Osteochondral Repair Research Articles

A Col I and BCP ceramic bi-layer scaffold implant promotes regeneration in osteochondral defects.

Osteochondral defects occur in the superficial cartilage region, intermediate calcified cartilage, and subchondral bone. Due to the limited regenerative capacity and complex zonal structure, it is critically difficult to develop strategies for osteochondral defect repair that could meet clinical requirements. In this study, type I collagen (Col I) and BCP ceramics were used to fabricate a new bi-layer scaffold for regeneration in osteochondral defects. The in vitro studies showed that the bi-layer scaffold provided special functions for cell migration, proliferation and secretion due to the layered scaffold structure. The in vivo results demonstrated that the bi-layered scaffold could effectively promote the regeneration of both the cartilage and the subchondral bone, and the newly formed cartilage layer, with a similar structure and thickness to the natural cartilaginous layer, could seamlessly integrate with the surrounding natural cartilage and regenerate an interface layer to mimic the native osteochondral structure.

Engineering a multiphasic, integrated graft with a biologically developed cartilage-bone interface for osteochondral defect repair.

Tissue engineering is a promising approach to repair osteochondral defects, yet successful reconstruction of different layers in an integrated graft, especially the interface remains challenging. The multiphasic, functionally integrated tissue engineering graft described herein mimics the entire osteochondral tissue in terms of structure and composition at the cartilage, bone and cartilage-bone interface layer to repair osteochondral defects. In this manuscript, we report the fabrication of a multiphasic graft via bonding of a cartilaginous hydrogel and a sintered poly(lactic-co-glycolic acid) microsphere scaffold by an endogenous fibrotic cartilaginous extracellular matrix. We demonstrated that culturing chondrocytes within the alginate hydrogel conjugated to the poly(lactic-co-glycolic acid) scaffold allows for (i) gradient transition and integration from the cartilage layer to the subchondral bone layer as assessed by scanning electron microscopy, histology and biochemistry, and (ii) superior tissue repair efficacy in a rabbit knee defect model. Industrialization of the graft remains an unsolved challenge as after decellularization the tissue repair efficacy of the graft decreased. Taken together, the multiphasic osteochondral graft repaired the osteochondral defects successfully and has the potential to be applied clinically as an implant in orthopaedic surgery.

Intra-articular injection of N-acetylglucosamine and hyaluronic acid combined with PLGA scaffolds for osteochondral repair in rabbits.

Repairing damaged articular cartilage is particularly challenging because of the limited ability of cartilage to perform self-repair. Intra-articular injections of N-acetylglucosamine (GlcNAc) comprise a method of repairing full-thickness articular cartilage defects in the rabbit knee joint model. To date, the effects of administration of GlcNAc and hyaluronic acid (HA) have been investigated only in the context of osteoarthritis treatment. Therefore, we evaluated the therapeutic effects of using cell-free porous poly lactic-co-glycolic acid (PLGA) graft implants and intra-articular injections of GlcNAc or HA in a rabbit model of osteochondral regeneration to investigate whether they have the potential for inducing osteochondral regeneration when used alone or simultaneously. Twenty-four rabbits were randomized into one of four groups: the scaffold-only group (PLGA), the scaffold with intra-articular injections of GlcNAc (PLGA+G) group, twice per week for four weeks; the scaffold with intra-articular injections of HA group (PLGA+HA) group, once per week for three weeks; and the scaffold with intra-articular injections of GlcNAc and HA (PLGA+G+HA) group, once per week for three weeks. Knees were evaluated at 4 and 12 weeks after surgery. At the end of testing, only the PLGA+G+HA group exhibited significant bone reconstruction, chondrocyte clustering, and good interactions with adjacent surfaces at 4 weeks. Additionally, the PLGA+G+HA group demonstrated essentially original hyaline cartilage structures that appeared to have sound chondrocyte orientation, considerable glycosaminoglycan levels, and reconstruction of the bone structure at 12 weeks. Moreover, the PLGA+G+HA group showed organized osteochondral integration and significantly higher bone volume per tissue volume and trabecular thickness. However, there were no significant differences between the PLGA+G and PLGA+HA groups except for gap formation on subchondral bone in the PLGA+G group. This study demonstrated that PLGA implantation combined with intra-articular injections of GlcNAc and HA allowed for cartilage and bone regeneration and significantly promoted osteochondral regeneration in rabbits without supplementation of exogenous growth factors. And the combination of this two supplements with PLGA scaffold could also prolong injection interval and better performance than either of them alone for the reconstruction of osteochondral tissue in the knee joints of rabbits.

Homogeneous hydroxyapatite/alginate composite hydrogel promotes calcified cartilage matrix deposition with potential for three-dimensional bioprinting

Calcified cartilage regeneration plays an important role in successful osteochondral repair, since it provides a biological and mechanical transition from the unmineralized cartilage at the articulating surface to the underlying mineralized bone. To biomimic native calcified cartilage in engineered constructs, here we test the hypothesis that hydroxyapatite (HAP) stimulates chondrocytes to secrete the characteristic matrix of calcified cartilage. Sodium citrate (SC) was added as a dispersant of HAP within alginate (ALG), and homogeneous dispersal of HAP within ALG hydrogel was confirmed using sedimentation tests, electron microscopy, and energy dispersive spectroscopy. To examine the biological performance of ALG/HAP composites, chondrocyte survival and proliferation, extracellular matrix production, and mineralization potential were evaluated in the presence or absence of the HAP phase. Chondrocytes in ALG/HAP constructs survived well and proliferated, but also expressed higher levels of calcified cartilage markers compared to controls, including Collagen type X secretion, alkaline phosphatase (ALP) activity, and mineral deposition. Compared to controls, ALG/HAP constructs also showed an elevated level of mineralized matrix in vivo when implanted subcutaneously in mice. The printability of ALG/HAP composite hydrogel precursors was verified by 3D printing of ALG/HAP hydrogel scaffolds with a porous structure. In summary, these results confirm the hypothesis that HAP in ALG hydrogel stimulates chondrocytes to secrete calcified matrix in vitro and in vivo and reveal that ALG/HAP composites have the potential for 3D bioprinting and osteochondral regeneration.

3D Molecularly Functionalized Cell‐Free Biomimetic Scaffolds for Osteochondral Regeneration

AbstractClinically, cartilage damage is frequently accompanied with subchondral bone injuries caused by disease or trauma. However, the construction of biomimetic scaffolds to support both cartilage and subchondral bone regeneration remains a great challenge. Herein, a novel strategy is adopted to realize the simultaneous repair of osteochondral defects by employing a self‐assembling peptide hydrogel (SAPH) FEFEFKFK (F, phenylalanine; E, glutamic acid; K, lysine) to coat onto 3D‐printed polycaprolactone (PCL) scaffolds. Results show that the SAPH‐coated PCL scaffolds exhibit highly improved hydrophilicity and biomimetic extracellular matrix (ECM) structures compared to PCL scaffolds. In vitro experiments demonstrate that the SAPH‐coated PCL scaffolds promote the proliferation and osteogenic differentiation of rabbit bone mesenchymal stem cells (rBMSCs) and maintain the chondrocyte phenotypes. Furthermore, 3% SAPH‐coated PCL scaffolds significantly induce simultaneous regeneration of cartilage and subchondral bone after 8‐ and 12‐week implantation in vivo, respectively. Mechanistically, by virtue of the enhanced deposition of ECM in SAPH‐coated PCL scaffolds, SAPH with increased stiffness facilitates and remodels the microenvironment around osteochondral defects, which may favor simultaneous dual tissue regeneration. These findings indicate that the 3% SAPH provides efficient and reliable modification on PCL scaffolds and SAPH‐coated PCL scaffolds appear to be a promising biomaterial for osteochondral defect repair.

Development of an Ex Vivo Murine Osteochondral Repair Model

Mouse models are commonly used in research applications due to the relatively low cost, highly characterized strains, as well as the availability of many genetically modified phenotypes. In this study, we characterized an ex vivo murine osteochondral repair model using human infrapatellar fat pad (IPFP) progenitor cells. Femurs from euthanized mice were removed and clamped in a custom multidirectional vise to create cylindrical osteochondral defects 0.5 mm in diameter and 0.5 mm deep in both condyles. The IPFP contains progenitors that are a promising cell source for the repair of osteochondral defects. For proof of concept, human IPFP-derived progenitor cells, from osteoarthritic (OA) patients, cultured as pellets, were implanted into the defects and cultured in serum-free medium with TGFβ3 for 3 weeks and then processed for histology and immunostaining. The custom multidirectional vise enabled reproducible creation of osteochondral defects in murine femoral condyles. Implantation of IPFP-derived progenitor cells led to development of cartilaginous tissue with Safranin O staining and deposition of collagen type II in the extracellular matrix. We showed feasibility in creating ex vivo osteochondral defects and demonstrated the regenerative potential of OA human IPFP-derived progenitors in mouse femurs. The murine model can be used to study the effects of aging and OA on tissue regeneration and to explore molecular mechanisms of cartilage repair using genetically modified mice.

Biomimetic Bacterial Cellulose-Enhanced Double-Network Hydrogel with Excellent Mechanical Properties Applied for the Osteochondral Defect Repair.

Although hydrogels based on biopolymers show many advantages, their low mechanical properties limit their applications in osteochondral tissue engineering. In this study, one part of our work aimed at preparing a high strength biohydrogel by using a double-network (DN) hydrogel system, which consisted of two interpenetrating polymer networks composed of γ-glutamic acid, lysine, and alginate, and meanwhile by incorporating bacterial cellulose into the DN structures. The results showed that compression modulus of the resultant hydrogel (0.322 MPa) was comparable with that of natural articular cartilage and swelling degree was greatly depressed by using these strategies. On this basis, a bilayer hydrogel scaffold based on the bionics principle for osteochondral regeneration was fabricated via chemical and physical cross-linking. Additionally, hydroxyapatite (HA) particles with two different sizes were introduced into the bilayer hydrogels, respectively: micro-HA in the top layer for promoting cartilage matrix deposition and HA nanocrystals in the bottom layer for enhancing compression modulus and osteogenesis. The osteochondral defect model of rabbits was used to evaluate the repair effect of the scaffolds with the bilayer structure, and the results showed such as-synthesized scaffolds had a good osteochondral repair effect.

OSTEOCHONDRAL AUTOGRAFT TRANSFER FOR TREATMENT OF STIFLE OSTEOCHONDRITIS DISSECANS IN TWO RELATED SNOW LEOPARDS ( PANTHERA UNCIA).

Two related female snow leopards ( Panthera uncia) were diagnosed with osteochondritis dissecans of the lateral femoral condyle via radiographs and computed tomography. Lesions were either bilateral (Patient 1) or unilateral (Patient 2). Surgical treatment was performed using an osteochondral autograft transfer system following cartilage flap removal. After a 6-wk recovery period, both animals had a markedly improved gait with mild pelvic limb stiffness. Patient 1 developed intermittent lameness 9 mo postsurgery and Patient 2 had mild lameness 3 yr postsurgery. Because of recurrent lameness, both animals were treated with platelet-rich plasma intra-articular injections and oral gabapentin (Patient 1) or oral meloxicam (Patient 2). Full incorporation of autografts was confirmed with computed tomography (both patients) and arthroscopy (Patient 1 only). Osteochondritis dissecans has been previously reported in snow leopards and these cases represent the first reported use of osteochondral autograft repair and platelet-rich plasma to treat the condition.

Bilayered PLGA/PLGA-HAp Composite Scaffold for Osteochondral Tissue Engineering and Tissue Regeneration.

This study is aimed at investigation of the osteochondral regeneration potential of bilayered PLGA/PLGA-HAp composite scaffolds with one layer made of biodegradable polymer poly(d,l-lactide-co-glycolide) (PLGA) and another layer made of PLGA polymeric matrix coated by bioactive ceramics hydroxyapatite (HAp). The composite scaffolds were fabricated by compression molding/particle leaching and plasma-treated surface deposition. The pore morphology, mechanical properties, and surface deposition of the scaffold were characterized, and the growth of bone marrow derived mesenchymal stem cells or medicinal signaling cells (MSCs) in the scaffold was verified. Thereafter, rabbit models with an artificial osteochondral defect in joint were randomized into three treatment groups: virgin bilayered scaffold, bilayered scaffold preseeded in vitro with MSCs, and untreated blank control. At 16-week postoperation, both the virgin scaffolds and cell-seeded bilayered scaffolds exhibited osteochondral repair, as verified by biomechanics analysis, histological evaluations, and Western blot. The results highlighted the potentiality of the bilayered PLGA/PLGA-HAp composite scaffold for osteochondral tissue engineering, and in particular tissue regeneration or in situ tissue induction, probably by recruiting the local cells toward chondrogenic and osteogenic differentiation in the porous biomaterials.

Tough hydrogel with enhanced tissue integration and in situ forming capability for osteochondral defect repair

Articular cartilage repair still remains a major challenge in today's clinical practice due to its poor self-healing capacity. Therefore, it is essential to develop a promising strategy to achieve a one-step cartilage repair for patients suffering from joint diseases and traumas. Inspired by the complex composition and microscopic architecture of native articular cartilage, an injectable hydrogel (M-O-G) with tough mechanical property and strong tissue adhesiveness is developed. All hydrogel material compositions are natural polymers or their derivatives resemble the normal cartilage extracellular matrix (ECM). This hydrogel showed superior tunable mechanical properties (mechanical strength ≈270kPa, compressibility ≈70%) and rapid recovery ability. Moreover, it exhibited strong adhesiveness and enhanced integration with tissues. Further studies demonstrated that the hydrogel had good biocompatibility and superior performance in cartilage defect regeneration. Thus, the presented hydrogel is a promising biomaterial for clinical cartilage regeneration and other biomedical applications.

Tailoring the subchondral bone phase of a multi-layered osteochondral construct to support bone healing and a cartilage analog

Focal chondral and osteochondral defects create significant pain and disability for working-aged adults. Current osteochondral repair grafts are limited in availability and often fail due to insufficient osseous support and integration. Thus, a need exists for an off-the-shelf osteochondral construct with the propensity to overcome these shortcomings. Herein, a scalable process was used to develop a multi-layered osteochondral graft with a subchondral bone (ScB) phase tailored to support bone healing and integration. Multiple ScB formulations and fabrication techniques were screened via degradation, bioactivity, and unconfined compression testing. An optimized ScB construct was selected and its cytotoxicity assessed. Additionally, a cartilage analog was secured to the optimized ScB construct via a calcified cartilage layer, and the resulting osteochondral construct was characterized via interfacial shear and dynamic mechanical testing. The optimized ScB construct did not significantly alter local pH during degradation, exhibited measurable bioactivity in vitro, and had significantly greater compressive mechanical strength compared to other constructs. The attachment strength of the cartilage analog was significantly greater by an increase in compressive dynamic mechanical properties. Furthermore, this ScB construct was found to be cytocompatible with human bone marrow-derived mesenchymal stromal cells. Taken together, this optimized ScB material forms the robust foundation of a novel, off-the-shelf osteochondral construct to be used in defect repair. Statement of SignificanceThe quality of life for millions of individuals worldwide is detrimentally affected by focal chondral or osteochondral defects. Current off-the-shelf biomaterial constructs often fail to repair these defects due to insufficient osseous support and integration. Herein, we used a scalable process to fabricate and optimize a novel boney construct. This optimized boney construct demonstrated biochemical, physical, and mechanical properties tailored to promote bone healing. Furthermore, a novel cartilage analog was successfully attached to the boney construct, forming a multi-layered osteochondral construct.

Chitosan-Based Nanofibrous Membrane Unit with Gradient Compositional and Structural Features for Mimicking Calcified Layer in Osteochondral Matrix.

Chitosan (CH), silk fibroin (SF), and hydroxyapatite (HA) were used to prepare CH/SF/HA composites and the resulting composites were electrospun into nanofibrous membrane units with gradient compositional and structural features. The optimal membrane unit was used together with CH/HA and CH/SF composites to fabricate a type of three-layer scaffold that is intended for osteochondral repair. The bottom layer of the scaffold was built with CH/HA composites and it served as a subchondral layer, the integrated nanofibrous membrane unit functioned as the middle layer for mimicking the calcified layer and the top layer was constructed using CH/SF composites for acting as a chondral layer. The nanofibrous membrane unit was found to be permeable to some molecules with limited molecular weight and was able to prevent the seeded cells from migrating cross the unit, functioning approximately like the calcified layer in the osteochondral matrix. Layered scaffolds showed abilities to promote the growth of both chondrocytes and osteoblasts that were seeded in their chondral layer and bony layer, respectively, and they were also able to support the phenotype preservation of seeded chondrocytes and the mineralization of neotissue in the bony layer. Results suggest that this type of layered scaffolds can function as an analogue of the osteochondral matrix and it has potential in osteochondral repair.

Functionally graded multilayer scaffolds for in vivo osteochondral tissue engineering

Osteochondral tissue repair remains a significant challenge in orthopedic surgery. Tissue engineering of osteochondral tissue has transpired as a potential therapeutic solution as it can effectively regenerate bone, cartilage, and the bone-cartilage interface. While advancements in scaffold fabrication and stem cell engineering have made significant progress towards the engineering of composite tissues, such as osteochondral tissue, new approaches are required to improve the outcome of such strategies. Herein, we discuss the use of a single-unit trilayer scaffold with depth-varying pore architecture and mineral environment to engineer osteochondral tissues in vivo. The trilayer scaffold includes a biomineralized bottom layer mimicking the calcium phosphate (CaP)-rich bone microenvironment, a cryogel middle layer with anisotropic pore architecture, and a hydrogel top layer. The mineralized bottom layer was designed to support bone formation, while the macroporous middle layer and hydrogel top layer were designed to support cartilage tissue formation. The bottom layer was kept acellular and the top two layers were loaded with cells prior to implantation. When implanted in vivo, these trilayer scaffolds resulted in the formation of osteochondral tissue with a lubricin-rich cartilage surface. The osteochondral tissue formation was a result of continuous differentiation of the transplanted cells to form cartilage tissue and recruitment of endogenous cells through the mineralized bottom layer to form bone tissue. Our results suggest that integrating exogenous cell-based cartilage tissue engineering along with scaffold-driven in situ bone tissue engineering could be a powerful approach to engineer analogs of osteochondral tissue. In addition to offering new therapeutic opportunities, such approaches and systems could also advance our fundamental understanding of osteochondral tissue regeneration and repair. Statement of SignificanceIn this work, we describe the use of a single-unit trilayer scaffold with depth-varying pore architecture and mineral environment to engineer osteochondral tissues in vivo. The trilayer scaffold was designed to support continued differentiation of the donor cells to form cartilage tissue while supporting bone formation through recruitment of endogenous cells. When implanted in vivo, these trilayer scaffolds partially loaded with cells resulted in the formation of osteochondral tissue with a lubricin-rich cartilage surface. Approaches such as the one presented here that integrates ex vivo tissue engineering along with endogenous cell-mediated tissue engineering can have a significant impact in tissue engineering composite tissues with diverse cell populations and functionality.

Therapeutic Effects of the Addition of Platelet-Rich Plasma to Bioimplants and Early Rehabilitation Exercise on Articular Cartilage Repair

Background: Treating articular cartilage lesions is clinically challenging. However, whether the addition of autologous platelet-rich plasma (PRP) to bioimplants along with early rehabilitation exercise provides therapeutic effects and regenerates the osteochondral defect remains uninvestigated. Hypothesis: The addition of PRP to a polylactic-co-glycolic acid (PLGA) scaffold along with continuous passive motion (CPM) in osteochondral defects may offer beneficial in situ microenvironment changes to facilitate hyaline cartilage and subchondral bone tissue repair. Study Design: Controlled laboratory study. Methods: In 26 rabbits, 52 critical osteochondral defects were created in bilateral femoral trochlear grooves. The rabbits were allocated to 1 of the following 3 groups: PRP gel (PG group), PRP + PLGA scaffold (PP group), and PRP + PLGA scaffold + CPM (PPC group). At 4 and 12 weeks after surgery, the specimens were assessed by a macroscopic examination, a histological evaluation with immunohistochemical staining, and micro–computed tomography. Results: The PPC group exhibited the most favorable therapeutic outcomes in terms of hyaline cartilage regeneration. At week 4, the PPC group exhibited significantly higher levels of glycosaminoglycan (GAG) and collagen (COL) II and modest increases in COL I, matrix metalloproteinase–3 (MMP-3), and inflammatory cells with tumor necrosis factor–alpha (TNF-α) and interleukin-6 (IL-6). At week 12, the PPC group had significantly higher tissue repair scores, corresponding to a sound articular cartilage surface and chondrocyte and collagen arrangement. This group demonstrated restored hyaline cartilage and mineralized bone volume per tissue volume, which had an integrating structure in the repair site. However, the PG and PP groups exhibited mainly fibrous tissue and fibrocartilage, corresponding to higher expressions of COL I, TNF-α, IL-6, and MMP-3. Conclusion: PRP with a PLGA graft along with early CPM exercise is promising for the repair of osteochondral defects in rabbit knee joints. Clinical Relevance: This study demonstrates the efficacy of a triad therapy involving the addition of PRP to bioimplants along with early CPM intervention for hyaline cartilage and subchondral regeneration. However, PRP alone (with or without PLGA implants) is limited to osteochondral defect repair without significant regeneration.

Multilayered Scaffold with a Compact Interfacial Layer Enhances Osteochondral Defect Repair.

Repairing osteochondral defect (OCD) using advanced biomaterials that structurally, biologically, and mechanically fulfill the criteria for stratified tissue regeneration remains a significant challenge for researchers. Here, a multilayered scaffold (MLS) with hierarchical organization and heterogeneous composition is developed to mimic the stratified structure and complex components of natural osteochondral tissues. Specifically, the intermediate compact interfacial layer within the MLS is designed to resemble the osteochondral interface to realize the closely integrated layered structure. Subsequently, macroscopic observations, histological evaluation, and biomechanical and biochemical assessments are performed to evaluate the ability of the MLS of repairing OCD in a goat model. By 48 weeks postimplantation, superior hyalinelike cartilage and sound subchondral bone are observed in the MLS group. Furthermore, the biomimetic MLS significantly enhances the biomechanical and biochemical properties of the neo-osteochondral tissue. Taken together, these results confirm the potential of this optimized MLS as an advanced strategy for OCD repair.

Biological Response of Osteoblastic and Chondrogenic Cells to Graphene-Containing PCL/Bioactive Glass Bilayered Scaffolds for Osteochondral Tissue Engineering Applications.

Graphene-containing 13-93 bioactive glass and poly(ε-caprolactone)-based bilayer, electrically conductive scaffolds were prepared for osteochondral tissue repair. Biological response of osteoblastic MC3T3-E1 and chondrogenic ATDC5 cells to the composite scaffolds was assessed under mono-culture and co-culture conditions. Cytotoxicity was investigated using MTT assay, cartilage matrix production was evaluated by Alcian blue staining, and mineralization of both types of cells in the different culture systems was observed by Alizarin red S staining. Results showed that osteoblastic and chondrogenic cells utilized in the study did not show toxic response to the prepared scaffolds under mono-culture conditions and higher cell viability rates were obtained in co-culture conditions. Larger mineralized areas were determined under co-culture conditions and calcium deposition amount significantly increased compared with that in control group samples after 21days. Additionally, the amount of glycosaminoglycans synthesized in co-culture was higher compared to mono-culture conditions. Electric stimulation applied under mono-culture conditions suppressed the viability of MC3T3-E1 cells whereas it enhanced the viability rates of ATDC5 cells. The study suggests that the designed bilayered osteochondral constructs have the potential for osteochondral defect repair.

Interpenetrating polymer network scaffold of sodium hyaluronate and sodium alginate combined with berberine for osteochondral defect regeneration

Degradation of the articular cartilage and structural remodeling of the subchondral bone are regarded as the two major pathological characteristics of osteoarthritis. This study aimed to investigate the effect of an interpenetrating polymer network (IPN) of a sodium hyaluronate and sodium alginate (HA/SA) scaffold combined with berberine (BER) on osteochondral repair. We first developed an IPN scaffold of HA/SA and evaluated its characteristics. Then, we analyzed the effect of the HA/SA scaffold combined with BER on the healing of osteochondral defects in vivo. Finally, we explored the mechanism of this system in osteochondral repair. The results showed that the system could simultaneously regenerate not only the cartilage but also the subchondral bone. Our results also revealed that the subchondral bone was partially repaired by activating the Wnt signaling pathway and the cartilage was protected from degeneration by the upregulation of autophagy. This study demonstrated that the combination of the IPN scaffold of HA/SA and BER is a promising strategy for the osteochondral defect regeneration.

Icariin conjugated hyaluronic acid/collagen hydrogel for osteochondral interface restoration

Over the past decades, numerous tissue-engineered constructs have been investigated for the osteochondral repair. However, it still remains a challenge to regenerate the functionalized calcified layer. In this study, the potential of icariin (Ica) conjugated hyaluronic acid/collagen (Ica-HA/Col) hydrogel to promote the osteochondral interface restoration was investigated. Compared with HA/Col hydrogel, Ica-HA/Col hydrogel simultaneously facilitated chondrogenesis and osteogenesis in vitro. The cells encapsulated in Ica-HA/Col hydrogel tended to aggregate into bigger clusters. The chondrogenic genes’ expression level was remarkably up-regulated, and the matrix synthesis of sGAG and type II collagen was significantly enhanced. Similarly, the osteogenic genes, including RUNX2, ALP, and OCN were also up-regulated at early stage. Consequently, more calcium deposition was observed in the Ica-HA/Col hydrogel construct. Moreover, the gene expression and matrix synthesis of type X collagen, an important marker for the formation of calcified layer; were significantly higher in the Ica-HA/Col hydrogel. Furthermore, the in vivo study showed that Ica-HA/Col constructs facilitated the reconstruction of osteochondral interface in rabbit subchondral defects. In the Ica-HA/Col group, the neo-cartilage layer contained more type II collagen and the newly formed subchondral bone deposited more abundant type I collagen. Overall, the results indicated that Ica-HA/Col hydrogel might be a promising scaffold to reconstruct an osteochondral interface, therefore promoting restoring of osteochondral defect. Statement of SignificanceThe osteochondral defect restoration not only involves the repair of damaged cartilage and the subchondral bone, but also the reconstruction of osteochondral interface (the functional calcified layer). The calcified layer regeneration is essential for integrative and functional osteochondral repair. Over the past decade, numerous tissue engineered constructs have been investigated for the osteochondral repair. However, it still remains a challenge to regenerate a functionalized calcified layer. The present study demonstrates that Ica-HA/Col hydrogel facilitates deposition of matrix related to calcified layer in mixed chondrogenic/osteogenic inductive media and restoration of osteochondral defect in vivo. Since, Ica-HA/Col hydrogel as is cheaper, easier and more efficient, it might be a desired scaffold for the osteochondral defects restoration.

Sustained spatiotemporal release of TGF-β1 confers enhanced very early chondrogenic differentiation during osteochondral repair in specific topographic patterns.

The continuous presence of TGF-β is critically important to induce effective chondrogenesis. To investigate chondrogenesis in a cartilage defect, we tested the hypothesis that the implantation of TGF-β1-releasing scaffolds improves very early cartilage repair in vivo. Spatiotemporal controlled release of TGF-β1 was achieved from multiblock scaffolds that were implanted in osteochondral defects in the medial femoral condyles of adult minipigs. We observed a sustained presence of TGF-β1 at 4 wk in vivo, which significantly promoted structural aspects of early overall cartilage repair, especially cellularity, cellular morphology, and safranin O staining intensity. Furthermore, early aggrecan and type II collagen production were both increased in specific topographic patterns in cartilaginous repair tissue. Sustained release of TGF-β1 also increased cell numbers and proliferation, staining intensities for the stem cell surface marker, CD105, and number of stromal cell-derived factor-1 (SDF-1) -positive cells within cartilaginous repair tissue. These data identify a mechanism by which TGF-β1 modulates early chondrogenesis by primarily increasing the number of progenitor cells arising from the subchondral bone marrow compartment via the SDF-1/chemokine (CXC motif) receptor 4 pathway, their proliferation, differentiation, and extracellular matrix deposition in specific topographic patterns, highlighting the pivotal role played by TGF-β1 during this crucial phase.-Asen, A.-K., Goebel, L., Rey-Rico, A., Sohier, J., Zurakowski, D., Cucchiarini, M., Madry, H. Sustained spatiotemporal release of TGF-β1 confers enhanced very early chondrogenic differentiation during osteochondral repair in specific topographic patterns.

Osteochondral Repair Using Porous Three-dimensional Nanocomposite Scaffolds in a Rabbit Model.

To evaluate the utility of a novel nanocomposite biomaterial consisting of poly-L/D-lactide, and hydroxyapatite bioceramics, enriched with sodium alginate in articular cartilage defect treatment. The biomaterial was prepared using the method of solvent casting and particle leaching. The study was conducted on 20 New Zealand White rabbits. Experimental osteochondral defects were created in the femoral trochlear grooves and filled with biomaterials. In control groups, the defects were left to spontaneously heal. The quality of newly-formed tissue was evaluated on the basis of macroscopic and histological assessment. Additionally the level of osteogenic and cartilage degradation markers were measured. The majority of the defects from the treatment group were covered with tissue similar in structure and colour to healthy cartilage, whereas in the control group, tissue was uneven, and not integrated into the surrounding cartilage. The results obtained validate the choice of biomaterial used in this study as well as the method of its application.