Articular Osteochondral Defects Research Articles

Trilayered biomimetic hydrogel scaffolds with dual-differential microenvironment for articular osteochondral defect repair

Commonly, articular osteochondral tissue exists significant differences in physiological architecture, mechanical function, and biological microenvironment. However, the development of biomimetic scaffolds incorporating upper cartilage, middle tidemark-like, and lower subchondral bone layers for precise articular osteochondral repair remains elusive. This study proposed here a novel strategy to construct the trilayered biomimetic hydrogel scaffolds with dual-differential microenvironment of both mechanical and biological factors. The cartilage-specific microenvironment was achieved through the grafting of kartogenin (KGN) into gelatin via p-hydroxyphenylpropionic acid (HPA)-based enzyme crosslinking reaction as the upper cartilage layer. The bone-specific microenvironment was achieved through the grafting of atorvastatin (AT) into gelatin via dual-crosslinked network of both HP-based enzyme crosslinking and glycidyl methacrylate (GMA)-based photo-crosslinking reactions as the lower subchondral bone layer. The introduction of tidemark-like middle layer is conducive to the formation of well-defined cartilage-bone integrated architecture. The in vitro experiments demonstrated the significant mechanical difference of three layers, successful grafting of drugs, good cytocompatibility and tissue-specific induced function. The results of in vivo experiments also confirmed the mechanical difference of the trilayered bionic scaffold and the ability of inducing osteogenesis and chondrogenesis. Furthermore, the articular osteochondral defects were successfully repaired using the trilayered biomimetic hydrogel scaffolds by the activation of endogenous recovery, which offers a promising alternative for future clinical treatment.

3D-printed gradient scaffolds for osteochondral defects: Current status and perspectives.

Articular osteochondral defects are quite common in clinical practice, and tissue engineering techniques can offer a promising therapeutic option to address this issue.The articular osteochondral unit comprises hyaline cartilage, calcified cartilage zone (CCZ), and subchondral bone.As the interface layer of articular cartilage and bone, the CCZ plays an essentialpart in stress transmission and microenvironmental regulation.Osteochondral scaffolds with the interface structure for defect repair are the future direction of tissue engineering. Three-dimensional (3D) printing has the advantages of speed, precision, and personalized customization, which can satisfy the requirements of irregular geometry, differentiated composition, and multilayered structure of articular osteochondral scaffolds with boundary layer structure. This paper summarizes the anatomy, physiology, pathology, and restoration mechanisms of the articular osteochondral unit, and reviews the necessity for a boundary layer structure in osteochondral tissue engineering scaffolds and the strategy for constructing the scaffolds using 3D printing. In the future, we should not only strengthen the basic research on osteochondral structural units, but also actively explore the application of 3D printing technology in osteochondral tissue engineering. This will enable better functional and structural bionics of the scaffold, which ultimately improve the repair of osteochondral defects caused by various diseases.

Bioinspired gradient scaffolds for osteochondral tissue engineering.

Repairing articular osteochondral defects present considerable challenges in self-repair due to the complex tissue structure and low proliferation of chondrocytes. Conventional clinical therapies have not shown significant efficacy, including microfracture, autologous/allograft osteochondral transplantation, and cell-based techniques. Therefore, tissue engineering has been widely explored in repairing osteochondral defects by leveraging the natural regenerative potential of biomaterials to control cell functions. However, osteochondral tissue is a gradient structure with a smooth transition from the cartilage to subchondral bone, involving changes in chondrocyte morphologies and phenotypes, extracellular matrix components, collagen type and orientation, and cytokines. Bioinspired scaffolds have been developed by simulating gradient characteristics in heterogeneous tissues, such as the pores, components, and osteochondrogenesis-inducing factors, to satisfy the anisotropic features of osteochondral matrices. Bioinspired gradient scaffolds repair osteochondral defects by altering the microenvironments of cell growth to induce osteochondrogenesis and promote the formation of osteochondral interfaces compared with homogeneous scaffolds. This review outlines the meaningful strategies for repairing osteochondral defects by tissue engineering based on gradient scaffolds and predicts the pros and cons of prospective translation into clinical practice.

Biomimetic Gradient Scaffolds Containing Hyaluronic Acid and Sr/Zn Folates for Osteochondral Tissue Engineering.

Regenerative therapies based on tissue engineering are becoming the most promising alternative for the treatment of osteoarthritis and rheumatoid arthritis. However, regeneration of full-thickness articular osteochondral defects that reproduces the complexity of native cartilage and osteochondral interface still remains challenging. Hence, in this work, we present the fabrication, physic-chemical characterization, and in vitro and in vivo evaluation of biomimetic hierarchical scaffolds that mimic both the spatial organization and composition of cartilage and the osteochondral interface. The scaffold is composed of a composite porous support obtained by cryopolymerization of poly(ethylene glycol) dimethacrylate (PEGDMA) in the presence of biodegradable poly(D,L-lactide-co-glycolide) (PLGA), bioactive tricalcium phosphate β-TCP and the bone promoting strontium folate (SrFO), with a gradient biomimetic photo-polymerized methacrylated hyaluronic acid (HAMA) based hydrogel containing the bioactive zinc folic acid derivative (ZnFO). Microscopical analysis of hierarchical scaffolds showed an open interconnected porous open microstructure and the in vitro behaviour results indicated high swelling capacity with a sustained degradation rate. In vitro release studies during 3 weeks indicated the sustained leaching of bioactive compounds, i.e., Sr2+, Zn2+ and folic acid, within a biologically active range without negative effects on human osteoblast cells (hOBs) and human articular cartilage cells (hACs) cultures. In vitro co-cultures of hOBs and hACs revealed guided cell colonization and proliferation according to the matrix microstructure and composition. In vivo rabbit-condyle experiments in a critical-sized defect model showed the ability of the biomimetic scaffold to promote the regeneration of cartilage-like tissue over the scaffold and neoformation of osteochondral tissue.

Biphasic CK2.1-coated β-glycerophosphate chitosan/LL37-modified layered double hydroxide chitosan composite scaffolds enhance coordinated hyaline cartilage and subchondral bone regeneration

• We fabricated peptide-modified bilayered scaffold for osteochondral defect. • Superficial CK2.1@GC could realize hyaline cartilage regeneration. • Bottom biomimetic LL37@LC could stimulate subchondral bone formation. Articular osteochondral defect is commonly seen after trauma or in patients with degenerative osteoarthritis. Currently, the treatment of osteochondral lesions is still challenging due to the limited healing ability of cartilage as well as the poorly effective traditional method. In this study, we fabricated a bilayer peptide-loaded scaffold consisting of CK2.1 coated β-glycerophosphate/chitosan (CK2.1@GC) for cartilage regeneration and LL37 modified layered double hydroxide/chitosan (LL37@LC) for subchondral bone regeneration, designed in an integrated strategy involving mesenchymal stem cells (MSCs) recruitment and multifunctional therapeutic biomaterials of bone regeneration and vascularization. The lower LC scaffold is highlighted with a biomimetic lamellar structural design, providing a novel platform for the integration of newborn bone tissue and blood vessels. In vitro results showed our peptide-loaded bilayer scaffold could induce the MSCs to differentiate into chondrocytes and osteoblasts in different layers respectively. LL37@LC could also attract MSCs and promote vasculogenesis in vitro. Meanwhile, osteochondral defect could be efficiently repaired by this peptide-modified bilayered scaffold in the rabbit model. This study demonstrated that our composite scaffold could smartly enhance the repair of hyaline cartilage and subchondral bone defect, which shed light on a novel therapeutic strategy for the intervention of patients with articular osteochondral defect.

Constructing Gene-Enhanced Tissue Engineering for Regeneration and Repair of Osteochondral Defects.

In situ sustained release of endogenous growth factors from cells is a challenge for repair and regeneration of tissue. Although recombinant adenovirus vectors are an effective delivery system that can prolong the release of growth factors and is very suitable for the therapy of growth factors, these recombinant adenovirus vectors that are widely used at present have low safety and stability in terms of long-term expression. In this study, the above problems are solved by knocking out both E1 and E3 genes at the same time and directly inserting the gene fragments encoding target proteins after the inverted terminal repeats. Finally, the combination of gene therapy with tissue engineering in regeneration and repair of full-thickness defects of osteochondral tissue are applied as an example. The results show that this strategy can achieve complete repair of articular osteochondral defects and recovery of their function, and meanwhile solve the problems of low safety and expression instability of recombinant adenovirus vectors. This method provides a bright prospect for the application of gene enhanced tissue engineering in the regeneration and repair of joint tissue, and also provides a reference for the repair and regeneration of other tissues.

CaAlg hydrogel containing bone morphogenetic protein 4-enhanced adipose-derived stem cells combined with osteochondral mosaicplasty facilitated the repair of large osteochondral defects.

Cartilage repair presents a challenge to clinicians and researchers. A more effective procedure that can produce hyaline-like cartilage is needed for articular cartilage repair. Mosaic osteochondral grafts for large osteochondral defects often show poor integration between the grafts and the surrounding normal cartilage, leading to defective cracks filled with fibrous tissue instead of hyaline-like cartilage. In the present study, we aimed to repair the defective cracks with a calcium alginate (CaAlg) hydrogel containing bone morphogenetic protein 4 (BMP4)-enhanced adipose-derived stem cells (ADSCs). ADSCs were transduced with BMP4 (B-ADSCs). The expression of BMP4 and type II collagen was confirmed using an enzyme-linked immunosorbent assay (ELISA). Swine models of large cartilage defects of the knee were constructed and received one of the four treatments: mosaicplasty only, mosaicplasty with the CaAlg hydrogel, mosaicplasty with the CaAlg hydrogel containing ADSCs, or mosaicplasty with the CaAlg hydrogel containing B-ADSCs injected into the defective cracks. Outcomes were evaluated at 12 and 24weeks after surgery. The in vitro study showed that the osteogenic and chondrogenic activities of the B-ADSCs were enhanced compared with those of the control. In vivo, in the group that received mosaicplasty-containing B-ADSCs, osteochondral tissue was completely integrated with an intact surface. Additionally, the histological scores of the mosaicplasty-containing B-ADSCs group were significantly higher than those of the other groups. Biomechanical examination confirmed that the neocartilage possessed properties similar to those of normal cartilage. Mosaicplasty and hydrogel containing B-ADSCs promoted the repair of large cartilage defects by regenerating hyaline cartilage and repairing dead spaces between osteochondral grafts and donor-site defects, thus improving the feasibility and success rate of one-stage complete repair surgery for large osteochondral defects. This proposed method provides a novel and effective means for the repair of large articular osteochondral defects.

Repair of Articular Osteochondral Defects Using an Integrated and Biomimetic Trilayered Scaffold.

Repair of articular cartilage defects using bilayered scaffolds is problematic because tissue-engineered cartilage is prone to overgrowth toward subchondral bone, resulting in structural abnormalities of cartilage and subchondral bone. A "twice freeze-drying" technique was used to construct a dense isolation layer between the cartilage and subchondral bone layers in an integrated bilayered scaffold to prevent cartilage from excessive downgrowth. Briefly, beta-tricalcium phosphate was used for the subchondral bone layer of the scaffold, high-concentration chitosan/gelatin solution for the dense isolation layer, and low-concentration chitosan/gelatin solution for the cartilage layer. As controls, cell-free trilayered scaffolds, autologous osteochondral transplantation, and the bilayered scaffolds were used for repair of osteochondral defects. After 6 months, two of the eight goats in the bilayered scaffold group showed conspicuous cartilage downgrowth, whereas no excessive downgrowth of cartilage was observed in the trilayered scaffold group. Moreover, there was no difference in the repair efficacy between the trilayered scaffold and mosaicplasty group. The results confirmed that the trilayered scaffold effectively prevented cartilage downgrowth with better cartilage repair.

[Demineralized cancellous bone seeded with allogeneic chondrocytes for repairing articular osteochondral defects in rabbits].

To evaluate the effect of demineralized cancellous bone (DCB) seeded with allogeneic chondrocytes for repairing articular osteochondral defects in rabbits. Articular chondrocytes were isolated from a 1-month-old male New Zealand rabbit for primary culture. The passage 1 chondrocytes were seeded onto prepared rabbit DCB scaffold to construct tissue-engineered cartilage and cultured in vitro for 2 weeks. Full-thickness articular osteochondral defects (3 mm both in diameter and depth) were created on both sides of the femoral medial condyles in 30 New Zealand white rabbits (age 4- 5 months). In 20 of the rabbits, the defects were filled with the tissue-engineered cartilage on the right side (group A) and with DCB only on the left side (group B); the remaining 10 rabbits did not receive any implantation in the defects to serve as the control (group C). At 1, 3, and 6 months after the implantation, tissue samples were collected from the defects for macroscopic observation and histological examination with Toluidine blue (TB) and collagen type Ⅱ staining. The effect of defect repair using the tissue-engineered cartilage was assessed at 6 months based on the histological scores. The prepared DCB had a spongy 3D structure with open and interconnected micropores of various sizes and showed good plasticity and mechanical strength. DCB began to degrade within 1 month after implantation and was totally absorbed at 3 months. At 6 months after implantation, the defects filled with the chondrocyte-seeded DCB were repaired mainly by hyaline-like cartilage tissues, which were well integrated to the adjacent cartilage without clear boundaries and difficult to recognize. The chondrocytes were located in the lacunate and arranged in vertical columns in the deep repaired tissue, where matrix proteoglycans and collagen type Ⅱ were distributed homogeneously close to the normal cartilage. The subchondral bone plate was reconstructed completely. The defects implanted with DCB only were filled with fibrocartilage tissue, as compared with fibrous tissue in the control defects. The histological scores in group A were significantly superior to those in group B and C (P < 0.05), but the scores for subchondral bone plate reconstruction were comparable between groups A and B at 6 months. DCB is a good scaffold material for preparing tissue-engineered cartilage, and chondrocyte- seeded DCB can repair articular osteochondral defects by inducing the generation of hayline-like cartilage.

Functional tissue-engineered microtissue derived from cartilage extracellular matrix for articular cartilage regeneration

We developed a promising cell carrier prepared from articular cartilage slices, designated cartilage extracellular matrix (ECM)-derived particles (CEDPs), through processes involving physical pulverization, size screening, and chemical decellularization. Rabbit articular chondrocytes (ACs) or adipose-derived stem cells (ASCs) rapidly attached to the surface of the CEDPs and proliferated with high cell viability under microgravity (MG) condition in a rotary cell culture system (RCCS) or static condition. Gene profiling results demonstrated that ACs expanded on CEDPs exhibited significantly enhanced chondrogenic phenotypes compared with monolayer culture, and that ASCs differentiated into a chondrogenic phenotype without the use of exogenous growth factors. Moreover, MG culture conditions in a RCCS bioreactor were superior to static culture conditions in terms of maintaining the chondrogenic phenotype of ACs and inducing ACS chondrogenesis. With prolonged expansion, functional microtissue aggregates of AC- or ASC-laden CEDPs were formed. Further, AC- or ASC-based microtissues were directly implanted in vivo to repair articular osteochondral defects in a rabbit model. Histological results, biomechanical evaluations, and radiographic assessments indicated that AC- and ASC-based microtissues displayed equal levels of superior hyaline cartilage repair, whereas the other two treatment groups, in which osteochondral defects were treated with CEDPs alone or fibrin glue, exhibited primarily fibrous tissue repair. These findings provide an alternative method for cell culture and stem cell differentiation and a promising strategy for constructing tissue-engineered cartilage microtissues for cartilage regeneration. Statement of SignificanceDespite the remarkable progress in cartilage tissue engineering, cartilage repair still remains elusive. In the present study, we developed a cell carrier, namely cartilage extracellular matrix-derived particles (CEDPs), for cell proliferation of articular chondrocytes (ACs) and adipose-derived stem cells (ASCs), which improved the maintenance of chondrogenic phenotype of ACs, and induced chondrogenesis of ASCs. Moreover, the functional microtissue aggregates of AC- or ASC-laden CEDPs induced equal levels of superior hyaline cartilage repair in a rabbit model. Therefore, our study demonstrated an alternative method for chondrocyte culture and stem cell differentiation, and a promising strategy for constructing tissue-engineered cartilage microtissues for in vivo articular cartilage repair and regeneration.

Restoration of articular osteochondral defects in rat by a bi-layered hyaluronic acid hydrogel plug with TUDCA-PLGA microsphere

Tauroursodeoxycholic acid (TUDCA) has a role in the regulation of the differentiation of mesenchymal stem cells. In this study, TUDCA was demonstrated to increase osteogenic differentiation at a low concentration (25μM) and chondrogenic differentiation at a high concentration (2500μM). We investigated the regeneration of osteochondral defects in a rat model using a bilayer plug loaded with two different concentration of TUDCA-PLGA microspheres (TUDCA-MS bilayer plug). The TUDCA-MS bilayer plug successfully regenerated cartilage and subchondral bone layer. Therefore, we suggest that the TUDCA-MS bilayer plug as a new treatment method for simultaneous regeneration of cartilage and subchondral bone layer.

Regeneration of osteochondral defects in vivo by a cell-free cylindrical poly(lactide-co-glycolide) scaffold with a radially oriented microstructure.

A scaffold with an oriented porous architecture to facilitate cell infiltration and bioactive interflow between neo-host tissues is of great importance for in situ inductive osteochondral regeneration. In this study, a poly(lactide-co-glycolide) (PLGA) scaffold with oriented pores in its radial direction was fabricated via unidirectional cooling of the PLGA solution in the radial direction, following with lyophilization. Micro-computed tomography evaluation and scanning electron microscopy observation confirmed the radially oriented microtubular pores in the scaffold. The scaffold had porosity larger than 90% and a compressive modulus of 4MPa in a dry state. Culture of bone marrow stem cells in vitro revealed faster migration and regular distribution of cells in the poly(lactide-co-glycolide) scaffold with oriented pores compared with the random PLGA scaffold. The cell-free oriented macroporous PLGA scaffold was implanted into rabbit articular osteochondral defect in vivo for 12weeks to evaluate its inductive tissue regeneration function. Histological analysis confirmed obvious tide mark formation and abundant chondrocytes distributed regularly with obvious lacunae in the cartilage layer. Safranin O-fast green staining showed an obvious boundary between the two layers with distinct staining results, indicating the simultaneous regeneration of the cartilage and subchondral bone layers, which is not the case for the random poly(lactide-co-glycolide) scaffold after the same implantation in vivo. The oriented macroporous PLGA scaffold is a promising material for the in situ inductive osteochondral regeneration without the necessity of preseeding cells.

Advances in Adult Stem Cell Differentiation and Cellular Reprogramming to Enhance Chondrogenesis

Cell-based therapies to treat articular cartilage and osteochondral defects as a result of osteoarthritis or traumatic injury are a promising approach. Traditional sources of cells have been autologous chondrocytes which are culture expanded and implanted; however, dedifferentiation of these cells results in a type of fibrocartilage which has reduced therapeutic benefit. Advances in cellular reprogramming technology are either through generation of induced pluripotent stem cells (iPSCs) and subsequent chondrogenic or through direct reprogramming of adult cells to chondrocytes. These approaches have the potential to provide an unlimited source of cartilage for therapeutic applications; however, challenges remain in terms of efficient cellular differentiation and ability to integrate and repair tissues. Growth factor-based strategies previously used in chondrogenic differentiation of adult stem cells and embryonic stem cells have been successfully applied to induced pluripotent stem cells, enhancing the ability of iPSCs to produce both patient-specific chondrocytes and to produce large quantities of these cells. A combination of novel biomaterials and additive bioprinting have also opened new approaches to recapitulate zonal cartilage structure and repair of osteochondral defects. The development of innovative protocols to generate chondrocytes from a variety of primary cells continues to proceed rapidly, allowing fine tuning of differentiation processes to produce an articular cartilage phenotype with improved mechanical and tissue integration capabilities.

[Experimental study on loading naringin composite scaffolds for repairing rabbit osteochondral defects].

To investigate the performance of loading naringin composite scaffolds and its effects on repair of osteochondral defects. The loading naringin and unloading naringin sustained release microspheres were prepared by W/O/W method; with the materials of the attpulgite and the collagen type I, the loading naringin, unloading naringin, and loading transforming growth factor β 1 (TGF-β 1) osteochondral composite scaffolds were constructed respectively by "3 layers sandwich method". The effect of sustained-release of loading naringin microspheres, the morphology of the composite scaffolds, and the biocompatibility were evaluated respectively by releasing in vitro, scanning electron microscope, and cell counting kit 8. Forty Japanese white rabbits were randomly divided into groups A, B, C, and D, 10 rabbits each group. After a osteochondral defect of 4.5 mm in diameter and 4 mm in depth was made in the intercondylar fossa of two femurs. Defect was not repaired in group A (blank control), and defect was repaired with unloading naringin composite scaffolds (negative control group), loading naringin composite scaffolds (experimental group), and loading TGF-β 1 composite scaffolds (positive control group) in groups B, C, and D respectively. At 3 and 6 months after repair, the intercondylar fossa was harvested for the general, HE staining, and toluidine blue staining to observe the repair effect. Western blot was used to detect the expression of collagen type II in the new cartilage. Loading naringin microspheres had good effect of sustained-release; the osteochondral composite scaffolds had good porosity; the cell proliferation rate on loading naringin composite scaffold was increased significantly when compared with unloading naringin scaffold ( P<0.05). General observation revealed that defect range of groups C and D was reduced significantly when compared with groups A and B at 3 months after repair; at 6 months after repair, defects of group C were covered by new cartilage, and new cartilage well integrated with the adjacent cartilage in group D. The results of histological staining revealed that defects were filled with a small amount of fibrous tissue in groups A and B, and a small amount of new cartilage in groups C and D at 3 months after repair; new cartilage of groups C and D was similar to normal cartilage, but defects were filled with a large amount of fibrous tissue in groups A and B at 6 months after repair. The expression of collagen type II in groups C and D was significantly higher than that in groups A and B ( P<0.05), but no significant difference was found between groups C and D ( P>0.05). Loading naringin composite scaffolds have good biocompatibility and effect in repair of rabbit articular osteochondral defects.

Repair of osteochondral defects with in vitro engineered cartilage based on autologous bone marrow stromal cells in a swine model

Functional reconstruction of large osteochondral defects is always a major challenge in articular surgery. Some studies have reported the feasibility of repairing articular osteochondral defects using bone marrow stromal cells (BMSCs) and biodegradable scaffolds. However, no significant breakthroughs have been achieved in clinical translation due to the instability of in vivo cartilage regeneration based on direct cell-scaffold construct implantation. To overcome the disadvantages of direct cell-scaffold construct implantation, the current study proposed an in vitro cartilage regeneration strategy, providing relatively mature cartilage-like tissue with superior mechanical properties. Our strategy involved in vitro cartilage engineering, repair of osteochondral defects, and evaluation of in vivo repair efficacy. The results demonstrated that BMSC engineered cartilage in vitro (BEC-vitro) presented a time-depended maturation process. The implantation of BEC-vitro alone could successfully realize tissue-specific repair of osteochondral defects with both cartilage and subchondral bone. Furthermore, the maturity level of BEC-vitro had significant influence on the repaired results. These results indicated that in vitro cartilage regeneration using BMSCs is a promising strategy for functional reconstruction of osteochondral defect, thus promoting the clinical translation of cartilage regeneration techniques incorporating BMSCs.

Repair of articular osteochondral defects of the knee joint using a composite lamellar scaffold.

ObjectivesThe major problem with repair of an articular cartilage injury is the extensive difference in the structure and function of regenerated, compared with normal cartilage. Our work investigates the feasibility of repairing articular osteochondral defects in the canine knee joint using a composite lamellar scaffold of nano-ß-tricalcium phosphate (ß-TCP)/collagen (col) I and II with bone marrow stromal stem cells (BMSCs) and assesses its biological compatibility.MethodsThe bone–cartilage scaffold was prepared as a laminated composite, using hydroxyapatite nanoparticles (nano-HAP)/collagen I/copolymer of polylactic acid–hydroxyacetic acid as the bony scaffold, and sodium hyaluronate/poly(lactic-co-glycolic acid) as the cartilaginous scaffold. Ten-to 12-month-old hybrid canines were randomly divided into an experimental group and a control group. BMSCs were obtained from the iliac crest of each animal, and only those of the third generation were used in experiments. An articular osteochondral defect was created in the right knee of dogs in both groups. Those in the experimental group were treated by implanting the composites consisting of the lamellar scaffold of ß-TCP/col I/col II/BMSCs. Those in the control group were left untreated.ResultsAfter 12 weeks of implantation, defects in the experimental group were filled with white semi-translucent tissue, protruding slightly over the peripheral cartilage surface. After 24 weeks, the defect space in the experimental group was filled with new cartilage tissues, finely integrated into surrounding normal cartilage. The lamellar scaffold of ß-TCP/col I/col II was gradually degraded and absorbed, while new cartilage tissue formed. In the control group, the defects were not repaired.ConclusionThis method can be used as a suitable scaffold material for the tissue-engineered repair of articular cartilage defects.Cite this article: Bone Joint Res 2015;4:56–64

Osteogenesis and chondrogenesis of biomimetic integrated porous PVA/gel/V-n-HA/pa6 scaffolds and BMSCs construct in repair of articular osteochondral defect.

A novel bi-layered osteochondral scaffold, including of PVA/Gel/V layer for the cartilage and n-HA/PA6 layer for the subchondral bone, has been proposed to evaluate the potential of the engineered of osteochondral grafts in repairing articular osteochondral defects in rabbits. The two different layers of the scaffolds were seeded with allogenic bone marrow-derived stem cells (BMSCs), which were chondrogenically and osteogenically induced respectively. The critical-size osteochondral defects were created in the knees of adult rabbits. The defects were treated with cell-bi-layered constructs (Group A), bi-layered constructs (Group B) and untreated group C as control group. The adhesion, proliferation and differentiation of BMSCs were demonstrated by immunohistochemical staining and scanning electron microscopy (SEM) in vitro. Cell survival was tracked via fluorescent labeling in vivo. Overall, the porous PVA/Gel/V-n-HA/PA6 scaffold was compatible and had no negative effects on the BMSCs in vitro culture. The cell-bi-layered scaffolds showed superior repair results as compared to the control group using gross examination and histological assessment. With BMSCs implantation, the two different layers of the composite biomimetic scaffolds provided a suitable environment for cells to form respective tissue. Simultaneously, the RT-PCR results confirmed the expression of specific extracellular matrix (ECM) markers for cartilaginous or osteoid tissue. This investigation showed that the porous PVA/Gel/V-n-HA/PA6 scaffold is a potential matrix for treatment of osteochondral defects, and the method of using chondrogenically and osteogenically differentiated BMSCs as seed cells on each layer might be a promising strategy in repair of articular osteochondral defect due to enhanced chondrogenesis and osteogenesis.

Spontaneous hyaline cartilage regeneration can be induced in an osteochondral defect created in the femoral condyle using a novel double-network hydrogel

BackgroundFunctional repair of articular osteochondral defects remains a major challenge not only in the field of knee surgery but also in tissue regeneration medicine. The purpose is to clarify whether the spontaneous hyaline cartilage regeneration can be induced in a large osteochondral defect created in the femoral condyle by means of implanting a novel double-network (DN) gel at the bottom of the defect.MethodsTwenty-five mature rabbits were used in this study. In the bilateral knees of each animal, we created an osteochondral defect having a diameter of 2.4-mm in the medial condyle. Then, in 21 rabbits, we implanted a DN gel plug into a right knee defect so that a vacant space of 1.5-mm depth (in Group I), 2.5-mm depth (in Group II), or 3.5-mm depth (in Group III) was left. In the left knee, we did not apply any treatment to the defect to obtain the control data. All the rabbits were sacrificed at 4 weeks, and the gross and histological evaluations were performed. The remaining 4 rabbits underwent the same treatment as used in Group II, and real-time PCR analysis was performed at 4 weeks.ResultsThe defect in Group II was filled with a sufficient volume of the hyaline cartilage tissue rich in proteoglycan and type-2 collagen. The Wayne's gross appearance and histology scores showed that Group II was significantly greater than Group I, III, and Control (p < 0.012). The relative expression level of type-2 collagen, aggrecan, and SOX9 mRNAs was significantly greater in Group II than in the control group (p < 0.023).ConclusionsThis study demonstrated that spontaneous hyaline cartilage regeneration can be induced in vivo in an osteochondral defect created in the femoral condyle by means of implanting the DN gel plug at the bottom of the defect so that an approximately 2-mm deep vacant space was intentionally left in the defect. This fact has prompted us to propose an innovative strategy without cell culture to repair osteochondral lesions in the femoral condyle.

Repair of knee joint articular osteochondral defects with collagen complex gradient hydroxyapatite biphasic scaffold loaded with chondrocytes in rabbits

Objective To evaluate the effectiveness and feasibility for the treatment of osteochondral defects on the femoral condyles by collagen/hydroxyapatite (Col/HA) biphasic scaffolds loaded with the cultured articular cartilage chondrocytes in rabbit knee joint. Methods Biphasic scaffolds were constructed with collagen complex gradient hydroxyapatite. The chondrocytes of third generation were embedded in the biphasic scaffolds' collagen. After culture for one week in vitro, the complexes of chondrocytesscaffold were transplanted to repair the articular osteochondral defects of the femoral condyle of rabbit knees ( the defects were 4 mm in diameter, 3.5 mm in depth, extending down to the subchondral bone). Healing of defects was assessed by gross and histological examination. Results Biphasic collagen/hydroxyapatite scaffold had good hydrophilia and permeability. Light microscopy and scanning electron microscopy revealed that chondrocytes attaching to the wall of microholes of the scaffold had largely maintained a rounded morphology and could secrete the extracellular matrix on the porous scaffold. Gross and light microscopic examination showed that the treatment of simple Col/HA scaffold improved defect filling compared with that left untreated, while the regenerated tissue was mainly fibrocartilage and showed little bone formation.When implanted with Col/HA scaffold combined with chondrocytes, most of the defects were filled with a well-established layer of cartilage tissue with new bone formation. Wakitani scoring showed that experimental group was superior to control groups in 16 weeks with the difference being significant between them (P ＜0.05). Conclusion The novel biphasic collagen/hydroxyapatite scaffold will possibly be an ideal scaffold for osteochondral tissue engineering. It may induce articular osteochondral regeneration to repair the defects of articular osteochondral in vivo after loaded with chondrocytes. Key words: Collagen;  Hydroxyapatite;  Tissue engineering;  Chondrocyte;  Osteochondral defect

Osteochondral repair using porous poly(lactide‐co‐glycolide)/nano‐hydroxyapatite hybrid scaffolds with undifferentiated mesenchymal stem cells in a rat model

In this study, a novel three-dimensional poly (lactide-co-glycolide) (PLGA)/nano-hydroxyapatite (NHA) scaffold was fabricated by a thermally induced phase separation technique and its potential application in cartilage tissue-engineering was investigated. The PLGA scaffold was used as a control and mesenchymal stem cells (MSCs) were seeded in both scaffolds. After 12-days culture, SEM images and confocal laser scanning microscopy illustrated that MSCs attached more moderately and more cells distributed in PLGA/NHA scaffolds. MTT test and DNA assay showed that the viability and proliferation of MSCs in PLGA/NHA scaffolds were significantly superior to PLGA scaffolds during in vitro culture. Through in vivo study, the efficacy of this scaffold combining with MSCs for repairing articular osteochondral defects was evaluated in a rat model. Osteochondral defects in rats knees were left untreated, or treated with PLGA/NHA-MSCs composites or PLGA-MSCs composites. Twelve weeks after operation, histological examination revealed that the defects in the PLGA/NHA-MSCs treated group were filled with smooth and hyaline-like cartilage with abundant glycosaminoglycan and collagen type II deposition, but deficient in collagen type I at 12 weeks after operation. To investigate the final fate of MSCs transplanted into the defect areas, the fluorescent dye CM-DiI was used to prelabel cells. At 12 weeks after transplantation, we still observed the red fluorescence in the repair area. These findings suggest that the PLGA/NHA-MSCs composite may be potentially used for cartilage repair in clinical application. (c) 2010 Wiley Periodicals, Inc. J Biomed Mater Res, 2010.