Transplantation of a Scaffold-Free Cartilage Tissue Analogue for the Treatment of Physeal Cartilage Injury of the Proximal Tibia in Rabbits

Enlightenment of Growth Plate Regeneration Based on Cartilage Repair Theory: A Review

The growth plate (GP) is a cartilaginous region situated between the epiphysis and metaphysis at the end of the immature long bone, which is susceptible to mechanical damage because of its vulnerable structure. Due to the limited regeneration ability of the GP, current clinical treatment strategies (e.g., bone bridge resection and fat engraftment) always result in bone bridge formation, which will cause length discrepancy and angular deformity, thus making satisfactory outcomes difficult to achieve. The introduction of cartilage repair theory and cartilage tissue engineering technology may encourage novel therapeutic approaches for GP repair using tissue engineered GPs, including biocompatible scaffolds incorporated with appropriate seed cells and growth factors. In this review, we summarize the physiological structure of GPs, the pathological process, and repair phases of GP injuries, placing greater emphasis on advanced tissue engineering strategies for GP repair. Furthermore, we also propose that three-dimensional printing technology will play a significant role in this field in the future given its advantage of bionic replication of complex structures. We predict that tissue engineering strategies will offer a significant alternative to the management of GP injuries.

Update on premature physeal closure. Diagnosis and treatment

PURPOSE OF REVIEW

Premature Physeal Closure (PPC) is the most common consequence of a mostly posttraumatic, physeal injury. They are of utmost importance because they can significantly alter physeal function and lead to disorders such as limb length discrepancies and angular deformities.

RECENT FINDINGS

The type of physeal fracture has not demonstrated a solid predictive value in the formation of PPC, especially in the knee where almost any type of fracture can produce it. The detection of physeal damage with imaging tests (simple radiology and MRI) is very accurate; however, their predictive capacity to foretell which injury will generate a physeal bridge is still poor. For this reason, it is not advisable to make surgical decisions at the first medical assessment. Direct surgical management of PPC's (resection-interposition technique) has generally shown high unpredictability. Nevertheless, the latest interposition materials (chondrocytes and mesenchymal stem cells) showed promising results.

SUMMARY

PPC is an often devastating consequence of physeal injury and as such deserves further research. To date little is known about etiopathogenesis, risk factors and natural history among other aspects. Until direct surgery offers more consistent results, acute osteotomies and bone distraction for progressive correction continue to be the most widespread treatments for PPCs.

[Experimental study on reconstruction of anterior labrum of shoulder joint by chemical extraction of allogeneic tendon and allogeneic chondrocytes]

OBJECTIVE

To study the effect of chemical extraction of allogeneic tendon and allogeneic chondrocytes for reconstruction of anterior labrum of shoulder joint in rabbits.

METHODS

The body weight of 45 adult New Zealand white rabbits ranged from 2.5 to 3.0 kg. The Achilles tendons of 15 rabbits were taken and the allogeneic tendons were prepared by chemical extraction with antigen inactivation. The extracted tendons were compared with untreated tendons by HE and Masson stainings. Chondrocytes were isolated and cultured by trypsin method and identified by immunohistochemical staining of collagen type Ⅱ. The remaining 30 rabbits were used to prepare the model of anterior labrum defect of shoulder joint. After the allogeneic tendon was transplanted to the damaged labrum, the rabbits was randomly divided into two groups (15 in each group). In group A, the allogeneic chondrocytes were injected into the joint immediately after transplantation, while in group B, no treatment was made. At 4, 6, and 8 weeks after operation, 5 transplanted tendons of each group were taken. After general observation, HE staining was used to observe the number of nuclei, Masson staining was used to observe the expression of collagen fibers in muscle fiber tissues, and AB staining was used to detect the glycosaminoglycan level after transplantation, to evaluate the cell growth in the tissues of the two groups of allogeneic tendon.

RESULTS

By HE and Masson stainings, the allogeneic tendon antigen prepared by chemical extraction method was inactivated and the fibrous tissue structure was intact; collagen type Ⅱ immunohisto-chemistry staining showed that the cultured cells were chondrocytes. After tendon transplantation, the content of glycosaminoglycan in group A was significantly higher than that in group B ( P<0.05). At 6 weeks after operation, HE staining showed that the nuclear in tendon tissue of group A was significantly more than that of group B ( t=20.043, P=0.000). Masson staining showed that the number of nuclei in tendon tissue of group A was significantly increased, the muscle fibers and collagen fibers were interlaced, the tissue structure was more compact, and the tendon tissue was mainly blue stained; while the number of nuclei in group B was less, mainly collagen fibers of the original graft.

CONCLUSION

The allogeneic tendon inactivated by chemical extraction can be used to reconstruct the defect of anterior labrum of shoulder joint in rabbits, and the combination of allogeneic chondrocytes can promote the healing of tendon transplantation.

Progress in Articular Cartilage Tissue Engineering: A Review on Therapeutic Cells and Macromolecular Scaffolds

Repair and regeneration of articular cartilage lesions have always been a major challenge in the medical field due to its peculiar structure (e.g., sparsely distributed chondrocytes, no blood supply, no nerves). Articular cartilage tissue engineering is considered as one promising strategy to achieve reconstruction of cartilage. With this perspective, the articular cartilage tissue engineering has been widely studied. Here, the recent progress of articular cartilage tissue engineering is reviewed. The ad hoc therapeutic cells and growth factors for cartilage regeneration are summarized and discussed. Various types of bio/macromolecular scaffolds together with their pros and cons are also reviewed and elaborated.

Physeal bridges: causes, diagnosis, characterization and post-treatment imaging

The cartilaginous primary physis, or growth plate, at the end of long bones in children allows for longitudinal bone growth. A variety of insults to the physis can lead to physeal bridge formation, which in turn can lead to limb-shortening and angular deformities. This paper begins with a description of the causes, risk factors and mechanisms by which bridges form. Then it reviews the use of imaging in the diagnosis and characterization of bridges and in the evaluation of treatment and post-treatment complications. It is important for radiologists taking care of children to be aware of the indirect and direct imaging findings of physeal bridges to aid in their diagnosis, to be able to characterize bridges as part of preoperative planning, and to know the imaging finding of post-resection complications.

Rabbit Model of Physeal Injury for the Evaluation of Regenerative Medicine Approaches

Physeal injuries can lead to bony repair tissue formation, known as a bony bar. This can result in growth arrest or angular deformity, which is devastating for children who have not yet reached their full height. Current clinical treatment involves resecting the bony bar and replacing it with a fat graft to prevent further bone formation and growth disturbance, but these treatments frequently fail to do so and require additional interventions. Novel treatments that could prevent bone formation but also regenerate the injured physeal cartilage and restore normal bone elongation are warranted. To test the efficacy of these treatments, animal models that emulate human physeal injury are necessary. The rabbit model of physeal injury quickly establishes a bony bar, which can then be resected to test new treatments. Although numerous rabbit models have been reported, they vary in terms of size and location of the injury, tools used to create the injury, and methods to assess the repair tissue, making comparisons between studies difficult. The study presented here provides a detailed method to create a rabbit model of proximal tibia physeal injury using a two-stage procedure. The first procedure involves unilateral removal of 25% of the physis in a 6-week-old New Zealand white rabbit. This consistently leads to a bony bar, significant limb length discrepancy, and angular deformity within 3 weeks. The second surgical procedure involves bony bar resection and treatment. In this study, we tested the implantation of a fat graft and a photopolymerizable hydrogel as a proof of concept that injectable materials could be delivered into this type of injury. At 8 weeks post-treatment, we measured limb length, tibial angle, and performed imaging and histology of the repair tissue. By providing a detailed, easy to reproduce methodology to perform the physeal injury and test novel treatments after bony bar resection, comparisons between studies can be made and facilitate translation of promising therapies toward clinical use. Impact Statement This study provides details to create a rabbit model of physeal injury that can facilitate comparisons between studies and test novel regenerative medicine approaches. Furthermore, this model mimics the human, clinical situation that requires a bony bar resection followed by treatment. In addition, identification of a suitable treatment can be seen in the correction of the growth deformity, allowing this model to facilitate the development of novel physeal cartilage regenerative medicine approaches.

Allogenic Tendon-Autologous Cartilage Cells Transplantation Enhances Adhesive/Growth Ability and Promotes Chondrogenesis in a Rabbit Model of Glenoid Labrum Damage

Background

Glenoid labrum injury of the shoulder commonly occurs in athletes, especially those who perform throwing motions. This study investigated the effects of the established allogenic tendon-autologous cartilage cells reconstruction approach in a rabbit model of glenoid labrum damage.

Material/Methods

The allogenic tendons were isolated and extracted using the chemical extraction method. Cartilage cells were isolated from New Zealand rabbits and identified by detecting type II collagenase. The allogenic tendon-autologous cartilage cells were transplanted to the damaged glenoid labrum. HE staining was used to observe inflammatory cells, Masson staining was used to observe muscle fibers, and scanning electron microscopy (SEM) was used to assess antigenicity of tendon tissues. PSA and AB staining were used to examine neutral protein mucopolysaccharide and acidic protein mucopolysaccharide, respectively. We assessed cartilage cell growth in autologous cartilage cells combined with allogenic tendon transplanted tissues.

Results

Allogenic tendons were well prepared using chemical extraction method due to use of HE staining, Masson staining, and SEM. TGF-β1 treatment induced cartilage cell formation and triggered expression of acidic and neutral protein mucopolysaccharides. HE staining, Masson staining, PAS staining, and AB staining methods showed that autologous cartilage cells combined with allogenic tendon transplanted tissues had better growth of cartilage cells.

Conclusions

This study establishes the allogenic tendon-autologous cartilage cells reconstruction and transplantation approach and illustrated higher adhesive ability and growth ability, and better chondrogenesis in a rabbit model of glenoid labrum damage.

Repair potential of nonsurgically delivered induced pluripotent stem cell-derived chondrocytes in a rat osteochondral defect model

Human induced pluripotent stem cells (hiPSCs) are thought to be an alternative cell source for future regenerative medicine. hiPSCs may allow unlimited production of cell types that have low turnover rates and are difficult to obtain such as autologous chondrocytes. In this study, we generated hiPSC-derived chondrogenic pellets, and chondrocytes were isolated. To confirm the curative effects, chondrogenic pellets and isolated chondrocytes were transplanted into rat joints with osteochondral defects. Isolated hiPSC-derived chondrocytes were delivered in the defect by a single intra-articular injection. The generated hiPSC-derived chondrogenic pellets had increased chondrogenic marker expression and accumulated extracellular matrix proteins. Chondrocytes were successfully isolated from the pellets. Alcian blue staining and collagen type II were detected in the cells. Chondrogenic marker expression was also increased in the isolated cells. Transplanted chondrogenic pellets and chondrocytes both had curative effects in the osteochondral defect rat model. Detection of human proteins in the joints proved that the cells were successfully delivered into the defect. Chondrogenic pellets or chondrocytes generated from hiPSCs have potential as regenerative medicine for cartilage recovery or regeneration. Chondrocytes isolated from hiPSC-derived chondrogenic pellets had curative effects in damaged cartilage. Injectable hiPSC-derived chondrocytes show the possibility of noninvasive delivery of regenerative medicine for cartilage recovery.

Hydrogels for Cartilage Regeneration, from Polysaccharides to Hybrids

The aims of this paper are: (1) to review the current state of the art in the field of cartilage substitution and regeneration; (2) to examine the patented biomaterials being used in preclinical and clinical stages; (3) to explore the potential of polymeric hydrogels for these applications and the reasons that hinder their clinical success. The studies about hydrogels used as potential biomaterials selected for this review are divided into the two major trends in tissue engineering: (1) the use of cell-free biomaterials; and (2) the use of cell seeded biomaterials. Preparation techniques and resulting hydrogel properties are also reviewed. More recent proposals, based on the combination of different polymers and the hybridization process to improve the properties of these materials, are also reviewed. The combination of elements such as scaffolds (cellular solids), matrices (hydrogel-based), growth factors and mechanical stimuli is needed to optimize properties of the required materials in order to facilitate tissue formation, cartilage regeneration and final clinical application. Polymer combinations and hybrids are the most promising materials for this application. Hybrid scaffolds may maximize cell growth and local tissue integration by forming cartilage-like tissue with biomimetic features.

A Rat Tibial Growth Plate Injury Model to Characterize Repair Mechanisms and Evaluate Growth Plate Regeneration Strategies

A third of all pediatric fractures involve the growth plate and can result in impaired bone growth. The growth plate (or physis) is cartilage tissue found at the end of all long bones in children that is responsible for longitudinal bone growth. Once damaged, cartilage tissue within the growth plate can undergo premature ossification and lead to unwanted bony repair tissue, which forms a "bony bar." In some cases, this bony bar can result in bone growth deformities, such as angular deformities, or it can completely halt longitudinal bone growth. There is currently no clinical treatment that can fully repair an injured growth plate. Using an animal model of growth plate injury to better understand the mechanisms underlying bony bar formation and to identify ways to inhibit it is a great opportunity to develop better treatments for growth plate injuries. This protocol describes how to disrupt the rat proximal tibial growth plate using a drill-hole defect. This small animal model reliably produces a bony bar and can result in growth deformities similar to those seen in children. This model allows for investigation into the molecular mechanisms of bony bar formation and serves as a means to test potential treatment options for growth plate injuries.