High quality repair of osteochondral defects in rats using the extracellular matrix of antler stem cells

BACKGROUND Cartilage defects are some of the most common causes of arthritis.Cartilage lesions caused by inflammation,trauma or degenerative disease normally result in osteochondral defects.Previous studies have shown that decellularized extracellular matrix(ECM)derived from autologous,allogenic,or xenogeneic mesenchymal stromal cells(MSCs)can effectively restore osteochondral integrity.AIM To determine whether the decellularized ECM of antler reserve mesenchymal cells(RMCs),a xenogeneic material from antler stem cells,is superior to the currently available treatments for osteochondral defects.METHODS We isolated the RMCs from a 60-d-old sika deer antler and cultured them in vitro to 70%confluence;50 mg/mL L-ascorbic acid was then added to the medium to stimulate ECM deposition.Decellularized sheets of adipocyte-derived MSCs(aMSCs)and antlerogenic periosteal cells(another type of antler stem cells)were used as the controls.Three weeks after ascorbic acid stimulation,the ECM sheets were harvested and applied to the osteochondral defects in rat knee joints.RESULTS The defects were successfully repaired by applying the ECM-sheets.The highest quality of repair was achieved in the RMC-ECM group both in vitro(including cell attachment and proliferation),and in vivo(including the simultaneous regeneration of well-vascularized subchondral bone and avascular articular hyaline cartilage integrated with surrounding native tissues).Notably,the antler-stem-cell-derived ECM(xenogeneic)performed better than the aMSC-ECM(allogenic),while the ECM of the active antler stem cells was superior to that of the quiescent antler stem cells.CONCLUSION Decellularized xenogeneic ECM derived from the antler stem cell,particularly the active form(RMC-ECM),can achieve high quality repair/reconstruction of osteochondral defects,suggesting that selection of decellularized ECM for such repair should be focused more on bioactivity rather than kinship.

Bioceramic-mediated chondrocyte hypertrophy promotes calcified cartilage formation for rabbit osteochondral defect repair

Osteochondral tissue is a highly specialized and complex tissue composed of articular cartilage and subchondral bone that are separated by a calcified cartilage interface.Multilayered or gradient scaffolds,often in conjunction with stem cells and growth factors,have been developed to mimic the respective layers for osteochondral defect repair.In this study,we designed a hyaline cartilage-hypertrophic cartilage bilayer graft(RGD/RGDW)with chondrocytes.Previously,we demonstrated that RGD peptide-modified chondroitin sulfate cryogel(RGD group)is chondro-conductive and capable of hyaline cartilage formation.Here,we incorporated whitlockite(WH),a Mg2+-containing calcium phosphate,into RGD cryogel(RGDW group)to induce chondrocyte hypertrophy and form collagen X-rich hypertrophic cartilage.This is the first study to use WH to produce hypertrophic cartilage.Chondrocytes-laden RGDW cryogel exhibited significantly upregulated expression of hypertrophy markers in vitro and formed ectopic hypertrophic cartilage in vivo,which mineralized into calcified cartilage in bone microenvironment.Subsequently,RGD cryogel and RGDW cryogel were combined into bilayer(RGD/RGDW group)and implanted into rabbit osteochondral defect,where RGD layer supports hyaline cartilage regeneration and bioceramic-containing RGDW layer promotes calcified cartilage formation.While the RGD group(monolayer)formed hyaline-like neotissue that extends into the subchondral bone,the RGD/RGDW group(bilayer)regenerated hyaline cartilage tissue confined to its respective layer and promoted osseointegration for integrative defect repair.

Type II collagen scaffolds repair critical-sized osteochondral defects under induced conditions of osteoarthritis in rat knee joints via inhibiting TGF-β-Smad1/5/8 signaling pathway

The bidirectional relationship between osteochondral defects(OCD)and osteoarthritis(OA),with each condition exacerbating the other,makes OCD regeneration in the presence of OA challenging.Type II collagen(Col2)is important in OCD regeneration and the management of OA,but its potential applications in cartilage tissue engineering are significantly limited.This study investigated the regeneration capacity of Col2 scaffolds in critical-sized OCDs under surgically induced OA conditions and explored the underlying mechanisms that promoted OCD regeneration.Furthermore,the repair potential of Col2 scaffolds was validated in over critical-sized OCD models.After 90 days or 150 days since scaffold implantation,complete healing was observed histologically in critical-sized OCD,evidenced by the excellent integration with surrounding native tissues.The newly formed tissue biochemically resembled adjacent natural tissue and exhibited comparable biomechanical properties.The regenerated OA tissue demonstrated lower expression of genes associated with cartilage degradation than native OA tissue but comparable expression of genes related to osteochondral anabolism compared with normal tissue.Additionally,transcriptome and proteome analysis revealed the hindrance of TGF-β-Smad1/5/8 in regenerated OA tissue.In conclusion,the engrafting of Col2 scaffolds led to the successful regeneration of critical-sized OCDs under surgically induced OA conditions by inhibiting the TGF-β-Smad1/5/8 signaling pathway.

Three-dimensional bioprinting biphasic multicellular living scaffold facilitates osteochondral defect regeneration

Due to tissue lineage variances and the anisotropic physiological character-istics,regenerating complex osteochondral tissues(cartilage and subchondral bone)remains a great challenge,which is primarily due to the distinct requirements for cartilage and subchondral bone regeneration.For cartilage regeneration,a significant amount of newly generated chondrocytes is required while maintaining their phenotype.Conversely,bone regeneration necessitates inducing stem cells to differentiate into osteoblasts.Additionally,the construction of the osteochondral interface is crucial.In this study,we fabricated a biphasic multicellular bioprinted scaffold mimicking natural osteochondral tissue employing three-dimensional(3D)bioprinting technol-ogy.Briefly,gelatin-methacryloyl(GelMA)loaded with articular chondrocytes and bone marrow mesenchymal stem cells(ACs/BMSCs),serving as the cartilage layer,preserved the phenotype of ACs and promoted the differentia-tion of BMSCs into chondrocytes through the interaction between ACs and BMSCs,thereby facilitating cartilage regeneration.GelMA/strontium-substituted xonotlite(Sr-CSH)loaded with BMSCs,serving as the subchondral bone layer,regulated the differentiation of BMSCs into osteoblasts and enhanced the secretion of cartilage matrix by ACs in the cartilage layer through the slow release of bioactive ions from Sr-CSH.Additionally,GelMA,serving as the matrix material,contributed to the reconstruction of the osteochondral interface.Ultimately,this biphasic multicellular bioprinted scaffold demonstrated satisfactory simultaneous regeneration of osteochondral defects.In this study,a promising strategy for the application of 3D bioprinting technology in complex tissue regeneration was proposed.

Multiphasic scaffolds for the repair of osteochondral defects:Outcomes of preclinical studies

Osteochondral defects are caused by injury to both the articular cartilage and subchondral bone within skeletal joints. They can lead to irreversible joint damage and increase the risk of progression to osteoarthritis. Current treatments for osteochondral injuries are not curative and only target symptoms, highlighting the need for a tissue engineering solution. Scaffold-based approaches can be used to assist osteochondral tissue regeneration, where biomaterials tailored to the properties of cartilage and bone are used to restore the defect and minimise the risk of further joint degeneration. This review captures original research studies published since 2015, on multiphasic scaffolds used to treat osteochondral defects in animal models. These studies used an extensive range of biomaterials for scaffold fabrication, consisting mainly of natural and synthetic polymers. Different methods were used to create multiphasic scaffold designs, including by integrating or fabricating multiple layers, creating gradients, or through the addition of factors such as minerals, growth factors, and cells. The studies used a variety of animals to model osteochondral defects, where rabbits were the most commonly chosen and the vast majority of studies reported small rather than large animal models. The few available clinical studies reporting cell-free scaffolds have shown promising early-stage results in osteochondral repair, but long-term follow-up is necessary to demonstrate consistency in defect restoration. Overall, preclinical studies of multiphasic scaffolds show favourable results in simultaneously regenerating cartilage and bone in animal models of osteochondral defects, suggesting that biomaterials-based tissue engineering strategies may be a promising solution.

Correlation of stress radiographs to injuries associated with lateral ankle instability

BACKGROUND Stress radiographs have demonstrated superior efficacy in the evaluation of ankle instability.AIM To determine if there is a degree of instability evidenced by stress radiographs that is associated with pathology concomitant with ankle ligamentous instability.METHODS A retrospective review of 87 consecutive patients aged 18-74 who had stress radiographs performed at a single institution between 2014 and 2020 was performed.These manual radiographic stress views were then correlated with magnetic resonance imaging and operative findings.RESULTS A statistically significant association was determined for the mean and median stress radiographic values and the presence of peroneal pathology(P=0.008 for tendonitis and P=0.020 for peroneal tendon tears).A significant inverse relationship was found between the presence of an osteochondral defect and increasing degrees of instability(P=0.043).CONCLUSION Although valuable in the clinical evaluation of ankle instability,stress radiographs are not an independent predictor of conditions associated with ankle in-stability.

Anti-inflammatory and anabolic biphasic scaffold facilitates osteochondral tissue regeneration in osteoarthritic joints

Osteochondral defects (OCD) are common but difficult to heal due to the low intrinsic repair capacity of cartilage and its complex hierarchical structure. In osteoarthritis (OA), OCD become more challenging to repair as both cartilage and subchondral bone regeneration are further impaired due to the arthritic environment. Numerous biomaterials have been developed and tested in osteochondral defects while ignoring the inflammatory environment. To target this challenging underlying pathophysiology, we designed and fabricated a biphasic porous and degradable scaffold incorporating anti-inflammatory and anabolic molecules by low-temperature rapid prototyping technology, and its effects on promoting osteochondral regeneration were evaluated using our well-established OA-OCD rabbit model. The biphasic porous scaffolds consisted of poly lactic-co-glycolic acid (PLGA) with kartogenin (KGN) for cartilage repair and PLGA and β-calcium phosphate (PLGA/β-TCP) with cinnamaldehyde (CIN) for subchondral bone repair. KGN is a molecule for promoting chondrogenesis and CIN is a phytomolecule for enhancing osteogenesis and alleviating inflammation. The biphasic scaffolds PLGA/KGN-PLGA/β-TCP/CIN (PK/PTC) with bio-mimic structure provided stable mechanical properties and exhibited excellent biocompatibility to support cell adhesion, proliferation, migration, and distribution. Furthermore, KGN and CIN within biphasic scaffolds could be released in a controlled and sustained mode, and the biphasic scaffold degraded slowly in vitro . Evaluating the repair of 16-weeks post-implantation into critically sized OA-OCD rabbit models revealed that the biphasic scaffold could promote subchondral bone and cartilage regeneration, as well as reverse subchondral osteosclerosis caused by inflammation in vivo . These findings support the utilization of the PK/PTC scaffold for osteochondral regeneration and provide a promising potential strategy for clinical application for the treatment of patients with OA-OCD.

Effect of porosities of bilayered porous scaffolds on spontaneous osteochondral repair in cartilage tissue engineering

Poly(lactide-co-glycolide)-bilayered scaffolds with the same porosity or different ones on the two layers were fabricated,and the porosity effect on in vivo repairing of the osteochondral defect was examined in a comparative way for the first time.The constructs of scaffolds and bone marrow-derived mesenchymal stem cells were implanted into pre-created osteochondral defects in the femoral condyle of New Zealand white rabbits.After 12 weeks,all experimental groups exhibited good cartilage repairing according to macroscopic appearance,cross-section view,haematoxylin and eosin staining,toluidine blue staining,immunohistochemical staining and real-time polymerase chain reaction of characteristic genes.The group of 92%porosity in the cartilage layer and 77%porosity in the bone layer resulted in the best efficacy,which was understood by more biomechanical mimicking of the natural cartilage and subchondral bone.This study illustrates unambiguously that cartilage tissue engineering allows for a wide range of scaffold porosity,yet some porosity group is optimal.It is also revealed that the biomechanical matching with the natural composite tissue should be taken into consideration in the design of practical biomaterials,which is especially important for porosities of a multi-compartment scaffold concerning connected tissues.

Osteoarthritis animal models for biomaterial-assisted osteochondral regeneration

Clinical therapeutics for the regeneration of osteochondral defects(OCD)in the early stages of osteoarthritis remain an enormous challenge in orthopaedics.For in-depth studies of tissue engineering and regenerative medicine in terms of OCD treatment,the utility of an optimal OCD animal model is crucial for assessing the effects of implanted biomaterials on the repair of damaged osteochondral tissues.Currently,the most frequently used in vivo animal models for OCD regeneration include mice,rats,rabbits,dogs,pigs,goats,sheep,horses and nonhuman primates.However,there is no single“gold standard”animal model to accurately recapitulate human disease in all aspects,thus understanding the benefits and limitations of each animal model is critical for selecting the most suitable one.In this review,we aim to elaborate the complex pathological changes in osteoarthritic joints and to summarise the advantages and limitations of OCD animal models utilised for biomaterial testing along with the methodology of outcome assessment.Furthermore,we review the surgical procedures of OCD creation in different species,and the novel biomaterials that promote OCD regeneration.Above all,it provides a significant reference for selection of an appropriate animal model for use in preclinical in vivo studies of biomaterial-assisted osteochondral regeneration in osteoarthritic joints.