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Cartilage tissue engineering strategies often rely on hydrogels with fixed covalent crosslinks for chondrocyte encapsulation, yet the resulting material properties are largely elastic and can impede matrix deposition. To address this limitation, hydrazone crosslinked poly(ethylene glycol) hydrogels were formulated to achieve tunable viscoelastic properties and to study how chondrocyte proliferation and matrix deposition vary with the time-dependent material properties of covalent adaptable networks. Hydrazone equilibrium differences were leveraged to produce average stress relaxation times from hours (4.01 × 10 3  s) to months (2.78 × 10 6  s) by varying the percentage of alkyl-hydrazone (aHz) and benzyl-hydrazone (bHz) crosslinks. Swelling behavior and degradation associated with adaptability were characterized to quantify temporal network changes that can influence the behavior of encapsulated chondrocytes. After four weeks, mass swelling ratios varied from 36 ± 3 to 17 ± 0.4 and polymer retention ranged from 46 ± 4% to 92 ± 5%, with higher aHz content leading to loss of network connectivity with time. Hydrogels were formulated near the Flory-Stockmayer bHz percolation threshold (17% bHz) to investigate chondrocyte response to distinct levels of covalent architecture adaptability. Four weeks post-encapsulation, formulations with average relaxation times of 3 days (2.6 × 10 5 s) revealed increased cellularity and an interconnected articular cartilage-specific matrix. Chondrocytes embedded in this adaptable formulation (22% bHz) deposited 190 ± 30% more collagen and 140 ± 20% more sulfated glycosaminoglycans compared to the 100% bHz control, which constrained matrix deposition to pericellular space. Collectively, these findings indicate that incorporating highly adaptable aHz crosslinks enhanced regenerative outcomes. However, connected networks containing more stable bHz bonds were required to achieve the highest quality neocartilaginous tissue. STATEMENT OF SIGNIFICANCE: Covalently crosslinked hydrogels provide robust mechanical support for cartilage tissue engineering applications in articulating joints. However, these materials traditionally demonstrate purely elastic responses to deformation despite the dynamic viscoelastic properties of native cartilage tissue. Here, we present hydrazone poly(ethylene glycol) hydrogels with tunable viscoelastic properties and study covalent adaptable networks for cartilage tissue engineering. Using hydrazone equilibrium and Flory-Stockmayer theory we identified average relaxation times leading to enhanced regenerative outcomes and showed that extracellular matrix deposition was biphasic as a function of the hydrazone covalent adaptability. We also showed that the incorporation of highly adaptable covalent crosslinks could improve cellularity of neotissue, but that a percolating network of more stable bonds was required to maintain scaffold integrity and form the highest quality neocartilaginous tissue., (Copyright © 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.)

Injuries to the articular cartilage surface are challenging to repair because cartilage possesses a limited capacity for self-repair. The outcomes of current clinical procedures aimed to address these injuries are inconsistent and unsatisfactory. We have developed a novel method for generating hyaline articular cartilage to improve the outcome of joint surface repair. A suspension of 10(7) swine chondrocytes was cultured under reciprocating motion for 14 days. The resulting dynamic self-regenerating cartilage (dSRC) was placed in a cartilage ring and capped with fibrin and collagen gel. A control group consisted of chondrocytes encapsulated in fibrin gel. Constructs were implanted subcutaneously in nude mice and harvested after 6 weeks. Gross, histological, immunohistochemical, biochemical, and biomechanical analyses were performed. In swine patellar groove, dSRC was implanted into osteochondral defects capped with collagen gel and compared to defects filled with osteochondral plugs, collagen gel, or left empty after 6 weeks. In mice, the fibrin- and collagen-capped dSRC constructs showed enhanced contiguous cartilage matrix formation over the control of cells encapsulated in fibrin gel. Biochemically, the fibrin and collagen gel dSRC groups were statistically improved in glycosaminoglycan and hydroxyproline content compared to the control. There was no statistical difference in the biomechanical data between the dSRC groups and the control. The swine model also showed contiguous cartilage matrix in the dSRC group but not in the collagen gel and empty defects. These data demonstrate the survivability and successful matrix formation of dSRC under the mechanical forces experienced by normal hyaline cartilage in the knee joint. The results from this study demonstrate that dSRC capped with hydrogels successfully engineers contiguous articular cartilage matrix in both nonload-bearing and load-bearing environments.

The objective of this study was to assess the ability of tissue engineered cartilage to adhere to and integrate with porous polyethylene (PPE) in vivo and to evaluate the biomechanical integrity of the bond formed at the interface. Porcine auricular, articular, and costal chondrocytes were suspended in fibrin gel polymer and placed between discs of PPE to form tri-layer constructs. Controls consisted of fibroblasts suspended in gel or gel alone between the discs. Constructs were implanted into nude mice for 6, 12, and 18 weeks. Upon harvest, specimens were evaluated for neocartilage formation and integration into the PPE, using histological, dimensional (mass, thickness, diameter), and biomechanical (adhesion strength, interfacial stiffness, failure energy and failure strain) analyses. Neotissue was formed in all experimental constructs, consisting mostly of neocartilage integrating with discs of PPE. Control samples contained only fibrous tissue. Biomechanical analyses demonstrated that adhesion strength, interfacial stiffness, and failure energy were all significantly higher in the chondrocyte-seeded samples than in fibroblast-seeded controls, with the exception of costal constructs at 12 weeks, which were not significantly greater than controls. In general, failure strains did not vary between groups. In conclusion, porous polyethylene supported the growth of neocartilage that formed mechanically functional bonds with the PPE., (© 2014 Wiley Periodicals, Inc.)

Cartilage damage and osteoarthritis (OA) impose an important burden on society, leaving both young, active patients and older patients disabled and affecting quality of life. In particular, cartilage injury not only imparts acute loss of function but also predisposes to OA. The increase in knowledge of the consequences of these diseases and the exponential growth in research of regenerative medicine have given rise to different treatment types. Of these, cell-based treatments are increasingly applied because they have the potential to regenerate cartilage, treat symptoms, and ultimately prevent or delay OA. Although these approaches give promising results, they require a costly in vitro cell culture procedure. The answer may lie in single-stage procedures that, by using cell combinations, render in vitro expansion redundant. In the last two decades, cocultures of cartilage cells and a variety of (mesenchymal) stem cells have shown promising results as different studies report cartilage regeneration in vitro and in vivo. However, there is considerable debate regarding the mechanisms and cellular interactions that lead to chondrogenesis in these models. This review, which included 52 papers, provides a systematic overview of the data presented in the literature and tries to elucidate the mechanisms that lead to chondrogenesis in stem cell cocultures with cartilage cells. It could serve as a basis for research groups and clinicians aiming at designing and implementing combined cellular technologies for single-stage cartilage repair and treatment or prevention of OA., (©AlphaMed Press.)

Purpose: Chondrocytes lose their ability to produce cartilaginous matrix during multiplication in culture through repeated passages, resulting in inferior tissue phenotype. To overcome the limited amount of primary chondrocytes, we aimed to determine the optimal culture condition for in vitro/in vivo cartilage regeneration using human adipose-derived mesenchymal stem cells (AMSCs)., Methods: To evaluate the effects exerted by the chondrocytic culture condition on AMSC, we utilized chondrocyte conditioned medium (CM) and/or co-culture methods to prime and differentiate AMSCs. We evaluated ultimate in vivo engineered cartilage with primed AMSCs with that of chondrocytes. To examine the link between conditioned factors and proliferation/differentiation, cell cycle progression of AMSCs were examined using 5-ethynyl-2'-deoxyuridine (EdU), and gene expression was monitored., Results: We report that AMSCs can be stimulated to become chondrogenic cells when expanded with chondrocyte CM. Polymeric scaffolds co-seeded with CM- expanded AMSCs and primary chondrocytes resulted in in vivo cartilaginous tissues with similar biochemical content to constructs seeded with chondrocytes alone., Conclusion: These results indicate that chondrocyte CM consists of suitable morphogenetic factors that induce the chondrogenic priming of AMSCs for cartilage tissue engineering.

Background: Limited options exist for the restoration of craniofacial cartilage. Autologous tissue or porous polyethylene is currently used for nasal and auricular reconstruction. Both options are associated with drawbacks, including donor site morbidity and implant extrusion. Poly(vinyl alcohol) (PVA) is a non-degradable flexible biocompatible polymer than can be engineered to mimic the properties of cartilage. The goal of this study was to engineer a biosynthetic hybrid construct using a combination of PVA-alginate hydrogels and human nasal septum chondrocytes., Materials and Methods: Chondrocytes isolated from human nasal septum cartilage were expanded and mixed with 2% sodium alginate hydrogel. The chondrocyte-alginate mix was injected into a non-degradable porous PVA hydrogel, creating biosynthetic constructs. A group of these constructs were implanted into the subcutaneous environment of nude mice, while the other group was cultured in a spinner flask bioreactor system for 10 d and then implanted. After 6 wk in vivo, the histologic, biochemical, and biomechanical properties were examined., Results: Histological analysis demonstrated sulfated glycosaminoglycans and deposition of collagen type II in constructs from both groups. Constructs cultured in the bioreactor system prior in vivo implantation demonstrated higher levels of DNA, glycosaminoglycans, and hydroxyproline. An increase of 22% in the compressive strength of the engineered constructs exposed to the bioreactor was also observed., Conclusion: A novel porous PVA-alginate gel hybrid was used to successfully engineer human cartilage in vivo. A 10-d period of bioreactor culturing increased levels of DNA, glycosaminoglycans, hydroxyproline, and the compressive modulus of the constructs., (Copyright © 2010 Elsevier Inc. All rights reserved.)

This study's purpose was to investigate whether photochemically crosslinking collagen gel to encapsulate chondrocytes (articular, auricular, costal) would permit new cartilage formation in vivo, and to determine whether this neocartilage had the ability to integrate with existing native cartilage. Chondrocytes from swine were embedded in collagen gel that was photochemically crosslinked using riboflavin and visible light. Controls were collagen gels containing cells that were not crosslinked. Cylindrical implants (0.1 cc) were placed in athymic mice for 4 and 8 weeks. To study integration, the constructs were crosslinked within articular cartilage rings and implanted in the mice. Samples were analyzed in terms of macroscopic, microscopic, and biochemical aspects. Photocrosslinking did not affect the amount of glycosaminoglycan and type II collagen produced by the cells. We found that photochemical crosslinking collagen gel enhances the physical parameters of the gel and permits new cartilage formation that can integrate with existing native cartilage.

More than a decade of work has been devoted to engineering cartilage for articular surface repair. This review covers the use of fibrin gel polymer as an injectable scaffold for generating new cartilage matrix from isolated articular chondrocytes beginning with studies in mice and culminating in an applied study in swine joints. These studies began with developing a formulation of fibrin that was injectable and promoted cartilage matrix formation. Subsequent studies addressed the problems of volume loss after the scaffolds were placed in vivo by adding lyophilized cartilage matrix. Additional studies focused on the ability of isolated chondrocytes to heal and repair cartilage in a model that could be biomechanically tested. In conclusion, this series of studies demonstrated that fibrin gel is a suitable polymer gel for generating new cartilage matrix from articular chondrocytes. The new matrix is capable of forming mechanical bonds between cartilage disks and can lead to healing and integration. Armed with these results, implantation of fibrin-cell constructs into defects in swine knees showed new cartilage formation and filling of the defects. Continuing work in these models with fibrin and other polymerizable hydrogels could result in a suitable cell-based therapy for articular cartilage lesions.

Background: Both native and engineered cartilage is brittle and fractures easily without perichondrium. The aim of this study was to understand the role of the perichondrium and try to enhance the flexible properties of tissue-engineered cartilage using expanded polytetrafluoroethylene (ePTFE) membrane as a pseudoperichondrium., Methods: The study was conducted in two phases. In phase I, native swine auricular cartilage of different thicknesses was studied by histologic evaluation and failure testing. Next, isolated perichondrium was bonded to native cartilage slices using fibrin glue or Dermabond and tested to failure. In phase II, swine auricular chondrocytes were suspended in fibrin glue. The chondrocyte-fibrin glue composites were then bound to expanded polytetrafluoroethylene membrane in two trilaminar configurations: In group EC-1, the membrane was in the center, whereas it was on the surfaces in group EC-2. Specimens were implanted into nude mice for 4 weeks, 8 weeks, 12 weeks, and 8 months and subjected to histologic evaluation and failure testing., Results: In phase I, the results demonstrated that perichondrium securely bonded to the cartilage plays an important role in maintaining the flexible nature of elastic cartilage. In phase II, failure testing revealed that specimens in group EC-1 (expanded polytetrafluoroethylene core) were fractured during bending and destroyed after torsion, whereas those in group EC-2 (cartilage core) returned to their original shape without fracturing even after rigorous torsion. Histologic analysis demonstrated that transplanted chondrocytes penetrated into the microporous structure of expanded polytetrafluoroethylene and created a bond to it., Conclusion: It is possible to engineer flexible cartilage using expanded polytetrafluoroethylene as a pseudoperichondrium.

Articular chondrocytes can synthesize new cartilaginous matrix in vivo that forms functional bonds with native cartilage. Other sources of chondrocytes may have a similar ability to form new cartilage with healing capacity. This study evaluates the ability of various chondrocyte sources to produce new cartilaginous matrix in vivo and to form functional bonds with native cartilage. Disks of articular cartilage and articular, auricular, and costal chondrocytes were harvested from swine. Articular, auricular, or costal chondrocytes suspended in fibrin glue (experimental), or fibrin glue alone (control), were placed between disks of articular cartilage, forming trilayer constructs, and implanted subcutaneously into nude mice for 6 and 12 weeks. Specimens were evaluated for neocartilage production and integration into native cartilage with histological and biomechanical analysis. New matrix was formed in all experimental samples, consisting mostly of neocartilage integrating with the cartilage disks. Control samples developed fibrous tissue without evidence of neocartilage. Ultimate tensile strength values for experimental samples were significantly increased (p < 0.05) from 6 to 12 weeks, and at 12 weeks they were significantly greater (p < 0.05) than those of controls. We conclude that articular, auricular, and costal chondrocytes have a similar ability to produce new cartilaginous matrix in vivo that forms mechanically functional bonds with native cartilage.

A large-deflection elasticity model was used to describe the mechanical behavior of cartilaginous tissues during three-point bending tests. Force-deflection curves were measured for 20-mm long x 4-mm wide x approximately 1-mm thick strips of porcine auricular and costal cartilage. Using a least-squares method with elastic modulus in bending as the only adjustable parameter, data were fit to a model based on the von Karman theory for large deflection of plates. This model described the data well, with an average RMS error of 14.8% and an average R(2) value of 0.98. Using this method, the bending modulus of auricular cartilage (4.6 MPa) was found to be statistically lower (p < 0.05) than that of costal cartilage (7.1 MPa). Material features of the cartilage samples influenced the mechanical behavior, including the orientation of the perichondrium in auricular cartilage. These methods also were used to determine the elastic moduli of engineered cartilage samples produced by seeding chondrocytes into fibrin glue. The modulus of tissue-engineered constructs increased statistically with time (p < 0.05), but still were statistically lower than the moduli of the native tissue samples (p > 0.05), reaching only about a third of the values of native samples., (Copyright 2004 Wiley Periodicals, Inc. J Biomed Mater Res 68A: 597-602, 2004)

The primary goal of engineering cartilage as a therapeutic approach is to restore the physiological conditions of an affected or defective tissue in the body. Cartilage tissue is distributed widely in the human body and possesses an organization related to the specific demand of a particular anatomical region. In selecting the proper material for engineering cartilage, the functional demands of the replacement tissue must be considered. In summary, there is a multitude of scaffolds, naturally occurring and synthetic, that are suitable for engineering cartilage. Investigators have shown that the characteristics of the neocartilage differ significantly depending upon which scaffold is used. There are also large differences when a single scaffold is tested in vitro as opposed to in vivo. Moreover, the addition of other materials internally or externally to the cartilage composite influences the physical and biomechanical properties of the newly formed tissue. The results achieved so far are extremely encouraging and motivate further investigative efforts in the field. The biochemical composition and, more importantly, the biomechanical properties of the native tissue still represent the ideal replacement tissue.

This study examined the morphology of chondrocytes in an established model of articular cartilage repair. Articular cartilage was harvested from young sheep and seeded onto pieces of devitalized sheep cartilage. The seeded pieces were stacked in pairs and wrapped in fibrin glue, and then implanted subcutaneously in the dorsum of athymic mice. Samples were harvested after 6 weeks and examined by transmission electron microscopy (TEM) or by light microscopy. TEM revealed that the cells in direct apposition to the devitalized cartilage were elongated, with an enlarged cytoplasm, and a ruffled border. TEM of cells far from the interface with scaffold tissue revealed rounded cells with large nuclei that appeared similar to normal chondrocytes. Quantitative morphometry of histologic specimens revealed that cell area, relative amount of cytoplasm, cell aspect ratio, and relative nuclear displacement were all higher in cells near the interface with the scaffold tissue, and decreased with distance from the interface. These indices of cell morphology are all consistent with an active remodeling of the scaffold at the cell-scaffold interface.

Background: Current clinical approaches to regenerate temporomandibular joint (TMJ) articulating cartilage defects only treat the symptoms (i.e. pain and dysfunction) and do not seek to restore joint integrity for long‐term relief. Therefore, we investigated a novel self‐assembling tissue‐engineered cartilage to overcome this significant clinical issue for TMJ regenerative purposes. Objectives: Examine the maturation of dynamic self‐regenerating cartilage (dSRC) using auricular chondrocytes and evaluate a novel combinatorial approach with fractional laser treatment and dSRC implantation for TMJ cartilage repair. Materials and Methods: A suspension of 107 freshly harvested rabbit ear chondrocytes was cultured under a continuous reciprocating motion to form the dSRC. After 2, 4 and 8 weeks of culture, dSRC samples were stained with H&E, Safranin‐O and Toluidine Blue. Immunohistochemistry (IHC) was performed for collagens type I and II. Channels (300–500 μm diameter and 1.2–1.5 mm depth) were created in six freshly harvested condyles using a fractional Erbium laser. Two groups were tested: dSRC in a laser‐ablated lesion (experimental) and an empty laser‐ablated channel (control). TMJ condyles were cultured for up to 8 weeks and analysed as described above. Results: H&E staining showed a high cell density in dSRC compared to native cartilage. All dSRC groups demonstrated intense Safranin‐O staining, indicating high glycosaminoglycan (GAG) production and intense Toluidine Blue staining showed high proteoglycan content. IHC confirmed that dSRC consisted predominantly of collagen type II. The experimental group showed improved cartilage repair at both time points compared to the empty channels. Conclusion: dSRC viability and successful matrix formation were demonstrated in vitro. The combination of fractional laser ablation and dSRC implantation enhanced cartilage repair. [ABSTRACT FROM AUTHOR]

Objectives: This study investigated a novel strategy for improving regenerative cartilage outcomes. It combines fractional laser treatment with the implantation of neocartilage generated from autologous dynamic Self-Regenerating Cartilage (dSRC). Methods: dSRC was generated in vitro from harvested autologous swine chondrocytes. Culture was performed for 2, 4, 8, 10, and 12 weeks to study matrix maturation. Matrix formation and implant integration were also studied in vitro in swine cartilage discs using dSRC or cultured chondrocytes injected into CO2 laser-ablated or mechanically punched holes. Cartilage discs were cultured for up to 8 weeks, harvested, and evaluated histologically and immunohistochemically. Results: The dSRC matrix was injectable by week 2, and matrices grew larger and more solid with time, generating a contiguous neocartilage matrix by week 8. Hypercellular density in dSRC at week 2 decreased over time and approached that of native cartilage by week 8. All dSRC groups exhibited high glycosaminoglycan (GAG) production, and immunohistochemical staining confirmed that the matrix was typical of normal hyaline cartilage, being rich in collagen type II. After 8 weeks in cartilage lesions in vitro, dSRC constructs generated a contiguous cartilage matrix, while isolated cultured chondrocytes exhibited only a sparse pericellular matrix. dSRC-treated lesions exhibited high GAG production compared to those treated with isolated chondrocytes. Conclusions: Isolated dSRC exhibits hyaline cartilage formation, matures over time, and generates contiguous articular cartilage matrix in fractional laser-created microenvironments in vitro, being well integrated with native cartilage. [ABSTRACT FROM AUTHOR]

Background: In the last decade, tissue‐engineering strategies for regenerating the temporomandibular joint (TMJ) have been investigated. This may be a promising strategy for the minimally invasive restoration of joint integrity. Objectives: To evaluate whether dental pulp stem cells (DPSCs) loaded in a light‐occured hydrogel made of gelatin methacryloyl (GelMA) enhance the regeneration of osteochondral defects in the rabbit TMJ. Materials and Methods: Defects were filled with GelMA alone (control group; n = 4) or filled with GelMA loaded with rabbit DPSCs (experimental group; n = 4), In one group, the TMJ capsule was opened without creating a defect (sham group; n = 2). The following micro‐CT parameters were analysed: bone volume to total volume ratio (BV/TV%) and bone mineral density (BMD). Histological evaluation was performed to assess cartilage regeneration features. A semi‐quantitative scoring system was also used to evaluate the defects. Results: All groups had no statistical difference regarding the micro‐CT parameters. The highest mean healing score was found for the experimental group. After 4 weeks, there were no signs of hydrogel in either group or no signs of inflammation in the adjacent tissues. The tissue formed in the defect was dense fibrous connective tissue. Conclusion: Adding DPSCs to GelMA did not provide a regenerative enhancement in TMJ osteochondral defects. This resulted in similar micro‐CT parameters after 4 weeks of healing, with improved signs of subchondral bone regeneration but no cartilage regeneration. [ABSTRACT FROM AUTHOR]

Background Carved autologous costal cartilage and porous polyethylene implants (Medpor) are the most common approaches for total ear reconstruction, but these approaches may have inconsistent cosmetic outcomes, a high risk of extrusion, or other surgical complications. Engineering ear cartilage to emulate native auricular tissue is an appealing approach, but often the cell-seeded scaffolds are susceptible to shrinkage and architectural changes when placed in vivo . The aim of this study was to assess the most favorable conditions for in vitro pre-culture of cell-seeded type I collagen scaffolds prior to in vivo implantation. Methods Sheep auricular chondrocytes were seeded into this type I collagen scaffold. The cell-seeded constructs were cultured in either static or dynamic conditions for two days or two weeks and then implanted into nude mice for another six weeks. The harvested constructs were evaluated histologically, immunohistochemically, and biochemically. Results Robust neo-cartilage formation was found in these collagen scaffolds seeded with auricular chondrocytes, which was comparable to native cartilage morphologically, histologically, and biochemically. Culture under dynamic conditions prior to implantation improved the neo-cartilage formation histologically and biochemically. Conclusion Dynamic culture of this cell-seeded fibrous collagen material could permit predictable engineered auricular cartilage and a promising approach for external ear reconstruction. [ABSTRACT FROM AUTHOR]

This study investigated the in vivo formation of engineering cartilage within living or devitalized cartilage discs using reflectance mode confocal microscopy and conventional light microscopy. Pig articular chondrocytes were suspended in fibrin glue and placed between two cartilage discs. Four experimental groups were prepared: in groups 1 and 2, the cell-hydrogel composite was placed between two live or between two devitalized cartilage discs, respectively; in groups 3 and 4, acellular fibrin glue was placed between two live or between two devitalized cartilage discs, respectively. Samples were implanted in the back of nude mice and analyzed after 2, 5, and 8 weeks. Results showed that engineered cartilage seems to grow more homogenously when the cell-seeded gel was placed between devitalized cartilages than when it was placed between live cartilage matrices. Confocal microscopy provides valuable information on the integration of tissue-engineered cartilage with native tissue and could be useful for nondestructive imaging in vivo . [ABSTRACT FROM AUTHOR]

Meniscus injury is common in today's active society. Despite the frequent presentation of meniscus injury, the decision to repair or resect a torn meniscus is not always straightforward. Current repair techniques are effective in the peripheral vascularized meniscus, but their success is not dependable in the avascularized zone. Tissue engineering, a discipline that combines the technologies of cell culture and biodegradable scaffolds to deliver a cellular repair, may be one future answer to this problem. The concept of using cell-based repair for torn menisci could improve healing of lesions in the avascular zone and broadly expand the indication for repair rather than removal, obviating the need for meniscectomy. This article reviews current advances in the relatively new field of tissue engineering toward the development of a tissue-engineered meniscal repair technique. [ABSTRACT FROM AUTHOR]

Focal defects in articular cartilage are unable to self-repair and, if left untreated, are a leading risk factor for osteoarthritis. This study examined cartilage degeneration surrounding a defect and then assessed whether infilling the defect prevents degeneration. We created a focal chondral defect in porcine osteochondral explants and cultured them ex vivo with and without dynamic compressive loading to decouple the role of loading. When compared to a defect in a porcine knee four weeks post-injury, this model captured loss in sulfated glycosaminoglycans (sGAGs) along the defect's edge that was observed in vivo , but this loss was not load dependent. Loading, however, reduced the indentation modulus of the surrounding cartilage. After infilling with in situ polymerized hydrogels that were soft (100 kPa) or stiff (1 MPa) and which produced swelling pressures of 13 and 310 kPa, respectively, sGAG loss was reduced. This reduction correlated with increased hydrogel stiffness and swelling pressure, but was not affected by loading. This ex vivo model recapitulates sGAG loss surrounding a defect and, when infilled with a mechanically supportive hydrogel, degeneration is minimized. • An ex vivo chondral defect recapitulated proteoglycan loss observed in vivo. • Infilling the defect with an in situ polymerized hydrogel reduces degeneration. • Cartilage-matched stiffness and exerted swelling pressures are beneficial. [ABSTRACT FROM AUTHOR]