The feasibility, safety, and efficacy of liverdirected gene transfer was evaluated in 5 male macaques (aged 2.5 to 6.5 years) by using a recombinant adeno-associated viral (rAAV) vector (rAAV-2 CAGG-hFIX) that had previously mediated persistent therapeutic expression of human factor IX (hFIX; 6%-10% of physiologic levels) in murine models. A dose of 4 ؋ 10 12 vector genomes (vgs)/kg of body weight was administered through the hepatic artery or portal vein. Persistence of the rAAV vgs as circular monomers and dimers and high-molecularweight concatamers was documented in liver tissue by Southern blot analysis for periods of up to 1 year. Vector particles were present in plasma, urine, or saliva for several days after infusion (as shown by polymerase chain reaction analysis), and the vgs were detected in spleen tissue at low copy numbers. An enzyme-linked immunosorption assay capable of detecting between 1% and 25% of normal levels of hFIX in rhesus plasma was developed by using hyperimmune serum from a rhesus monkey that had received an adenoviral vector encoding hFIX. Two macaques having 3 and 40 rAAV genome equivalents/cell, respectively, in liver tissue had 4% and 8% of normal physiologic plasma levels of hFIX, respectively. A level of hFIX that was 3% of normal levels was transiently detected in one other macaque, which had a genome copy number of 25 before abrogation by a neutralizing antibody (inhibitor) to hFIX. This nonhuman-primate model will be useful in further evaluation and development of rAAV vectors for gene therapy of hemophilia B. IntroductionRecombinant adeno-associated viral vectors (rAAVs) hold great promise for the treatment of hemophilia B. Preclinical studies in murine and canine models of hemophilia B have demonstrated persistent therapeutic expression of factor IX (FIX) leading to correction of the bleeding phenotype after intramuscular or portal vein administration of rAAV. 1-7 Liver-targeted delivery of rAAV resulted in significantly higher levels of FIX than observed after intramuscular administration of an equivalent dose of vector in immunodeficient mice. 8 More important, the development of neutralizing antibodies (NAbs) to human FIX (hFIX) is more common after intramuscular injection of rAAV than after intraportal administration of the same dose of vector. [8][9][10][11] Mice with persistent hFIX expression after liver-targeted delivery of rAAV could not mount a substantial antibody (Ab) response when challenged repeatedly with hFIX antigen in Freund adjuvant, a result suggesting that the liver has a unique ability to induce immune tolerance to neoantigens. 12 Endothelial cells of the liver, which can efficiently process and cross-present exogenous soluble antigens to CD8 ϩ T cells, are intimately involved in antigenspecific immune tolerance after liver-targeted gene transfer with rAAV vectors. 13 The findings of sustained expression of hFIX at therapeutic levels after a single bolus injection of rAAV vector into the portal vein of mice [3][4][5][6]8 and the absence of toxicity aft...

A cross-linking reagent is required to improve mechanical strength and degradation properties of biopolymers for tissue engineering. To find the optimal preparative method, we prepared diverse genipin-cross-linked chitosan/collagen scaffolds using different genipin concentrations and various cross-linking temperatures and cross-linking times. The compressive strength increased with the increasing of genipin concentration from 0.1 to 1.0%, but when concentration exceeded 1.0%, the compressive strength decreased. Similarly, the compressive strength increased with the increasing of temperature from 4 to 20°C, but when temperature reached 37°C, the compressive strength decreased. Showing a different trend from the above two factors, the effect of cross-linking time on the compressive strength had a single increasing tendency. The other results also demonstrated that the pore size, degradation rate and swelling ratio changed significantly with different cross-linking conditions. Based on our study, 1.0% genipin concentration, 20°C cross-linking temperature and longer cross-linking time are recommended.

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The study is to investigate the chondrogenesis of a kind of modified cell pellet formed using mesenchymal stem cells (MSCs) and gelatin microspheres containing transforming growth factor beta3 (TGF-beta3). The gelatin microspheres loaded with TGF-beta3 (MS-TGF) were prepared and showed the controlled release of cytokine in a biphasic fashion. Then the mixture of MSCs and MS-TGF was centrifuged to form pellet. The pellet was cultured over 4 weeks to determine the effects of MS-TGF on cartilage matrix production by biochemical analysis, immunohistochemistry staining, and Western blot test. The transcription level of cartilage-related genes was also evaluated by real-time quantitative RT-PCR assay. After 4 weeks of culture, the MSCs were distributed uniformly in the pellet and had good viability. Cells showed faster proliferation and higher DNA content compared to MSCs in a conventional pellet. The production of collagen and glycosaminoglycan also increased significantly. The immunohistochemistry staining and alcian blue staining confirmed the synthesis of cartilage extracellular matrix (ECM). Furthermore, the differentiated MSCs located in lacunae within the metachromatic staining matrix exhibited the typical chondrocyte morphology. The chondrogenic differentiation of MSCs was proved by the expression of collagen II gene in mRNA and protein level. The results indicate that MS-TGF can induce chondrogenic differentiation of MSCs and increase cartilage ECM production, which result in a bigger cartilage pellet. In conclusion, this modified pellet culture can provide an easy and effective way to construct the tissue-engineered cartilage in vitro.

The aim of the study was to produce a novel porous gelatin-chondroitin-hyaluronate scaffold in combination with a controlled release of transforming growth factor beta1 (TGF-beta1), which induced the differentiation of mesenchymal stem cells (MSCs) in vivo for enhancing cartilage repair. Gelatin microspheres loaded with TGF-beta1 (MS-TGFbeta1) showed a fast release at the initial phase (37.4%), and the ultimate accumulated release was 83.1% by day 18. The autologous MSCs seeded on MS-TGFbeta1/scaffold were implanted to repair full-thickness cartilage defects in rabbits as in vivo differentiation repair group, while MSCs differentiated in vitro were seeded on scaffold without MS-TGFbeta1 to repair the contra lateral cartilage defects (n = 30). Fifteen additional rabbits without treatment for defects were used as control. Histology observation showed that the in vivo differentiation repair group had better chondrocyte morphology, integration, continuous subchondral bone, and much thicker newly formed cartilage layer when compared to in vitro differentiation repair group 12 and 24 weeks, postoperatively. There was a significant difference in histological grading score between these two experimental groups, and both showed much better repair than that of the control. The present study implied that the novel scaffold with MS-TGFbeta1 might serve as a new way to induce the differentiation of MSCs in vivo to enhance the cartilage repair.

A hydroxyapatite/collagen (HAC) composite was produced to mimic the natural extracellular matrix of bone, with the collagen serving as a template for apatite formation. A three-dimensional highly porous scaffold was developed by mixing HAC with poly(L-lactic acid) (PLA) using a thermally induced phase separation technique. Naturally derived bovine bone morphogenetic protein (bBMP) was incorporated into the porous HAC-PLA scaffolds, and the composite then was implanted in diaphyseal defects (2 cm in radius) of adult beagle dogs. Controls were implanted with scaffolds without BMP. The dogs were sacrificed at 6 months, at which time biocompatibility, biodegradability, and osteoinduction were evaluated by histologic and radiologic examination and by bone mineral density (BMD) measurements. All defects healed after treatment with BMP combined with HAC-PLA, and BMD at the site of the defect was higher than the BMD of the intact radius. Fibrous union developed in the control group animals. Histologic observation indicated that the presence of BMP not only promoted osteogenesis but that it also accelerated degradation of the biomaterials. Optimized design parameters of a three-dimensional porous biomaterial would give full scope to the role of BMP as an osteoinductive growth factor.

Although most in vitro studies indicate that transforming growth factor β3 (TGF-β3) immobilized scaffold is suitable for cartilage tissue engineering, in vivo studies of implanting immobilized scaffold for chondral defect repair are still lacking. This study is to evaluate the potentials of TGF-β3 immobilized poly-(lactic-co-glycolic acid)-gelatin/chondroitin sulfate/hyaluronic acid (PLGA-GCH) hybrid scaffold for cartilage regeneration. The scaffold was fabricated by incorporating GCH micro-sponges into PLGA frameworks and then crosslinked with TGF-β3 to mimic natural cartilaginous extra cellular matrix (ECM). In vitro study demonstrated that MSCs proliferated vigorously and produced abundant ECM on scaffold. The immunohistochemistry staining and alcian blue staining confirmed the cartilaginous ECM production. The chondrogenic differentiation of MSCs on scaffold was proved by the expression of collagen II gene in mRNA and protein level. Then MSCs/TGF-β3 immobilized scaffolds were implanted in rabbits for chondral defects repair. After eight weeks, histological observation showed that differentiated MSCs were located in lacunae within the metachromatic staining matrix and exhibited typical chondrocyte morphology. Histological grading scores also indicated the congruent cartilage was regenerated. In conclusion, the TGF-β3 immobilized PLGA-GCH hybrid scaffold has great potential in constructing the tissue-engineered cartilage.

Cell-based tissue engineering is thought to be a new therapy for treatment of bone defects and nonunions after trauma and tumor resection. In this study, we explore the in vitro and in vivo osteogenesis of a novel biomimetic construct fabricated by using collagen I gel to suspend rabbit adipose-derived stem cells (rASCs) into a porous poly(lactic-co-glycolic)acid-β-tricalcium phosphate (PLGA-β-TCP) scaffold (rASCs-COL/PLGA-β-TCP). In vitro and in vivo studies of the rASCs-COL/PLGA-β-TCP composite (group A) were carried out compared with the single combination of rASCs and PLGA-β-TCP (rASCs/PLGA-β-TCP; group B), the combination of acellular collagen I gel and PLGA-β-TCP (COL/PLGA-β-TCP; group C), and the PLGA-β-TCP scaffold (group D). Composites of different groups were cultured in vitro for 2 weeks in osteogenic medium and then implanted into the autologous muscular intervals for 8 weeks. After 2 weeks of in vitro culture, alkaline phosphatase activity and extracellular matrix mineralization in group A were significantly higher than in group B (p < 0.01, n = 4). In vivo osteogenesis was evaluated by radiographic and histological analyses. The calcification level was radiographically evident in group A, whereas no apparent calcification was observed in groups B, C and D (n = 4). In group A, woven bone with a trabecular structure was formed, while in group B, only osteoid tissue was observed. Meanwhile, the bone-forming area in group A was significantly higher than in group B (p < 0.01, n = 4). No bone formation was observed in groups C or D (n = 4). In conclusion, by using collagen I gel to suspend rASCs into porous PLGA-β-TCP scaffold, osteogenic differentiation of rASCs can be improved and homogeneous bone tissue can be successfully formed in vivo.