Perspectives on Animal Models Utilized for the Research and Development of Regenerative Therapies for Articular Cartilage

Mesenchymal stem cells for osteoarthritis: Recent advances in related cell therapy

Osteoarthritis (OA) is a degenerative joint disease that affects the entire joint and has been a huge burden on the health care system worldwide. Although traditional therapy and targeted cartilage cell therapy have made significant progress in the treatment of OA and cartilage regeneration, there are still many problems. Mesenchymal stem cells from various tissues are the most studied cell type and have been used in preclinical and clinical studies of OA, because they are more widely available, have a greater capacity for in vitro expansion, and have anti-inflammatory and immunomodulatory properties compared to autologous chondrocytes. This article will systematically review the latest developments in these areas. It may provide new insights for improving OA and cartilage regeneration.

A New Bioactive Fibrin Formulation Provided Superior Cartilage Regeneration in a Caprine Model

The effective and long-term treatment of cartilage defects is an unmet need among patients worldwide. In the past, several synthetic and natural biomaterials have been designed to support functional articular cartilage formation. However, they have mostly failed to enhance the terminal stage of chondrogenic differentiation, leading to scar tissue formation after the operation. Growth factors substantially regulate cartilage regeneration by acting on receptors to trigger intracellular signaling and cell recruitment for tissue regeneration. In this study, we investigated the effect of recombinant insulin-like growth factor 1 (rIGF-1), loaded in fibrin microbeads (FibIGF1), on cartilage regeneration. rIGF-1-loaded fibrin microbeads were injected into full-thickness cartilage defects in the knees of goats. The stability, integration, and quality of tissue repair were evaluated at 1 and 6 months by gross morphology, histology, and collagen type II staining. The in vivo results showed that compared to plain fibrin samples, particularly at 6 months, FibIGF1 improved the functional cartilage formation, confirmed through gross morphology, histology, and collagen type II immunostaining. FibIGF1 could be a promising candidate for cartilage repair in the clinic.

A guide to preclinical evaluation of hydrogel-based devices for treatment of cartilage lesions

The drive to develop cartilage implants for the treatment of major defects in the musculoskeletal system has resulted in a major research thrust towards developing biomaterial devices for cartilage repair. Investigational devices for the restoration of articular cartilage are considered as significant risk materials by regulatory bodies and therefore proof of efficacy and safety prior to clinical testing represents a critical phase of the multidisciplinary effort to bridge the gap between bench and bedside. To date, review articles have thoroughly covered different scientific facets of cartilage engineering paradigm, but surprisingly, little attention has been given to the preclinical considerations revolving around the validation of a biomaterial implant. Considering hydrogel-based cartilage products as an example, the present review endeavors to provide a summary of the critical prerequisites that such devices should meet for cartilage repair, for successful implantation and subsequent preclinical validation prior to clinical trials. Considerations pertaining to the choice of appropriate animal model, characterization techniques for the quantitative and qualitative outcome measures, as well as concerns with respect to GLP practices are also extensively discussed. This article is not meant to provide a systematic review, but rather to introduce a device validation-based roadmap to the academic investigator, in anticipation of future healthcare commercialization. STATEMENT OF SIGNIFICANCE: There are significant challenges around translation of in vitro cartilage repair strategies to approved therapies. New biomaterial-based devices must undergo exhaustive investigations to ensure their safety and efficacy prior to clinical trials. These considerations are required to be applied from early developmental stages. Although there are numerous research works on cartilage devices and their in vivo evaluations, little attention has been given into the preclinical pathway and the corresponding approval processes. With a focus on hydrogel devices to concretely illustrate the preclinical path, this review paper intends to highlight the various considerations regarding the preclinical validation of hydrogel devices for cartilage repair, from regulatory considerations, to implantation strategies, device performance aspects and characterizations.

Tissue Engineering for Tracheal Replacement: Strategies and Challenges

The critical feature in trachea replacement is to provide a hollow cylindrical framework that is laterally stable and longitudinally flexible, facilitating cartilage and epithelial tissue formation. Despite advanced techniques and sources of materials used, most inherent challenges are related to the complexity of its anatomy. Limited blood supply leads to insufficient regenerative capacity for cartilage and epithelium. Natural and synthetic scaffolds, different types of cells, and growth factors are part of tissue engineering approaches with varying outcomes. Pre-vascularization remains one of the crucial factors to expedite the regenerative process in tracheal reconstruction. This review discusses the challenges and strategies used in tracheal tissue engineering, focusing on scaffold implantation in clinical and preclinical studies conducted in recent decades.

Evaluation of Tissue Engineering Approaches for Intervertebral Disc Regeneration in Relevant Animal Models

Translation of tissue engineering strategies for the regeneration of intervertebral disc (IVD) requires a strong understanding of pathophysiology through the relevant animal model. There is no relevant animal model due to differences in disc anatomy, cellular composition, extracellular matrix components, disc physiology, and mechanical strength from humans. However, available animal models if used correctly could provide clinically relevant information for the translation into humans. In this review, we have investigated different types of strategies for the development of clinically relevant animal models to study biomaterials, cells, biomolecular or their combination in developing tissue engineering-based treatment strategies. Tissue engineering strategies that utilize various animal models for IVD regeneration are summarized and outcomes have been discussed. The understanding of animal models for the validation of regenerative approaches is employed to understand and treat the pathophysiology of degenerative disc disease (DDD) before proceeding for human trials. These animal models play an important role in building a therapeutic regime for IVD tissue regeneration, which can serve as a platform for clinical applications.

Thoughts on cartilage tissue engineering: A 21st century perspective

In mature individuals, hyaline cartilage demonstrates a poor intrinsic capacity for repair, thus even minor defects could result in progressive degeneration, impeding quality of life. Although numerous attempts have been made over the past years for the advancement of effective treatments, significant challenges still remain regarding the translation of in vitro cartilage engineering strategies from bench to bedside. This paper reviews the latest concepts on engineering cartilage tissue in view of biomaterial scaffolds, tissue biofabrication, mechanobiology, as well as preclinical studies in different animal models. The current work is not meant to provide a methodical review, rather a perspective of where the field is currently focusing and what are the requirements for bridging the gap between laboratory-based research and clinical applications, in light of the current state-of-the-art literature. While remarkable progress has been accomplished over the last 20 years, the current sophisticated strategies have reached their limit to further enhance healthcare outcomes. Considering a clinical aspect together with expertise in mechanobiology, biomaterial science and biofabrication methods, will aid to deal with the current challenges and will present a milestone for the furtherance of functional cartilage engineering.

Comparative anatomy and morphology of the knee in translational models for articular cartilage disorders. Part I: Large animals

BACKGROUND

The human knee is a complex joint, and affected by a variety of articular cartilage disorders. Large animal models are critical to model the complex disease mechanisms affecting a functional joint. Species-dependent differences highly affect the results of a pre-clinical study and need to be considered, necessitating specific knowledge not only of macroscopic and microscopic anatomical and pathological aspects, but also characteristics of their individual gait and joint movements.

METHODS

Literature search in Pubmed.

RESULTS AND DISCUSSION

This narrative review summarizes the most relevant anatomical structural and functional characteristics of the knee (stifle) joints of the major translational large animal species, comprising dogs, (mini)pigs, sheep, goats, and horses in comparison with humans. Specific characteristics of each species, including kinematical gait parameters are provided. Considering these multifactorial dimensions will allow to select the appropriate model for answering the research questions in a clinically relevant fashion.

Mapping molecular landmarks of human skeletal ontogeny and pluripotent stem cell-derived articular chondrocytes

Tissue-specific gene expression defines cellular identity and function, but knowledge of early human development is limited, hampering application of cell-based therapies. Here we profiled 5 distinct cell types at a single fetal stage, as well as chondrocytes at 4 stages in vivo and 2 stages during in vitro differentiation. Network analysis delineated five tissue-specific gene modules; these modules and chromatin state analysis defined broad similarities in gene expression during cartilage specification and maturation in vitro and in vivo, including early expression and progressive silencing of muscle- and bone-specific genes. Finally, ontogenetic analysis of freshly isolated and pluripotent stem cell-derived articular chondrocytes identified that integrin alpha 4 defines 2 subsets of functionally and molecularly distinct chondrocytes characterized by their gene expression, osteochondral potential in vitro and proliferative signature in vivo. These analyses provide new insight into human musculoskeletal development and provide an essential comparative resource for disease modeling and regenerative medicine.