An arthroscopic device to assess articular cartilage defects and treatment with a hydrogel

Hydrogel-Guided, rAAV-Mediated IGF-I Overexpression Enables Long-Term Cartilage Repair and Protection against Perifocal Osteoarthritis in a Large-Animal Full-Thickness Chondral Defect Model at One Year In Vivo

The regeneration of focal articular cartilage defects is complicated by the reduced quality of the repair tissue and the potential development of perifocal osteoarthritis (OA). Biomaterial-guided gene therapy may enhance cartilage repair by controlling the release of therapeutic sequences in a spatiotemporal manner. Here, the benefits of delivering a recombinant adeno-associated virus (rAAV) vector coding for the human insulin-like growth factor I (IGF-I) via an alginate hydrogel (IGF-I/AlgPH155) to enhance repair of full-thickness chondral defects following microfracture surgery after one year in minipigs versus control (lacZ/AlgPH155) treatment are reported. Sustained IGF-I overexpression is significantly achieved in the repair tissue of defects treated with IGF-I/AlgPH155 versus those receiving lacZ/AlgPH155 for one year and in the cartilage surrounding the defects. Administration of IGF-I/AlgPH155 significantly improves parameters of cartilage repair at one year relative to lacZ/AlgPH155 (semiquantitative total histological score, cell densities, matrix deposition) without deleterious or immune reactions. Remarkably, delivery of IGF-I/AlgPH155 also significantly reduces perifocal OA and inflammation after one year versus lacZ/AlgPH155 treatment. Biomaterial-guided rAAV gene transfer represents a valuable clinical approach to promote cartilage repair and to protect against OA.

Mechanism research on a bioactive resveratrol- PLA-gelatin porous nano-scaffold in promoting the repair of cartilage defect

BACKGROUND

Articular cartilage defects are difficult to treat, but drug-loaded tissue engineering scaffolds provide a possible treatment option for these types of injuries.

PURPOSE

In this study, we designed a bioactive resveratrol-PLA-gelatin porous nano-scaffold using electrospinning, freeze drying, and uniform dispersion techniques to repair articular cartilage defects, and then investigated the possible mechanism behind the successful repair.

METHODS

We established an articular cartilage defect rat model with a 2 mm diameter wound in the middle of the knee joint femoral condyle non-weight-bearing area, with a depth reaching the full thickness of the subchondral bone. Postmodel specimens and micro computed tomography (CT) were used to observe any macroscopic morphological changes in the articular cartilage and subchondral bone, whereas multiple staining methods were used to observe all microcosmic morphological changes. Gross scores and Mankin scores were used to evaluate the repair condition. Immunohistochemical staining was employed to detect protein expression.

RESULTS

When the repair included the resveratrol-PLA-gelatin porous nano-scaffold, the repaired cartilage and subchondral bone were in better condition. The expression levels of SIRT1, type II collagen, and PI3K/AKT signaling pathway-related proteins (AKT, VEGF, PTEN, Caspase 9, and MMP13) changed significantly. The expression levels of SIRT1,AKT and type II collagen proteins increased significantly, while the expression levels of VEGF, PTEN, Caspase9 and MMP13 proteins decreased significantly compared with the repair included blank porous PLA-gelatin nano-scaffold and without scaffold.

CONCLUSION

We designed a bioactive resveratrol-PLA-gelatin porous nano-scaffold with better performance, which promoted the repair of cartilage injury as a whole, and explained its possible mechanism in accelerating cartilage repair via the PI3K/AKT signaling pathway.

Injectable and 3D Bioprinted Polysaccharide Hydrogels: From Cartilage to Osteochondral Tissue Engineering

Biomechanical performance of functional cartilage is executed by the exclusive anisotropic composition and spatially varying intricate architecture in articulating ends of diarthrodial joint. Osteochondral tissue constituting the articulating ends comprise superfical soft cartilage over hard subchondral bone sandwiching interfacial soft-hard tissue. The shock-absorbent, lubricating property of cartilage and mechanical stability of subchondral bone regions are rendered by extended chemical structure of glycosaminoglycans and mineral deposition, respectively. Extracellular matrix glycosaminoglycans analogous polysaccharides are major class of hydrogels investigated for restoration of functional cartilage. Recently, injectable hydrogels have gained momentum as it offers patient compliance, tunable mechanical properties, cell deliverability, and facile administration at physiological condition with long-term functionality and hyaline cartilage construction. Interestingly, facile modifiable functional groups in carbohydrate polymers impart tailorability of desired physicochemical properties and versatile injectable chemistry for the development of highly potent biomimetic in situ forming scaffold. The scaffold design strategies have also evolved from single component to bi- or multilayered and graded constructs with osteogenic properties for deep subchondral regeneration. This review highlights the significance of polysaccharide structure-based functions in engineering cartilage tissue, injectable chemistries, strategies for combining analogous matrices with cells/stem cells and biomolecules and multicomponent approaches for osteochondral mimetic constructs. Further, the rheology and precise spatiotemporal positioning of cells in hydrogel bioink for rapid prototyping of complex three-dimensional anisotropic cartilage have also been discussed.

Effects of gamma and e-beam sterilization on the chemical, mechanical and tribological properties of a novel hydrogel

Hydrogels are known to possess cartilage-like mechanical and lubrication properties; however, hydrogel sterilization is challenging. Cyborgel(™), a proprietary hydrogel, is intended for use as a cartilage replacement implant. This study evaluated the effect of 30-35 kGy e-beam and gamma radiation on the polymer swell ratio, and the mechanical, chemical and tribological behavior of this hydrogel. Three different formulations were mechanically tested, and material parameters were identified using finite element analysis. FTIR spectroscopy was used to investigate chemical changes. Wear test was carried out for 2 million cycles in bovine serum, followed by 2 million cycles in distilled water. No significant difference was found in the swell ratio, mechanical and tribological properties of control hydrogel samples and those exposed to e-beam or gamma radiation; however, chemical spectra of e-beam sterilized samples revealed minor changes, which were absent in unsterilized and gamma sterilized samples.

Advancing regenerative surgery in orthopaedic sports medicine: the critical role of the surgeon

The constant desire to improve outcomes in orthopaedic sports medicine requires us to continuously consider the challenges faced in the surgical repair or reconstruction of soft tissue and cartilaginous injury. In many cases, surgical efforts targeted at restoring normal anatomy and functional status are ultimately impaired by the biological aspect of the natural history of these injuries, which acts as an obstacle to a satisfactory repair process after surgery. The clinical management of sports injuries and the delivery of appropriate surgical intervention are continuously evolving, and it is likely that the principles of regenerative medicine will have an increasing effect in this specialized field of orthopaedic practice going forward. Ongoing advances in arthroscopy and related surgical techniques should facilitate this process. In contrast to the concept of engineered replacement of entire tissues, it is probable that the earliest effect of regenerative strategies seen in clinical practice will involve biological augmentation of current operative techniques via a synergistic process that might be best considered "regenerative surgery." This article provides an overview of the principles of regenerative surgery in cartilage repair and related areas of orthopaedic surgery sports medicine. The possibilities and challenges of a gradual yet potential paradigm shift in treatment through the increased use of biological augmentation are considered. The translational process and critical role to be played by the specialist surgeon are also addressed. We conclude that increased understanding of the potential and challenges of regenerative surgery should allow those specializing in orthopaedic surgery sports medicine to lead the way in advancing the frontiers of biological strategies to enhance modern clinical care in an evidence-based manner.

Friction coefficients for mechanically damaged bovine articular cartilage

We used a pin-on-disc tribometer to measure the friction coefficient of both pristine and mechanically damaged cartilage samples in the presence of different lubricant solutions. The experimental set up maximizes the lubrication mechanism due to interstitial fluid pressurization. In phosphate buffer solution (PBS), the measured friction coefficient increases with the level of damage. The main result is that when poly(ethylene oxide) (PEO) or hyaluronic acid (HA) are dissolved in PBS, or when synovial fluid (SF) is used as lubricant, the friction coefficients measured for damaged cartilage samples are only slightly larger than those obtained for pristine cartilage samples, indicating that the surface damage is in part alleviated by the presence of the various lubricants. Among the lubricants considered, 100 mg/mL of 100,000 Da MW PEO in PBS appears to be as effective as SF. We attempted to discriminate the lubrication mechanism enhanced by the various compounds. The lubricants viscosity was measured at shear rates comparable to those employed in the friction experiments, and a quartz crystal microbalance with dissipation monitoring was used to study the adsorption of PEO, HA, and SF components on collagen type II adlayers pre-formed on hydroxyapatite. Under the shear rates considered the viscosity of SF is slightly larger than that of PBS, but lower than that of lubricant formulations containing HA or PEO. Neither PEO nor HA showed strong adsorption on collagen adlayers, while evidence of adsorption was found for SF. Combined, these results suggest that synovial fluid is likely to enhance boundary lubrication. It is possible that all three formulations enhance lubrication via the interstitial fluid pressurization mechanism, maximized by the experimental set up adopted in our friction tests.