of full thickness skin defect with collagen-chitosan porous scaffold transplantation, and to determinate differences between wound repair with the scaffold transplantation and scar healing without the scaffold transplantation. METHODS: The full thickness skin defects were made on 10 Bama miniature pigs and the bilayer dermal equivalent (BDE) composed of collagen-chitosan porous scaffold and silicone membrane was transplanted on wounds. Surfaces of wounds were observed at 1, 2, and 3 weeks after the BDE transplantation, and so were done the wound repairs after epidermis had been grafted for 2 weeks on surface of the scaffold which had been transplanted on skin defect wounds for 2 weeks. At the same time, TGF-beta1 expressions, apoptosis and self collagen replacement of scaffolds in wounds were detected in situ by immunohistochemical staining, terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end labeling (TUNEL) and picrosirius red polarized light. Wounds without scaffold transplantation were studied as control. RESULTS: 1) Wounds with the scaffold transplantation were different from granulation tissue. 2) The peak of TGF-beta1 expression in the scaffold wounds was from 1 to 2 weeks after BDE transplantation, and TGF-beta1 expressions decreased continuously from 3 to 4 weeks. TGF-beta1 expressions increased continuously in the control wounds from 1 to 3 weeks and decreased on 4 weeks. TGF-beta1 expressions in the scaffold wounds on 1st and 2nd week were significantly higher than those in the corresponding control wounds, whereas, TGF-beta1 expressions in the scaffold wounds on 3rd and 4th week were significantly lower than those in the corresponding control wounds. 3) Apoptosis increased continuously in the scaffold wounds from 2 to 4 weeks after BDE transplantation, and so did in the control wounds from 3 to 4 weeks. However, apoptosis signals in the scaffold wounds on 2nd, 3rd, and 4th week after BDE transplantation were significantly more than those in the corresponding control wounds, and there was no difference between apoptosis signals in the scaffold wounds on 1st week after BDE transplantation and those in the corresponding control wounds. 4) Observation by picrosirius red polarized light method: self collagen began to synthesize in the scaffold wounds on 1st week after BDE transplantation, and scaffolds had been replaced by self collagen from 2 to 3 weeks after BDE transplantation. CONCLUSIONS: Collagen-chitosan porous scaffold plays a very important role in wound healing of full thickness skin defect. The mechanisms of wound repair by dermal scaffold are different from those by granulation and scar healing. It has a good future in repairing skin defect.

[Study on repair of full-thickness skin defect with collagen-chitosan dermal stent in pigs].

OBJECTIVE: To investigate angiogenesis of collagen-chitosan porous scaffold, and to study survive of skin grafts on the scaffold after bilayer dermal equivalent (BDE) was transplanted on wounds with full thickness skin defects. METHODS: The full thickness skin defects were made on 10 Bama miniature pigs and the BDE composed of collagen-chitosan porous scaffold and silicone membrane was transplanted on wound. Angiogenesis in dermal equivalent, wound healing, and healing and survive of skin grafts on dermal equivalent were observed in 1, 2, and 3 weeks after the BDE transplantation. At the same time, CD34 positive signals (neo-forming micro-vessels) were detected by immunohistochemical staining. RESULTS: Inflammatory cells and fibroblasts infiltrated into dermal equivalent and a few new micro-vessels had been formed in 1 week after the BDE transplantation; neo-forming micro-vessels perpendicular to wound bed had increased significantly in 2 weeks after the BDE transplantation; neo-forming micro-vessels could be observed in almost all dermal equivalents in 3 weeks after the BDE transplantation. CD34 positive signals (neo-forming micro-vessels) in 3 weeks after the BDE transplantation was much more than those in 2 weeks after the BDE transplantation, and CD34 positive signals in 2 weeks after the BDE transplantation was much more than those in 1 week after the BDE transplantation. Survival rate of intermediate split thickness skin graft were 10%, 70% and 100% respectively after the skin grafts had been grafted for 2 weeks on surface of the scaffold which had been transplanted for 1, 2 and 3 weeks. Epidermis which had been grafted on surface of the scaffold for 1 or 2 weeks could perfectly survive after BDE had been transplanted for 1 or 2 weeks. CONCLUSIONS: Collagen-chitosan porous scaffold plays a very important role in wound healing of full thickness skin defect and can induce fibroblast infiltration and new micro-vessel formation. Epidermis grafted on surface of collagen-chitosan porous scaffold can perfectly repair wounds, and it has brilliant applied prospects in repairing skin defect.

[Study on the interface of human hepatocyte L-02 polypropylene:simple culture method of human hepatocyte with spheroidal aggregate culture].

OBJECTIVE: To found new interface of human hepatocyte/poly propylene with good cytocompatibility for made polypropylene hollow fibers bioreactor of bioartificial liver in future. METHODS: Using the macromolecular hydroperoxide groups on the polypropylene membrane surface as initiators, acrylamides were polymerized on the polypropylene membranes, under induction by both UV irradiation and Fe2+ reduction. Growth characteristics of human hepatocyte L-02 were detected when it was cultured on polystyrene, polypropylene and modified polypropylene membrane surface. RESULTS: Water contact angle measurement of the polypropylene and the modified polypropylene membranes decreased from (72 +/- 5) degrees to (30 +/- 4) degrees , which indicated that the hydrophilicity of the membrane was improved obviously after the grafting modification. Human hepatocyte L-02 could not adhere and spread on modified polypropylene membrane surface, and grown in spheroidal aggregate with higher density and higher proliferation ratio measured by MTT method. CONCLUSIONS: Acrylamide polymerized on the polypropylene membranes is a good method which not only improved human hepatocytes cytocompatibility but also found a new simple culture method with spheroidal aggregate culture of human hepatocyte.

[Study on the interface of human hepatocyte/micropore polypropylene ultrafiltration membrane].

OBJECTIVE: To found a new interface of human hepatocyte/micropore polypropylene ultrafiltration membrane (MPP) with good cytocompatibility so as to construct bioartificial bioreactor with polypropylene hollow fibers in future. METHODS: MPP ultrafiltration membrane underwent chemical grafting modification through ultraviolet irradiation and Fe(2+) reduction. The contact angles of MPP and the modified MPP membranes were measured. Human hepatic cells L-02 were cultured. MPP and modified MPP membranes were spread on the wells of culture plate and human hepatic cells and cytodex 3 were inoculated on them. Different kinds of microscopy were used to observe the morphology of these cells. RESULTS: The water contact angle of MPP and the modified MPP membranes decreased from 78 degrees +/- 5 degrees to 27 degrees +/- 4 degrees (P < 0.05), which indicated that the hydrophilicity of the membrane was improved obviously after the grafting modification. Human hepatocyte L-02 did not adhere to and spread on the modified MPP membrane surface, and only grew on the microcarrier cytodex 3 with higher density and higher proliferation ratio measured by MTT. CONCLUSION: Grafting modification of acrylamide on MPP membrane is a good method to improve the human hepatocyte cytocompatibility with MPP ultrafiltration membrane.

[Skin-like structure generated from implantation of hair follicle bulb cells into collagen/chitosan porous scaffolds in vitro].

OBJECTIVE: To observe the skin regeneration after hair follicle bulb cells were implanted into collagen/chitosan porous scaffolds in vitro. METHODS: The cultured dorsal hair follicle bulb cells of 4d-old C57BL/6J mice were implanted into collagen/chitosan porous scaffolds in vitro. The skin regeneration was observed. RESULT: The skin-like structure was formed on the collagen/chitosan porous scaffolds where were cultured the hair follicle bulb cells before 4th passages. CONCLUSION: The skin-like structure is generated in vitro when early passages of cultured hair bulb cells are implanted into collagen/chitosan porous scaffolds.

Water-dispersed bone morphogenetic protein nanospheres prepared by co-precipitation method.

A modified complex coacervation-co-precipitation method was used to prepare bone morphogenetic protein (BMP)-loaded nanospheres. Three natural polymers were used as packing materials to obtain nanoscale delivery device for BMP, in the presence of phosphatidylcholine functioning as stabilizer. Positively charged polysaccharide, N,N-diethylaminoethyl dextran (DEAE-dextran) tended to form stable, uniform and smaller size particles carrying BMP. Negatively charged bovine serum albumin (BSA) induced precipitation of the produced BMP particles due to its weak interaction with BMP molecules, although it produced nanosized BMP spheres. While collagen, a weakly positively charged protein shaped larger particles due to the strong interaction among themselves. A mechanism of co-precipitation process was also deduced to depict the formation of stable nanospheres.