Proposal for a New Histological Scoring System for Cartilage Repair

Auricular and laryngeal chondritis in nursery and finishing pigs

This work aimed to characterize the clinic-pathological presentation of an outbreak of auricular and laryngeal chondritis in pigs. Visits were made to pig farms, where the clinical history was obtained, and clinical and postmortem examinations were performed. In those farms, 3% to 4% of pigs presented otohematomas, which started in the nursery and extended to the finishing phase. Moreover, some finishing pigs presented with respiratory distress, initially characterized as inspiratory dyspnea, associated by an uncommon respiratory stridor and culminating in death. Grossly, nursery piglets had enlarged ears, and on the cut surface, the cartilage was fragmented and associated with blood clots. In the finishing phase, in addition to auricular lesions, the epiglottis and arytenoid cartilages were thickened and distorted, which partially occluded the lumen. Microscopically, the laryngeal and auricular cartilages were fragmented, displayed a loss of matrix basophilia, and were surrounded by lymphohistiocytic inflammatory infiltrate, with occasional multinucleated giant cells and fibrosis. The lesions exclusively affected elastic cartilages. The disease in finishing pigs led to increased mortality and was a differential diagnosis to respiratory challenges. It was not possible to determine the factor that triggered this condition; however, a nutritional association is suspected. To the authors' knowledge, this is the first report of primary auricular and laryngeal chondritis in pigs.

CHANGES IN ARTICULAR CARTILAGE OF THE HIP JOINT INDUCED BY ACETABULAR LABRUM DAMAGE

OBJECTIVE

The aim: Histological studies of hip joint cartilage after articular labrum resection.

PATIENTS AND METHODS

Materials and methods: Articular labrum of hip joint was excised in adult rabbits. In 1,5 and 4 months, the histology of the joint was studied. The condi¬tion of the cartilage after reverse fixation of labrum was separately investigated. The morphology of the joint was assessed according to the OARSI scale and morphometric measurements.

RESULTS

Results: The morphology of hip joint cartilage was changed after labrum resection including chondrocyte injury, cell heterogeneity and chondrocyte clus¬tering, less signs of fibrosis. Cartilage erosion was correlated with grade of OARSI scale, but not necessarily with cartilage thickness. The extracellular matrix / chondrocyte ratio was more significant indicator of cartilage condition than multipoint analysis of cartilage thickness.

CONCLUSION

Conclusions: Injury of acetabular labrum cause change morphology of joint cartilage, which observed in the dynamics. In animal model the cartilage injury scoring scales are more accurate in long term studies while early changes can be interpreted with limitations.

Tissue Engineering and Cell Therapy for Cartilage Repair: Preclinical Evaluation Methods

A chondral injury is a limiting disease that can affect the quality of life and be an economic burden due to the cost of immediate treatment and loss in work productivity. If left untreated, such an injury may progress to osteoarthritis, a degenerative and debilitating joint disease characterized by pain and functional impairment. Mesenchymal stromal cells (MSCs), which have immune-modulatory properties and the ability to differentiate into chondroblasts and osteoblasts, are a predictable source for the treatment of cartilage injuries. This article presents tools to evaluate cartilage restoration by tissue engineering and cell therapy treatment in a translational and preclinical large animal model. In this controlled experimental study with 14 miniature pigs, a scaffold-free tissue engineering construct (TEC) derived from dental pulp and synovial MSCs for cartilage therapy was tested. Total thickness cartilage defects were performed in both posterior knees. The defect was left empty in one of the knees, and the other received the TEC. The tissue repair was morphologically assessed by magnetic resonance imaging (MRI) using the three-dimensional double echo steady-state (3D-DESS) sequence, and compositional assessment was carried out based on the T2 mapping technique. The osteochondral specimens were fixed for histopathology, decalcified, subjected to standard histological processing, sectioned, and stained with hematoxylin and eosin. The sections stained for immunohistochemical detection of collagen types were digested with pepsin and chondroitinase and incubated with antibodies against them. The mechanical evaluation involved analysis of Young's modulus of the cartilage samples based on the indentation and maximum compression test. In addition, a finite element model was used to simulate and characterize properties of the osteochondral block. At 6 months after surgery, there were no complications with the animals and the MRI, histological, immunohistochemical, and biomechanical evaluations proved to be effective and qualified to differentiate good quality chondral repair from inadequate repair tissue. The proposed methods were feasible and capable to properly evaluate the defect filled with TEC containing stromal cells after 6 months of follow-up in a large animal model for articular cartilage restoration. Impact Statement Articular chondral injuries are prevalent and represent an economic burden due to the cost of treatment. The engineering of cartilage tissue can promote the repair of chondral injuries and is dependent on selecting appropriate cells and biocompatible frameworks. In this article, methods for evaluation of a scaffold-free cell delivery system made from mesenchymal stromal cells were present in a translational study that allows further clinical safety and efficacy trials.

Quality control methods in musculoskeletal tissue engineering: from imaging to biosensors

Tissue engineering is rapidly progressing toward clinical application. In the musculoskeletal field, there has been an increasing necessity for bone and cartilage replacement. Despite the promising translational potential of tissue engineering approaches, careful attention should be given to the quality of developed constructs to increase the real applicability to patients. After a general introduction to musculoskeletal tissue engineering, this narrative review aims to offer an overview of methods, starting from classical techniques, such as gene expression analysis and histology, to less common methods, such as Raman spectroscopy, microcomputed tomography, and biosensors, that can be employed to assess the quality of constructs in terms of viability, morphology, or matrix deposition. A particular emphasis is given to standards and good practices (GXP), which can be applicable in different sectors. Moreover, a classification of the methods into destructive, noninvasive, or conservative based on the possible further development of a preimplant quality monitoring system is proposed. Biosensors in musculoskeletal tissue engineering have not yet been used but have been proposed as a novel technology that can be exploited with numerous advantages, including minimal invasiveness, making them suitable for the development of preimplant quality control systems.

Effect of Pore Size on Cell Behavior Using Melt Electrowritten Scaffolds

Tissue engineering technology has made major advances with respect to the repair of injured tissues, for which scaffolds and cells are key factors. However, there are still some issues with respect to the relationship between scaffold and cell growth parameters, especially that between the pore size and cells. In this study, we prepared scaffolds with different pore sizes by melt electrowritten (MEW) and used bone marrow mensenchymal stem cells (BMSCs), chondrocytes (CCs), and tendon stem cells (TCs) to study the effect of the scaffold pore size on cell adhesion, proliferation, and differentiation. It was evident that different cells demonstrated different adhesion and proliferation rates on the scaffold. Furthermore, different cell types showed differential preferences for scaffold pore sizes, as evidenced by variations in cell viability. The pore size also affected the differentiation and gene expression pattern of cells. Among the tested cells, BMSCs exhibited the greatest viability on the 200-μm-pore-size scaffold, CCs on the 200- and 100-μm scaffold, and TCs on the 300-μm scaffold. The scaffolds with 100- and 200-μm pore sizes induced a significantly higher proliferation, chondrogenic gene expression, and cartilage-like matrix deposition after in vitro culture relative to the scaffolds with smaller or large pore sizes (especially 50 and 400 μm). Taken together, these results show that the architecture of 10 layers of MEW scaffolds for different tissues should be different and that the pore size is critical for the development of advanced tissue engineering strategies for tissue repair.

Development of injectable chitosan/biphasic calcium phosphate bone cement and in vitro and in vivo evaluation

Injectable biphasic calcium phosphate bone cements (BCPCs) composed of β-tricalcium phosphate (β-TCP) and hydroxyapatite (HA) have been intensively investigated because of their high rate of biodegradation, bioactivity and osteoconductivity, which can be adjusted by changing the ratio between β-TCP and HA phases after setting. The aim of this study was to evaluate the performance of 1 wt% chitosan fiber additive with biphasic calcium phosphate as an injectable bone cement both in vitro and in vivo. In vitro evaluation of compressive strength, degradation rate, morphology, and cell and alkaline phosphatase activities was done by comparison with bone cement without β-TCP. The in vivo results for micro-CT scanning and histological examinations for three groups (control, BCPC and commercial biphasic calcium phosphate granules) were characterized and compared. After the addition of 20 wt% β-TCP to calcium phosphate cement, the initial and final setting times of the sample were 3.92 min and 11.46 min, respectively, which were not significantly different from cement without β-TCP. The degradation time of the BCPC material was longer than that of calcium phosphate cement alone. The healing process was significantly faster for BCPC than for the control and commercial product groups. Therefore, this is the first evidence that BCPC is an attractive option for bone surgery due to its faster stimulation of healing and faster degradation rate.