Chisa Hidaka

Tendon-healing in a bone tunnel. A biomechanical and histological study in the dog.

Our study evaluated tendon-to-bone healing in a dog model. Twenty adult mongrel dogs had a transplantation of the long digital extensor tendon into a 4.8-millimeter drill-hole in the proximal tibial metaphysis. Four dogs were killed at each of five time-periods (two, four, eight, twelve, and twenty-six weeks after the transplantation), and the histological and biomechanical characteristics of the tendon-bone interface were evaluated. Serial histological analysis revealed progressive reestablishment of collagen-fiber continuity between the bone and the tendon. A layer of cellular, fibrous tissue was noted between the tendon and the bone, along the length of the bone tunnel; this layer progressively matured and reorganized during the healing process. The collagen fibers that attached the tendon to the bone resembled Sharpey fibers. High-resolution radiographs showed remodeling of the trabecular bone that surrounded the tendon. At the two, four, and eight-week time-periods, all specimens had failed by pull-out of the tendon from the bone tunnel. The strength of the interface was noted to have significantly and progressively increased between the second and the twelfth week after the transplantation. At the twelve and twenty-six-week time-periods, all specimens had failed by pull-out of the tendon from the clamp or by mid-substance rupture of the tendon. The progressive increase in strength was correlated with the degree of bone ingrowth, mineralization, and maturation of the healing tissue, noted histologically.

CAR-dependent and CAR-independent pathways of adenovirus vector–mediated gene transfer and expression in human fibroblasts

Primary fibroblasts are not efficiently transduced by subgroup C adenovirus (Ad) vectors because they express low levels of the high-affinity Coxsackie virus and adenovirus receptor (CAR). In the present study, we have used primary human dermal fibroblasts as a model to explore strategies by which Ad vectors can be designed to enter cells deficient in CAR. Using an Ad vector expressing the human CAR cDNA (AdCAR) at high multiplicity of infection, primary fibroblasts were converted from being CAR deficient to CAR sufficient. Efficiency of subsequent gene transfer by standard Ad5-based vectors and Ad5-based vectors with alterations in penton and fiber was evaluated. Marked enhancement of binding and transgene expression by standard Ad5 vectors was achieved in CAR-sufficient fibroblasts. Expression by AdDeltaRGDbetagal, an Ad5-based vector lacking the arginine-glycine-aspartate (RGD) alphaV integrin recognition site from its penton base, was achieved in CAR-sufficient, but not CAR-deficient, cells. Fiber-altered Ad5-based vectors, including (a) AdF(pK7)betagal (bearing seven lysines on the end of fiber) (b) AdF(RGD)betagal (bearing a high-affinity RGD sequence on the end of fiber), and (c) AdF9sK betagal (bearing a short fiber and Ad9 knob), demonstrated enhanced gene transfer in CAR-deficient fibroblasts, with no further enhancement in CAR-sufficient fibroblasts. Together, these observations demonstrate that CAR deficiency on Ad targets can be circumvented either by supplying CAR or by modifying the Ad fiber to bind to other cell-surface receptors.

Acceleration of cartilage repair by genetically modified chondrocytes over expressing bone morphogenetic protein-7

Background: Cartilage has a limited capacity to heal. Although chondrocyte transplantation is a useful therapeutic strategy, the repair process can be lengthy. Previously we have shown that over expression of bone morphogenetic protein‐7 (BMP‐7) in chondrocytes by adenovirus‐mediated gene transfer leads to increased matrix synthesis and cartilage‐like tissue formation in vitro. In this context we hypothesized that implantation of genetically modified chondrocytes expressing BMP‐7 would accelerate the formation of hyaline‐like repair tissue in an equine model of cartilage defect repair.

Combined Bone Morphogenetic Protein-2 and −7 Gene Transfer Enhances Osteoblastic Differentiation and Spine Fusion in a Rodent Model†

To enhance the osteogenic activity of BMP, combination BMP2 and BMP7 gene transfer was performed. This approach led to a significant increase in osteoblastic differentiation of mesenchymal precursors compared with single BMP gene transfer in vitro. When tested in 78 rats, combination gene transfer enhanced mechanically stable spine fusion and bone formation rate versus single BMP gene transfer.

Genetic modification of chondrocytes with insulin-like growth factor-1 enhances cartilage healing in an equine model

Gene therapy with insulin-like growth factor-1 (IGF-1) increases matrix production and enhances chondrocyte proliferation and survival in vitro. The purpose of this study was to determine whether arthroscopically-grafted chondrocytes genetically modified by an adenovirus vector encoding equine IGF-1 (AdIGF-1) would have a beneficial effect on cartilage healing in an equine femoropatellar joint model. A total of 16 horses underwent arthroscopic repair of a single 15 mm cartilage defect in each femoropatellar joint. One joint received 2 x 10(7) AdIGF-1 modified chondrocytes and the contralateral joint received 2 x 10(7) naive (unmodified) chondrocytes. Repairs were analysed at four weeks, nine weeks and eight months after surgery. Morphological and histological appearance, IGF-1 and collagen type II gene expression (polymerase chain reaction, in situ hybridisation and immunohistochemistry), collagen type II content (cyanogen bromide and sodium dodecyl sulphate-polyacrylamide gel electrophoresis), proteoglycan content (dimethylmethylene blue assay), and gene expression for collagen type I, matrix metalloproteinase (MMP)-1, MMP-3, MMP-13, aggrecanase-1, tissue inhibitor of matrix metalloproteinase-1 (TIMP-1) and TIMP-3 were evaluated. Genetic modification of chondrocytes significantly increased IGF-1 mRNA and ligand production in repair tissue for up to nine weeks following transplantation. The gross and histological appearance of IGF-1 modified repair tissue was improved over control defects. Gross filling of defects was significantly improved at four weeks, and a more hyaline-like tissue covered the lesions at eight months. Histological outcome at four and nine weeks post-transplantation revealed greater tissue filling of defects transplanted with genetically modified chondrocytes, whereas repair tissue in control defects was thin and irregular and more fibrous. Collagen type II expression in IGF-1 gene-transduced defects was increased 100-fold at four weeks and correlated with increased collagen type II immunoreaction up to eight months. Genetic modification of chondrocytes with AdIGF-1 prior to transplantation improved early (four to nine weeks), and to a lesser degree long-term, cartilage healing in the equine model. The equine model of cartilage healing closely resembles human clinical cartilage repair. The results of this study suggest that cartilage healing can be enhanced through genetic modification of chondrocytes prior to transplantation.

Formation of vascularized meniscal tissue by combining gene therapy with tissue engineering.

Ingrowth of host blood vessels into engineered tissues has potential benefits for successful transplantation of engineered tissues as well as healing of surrounding host tissues. In particular, the use of a vascularized bioengineered tissue could be beneficial for treating injuries to the meniscus, a structure in the knee where the lack of a vascular supply is associated with an inadequate healing response. In this study, gene transfer using an adenovirus vector encoding the hepatocyte growth factor gene (AdHGF) was used to induce blood vessel formation in tissue-engineered meniscus. Bovine meniscal cells were treated with AdHGF, a vector encoding a marker gene E. coli beta-galactosidase (Adbetagal), or no virus. Cells were seeded onto poly-glycolic acid felt scaffolds and then transplanted into the subcutaneous pouch of athymic nude mice for 8 weeks. Expression of the marker gene and HGF was detectable for several weeks after gene transfer. Ink injection studies showed that AdHGF-treated meniscal cells formed tissue which contained fourfold more blood vessels at 2 weeks (p < 0.02) and 2.5-fold more blood vessels at 8 weeks (p < 0.001) posttransplantation than controls. This study demonstrates the feasibility of using adenovirus-mediated gene transfer to engineer a blood supply in the bioengineered meniscal tissue.

Chondrogenesis, joint formation, and articular cartilage regeneration

The repair of joint surface defects remains a clinical challenge, as articular cartilage has a limited healing response. Despite this, articular cartilage does have the capacity to grow and remodel extensively during pre‐ and post‐natal development. As such, the elucidation of developmental mechanisms, particularly those in post‐natal animals, may shed valuable light on processes that could be harnessed to develop novel approaches for articular cartilage tissue engineering and/or regeneration to treat injuries or degeneration in adult joints. Much has been learned through mouse genetics regarding the embryonic development of joints. This knowledge, as well as the less extensive available information regarding post‐natal joint development is reviewed here and discussed in relation to their possible relevance to future directions in cartilage tissue repair and regeneration. J. Cell. Biochem. 107: 383–392, 2009.

Enhancement of spine fusion using combined gene therapy and tissue engineering BMP-7-expressing bone marrow cells and allograft bone.

Study Design. Prospective study to assess the enhancement of spine fusion using a tissue engineering construct consisting of bone marrow cells genetically modified by adenovirus (Ad) vector-encoding bone morphogenetic protein-7 (BMP-7) seeded onto an allograft scaffold in a rat model. Objectives. To evaluate Ad transgene expression at the fusion site and the effect of AdBMP-7-treatment on fusion rates, mechanical stability, microscopic anatomy, and bone formation rates. Summary of Background Data. Nonunion is a major complication of spine fusion. Gene transfer may be an effective method for locally overexpressing BMP-7, a gene important for bone formation and regeneration to enhance allograft spine fusion. Materials and Methods. Bone marrow cells were treated with AdBMP-7 or Ad&bgr;gal (encoding the marker gene &bgr;-galactosidase), AdNull (with no gene), or no vector and implanted with allograft in a site of posterior spine fusion. Marker gene expression was assessed up to 14 days after administration. Fusions were evaluated at 8 weeks. Results. Ad gene expression was maximal on day 3, waning to background levels by 14 days. With AdBMP-7 treatment, radiographic fusion rate was 70% and mechanical fusion rate was 80%versus 0% by either parameter in control groups. Fused AdBMP-7-treated spines had a 2.5-fold to 3.0-fold lower range of motion and 1.7-fold to 1.9-fold lower hysteresis than controls. Fusion masses of AdBMP-7-treated spines had the microscopic appearance of normal trabecular bone and showed a 23-fold higher uptake of fluorochrome indicating increased bone formation. Conclusions. Addition of AdBMP-7-modified marrow cells can enhance allograft spine fusion.

Enhanced matrix synthesis and in vitro formation of cartilage-like tissue by genetically modified chondrocytes expressing BMP-7

Bone morphogenic protein‐7 (BMP‐7) supports ectopic cartilage and bone formation, is expressed in normal articular cartilage, and increases matrix synthesis in chondrocytes. Based on this knowledge, we hypothesized that an adenovirus (Ad) vector encoding human BMP‐7 could be used to modify chondrocytes genetically to improve their capacity for cartilage repair. An adenovirus vector encoding BMP‐7 (AdBMP‐7) was constructed and its bioactivity confirmed by ectopic bone formation assay. AdBMP‐7 modification of bovine chondrocytes induced expression of BMP‐7 mRNA and bioactive protein, resulting in an increase in incorporation of 35SO  4− into proteoglycan, 3H‐proline uptake into protein, and the expression of the cartilage‐specific matrix genes, aggrecan and type II collagen. An in vitro model of chondrocyte transplantation was used to demonstrate the feasibility of using genetically modified chondrocytes to enhance formation of cartilage‐like tissue. When transplanted onto cartilage explants and maintained in vitro for 3 weeks, chondrocytes modified with AdBMP‐7 formed 1.9‐fold thicker tissue than chondrocytes modified with a control vector (P < 0.001). This tissue was positive for type II collagen and proteoglycan but negative for type X collagen and demonstrated a cartilage‐like morphology. These observations suggest that Ad‐mediated transfer of BMP‐7 gene to chondrocytes enhances the chondrocyte‐specific matrix synthesis and their capacity to form cartilage‐like tissue, thus representing a strategy that may improve cell‐based cartilage repair.

Biochemical and Biomechanical Properties of Lesion and Adjacent Articular Cartilage after Chondral Defect Repair in an Equine Model

Background Chondral defects may lead to degradative changes in the surrounding cartilage, predisposing patients to developing osteoarthritis. Purpose To quantify changes in the biomechanical and biochemical properties of the articular cartilage adjacent to chondral defects after experimental defect repair. Study Design Controlled laboratory study. Methods Specimens were harvested from tissue within (lesion), immediately adjacent to, and at a distance from (remote area) a full-thickness cartilage defect 8 months after cartilage repair with genetically modified chondrocytes expressing insulin-like growth factor-I or unmodified, control chondrocytes. Biomechanical properties, including instantaneous Youngs and equilibrium aggregate moduli, were determined by confined compression testing. Biochemical properties, such as water and proteoglycan content, were also measured. Results The instantaneous Youngs modulus, equilibrium modulus, and proteoglycan content increased, whereas water content decreased with increasing distance from the repaired lesion. The instantaneous Youngs and equilibrium moduli of the adjacent articular cartilage were 80% and 50% that of remote area samples, respectively, whereas water content increased 0.9% and proteoglycan content was decreased by 35%. No significant changes in biomechanical and biochemical properties were found either in the lesion tissue or in adjacent cartilage with genetic modification of the chondrocytes. Conclusion Articular cartilage adjacent to repaired chondral defects showed significant remodeling 8 months after chondral defect repair, regardless of whether genetically modified or unmodified cells were implanted. Clinical Relevance Changes in the biochemical and biomechanical properties of articular cartilage adjacent to repaired chondral defects may represent remodeling as part of an adaptive process or degeneration secondary to an altered distribution of joint forces. Quantification of these changes could provide important parameters for assessing progress after operative chondral defect repair.