Endogenous regeneration of critical-size chondral defects in immunocompromised rat xiphoid cartilage using decellularized human bone matrix scaffolds

Engraftment of allogeneic iPS cell-derived cartilage organoid in a primate model of articular cartilage defect

Induced pluripotent stem cells (iPSCs) are a promising resource for allogeneic cartilage transplantation to treat articular cartilage defects that do not heal spontaneously and often progress to debilitating conditions, such as osteoarthritis. However, to the best of our knowledge, allogeneic cartilage transplantation into primate models has never been assessed. Here, we show that allogeneic iPSC-derived cartilage organoids survive and integrate as well as are remodeled as articular cartilage in a primate model of chondral defects in the knee joints. Histological analysis revealed that allogeneic iPSC-derived cartilage organoids in chondral defects elicited no immune reaction and directly contributed to tissue repair for at least four months. iPSC-derived cartilage organoids integrated with the host native articular cartilage and prevented degeneration of the surrounding cartilage. Single-cell RNA-sequence analysis indicated that iPSC-derived cartilage organoids differentiated after transplantation, acquiring expression of PRG4 crucial for joint lubrication. Pathway analysis suggested the involvement of SIK3 inactivation. Our study outcomes suggest that allogeneic transplantation of iPSC-derived cartilage organoids may be clinically applicable for the treatment of patients with chondral defects of the articular cartilage; however further assessment of functional recovery long term after load bearing injuries is required.

Deer antler extract potentially facilitates xiphoid cartilage growth and regeneration and prevents inflammatory susceptibility by regulating multiple functional genes

BACKGROUND

Deer antler is a zoological exception due to its fantastic characteristics, including amazing growth rate and repeatable regeneration. Deer antler has been used as a key ingredient in traditional Chinese medicine relating to kidney and bone health for centuries. The aim of this study was to dissect the molecular regulation of deer antler extract (DAE) on xiphoid cartilage (XC).

METHODS

The DAE used in this experiment was same as the one that was prepared as previously described. The specific pathogen-free (SPF) grade Sprague-Dawley (SD) rats were randomly divided into blank group (n =10) and DAE group (n =10) after 1-week adaptive feeding. The DAE used in this experiment was same as the one that was prepared as previously described. The rats in DAE group were fed with DAE for 3 weeks at a dose of 0.2 g/kg per day according to the body surface area normalization method, and the rats in blank group were fed with drinking water. Total RNA was extracted from XC located in the most distal edge of the sternum. Illumina RNA sequencing (RNA-seq) in combination with quantitative real-time polymerase chain reaction (qRT-PCR) validation assay was carried out to dissect the molecular regulation of DAE on XC.

RESULTS

We demonstrated that DAE significantly increased the expression levels of DEGs involved in cartilage growth and regeneration, but decreased the expression levels of DEGs involved in inflammation, and mildly increased the expression levels of DEGs involved in chondrogenesis and chondrocyte proliferation.

CONCLUSIONS

Our findings suggest that DAE might serve as a complementary therapeutic regent for cartilage growth and regeneration to treat cartilage degenerative disease, such as osteoarthritis.

Automated MicroCT-based bone and articular cartilage analysis using iterative shape averaging and atlas-based registration

Micro-computed tomography (μCT) and contrast-enhanced μCT are important tools for preclinical analysis of bone and articular cartilage (AC). Quantitative data from these modalities is highly dependent on the accuracy of tissue segmentations, which are often obtained via time-consuming manual contouring and are prone to inter- and intra-observer variability. Automated segmentation strategies could mitigate these issues, but few such approaches have been described in the context of μCT. Here, we validated a fully-automated strategy for bone and AC segmentation based on registration of an average tissue atlas. Femora from healthy and arthritic rats underwent μCT scanning, and epiphyseal trabecular bone and AC volumes were manually contoured by an expert. Average tissue atlases composed of 1, 3, 5, 10 and 20 pre-contoured training images (n = 10 atlases/group) were generated using iterative shape averaging and registered onto unknown images via affine and non-rigid registration. Atlas-based and expert-defined volumes for bone and AC were compared in terms of shape-based similarity metrics, as well as morphometric and densitometric parameters. Our results demonstrate that atlas-based registrations were capable of highly accurate and consistent segmentation. Atlases built from as few as 3 training images had no incidence of mal-registration and exhibited improved incidence of accurate registration, and higher sensitivity and specificity compared to atlases built from only one training image. Atlas-based segmentation of bone and AC from μCT images is a robust and accurate alternative to manual tissue segmentation, enabling faster, more consistent segmentation of pre-clinical datasets.

Contrast enhanced computed tomography for real-time quantification of glycosaminoglycans in cartilage tissue engineered constructs

Tissue engineering and regenerative medicine are two therapeutic strategies to treat, and to potentially cure, diseases affecting cartilaginous tissues, such as osteoarthritis and cartilage defects. Insights into the processes occurring during regeneration are essential to steer and inform development of the envisaged regenerative strategy, however tools are needed for longitudinal and quantitative monitoring of cartilage matrix components. In this study, we introduce a contrast-enhanced computed tomography (CECT)-based method using a cationic iodinated contrast agent (CA4+) for longitudinal quantification of glycosaminoglycans (GAG) in cartilage-engineered constructs. CA4+ concentration and scanning protocols were first optimized to ensure no cytotoxicity and a facile procedure with minimal radiation dose. Chondrocyte and mesenchymal stem cell pellets, containing different GAG content were generated and exposed to CA4+. The CA4+ content in the pellets, as determined by micro computed tomography, was plotted against GAG content, as measured by 1,9-dimethylmethylene blue analysis, and showed a high linear correlation. The established equation was used for longitudinal measurements of GAG content over 28 days of pellet culture. Importantly, this method did not adversely affect cell viability or chondrogenesis. Additionally, the CA4+ distribution accurately matched safranin-O staining on histological sections. Hence, we show proof-of-concept for the application of CECT, utilizing a positively charged contrast agent, for longitudinal and quantitative imaging of GAG distribution in cartilage tissue-engineered constructs. STATEMENT OF SIGNIFICANCE: Tissue engineering and regenerative medicine are promising therapeutic strategies for different joint pathologies such as cartilage defects or osteoarthritis. Currently, in vitro assessment on the quality and composition of the engineered cartilage mainly relies on destructive methods. Therefore, there is a need for the development of techniques that allow for longitudinal and quantitative imaging and monitoring of cartilage-engineered constructs. This work harnesses the electrostatic interactions between the negatively-charged glycosaminoglycans (GAGs) and a positively-charged contrast agent for longitudinal and non-destructive quantification of GAGs, providing valuable insight on GAG development and distribution in cartilage engineered constructs. Such technique can advance the development of regenerative strategies, not only by allowing continuous monitoring but also by serving as a pre-implantation screening tool.

THE EFFECT OF MESENCHYMAL STEM CELL DERIVED MICROVESICLES IN REPAIR OF FEMORAL CHONDRAL DEFECTS IN DOGS

Mesenchymal stem cells (MSCs) releases in culture extracellular vesicles called microvesicles (MVs). MVs have beneficial cytokines that prevent progression of the disease and help in the regeneration process. This study is aimed to evaluate the effect of MSCs derived MVs in repair of induced chondral defect in a dog model. Methods: Chondral defects were created surgically ([Formula: see text][Formula: see text]mm) in both femoral condyles of nine dogs, autologous MSCs were isolated and MVs were prepared and injected intraarticularly in the right joint. The left joint was injected with normal saline as control negative. Evaluation of the treatment after first injection was carried out by physical examination and histopathology at different time periods ([Formula: see text]½, 3 and 6 months). Results: Treated joints showed marked degree of cartilage regeneration and restoration of chondral histomorphological picture on the contrary of the control joints that showed deterioration over time and defect filling with only fibrous tissue forming a fibrocartilage at the end of six months period. Conclusion: We demonstrated in this study that administration of MVs was effective on the functional and morphological recovery of the injured cartilage and could be exploited as a cell free therapeutic approach in regenerative medicine.

Reconstructing Bone with Natural Bone Graft: A Review of In Vivo Studies in Bone Defect Animal Model

Bone defects caused by fracture, disease or congenital defect remains a medically important problem to be solved. Bone tissue engineering (BTE) is a promising approach by providing scaffolds to guide and support the treatment of bone defects. However, the autologous bone graft has many defects such as limited sources and long surgical procedures. Therefore, xenograft bone graft is considered as one of the best substitutions and has been effectively used in clinical practice. Due to better preserved natural bone structure, suitable mechanical properties, low immunogenicity, good osteoinductivity and osteoconductivity in natural bone graft, decellularized and demineralized bone matrix (DBM) scaffolds were selected and discussed in the present review. In vivo animal models provide a complex physiological environment for understanding and evaluating material properties and provide important reference data for clinical trials. The purpose of this review is to outline the in vivo bone regeneration and remodeling capabilities of decellularized and DBM scaffolds in bone defect models to better evaluate the potential of these two types of scaffolds in BTE. Taking into account the limitations of the state-of-the-art technology, the results of the animal bone defect model also provide important information for future design of natural bone composite scaffolds.

Functionality of decellularized matrix in cartilage regeneration: A comparison of tissue versus cell sources

Increasing evidence indicates that decellularized extracellular matrices (dECMs) derived from cartilage tissues (T-dECMs) or chondrocytes/stem cells (C-dECMs) can support proliferation and chondrogenic differentiation of cartilage-forming cells. However, few review papers compare the differences between these dECMs when they serve as substrates for cartilage regeneration. In this review, after an introduction of cartilage immunogenicity and decellularization methods to prepare T-dECMs and C-dECMs, a comprehensive comparison focuses on the effects of T-dECMs and C-dECMs on proliferation and chondrogenic differentiation of chondrocytes/stem cells in vitro and in vivo. Key factors within dECMs, consisting of microarchitecture characteristics and micromechanical properties as well as retained insoluble and soluble matrix components, are discussed in-depth for potential mechanisms underlying the functionality of these dECMs in regulating chondrogenesis. With this information, we hope to benefit dECM based cartilage engineering and tissue regeneration for future clinical application.

STATEMENT OF SIGNIFICANCE

The use of decellularized extracellular matrix (dECM) is becoming a promising approach for tissue engineering and regeneration. Compared to dECM derived from cartilage tissue, recently reported dECM from cell sources exhibits a distinct role in cell based cartilage regeneration. In this review paper, for the first time, tissue and cell based dECMs are comprehensively compared for their functionality in cartilage regeneration. This information is expected to provide an update for dECM based cartilage regeneration.

Contrast-enhanced μCT of the intervertebral disc: A comparison of anionic and cationic contrast agents for biochemical and morphological characterization

The objective of this study was to quantify and compare the contrast-enhancing properties of the anionic contrast agent ioxaglate/Hexabrix, and cationic contrast agent CA⁴⁺ for biochemical and morphological characterization of the intervertebral disc (IVD) via μCT. Optimal contrast agent concentrations were determined by incubating rat lumbar IVDs in dilutions of Hexabrix-320 (20%, 30%, 40%, and 50%) and CA⁴⁺ (10, 20, 30, and 40 mg I/ml). μCT imaging was performed at 70 kVp, 114 μA, and 250 ms integration time, 12 μm voxel size. The kinetics of contrast enhancement were quantified with cumulative incubations for 0.5, 1, 2, 12, 16, 20, and 24 h using both agents. Agreement in morphological quantification was assessed via serial scans of the same IVDs. Correlation of attenuation to glycosaminoglycan (GAG) content was determined by enzymatic digestion of IVDs, subsequent μCT imaging, and GAG quantification via dimethylmethylene blue assay. Forty percent Hexabrix and 30 mg I/ml CA⁴⁺ were chosen as optimal concentrations. Hexabrix enabled greater delineation of the IVD from surrounding tissues, and CA⁴⁺ had the lowest uptake in surrounding soft tissue. Twenty-four hour incubation was sufficient for >99% equilibration of both agents. A high level of agreement was observed in the quantification of IVD volume (ICC = 0.951, r = 0.997) and height (ICC = 0.947, r = 0.991). Both agents exhibited strong linear correlations between μCT attenuation and GAG content (Hexabrix: r = -0.940; CA⁴⁺ : r = 0.887). Both agents enable biochemical and morphological quantification of the IVD via contrast-enhanced μCT and are effective tools for preclinical characterization. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1067-1075, 2017.

The use of nano-computed tomography to enhance musculoskeletal research

Advances in computed tomography (CT) imaging are opening new avenues toward more precise characterization and quantification of connective tissue microarchitecture. In the last two decades, micro-computed tomography (microCT) has significantly augmented destructive methods for the 3D micro-analysis of tissue structure, primarily in the bone research field. Recently, microCT has been employed in combination with contrast agents to generate contrast-enhanced images of soft tissues that are otherwise difficult to visualize due to their native radiodensity. More recent advances in CT technology have enabled ultra-high resolution imaging by utilizing a more powerful nano-focused X-ray source, such as that found in nano-computed tomography (nanoCT) systems. NanoCT imaging has facilitated the expansion of musculoskeletal research by reducing acquisition time and significantly expanding the range of samples that can be imaged in terms of size, age and tissue-type (bone, muscle, tendon, cartilage, vessels and adipose tissue). We present the application and early results of nanoCT imaging in various tissue types and how this ultra-high resolution imaging modality is capable of characterizing microstructures at levels of details previously not possible. Contrast-enhanced imaging techniques to enable soft-tissue visualization and characterization are also outlined.

The bioactivity of cartilage extracellular matrix in articular cartilage regeneration

Cartilage matrix is a promising material for cartilage regeneration given the evidence supporting its chondroinductive character. The "raw materials" of cartilage matrix can serve as building blocks and signals for tissue regeneration. These matrices can be created by chemical or physical processing: physical methods disrupt cellular membranes and nuclei but may not fully remove all cell components and DNA, whereas chemical methods combined with physical methods are effective in fully decellularizing such materials. It is important to delineate between the sources of the cartilage matrix, that is, derived from matrix in vitro or from native tissue, and then to further characterize the cartilage matrix based on the processing method, decellularization or devitalization. With these distinctions, four types of cartilage matrices exist: decellularized native cartilage (DCC), devitalized native cartilage (DVC), decellularized cell-derived matrix (DCCM), and devitalized cell-derived matrix (DVCM). One currently marketed cartilage matrix device is decellularized, although trends in patents suggest additional decellularized products may be available in the future. To identify the most relevant source and processing for cartilage matrix, testing needs to include targeting the desired application, optimizing delivery of the material, identify relevant FDA regulations, assess availability of materials, and immunogenic properties of the product.

Three-dimensional characterization of in vivo intervertebral disc degeneration using EPIC-μCT

OBJECTIVE

Small animal models are commonly employed to study progression of and potential treatment techniques for degenerative disc disease (DDD), but assessment using conventional imaging techniques is challenging due to resolution. The objective of this study was to employ equilibrium partitioning of an ionic contrast agent micro computed tomography (EPIC - μCT) to map three-dimensional (3D) degenerative changes in the rabbit intervertebral disc (IVD).

MATERIALS AND METHODS

In vivo degeneration was induced surgically in 12 New Zealand White rabbits via percutaneous annular puncture and percutaneous nucleotomy. IVDs were harvested after 3 and 6 weeks. EPIC-μCT imaging was performed on fresh, IVDs before and after formalin fixation, and 3D IVD volumes were segmented. IVDs were histologically stained with Safranin-O/Fast-Green and Hematoxylin & Eosin (H&E). EPIC-μCT attenuation and 3D morphological measurements were assessed in healthy and degenerate IVDs and compared to qualitative grading and disc height measurement from histology.

RESULTS

EPIC-μCT caused pronounced contrast enhancement of the IVD. Annular puncture and nucleotomy produced mild and severe degenerative changes, respectively. IVD attenuation following contrast enhancement increased significantly in nucleotomized discs at 3 and 6 weeks. IVD attenuation correlated significantly with histologic score and disc height measurements. Disc height decreased most extensively in the posterior and lateral aspects of the IVD. 3D morphological measurements correlated strongly to IVD attenuation and were more sensitive to degenerative changes than histologic measurements. Formalin fixation reduced the attenuation of IVDs by ∼10%.

CONCLUSION

EPIC-μCT is sensitive to in vivo DDD induced by nucleotomy and provides a high resolution 3D method for mapping degenerative changes in rabbit IVDs.

Posttraumatic Chondrocyte Apoptosis in the Murine Xiphoid

OBJECTIVE

To demonstrate posttraumatic chondrocyte apoptosis in the murine xiphoid after a crush-type injury and to ultimately determine the pathway (i.e., intrinsic or extrinsic) by which chondrocytes undergo apoptosis in response to mechanical injury.

DESIGN

The xiphoids of adult female wild-type mice were injured with the use of a modified Kelly clamp. Postinjury xiphoid cartilage was analyzed via 3 well-described independent means of assessing apoptosis in chondrocytes: hematoxylin and eosin staining, terminal deoxynucleotidyl transferase dUTP nick end labeling assay, and activated caspase-3 staining.

RESULTS

Injured specimens contained many chondrocytes with evidence of apoptosis, which is characterized by cell shrinkage, chromatin condensation, nuclear fragmentation, and the liberation of apoptotic bodies. There was a statistically significant increase in the number of chondrocytes undergoing apoptosis in the injured specimens as compared with the uninjured specimens.

CONCLUSIONS

Chondrocytes can be stimulated to undergo apoptosis as a result of mechanical injury. These experiments involving predominantly cartilaginous murine xiphoid in vivo establish a baseline for future investigations that employ the genetic and therapeutic modulation of chondrocyte apoptosis in response to mechanical injury.