A Rabbit Femoral Condyle Defect Model for Assessment of Osteochondral Tissue Regeneration

A rabbit osteochondral defect (OCD) model for evaluation of tissue engineered implants on their biosafety and efficacy in osteochondral repair

Osteochondral defect (OCD) is a common but challenging condition in orthopaedics that imposes huge socioeconomic burdens in our aging society. It is imperative to accelerate the R&D of regenerative scaffolds using osteochondral tissue engineering concepts. Yet, all innovative implant-based treatments require animal testing models to verify their feasibility, biosafety, and efficacy before proceeding to human trials. Rabbit models offer a more clinically relevant platform for studying OCD repair than smaller rodents, while being more cost-effective than large animal models. The core-decompression drilling technique to produce full-thickness distal medial femoral condyle defects in rabbits can mimic one of the trauma-relevant OCD models. This model is commonly used to evaluate the implant's biosafety and efficacy of osteochondral dual-lineage regeneration. In this article, we initially indicate the methodology and describe a minimally-invasive surgical protocol in a step-wise manner to generate a standard and reproducible rabbit OCD for scaffold implantation. Besides, we provide a detailed procedure for sample collection, processing, and evaluation by a series of subsequent standardized biochemical, radiological, biomechanical, and histological assessments. In conclusion, the well-established, easy-handling, reproducible, and reliable rabbit OCD model will play a pivotal role in translational research of osteochondral tissue engineering.

In vivo study of dual functionalized mussel-derived bioactive peptides promoting 3D-printed porous Ti6Al4V scaffolds for repair of rabbit femoral defects

The 3D printed porous titanium alloy scaffolds are beneficial to enhance angiogenesis, osteoblast adhesion, and promote osseointegration. However, titanium alloys are biologically inert, which makes the bond between the implant and bone tissue weak and prone to loosening. Inspired by the natural biological marine mussels, we designed four-claw-shaped mussel-derived bioactive peptides for the decoration of porous titanium alloy scaffolds: adhesion peptide-DOPA, anchoring peptide-RGD and osteogenic-inducing peptide-BMP-2. And the bifunctionalization of 3D-printed porous titanium alloy scaffolds was evaluated in vivo in a rabbit model of bone defect with excellent promotion of osseointegration and mechanical stability. Our results show that the in vivo osseointegration ability of the modified 3D printed porous titanium alloy test piece is significantly improved, and the bifunctional polypeptide coating group E has the strongest osseointegration ability. In conclusion, our experimental design partially solves the problems of stress shielding effect and biological inertness, and provides a convenient and feasible method for the clinical application of titanium alloy implants in biomedical implant materials.

A rabbit model to investigate temporomandibular joint osteochondral regeneration

OBJECTIVE

The objective of this study was 2-fold: (1) to describe the rabbit temporomandibular joint (TMJ) anatomy and (2) to provide a detailed, step-by-step description of a minimally invasive approach to perform a standard osteochondral TMJ defect that can be used to investigate the regenerative potential of biomaterials.

STUDY DESIGN

This study was performed in 2 steps. In the first, a total of 8 rabbit carcasses (n = 16 joints) were used to study the normal TMJ anatomy and histology to develop a minimally invasive approach to access the articulating surface of the condyle to perform a standard osteochondral defect. In the second, the surgical procedure was performed in 10 live animals to evaluate the feasibility of the model and to evaluate the regenerative potential of a biodegradable light-cured hydrogel seeded with stem cells (results not shown).

RESULTS

The cartilage of the mandibular condyle showed 4 layers: fibrous, proliferative, hypertrophic, and a zone of calcified cartilage. Positive safranin O staining was observed in the cartilage. The mean duration of the procedure (from incision to last stitch) was 35.5 (±9.21) minutes. All animals survived the procedures without any major complications.

CONCLUSIONS

This animal model represents an easy and nonmorbid surgical approach to rabbit TMJ.

Bilayered, peptide-biofunctionalized hydrogels for in vivo osteochondral tissue repair

Osteochondral defects present a unique clinical challenge due to their combination of phenotypically distinct cartilage and bone, which require specific, stratified biochemical cues for tissue regeneration. Furthermore, the articular cartilage exhibits significantly worse regeneration than bone due to its largely acellular and avascular nature, prompting significant demand for regenerative therapies. To address these clinical challenges, we have developed a bilayered, modular hydrogel system that enables the click functionalization of cartilage- and bone-specific biochemical cues to each layer. In this system, the crosslinker poly(glycolic acid)-poly(ethylene glycol)-poly(glycolic acid)-di(but-2-yne-1,4-dithiol) (PdBT) was click conjugated with either a cartilage- or bone-specific peptide sequence of interest, and then mixed with a suspension of thermoresponsive polymer and mesenchymal stem cells (MSCs) to generate tissue-specific, cell-encapsulated hydrogel layers targeting the cartilage or bone. We implanted bilayered hydrogels in rabbit femoral condyle defects and investigated the effects of tissue-specific peptide presentation and cell encapsulation on osteochondral tissue repair. After 12 weeks implantation, hydrogels with a chondrogenic peptide sequence produced higher histological measures of overall defect filling, cartilage surface regularity, glycosaminoglycan (GAG)/cell content of neocartilage and adjacent cartilage, and bone filling and bonding compared to non-chondrogenic hydrogels. Furthermore, MSC encapsulation promoted greater histological measures of overall defect filling, cartilage thickness, GAG/cell content of neocartilage, and bone filling. Our results establish the utility of this click functionalized hydrogel system for in vivo repair of the osteochondral unit. STATEMENT OF SIGNIFICANCE: Osteochondral repair requires mimicry of both cartilage- and bone-specific biochemical cues, which are highly distinct. While traditional constructs for osteochondral repair have mimicked gross compositional differences between the cartilage and bone in mineral content, mechanical properties, proteins, or cell types, few constructs have recapitulated the specific biochemical cues responsible for the differential development of cartilage and bone. In this study, click biofunctionalized, bilayered hydrogels produced stratified presentation of developmentally inspired peptide sequences for chondrogenesis and osteogenesis. This work represents, to the authors' knowledge, the first application of bioconjugation chemistry for the simultaneous repair of bone and cartilage tissue. The conjugation of tissue-specific peptide sequences successfully promoted development of both cartilage and bone tissues in vivo.

Orchestrated cellular, biochemical, and biomechanical optimizations endow platelet-rich plasma-based engineered cartilage with structural and biomechanical recovery

Recently, biomaterials for cartilage regeneration has been intensively investigated. However, the development of scaffolds that capture regenerated cartilage with biomechanical and structural recovery has rarely been reported. To address this challenge, platelet-rich plasma (PRP)-based cartilage constructs with a well-orchestrated symphony of cellular, biochemical and biomechanical elements were prepared by simultaneously employing chondrogenic progenitor cells (CPCs) as a cell source, optimizing platelet concentration, and adding an enzyme-ion activator. It was shown that this triple-optimized PRP + CPC construct possessed increased biomechanical properties and suitable biochemical signals. The following in vitro study demonstrated that the triple-optimized PRP + CPC constructs generated cartilage-like tissue with higher expression levels of chondrogenic-specific markers, more deposition of cartilage-specific extracellular matrix (ECM), and greater biomechanical values than those of the other constructs. Twelve weeks after the construct was implanted in a cartilage defect in vivo, histological analysis, qPCR, and biomechanical tests collectively showed that the triple-optimized constructs yielded a more chondrocyte-like cell phenotype with a higher synthesis of Col-II and aggrecan. More importantly, the triple-optimized constructs facilitated cartilage regeneration with better biomechanical recovery than that of the other constructs. These results demonstrate the efficacy of the triple-optimization strategy and highlight the simplicity and potency of this PRP + CPC construct for cartilage regeneration.

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Cartilage tissue engineering has been intensively investigated.

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We designed a PRP-based construct with favorable cell source, reinforced scaffold and appropriate biofactors.

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This designed construct can facilitate cartilage regeneration with biomechanical and structural recovery simultaneously.

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The favorable performance of the proposed scaffolds highlights the triple-optimization strategy to improve cartilage engineering.