Articular cartilage repair and transplantation

Initiating human articular chondrocyte re-differentiation in a 3D system after 2D expansion

Cartilage damage affects a large population via acute and chronic injury and disease. Since native cartilage does not self-renew, cartilage tissue engineering has gained traction as a potential treatment. However, a limiting factor is that the primary cell type in cartilage, the articular chondrocyte, tends to de-differentiate when grown on 2D surfaces for in vitro expansion. Thus, 3D systems are being developed and used to counter this loss of chondrogenic capabilities. We hypothesize that a 3D matrix that can be remodeled may be more supportive of the chondrogenic phenotype of encapsulated articular chondrocytes than a 2D surface and may allow for the re-differentiation of chondrocytes after 2D expansion. Hence, in this study, enzymatically degradable polyethylene glycol (PEG) hydrogels containing two different protease degradable peptide segments, with different degradation rates, were tested in combination with chondrogenic medium as a 3D in vitro culture system to better recapitulate the native environment of human articular chondrocytes (hACs). In addition, the effect of incorporation of the integrin binding ligand Arg-Gly-Asp (RGD) in the hydrogels was explored. Hydrogels crosslinked with a slower degrading crosslinker and not functionalized with RGD maintained hAC viability and led to increased GAG production and chondrogenic gene expression over time, suggesting that this system can initiate hAC re-differentiation after 2D expansion.

Effects of insulin-like growth factor 1 and basic fibroblast growth factor on the morphology and proliferation of chondrocytes embedded in Matrigel in a microfluidic platform

An integrated microfluidic device was utilized in the present study to investigate the morphology and proliferation of rabbit articular chondrocytes embedded in Matrigel in the presence of insulin-like growth factor 1 (IGF-1) and/or basic fibroblast growth factor (bFGF). The microfluidic device was composed of two parallel channels and a central perfusion-based three-dimensional cell culture module. The rabbit chondrocytes were cultured for 2 weeks at series of concentration gradients of IGF-1 and/or bFGF, which were generated through a diffusion process. At the end of the experiment, the morphology and quantity of cells were measured. Since high expression of collagen II is essential to the function of hyaline cartilage, immunofluorescent images of collagen II expression prior to and after the experiments were gathered for each group. The mean fluorescence intensity ratio (MIR) of collagen II in each group was calculated. The MIRs of collagen II in chondrocytes treated with IGF-1 ranged from 0.6-0.81, those in the cells treated with bFGF ranged from 0.47-0.52, and those in cells treated with a combination of IGF-1 and bFGF ranged from 0.63-0.83. Chondrocyte aggregations were observed in the group treated with 75-100 ng/ml IGF-1 (3.46-fold proliferation ratio). Similarly, a 3.83-fold proliferation ratio was identified in chondrocytes treated with 2.5-5.0 ng/ml bFGF. The group treated with 50-75 ng/ml IGF-1 and 2.5-5.0 ng/ml bFGF exhibited the optimum increase in proliferation (4.83-fold proliferation ratio). The microfluidic device used in the present study can be easily adapted to investigate other growth factors at any concentration gradient. In addition, parallel experiments can be performed simultaneously with a small quantity of cells, making it an attractive platform for the high-throughput screening of cell culture parameters. This platform will aid in the optimization of culture conditions for the in vitro expansion of chondrocytes while maintaining their in vivo morphology, which will improve autologous chondrocyte implantation capabilities for the treatment of cartilage injury.

Effect of hypoxia on human adipose-derived mesenchymal stem cells and its potential clinical applications

Human adipose-derived mesenchymal stem cells (hASCs) are an ideal cell source for regenerative medicine due to their capabilities of multipotency and the readily accessibility of adipose tissue. They have been found residing in a relatively low oxygen tension microenvironment in the body, but the physiological condition has been overlooked in most studies. In light of the escalating need for culturing hASCs under their physiological condition, this review summarizes the most recent advances in the hypoxia effect on hASCs. We first highlight the advantages of using hASCs in regenerative medicine and discuss the influence of hypoxia on the phenotype and functionality of hASCs in terms of viability, stemness, proliferation, differentiation, soluble factor secretion, and biosafety. We provide a glimpse of the possible cellular mechanism that involved under hypoxia and discuss the potential clinical applications. We then highlight the existing challenges and discuss the future perspective on the use of hypoxic-treated hASCs.

Comparison of Chondral Defects Repair with In Vitro and In Vivo Differentiated Mesenchymal Stem Cells

The purpose of this study was to compare chondral defects repair with in vitro and in vivo differentiated mesenchymal stem cells (MSCs). A novel PLGA-gelatin/chondroitin/hyaluronate (PLGA-GCH) hybrid scaffold with transforming growth factor-β1 (TGF-β1)-impregnated microspheres (MS-TGF) was fabricated to mimic the extracellular matrix. MS-TGF showed an initial burst release (22.5%) and a subsequent moderate one that achieved 85.1% on day 21. MSCs seeded on PLGA-GCH/MS-TGF or PLGA-GCH were incubated in vitro and showed that PLGA-GCH/MS-TGF significantly augmented proliferation of MSCs and glycosaminoglycan synthesis compared with PLGA-GCH. Then MSCs seeded on PLGA-GCH/MS-TGF were implanted and differentiated in vivo to repair chondral defect on the right knee of rabbit (in vivo differentiation repair group), while the contralateral defect was repaired with in vitro differentiated MSCs seeded on PLGA-GCH (in vitro differentiation repair group). The histology observation demonstrated that in vivo differentiation repair showed better chondrocyte morphology, integration, and subchondral bone formation compared with in vitro differentiation repair 12 and 24 weeks postoperatively, although there was no significant difference after 6 weeks. The histology grading score comparison also demonstrated the same results. The present study implies that in vivo differentiation induced by PLGA-GCH/MS-TGF and the host microenviroment could keep chondral phenotype and enhance repair. It might serve as another way to induce and expand seed cells in cartilage tissue engineering.

Impact of mechanical stimulation on the chondrogenic processes in human bone marrow aspirates modified to overexpress sox9 via rAAV vectors

Background

Evaluation of gene-based approaches to target human bone marrow aspirates in conditions of mechanical stimulation that aim at reproducing the natural joint environment may allow to develop improved treatments for articular cartilage injuries. In the present study, we investigated the potential of rAAV-mediated sox9 gene transfer to enhance the chondrogenic differentiation processes in human bone marrow aspirates under established hydrodynamic conditions compared with the more commonly employed static culture conditions.

Methods

Fresh human bone marrow aspirates were transduced with rAAV-FLAG-hsox9 (40 μl) and maintained for up to 28 days in chondrogenic medium under mechanically-induced conditions in dynamic flow rotating bioreactors that permit tissue growth and matrix deposition relative to static culture conditions. The samples were then processed to examine the potential effects of sox9 overexpression on the cellular activities (matrix synthesis, proliferation) and on the chondrogenic differentiation potency compared with control treatments (absence of rAAV vector; reporter rAAV-lacZ, rAAV-RFP, and rAAV-luc gene transfer).

Results

Prolonged, significant sox9 overexpression via rAAV was achieved in the aspirates for at least 28 days when applying the rAAV-FLAG-hsox9 construct, leading to higher, prolonged levels of matrix biosynthesis and to enhanced chondrogenic activities relative to control treatments especially when maintaining the samples under mechanical stimulation. Administration of sox9 however did not impact the indices of proliferation in the aspirates. Remarkably, sox9 gene transfer also durably delayed hypertrophic and osteogenic differentiation in the samples regardless of the conditions of culture applied versus control treatments.

Conclusions

The current observations show the value of genetically modifying human bone marrow aspirates upon mechanical stimulation by rAAV sox9 as a promising strategy for future treatments to improve cartilage repair by implantation in lesions where the tissue is submitted to natural mechanical forces.

Effects of osteochondral defect size on cartilage regeneration using a double-network hydrogel

Background

There has been increased interest in one-step cell-free procedures to avoid the problems related to cell manipulation and its inherent disadvantages. We have studied the chondrogenic induction ability of a PAMPS/PDMAAm double-network (DN) gel and found it to induce chondrogenesis in animal osteochondral defect models. The purpose of this study was to investigate whether the healing process and the degree of cartilage regeneration induced by the cell-free method using DN gel are influenced by the size of osteochondral defects.

Methods

A total of 63 mature female Japanese white rabbits were used in this study, randomly divided into 3 groups of 21 rabbits each. A 2.5-mm diameter osteochondral defect was created in the femoral trochlea of the patellofemoral joint of bilateral knees in Group I, a 4.3-mm osteochondral defect in Group II, and a 5.8-mm osteochondral defect in Group III. In the right knee of each animal, a DN gel plug was implanted so that a vacant space of 2-mm depth was left above the plug. In the left knee, we did not conduct any treatment to obtain control data. Animals were sacrificed at 2, 4, and 12 weeks after surgery, and gross and histological evaluations were made.

Results

The present study demonstrated that all sizes of the DN gel implanted defects as well as the 2.5mm untreated defects showed cartilage regeneration at 4 and 12 weeks. The 4.3-mm and 5.8-mm untreated defects did not show cartilage regeneration during the 12-week period. The quantitative score reported by O’Driscoll et al. was significantly higher in the 4.3-mm and 5.8-mm DN gel-implanted defects than the untreated defects at 4 and 12 weeks (p < 0.05). The 2.5-mm and 4.3-mm DN gel implanted defects maintained relatively high macroscopic and histological scores for the 12-week implantation period, while the histological score of the 5.8-mm DN gel implanted defect had decreased somewhat but statistically significantly at 12 weeks (p = 0.0057).

Conclusions

The DN gel induced cartilage regeneration in defects between 2.5 and 5.8 mm, offering a promising device to establish a cell-free cartilage regeneration therapy and applicable to various sizes of osteochondral defects.

Complex mechanical conditioning of cell-seeded agarose constructs can influence chondrocyte biosynthetic activity

Articular cartilage with its inherently poor capacity for self-regeneration represents a primary target for tissue engineering strategies, with approaches focusing on the in vitro generation of neo-cartilage using chondrocyte-seeded 3D scaffolds subjected to mechanical conditioning. Although uniaxial compression regimens have significantly up-regulated proteoglycan synthesis, their effects on the synthesis of collagen have been modest. Articular cartilage is subjected to shear forces during joint motion. Accordingly, this study utilized an apparatus to apply biaxial loading to chondrocytes seeded within agarose constructs with endplates. The chondrocytes yielded a monotonic increase in proteoglycan synthesis both in free swelling culture up to day 8 and when the constructs were subjected to dynamic compression alone (15% amplitude at a frequency of 1 Hz for 48 h). However, when dynamic shear (10% amplitude at 1 Hz) was superimposed on dynamic compression, total collagen synthesis was also up-regulated, within 3 days of culture, without compromising proteoglycan synthesis. Histological analysis revealed marked collagen deposition around individual chondrocytes. A significant proportion (50%) of collagen was released into the culture medium, suggesting that it had only been partially synthesized in its mature state. The overall biosynthetic activity was enhanced more when the biaxial stimulation was applied in a continuous mode as opposed to intermittent loading. Results of the present study strongly suggest that proteoglycan and collagen synthesis may be triggered by uncoupled mechanosensitive cellular responses. The proposed in vitro model and the prescribed conditioning protocols demonstrated that a short pre-culture period is preferable to long free swelling culture condition as it enables a significantly higher up-regulation of collagen. Biotechnol. Bioeng. 2017;114: 1614-1625. © 2017 Wiley Periodicals, Inc.

Comparative evaluation of leukocyte- and platelet-rich plasma and pure platelet-rich plasma for cartilage regeneration

Platelet-rich plasma (PRP) has gained growing popularity in the treatment of articular cartilage lesions in the last decade. However, the potential harmful effects of leukocytes in PRP on cartilage regeneration have seldom been studied in vitro, and not at all in vivo yet. The objective of the present study is to compare the effects of leukocyte- and platelet-rich plasma (L-PRP) and pure platelet-rich plasma (P-PRP) on cartilage repair and NF-κB pathway, in order to explore the mechanism underlying the function of leukocytes in PRP in cartilage regeneration. The constituent analysis showed that P-PRP had significantly lower concentrations of leukocytes and pro-inflammatory cytokines compared with L-PRP. In addition, cell proliferation and differentiation assays indicated P-PRP promoted growth and chondrogenesis of rabbit bone marrow mesenchymal stem cells (rBMSC) significantly compared with L-PRP. Despite similarity in macroscopic appearance, the implantation of P-PRP combining rBMSC in vivo yielded better cartilage repair results than the L-PRP group based on histological examination. Importantly, the therapeutic effects of PRP on cartilage regeneration could be enhanced by removing leukocytes to avoid the activation of the NF-κB pathway. Thus, PRP without concentrated leukocytes may be more suitable for the treatment of articular cartilage lesions.

The use of embryonic cells in the treatment of osteochondral defects of the knee: an ovine in vivo study

PURPOSE

the aim of this study was to determine whether local delivery of embryonic stem-like (ESL) cells into osteochondral defects in the femoral condyles of sheep would enhance regeneration of hyaline articular cartilage.

METHODS

male ESL cells embedded in fibrin glue were engrafted into osteochondral defects in the medial condyles (ESL-M) of the left femur in 22 ewes. An identical defect was created in the medial condyle of the contralateral stifle joint and left untreated as a control (empty defect, ED). The ewes were divided into 5 groups. Four sheep each were euthanized at 1, 2, 6, and 12 months from surgery, and 6 ewes were euthanized 24 months post-implantation. To study the effect of varying loads on the long-term regeneration process, an identical defect was also created and ESL cell engraftment performed in the lateral condyle (ESL-L) of the left stifle joint of the animals in the 12- and 24-month groups. The evaluation of regenerated tissue was performed by biomechanical, macroscopic, histological, immunohistochemical (collagen type II) and fluorescent in situ hybridization (FISH) assays.

RESULTS

no significant differences were found between treated and control sites in the biomechanical assays at any time point. ESL cell grafts showed significantly greater macroscopic evidence of regeneration as compared to controls at 24 months after surgery; significantly better histological evidence of repair in ESL-M samples versus controls was found throughout the considered period. At 24 months from surgery there was significantly improved integration of graft edges with the host tissue in the ESL-M as compared to the ESL-L samples, demonstrating that load bearing positively affects the long-term regeneration process.

CONCLUSIONS

ESL cells enhanced the regeneration of hyaline cartilage. FISH confirmed that the regenerative tissue originated from ESL cells.

CLINICAL RELEVANCE

ESL cells are able to self-renew for prolonged periods without differentiation and, most importantly, to differentiate into a large variety of tissues.

Disc-type hyaline cartilage reconstruction using 3D-cell sheet culture of human bone marrow stromal cells and human costal chondrocytes and maintenance of its shape and phenotype after transplantation

In this study, we developed the disc-type bio-cartilage reconstruction strategies for transplantable hyaline cartilage for reconstructive surgery using 3D-cell sheet culture of human bone marrow stromal cells and human costal chondrocytes. We compared chondrogenesis efficiency between different chondrogenic-induction methods such as micromass culture, pellet culture, and 3D-cell sheet culture. Among them, the 3D-cell sheet culture resulted in the best chondrogenesis with the disc-type bio-cartilage (>12 mm diameter in size) in vitro, but sometimes spontaneous curling and contraction of 3D-cell sheet culture resulted in the formation of bead-type cartilage, which was prevented by type I collagen coating or by culturing on amniotic membrane. Previously, it was reported that tissue-engineered cartilage reconstructed in vitro does not maintain its cartilage phenotype after transplantation but tends to transform to other tissue type such as bone or connective tissue. However, the disc-type bio-cartilage of 3D-cell sheet culture maintained its hyaline cartilage phenotype even after exposure to the osteogenic-induction condition in vitro for 3 weeks or after the transplantation for 4 weeks in mouse subcutaneous. Collectively, the disc-type bio-cartilage with 12 mm diameter can be reproducibly reconstructed by the 3D-cell sheet culture, whose hyaline cartilage phenotype and shape can be maintained under the osteogenic-induction condition as well as after the transplantation. This disc-type bio-cartilage can be proposed for the application to reconstructive surgery and repair of disc-type cartilage such as mandibular cartilage and digits.

Electronic Supplementary Material

Supplementary material is available for this article at 10.1007/s13770-016-9065-6 and is accessible for authorized users.

Double-Network Hydrogels Strongly Bondable to Bones by Spontaneous Osteogenesis Penetration

On implanting hydroxyapatite-mineralized tough hydrogel into osteochondral defects of rabbits, osteogenesis spontaneously penetrates into the gel matrix owing to the semi-permeablility of the hydrogel. The gradient layer (around 40 μm thick) contributes quite strong bonding of the gel to bone. This is the first success in realizing the robust osteointegration of tough hydrogels, and the method is simple and feasible for practical use.

Nondestructive evaluation of a new hydrolytically degradable and photo-clickable PEG hydrogel for cartilage tissue engineering

Photopolymerizable and hydrolytically labile poly(ethylene glycol) (PEG) hydrogels formed from photo-clickable reactions were investigated as cell delivery platforms for cartilage tissue engineering (TE). PEG hydrogels were formed from thiol-norbornene PEG macromers whereby the crosslinks contained caprolactone segments with hydrolytically labile ester linkages. Juvenile bovine chondrocytes encapsulated in the hydrogels were cultured for up to four weeks and assessed biochemically and histologically, using standard destructive assays, and for mechanical and ultrasound properties, as nondestructive assays. Bulk degradation of acellular hydrogels was confirmed by a decrease in compressive modulus and an increase in mass swelling ratio over time. Chondrocytes deposited increasing amounts of sulfated glycosaminoglycans and collagens in the hydrogels with time. Spatially, collagen type II and aggrecan were present in the neotissue with formation of a territorial matrix beginning at day 21. Nondestructive measurements revealed an 8-fold increase in compressive modulus from days 7 to 28, which correlated with total collagen content. Ultrasound measurements revealed changes in the constructs over time, which differed from the mechanical properties, and appeared to correlate with ECM structure and organization shown by immunohistochemical analysis. Overall, non-destructive and destructive measurements show that this new hydrolytically degradable PEG hydrogel is promising for cartilage TE.

STATEMENT OF SIGNIFICANCE

Designing synthetic hydrogels whose degradation matches tissue growth is critical to maintaining mechanical integrity as the hydrogel degrades and new tissue forms, but is challenging due to the nature of the hydrogel crosslinks that inhibit diffusion of tissue matrix molecules. This study details a promising, new, photo-clickable and synthetic hydrogel whose degradation supports cartilaginous tissue matrix growth leading to the formation of a territorial matrix, concomitant with an increase in mechanical properties. Nondestructive assays based on mechanical and ultrasonic properties were also investigated using a novel instrument and found to correlate with matrix deposition and evolution. In sum, this study presents a new hydrogel platform combined with nondestructive assessments, which together have potential for in vitro cartilage tissue engineering.

AIMP1 downregulation restores chondrogenic characteristics of dedifferentiated/degenerated chondrocytes by enhancing TGF-β signal

Dedifferentiation and degeneration of chondrocytes critically influences the efficiency of cartilage repair. One of the causes is the defect of transforming growth factor (TGF)-β signaling that promotes chondrogenic differentiation and degeneration. In the present study, we found that aminoacyl-tRNA synthetase-interacting multifunctional protein 1 (AIMP1) negatively regulates TGF-β signaling via interactions with Smad2 and Smad3 in immunoprecipitation assay and luciferase assay. In addition, we observed that the AIMP1 expression level was significantly increased in osteoarthritis (OA) patient-derived degenerated chondrocytes compared with healthy control. So, we hypothesized that downregulation of AIMP1 using small-interfering RNA (siRNA) technology in dedifferentiated (collected at passage #6) and degenerated (obtained from OA-affected areas) chondrocytes could lead to recover TGF-β signaling in both chondrocytes. Indeed, AIMP1 downregulation restored TGF-β signaling by promoting phosphorylation of Smad2 and Smad3, which shows redifferentiated characteristics in both dedifferentiated and degenerated chondrocytes. Additionally, implantation analyses using in vivo mouse model clearly showed that AIMP1 downregulation resulted in the increased chondrogenic potential as well as the enhanced cartilage tissue formation in both dedifferentiated and degenerated chondrocytes. Histological analyses clarified that AIMP1 downregulation increased expression levels of collagen type II (Col II) and aggrecan, but not Col I expression. Taken together, these data indicate that AIMP1 downregulation using siRNA is a novel tool to restore TGF-β signaling and thereby increases the chondrogenic potential of dedifferentiated/degenerated chondrocytes, which could be further developed as a therapeutic siRNA to treat OA.

Role of sox9 in growth factor regulation of articular chondrocytes

Chondrogenic polypeptide growth factors influence articular chondrocyte functions that are required for articular cartilage repair. Sox9 is a transcription factor that regulates chondrogenesis, but its role in the growth factor regulation of chondrocyte proliferation and matrix synthesis is poorly understood. We tested the hypotheses that selected chondrogenic growth factors regulate sox9 gene expression and protein production by adult articular chondrocytes and that sox9 modulates the actions of these growth factors. To test these hypotheses, we delivered insulin-like growth factor-I (IGF-I), fibroblast growth factor-2 (FGF-2), bone morphogenetic protein-2 (BMP-2) and/or bone morphogenetic protein-7 (BMP-7), or their respective transgenes to adult bovine articular chondrocytes, and measured changes in sox9 gene expression and protein production. We then knocked down sox9 gene expression with sox9 siRNA, and measured changes in the expression of the genes encoding aggrecan and types I and II collagen, and in the production of glycosaminoglycan, collagen and DNA. We found that FGF-2 or the combination of IGF-I, BMP-2, and BMP-7 increased sox9 gene expression and protein production and that sox9 knockdown modulated growth factor actions in a complex fashion that differed both with growth factors and with chondrocyte function. The data suggest that sox9 mediates the stimulation of matrix production by the combined growth factors and the stimulation of chondrocyte proliferation by FGF-2. The mitogenic effect of the combined growth factors and the catabolic effect of FGF-2 appear to involve sox9-independent mechanisms. Control of these molecular mechanisms may contribute to the treatment of cartilage damage.

Osteochondral allograft transplantation in cartilage repair: Graft storage paradigm, translational models, and clinical applications

The treatment of articular cartilage injury and disease has become an increasingly relevant part of orthopaedic care. Articular cartilage transplantation, in the form of osteochondral allografting, is one of the most established techniques for restoration of articular cartilage. Our research efforts over the last two decades have supported the transformation of this procedure from experimental "niche" status to a cornerstone of orthopaedic practice. In this Kappa Delta paper, we describe our translational and clinical science contributions to this transformation: (1) to enhance the ability of tissue banks to process and deliver viable tissue to surgeons and patients, (2) to improve the biological understanding of in vivo cartilage and bone remodeling following osteochondral allograft (OCA) transplantation in an animal model system, (3) to define effective surgical techniques and pitfalls, and (4) to identify and clarify clinical indications and outcomes. The combination of coordinated basic and clinical studies is part of our continuing comprehensive academic OCA transplant program. Taken together, the results have led to the current standards for OCA processing and storage prior to implantation and also novel observations and mechanisms of the biological and clinical behavior of OCA transplants in vivo. Thus, OCA transplantation is now a successful and increasingly available treatment for patients with disabling osteoarticular cartilage pathology.

Platelet-Rich Plasma May Improve Osteochondral Donor Site Healing in a Rabbit Model

PURPOSE

The purpose of this study was to assess the effect(s) of platelet-rich plasma (PRP) on osteochondral donor site healing in a rabbit model.

METHODS

Osteochondral donor sites 3 mm in diameter and 5 mm in depth were created bilaterally on the femoral condyles of 12 New Zealand White rabbits. Knees were randomized such that one knee in each rabbit received an intra-articular injection of PRP and the other received saline (placebo). Rabbits were euthanized at 3, 6, and 12 weeks following surgery. Repair tissue was evaluated using the International Cartilage Repair Society (ICRS) macroscopic and histological scores.

RESULTS

No complications occurred as a result of the interventions. There was no significant difference in macroscopic scores between the 2 groups (5.5 ± 3.8 vs. 3.8 ± 3.5; P = 0.13). Subjective macroscopic assessment determined greater tissue infill with fewer fissures and a more cartilage-like appearance in PRP-treated knees. Overall ICRS histological scores were better in the PRP group compared with the placebo (9.8 ± 2.0 vs. 7.8 ± 1.8; P = 0.04). Histological scores were also higher in the PRP group compared with the placebo group at each time point. Greater glycosaminoglycan and type II collagen content were noted in the repair tissue of the PRP group compared with the placebo group.

CONCLUSION

The results of this study indicate that PRP used as an intra-articular injection may improve osteochondral healing in a rabbit model.

Surgical treatment of early knee osteoarthritis with a cell-free osteochondral scaffold: results at 24 months of follow-up

PURPOSE

"Early Osteoarthritis (EOA)" has been defined combining clinical, imaging and surgical parameters, with the aim to identify patients in early degenerative phases, who might benefit from the use of available regenerative procedures. Aim of this first clinical trial is to prospectively evaluate the results obtained in a group of patients meeting the inclusion criteria of "EOA" as proposed by the ESSKA Cartilage Committee, and surgically treated with the implantation of a multi-phasic osteochondral scaffold.

METHODS

23 patients were prospectively evaluated at 12 and 24 months of follow-up. Etiology of the chondral or osteochondral defect was rated as microtraumatic or degenerative in 18 cases, and traumatic in 5 cases. Patients included were complaining of clinical symptoms like knee pain and affected by chondral and osteochondral lesions located at the femoral condyles or trochlea and MRI findings demonstrating articular cartilage degeneration and/or meniscal degeneration and/or subchondral bone marrow lesions.

RESULTS

All patients increased significantly in any clinical score adopted. The IKDC subjective score increased from 42.8 ± 13.8 at basal evaluation to 74.3 ± 17.4 at 12 months' (p < 0.0005), being stable (74.9 ± 20.4) up to the final follow-up of 24 months. Tegner score showed a statistically significant improvement in sports activity from 3.3 ± 2.7 pre-operative to 4.6 ± 2.2 at 12 months (p < 0.005), with a slight improvement to the final evaluation (4.7 ± 2.1; n.s.). However, the activity level was significantly lower than the pre-injury one (6.1 ± 2.6; p = 0.004). A significant difference was shown between patients younger versus older than 40 years, with younger patients had better clinical improvement (76.0 ± 18.6 vs 45.1 ± 38.8 respectively, p = 0.037).

CONCLUSIONS

The implantation of a multi-phasic osteochondral scaffold represents a good option after failure of conservative management for Early OA patients, where younger age represent an important factor for a better outcome. Longer follow-up is needed to evaluate the benefit over time.

LEVEL OF EVIDENCE

IV, case series.

Porous titanium bases for osteochondral tissue engineering

Tissue engineering of osteochondral grafts may offer a cell-based alternative to native allografts, which are in short supply. Previous studies promote the fabrication of grafts consisting of a viable cell-seeded hydrogel integrated atop a porous, bone-like metal. Advantages of the manufacturing process have led to the evaluation of porous titanium as the bone-like base material. Here, porous titanium was shown to support the growth of cartilage to produce native levels of Young's modulus, using a clinically relevant cell source. Mechanical and biochemical properties were similar or higher for the osteochondral constructs compared to chondral-only controls. Further investigation into the mechanical influence of the base on the composite material suggests that underlying pores may decrease interstitial fluid pressurization and applied strains, which may be overcome by alterations to the base structure. Future studies aim to optimize titanium-based tissue engineered osteochondral constructs to best match the structural architecture and strength of native grafts.

STATEMENT OF SIGNIFICANCE

The studies described in this manuscript follow up on previous studies from our lab pertaining to the fabrication of osteochondral grafts that consist of a bone-like porous metal and a chondrocyte-seeded hydrogel. Here, tissue engineered osteochondral grafts were cultured to native stiffness using adult chondrocytes, a clinically relevant cell source, and a porous titanium base, a material currently used in clinical implants. This porous titanium is manufactured via selective laser melting, offering the advantages of precise control over shape, pore size, and orientation. Additionally, this manuscript describes the mechanical influence of the porous base, which may have applicability to porous bases derived from other materials.

A novel photocrosslinkable and cytocompatible chitosan coating for Ti6Al4V surfaces

BACKGROUND

In this work, chitosan (CH) was used to produce a novel coating for Ti6Al4V, the most widely used alloy in orthopedic implants, so as to improve the biological tissue response at the metallic surface.

METHODS

The Ti6Al4V surface was sandblasted with alumina particles. CH was chemically modified, via carbodiimide chemistry, using lactobionic and 4-azidebenzoic acid to make it soluble at physiological pH and photocrosslinkable, respectively. The reaction was verified by FTIR, NMR and UV/vis spectroscopy. Ti6Al4V surfaces were coated with solutions of the modified CH and exposed to UV light, causing polymer crosslinking and formation of a hydrogel on the surface. The crosslinking reaction was monitored by FTIR at different exposure times. Coating morphology was observed by SEM. The coating's cytocompatibility was determined in vitro through the culture of rat bone marrow mesenchymal stem cells, using an MTT assay, with their morphology assessed by SEM.

RESULTS

The developed coating behaved as a hydrogel on the Ti6Al4V and was stable on the surface. FTIR and NMR confirmed the crosslinking mechanism, based on an arile ring expansion, and subsequent reaction with the CH amine groups. Furthermore, the coating was able to support cell proliferation and osteogenic differentiation.

CONCLUSIONS

UV crosslinking of CH is easy to apply and has potential for future metallic implant surface modifications. Due to its nature as a hydrogel, the coating could be used for further studies in the encapsulation of bioactive molecules to improve osteogenic potential at the tissue-implant interface.

Depth-Dependent Glycosaminoglycan Concentration in Articular Cartilage by Quantitative Contrast-Enhanced Micro-Computed Tomography

OBJECTIVE

A quantitative contrast-enhanced micro-computed tomography (qCECT) method was developed to investigate the depth dependency and heterogeneity of the glycosaminoglycan (GAG) concentration of ex vivo cartilage equilibrated with an anionic radiographic contrast agent, Hexabrix.

DESIGN

Full-thickness fresh native (n = 19 in 3 subgroups) and trypsin-degraded (n = 6) articular cartilage blocks were imaged using micro-computed tomography (μCT) at high resolution (13.4 μm(3)) before and after equilibration with various Hexabrix bathing concentrations. The GAG concentration was calculated depth-dependently based on Gibbs-Donnan equilibrium theory. Analysis of variance with Tukey's post hoc was used to test for statistical significance (P < 0.05) for effect of Hexabrix bathing concentration, and for differences in bulk and zonal GAG concentrations individually and compared between native and trypsin-degraded cartilage.

RESULTS

The bulk GAG concentration was calculated to be 74.44 ± 6.09 and 11.99 ± 4.24 mg/mL for native and degraded cartilage, respectively. A statistical difference was demonstrated for bulk and zonal GAG between native and degraded cartilage (P < 0.032). A statistical difference was not demonstrated for bulk GAG when comparing Hexabrix bathing concentrations (P > 0.3214) for neither native nor degraded cartilage. Depth-dependent GAG analysis of native cartilage revealed a statistical difference only in the radial zone between 30% and 50% Hexabrix bathing concentrations.

CONCLUSIONS

This nondestructive qCECT methodology calculated the depth-dependent GAG concentration for both native and trypsin-degraded cartilage at high spatial resolution. qCECT allows for more detailed understanding of the topography and depth dependency, which could help diagnose health, degradation, and repair of native and contrived cartilage.

Lentiviral-mediated multiple gene transfer to chondrocytes promotes chondrocyte differentiation and bone formation in rabbit bone marrow-derived mesenchymal stem cells

The aim of the present study was to provide a theoretical and experimental foundation on the differentiation of stem cells through the induction of multiple genes. The lentiviral vector carrying TGF-β1 and IL-10 genes was transfected to bone marrow-derived mesenchymal stem cells (BMSCs) which differentiated into chondrogenesis. Healthy New Zealand white rabbits, 2-3 months of age were used in the present study. A 6-8 ml of bone marrow was isolated from the iliac and tibial shaft of each rabbit. The BMSCs suspension was aspired following centrifugation of the bone marrow by percoll separating medium. The BMSCs were primarily cultured and subcultured in vitro, then divided into four groups according to the difference of lentivirus vectors: group A, receiving transforming growth factor β1 (TGF‑β1); group B, receiving TGF-β1 and Interleukin-10 (IL-10); group C, empty vector transfection; and group D, receiving no cell growth factor. Fluorescence expression was detected 12 h after transfecting the lentiviral vector carrying the TGF-β1 and IL-10 gene to BMSCs. The transfection efficiency was approximately 70% with a MOI=100 after 96 h. Expression of SOX-9 aggrecan and Type Ⅱ collagen in groups A-E on day 7 and 14 was detected by RT-PCR and western blot analysis. The expression level of three genes expressed in groups A and C were higher compared to the expression in groups B, D and E. The expression level of the three genes expressed in group B was higher compared to the expression in group D. The expression level of three genes expressed in group A and C showed no statistical difference. Cytokines therefore play an important role in cell proliferation and chondrogenic differentiation. TGF-β1 has a synergistic effect in the differentiation. In addition, IL-10 may have a protective role in the restoration of cartilaginous tissue.

Peripheral blood derived mononuclear cells enhance osteoarthritic human chondrocyte migration

Introduction

A major problem in cartilage repair is the lack of chondrogenic cells migrating from healthy tissue into defects. Cartilage is essentially avascular and therefore its healing is not considered to involve mononuclear cells. Peripheral blood derived mononuclear cells (PBMC) offer a readily available autologous cell source for clinical use and therefore this study was designed to evaluate the effects of PBMCs on chondrocytes and cartilage.

Methods

Human primary chondrocytes and cartilage tissue explants were taken from patients undergoing total knee replacement (n = 17). Peripheral blood samples were obtained from healthy volunteers (n = 12) and mononuclear cells were isolated by density-gradient centrifugation. Cell migration and chemokinetic potential were measured using a scratch assay, xCELLigence and CyQuant assay. PCR array and quantitative PCR was used to evaluate mRNA expression of 87 cell motility and/or chondrogenic genes.

Results

The chondrocyte migration rate was 2.6 times higher at 3 hour time point (p < 0.0001) and total number of migrating chondrocytes was 9.7 times higher (p < 0.0001) after three day indirect PBMC stimulus and 8.2 times higher (p < 0.0001) after three day direct co-culture with PBMCs. A cartilage explant model confirmed that PBMCs also exert a chemokinetic role on ex vivo tissue. PBMC stimulation was found to significantly upregulate the mRNA levels of 2 chondrogenic genes; collagen type II (COL2A1 600–fold, p < 0.0001) and SRY box 9 (SOX9 30–fold, p < 0.0001) and the mRNA levels of 7 genes central in cell motility and migration were differentially regulated by 24h PBMC stimulation.

Conclusion

The results support the concept that PBMC treatment enhances chondrocyte migration without suppressing the chondrogenic phenotype possibly via mechanistic pathways involving MMP9 and IGF1. In the future, peripheral blood mononuclear cells could be used as an autologous point-ofcare treatment to attract native chondrocytes from the diseased tissue to aid in cartilage repair.

An Equilibrium Constitutive Model of Anisotropic Cartilage Damage to Elucidate Mechanisms of Damage Initiation and Progression

Traumatic injuries and gradual wear-and-tear of articular cartilage (AC) that can lead to osteoarthritis (OA) have been hypothesized to result from tissue damage to AC. In this study, a previous equilibrium constitutive model of AC was extended to a constitutive damage articular cartilage (CDAC) model. In particular, anisotropic collagen (COL) fibril damage and isotropic glycosaminoglycan (GAG) damage were considered in a 3D formulation. In the CDAC model, time-dependent effects, such as viscoelasticity and poroelasticity, were neglected, and thus all results represent the equilibrium response after all time-dependent effects have dissipated. The resulting CDAC model was implemented in two different finite-element models. The first simulated uniaxial tensile loading to failure, while the second simulated spherical indentation with a rigid indenter displaced into a bilayer AC sample. Uniaxial tension to failure simulations were performed for three COL fibril Lagrangian failure strain (i.e., the maximum elastic COL fibril strain) values of 15%, 30%, and 45%, while spherical indentation simulations were performed with a COL fibril Lagrangian failure strain of 15%. GAG damage parameters were held constant for all simulations. Our results indicated that the equilibrium postyield tensile response of AC and the macroscopic tissue failure strain are highly dependent on COL fibril Lagrangian failure strain. The uniaxial tensile response consisted of an initial nonlinear ramp region due to the recruitment of intact fibrils followed by a rapid decrease in tissue stress at initial COL fibril failure, as a result of COL fibril damage which continued until ultimate tissue failure. In the spherical indentation simulation, damage to both the COL fibril and GAG constituents was located only in the superficial zone (SZ) and near the articular surface with tissue thickening following unloading. Spherical indentation simulation results are in agreement with published experimental observations. Our results indicate that the proposed CDAC model is capable of simulating both initial small magnitude damage as well as complete failure of AC tissue. The results of this study may help to elucidate the mechanisms of AC tissue damage, which initiate and propagate OA.

Matrix-induced autologous mesenchymal stem cell implantation versus matrix-induced autologous chondrocyte implantation in the treatment of chondral defects of the knee: a 2-year randomized study

BACKGROUND

Cell-based strategies that combine in vitro- expanded autologous chondrocytes with matrix scaffolds are currently preferred for full-thickness cartilage lesions of the knee ≥2 cm(2). Although this approach is reasonable, continuing advances in the field of cartilage repair will further expand the options available to improve outcomes.

HYPOTHESIS/PURPOSE

In the present clinical study, we compared the outcomes of matrix-induced autologous mesenchymal stem cell implantation (m-AMI) with matrix-induced autologous chondrocyte implantation (m-ACI) for the treatment of isolated chondral defects of the knee.

STUDY DESIGN

Prospective, single-site, randomized, single-blind pilot study.

METHODS

Fourteen patients with isolated full-thickness chondral lesions of the knee >2 cm(2) were randomized into two treatment groups: m-AMI and m-ACI. Outcomes were assessed pre-operatively and 3, 6, 12 and 24 months post-operatively.

RESULTS

Clinical evaluations revealed that improvement from pre-operation to 24 months post-operation occurred in both groups (p < 0.05). At all follow-up intervals, m-AMI demonstrated significantly better functional outcomes (motion deficit and straight leg raise strength) than did m-ACI (p < 0.05). At all follow-up intervals, m-AMI demonstrated significantly better subjective sub-scale scores for pain, symptoms, activities of daily living and sport and recreation of the knee injury and osteoarthritis outcome score (KOOS) than did m-ACI (p < 0.05). Additionally, m-AMI demonstrated significantly better (p < 0.05) scores than m-ACI for the quality of life sub-scale of the KOOS and visual analog scale (VAS) severity at the 6-month follow-up. The Tegner activity score and VAS frequency were not significantly different between the two groups. Graft failure was not observed on magnetic resonance imaging at the 24-month follow-up. m-AMI and m-ACI demonstrated very good-to-excellent and good-to-very good infill, respectively, with no adverse effects from the implant, regardless of the treatment.

CONCLUSION

For the treatment of isolated full-thickness chondral lesion of the knee, m-AMI can be used effectively and may potentially accelerate recovery. A larger patient cohort and follow-up supported by histological analyses are necessary to determine long-term outcomes.

Potential benefits and limitations of utilizing chondroprogenitors in cell-based cartilage therapy

Chondroprogenitor cells are a subpopulation of multipotent progenitors that are primed for chondrogenesis. They are believed to have the biological repertoire to be ideal for cell-based cartilage therapy. In addition to summarizing recent advances in chondroprogenitor cell characterization, this review discusses the projected pros and cons of utilizing chondroprogenitors in regenerative medicine and compares them with that of pre-existing methods, including autologous chondrocyte implantation (ACI) and the utilization of bone marrow derived mesenchymal stem cells (MSCs) for the purpose of cartilage tissue repair.

Chondrocytes behaviors within type I collagen microspheres and bulk hydrogels: an in vitro study

Cell niche, which is considered to be critical to the proliferation and differentiation of cells, is one of the most important aspects for the design and development of ideal scaffolds in tissue engineering.

Treatment with embryonic stem-like cells into osteochondral defects in sheep femoral condyles

Background

Articular cartilage has poor intrinsic capacity for regeneration because of its avascularity and very slow cellular turnover. Defects deriving from trauma or joint disease tend to be repaired with fibrocartilage rather than hyaline cartilage. Consequent degenerative processes are related to the width and depth of the defect. Since mesenchymal stem cells (MSCs) deriving from patients affected by osteoarthritis have a lower proliferative and chondrogenic activity, the systemic or local delivery of heterologous cells may enhance regeneration or inhibit the progressive loss of joint tissue. Embryonic stem cells (ESCs) are very promising, since they can self-renew for prolonged periods without differentiation and can differentiate into tissues from all the 3 germ layers. To date only a few experiments have used ESCs for the study of the cartilage regeneration in animal models and most of them used laboratory animals. Sheep, due to their anatomical, physiological and immunological similarity to humans, represent a valid model for translational studies. This experiment aimed to evaluate if the local delivery of male sheep embryonic stem-like (ES-like) cells into osteochondral defects in the femoral condyles of adult sheep can enhance the regeneration of articular cartilage. Twenty-two ewes were divided into 5 groups (1, 2, 6, 12 and 24 months after surgery). Newly formed tissue was evaluated by macroscopic, histological, immunohistochemical (collagen type II) and fluorescent in situ hybridization (FISH) assays.

Results

Regenerated tissue was ultimately evaluated on 17 sheep. Samples engrafted with ES-like cells had significantly better histologic evidence of regeneration with respect to empty defects, used as controls, at all time periods.

Conclusions

Histological assessments demonstrated that the local delivery of ES-like cells into osteochondral defects in sheep femoral condyles enhances the regeneration of the articular hyaline cartilage, without signs of immune rejection or teratoma for 24 months after engraftment.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-014-0301-9) contains supplementary material, which is available to authorized users.

Tibial plateau lesions. Surface reconstruction with a biomimetic osteochondral scaffold: Results at 2 years of follow-up

INTRODUCTION

Tibial plateau articular pathology caused by post-traumatic or degenerative lesions is a challenge for the orthopaedic surgeon and can lead to early osteoarthritis. The aim of the present study was to evaluate the results of treatment of these complex defects with implantation of an osteochondral scaffold, which is designed to target the cartilage surface and to reconstruct joint anatomy by addressing the entire osteochondral unit.

MATERIALS AND METHODS

Eleven patients (5 female and 6 male) with a mean age of 37.3 ± 11.0 years and osteochondral lesions of the tibial plateau (mean 5.1 ± 2.7 cm(2); range 3.0-12.5 cm(2)) were treated with the implantation of an osteochondral biomimetic collagen-hydroxyapatite scaffold (Maioregen(®), Fin-Ceramica, Faenza, Italy). Comorbidities were addressed taking care to restore the correct limb alignment. Patients were evaluated pre-operatively and prospectively followed-up for 2 years using the International Knee Documentation Committee (IKDC) subjective and objective scores; activity level was documented using the Tegner score.

RESULTS

Three patients experienced minor adverse events. No patients required further surgery for treatment failure during the study follow-up period, and 8 patients (72.7%) reported a marked improvement. The IKDC subjective score improved from 42.5 ± 10.2 before treatment to 69.8 ± 19.0 at 12 months (p<0.05), with stable results at 24 months. The IKDC objective score increased from 27.3% normal and nearly normal knees before treatment to 85.7% normal and nearly normal knees at 24 months of follow-up. The Tegner score increased from 2.3 ± 2.1 before treatment to 4.8 ± 2.4 at 12 months (p<0.05), and was stable at the final follow-up.

CONCLUSION

The present study on the implantation of an osteochondral scaffold for the treatment of tibial plateau lesions showed a promising clinical outcome at short-term follow-up, which indicates that this procedure can be considered as a possible treatment option, even in these complex defects, when comorbidities are concomitantly addressed.

Simultaneous regeneration of full-thickness cartilage and subchondral bone defects in vivo using a three-dimensional scaffold-free autologous construct derived from high-density bone marrow-derived mesenchymal stem cells

BACKGROUND

In recent years, several methods have been developed for repairing full-thickness cartilage defects by tissue engineering using mesenchymal stem cells. Most of these use scaffolds to achieve sufficient thickness. However, considering the potential influence of scaffolds on the surrounding microenvironment, as well as immunological issues, it is desirable to develop a scaffold-free technique. In this study, we developed a novel technique, a scaffold-free autologous construct derived from bone marrow-derived mesenchymal stem cells (BM-MSCs), and successfully use this technique to regenerate cartilage and subchondral bone to repair an osteochondral defect in rabbit knees.

METHODS

BM-MSCs were isolated from bone marrow liquid aspirated from the iliac crest of rabbits. After expansion in culture dishes and re-suspension in 96-well plates, the cells spontaneously aggregated into a spheroid-like structure. The spheroids were loaded into a tube-shaped Teflon mold with a 5-mm height and maintained under air-liquid interface conditions. These loaded spheroids fused with each other, resulting in a cylinder-shaped construct made of fused cells that conformed to the inner shape of the mold. The construct was implanted into an osteochondral defect in rabbit knees and histologically analyzed 24 and 52 weeks after implantation using Wakitani's scoring system.

RESULTS

Both bone and cartilage were regenerated, maintaining a constant thickness of cartilage. The mean histological score was 10 ± 1.7 in the 24-week group and 9.7 ± 0.6 in the 52-week group. There was no significant difference between the 24- and 52-week groups in either parameter of the score, indicating that no deterioration of the repaired tissue occurred during the intervening period.

CONCLUSIONS

Using our novel technique, which employs a three-dimensional scaffold-free autologous construct derived from BM-MSCs, we successfully achieved simultaneous regeneration of bone and cartilage for up to 1 year in vivo. This method has potential for clinical use as a safe and effective method for repairing bone and cartilage defects.

Effects of culture on PAMPS/PDMAAm double-network gel on chondrogenic differentiation of mouse C3H10T1/2 cells: in vitro experimental study

Background

Recently, several animal studies have found that spontaneous hyaline cartilage regeneration can be induced in vivo within a large osteochondral defect by implanting a synthetic double-network (DN) hydrogel, which is composed of poly-(2-acrylamido-2-methylpropanesulfonic acid) (PAMPS) and poly-(N,N’-dimethyl acrylamide) (PDMAAm), at the bottom of the defect. However, the effect of hydrogel on hyaline cartilage regeneration remains unexplained. The purpose of this study was to investigate the chondrogenic differentiation of C3H10T1/2 cells on PAMPS/PDMAAm DN gel.

Methods

C3H10T1/2 cells of 1.0 × 10⁵ were cultured on PAMPS/PDMAAm DN gel in polystyrene tissue culture dishes or directly on polystyrene tissue culture dishes. We compared cultured cells on PAMPS/PDMAAm DN gel with those on polystyrene dishes by morphology using phase-contrast microscopy, mRNA expression of aggrecan, type I collagen, type II collagen, Sox 9 and osteocalcin using real-time RT-PCR, and local expression of type II collagen using immunocytochemistry.

Results

C3H10T1/2 cells cultured on the PAMPS/PDMAAm DN gels formed focal adhesions, aggregated rapidly and developed into large nodules within 7 days, while the cells cultured on the polystyrene surface did not. The mRNA levels of aggrecan, type I collagen, type II collagen, Sox 9 and osteocalcin were significantly greater in cells cultured on the PAMPS/PDMAAm DN gel than in those cultured on polystyrene dishes. In addition, C3H10T1/2 cells cultured on PAMPS/PDMAAm DN gel expressed more type II collagen at the protein level when compared with cells cultured on polystyrene dishes.

Conclusions

The present study showed that PAMPS/PDMAAm DN gel enhanced chondrogenesis of C3H10T1/2 cells, which are functionally similar to mesenchymal stem cells. This suggests that mesenchymal stem cells from the bone marrow contribute to spontaneous hyaline cartilage regeneration in vivo in large osteochondral defects after implantation of PAMPS/PDMAAm DN gels.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2474-15-320) contains supplementary material, which is available to authorized users.

Involvement of the endocannabinoid system in osteoarthritis pain

Osteoarthritis is a degenerative joint disease associated with articular cartilage degradation. The major clinical outcome of osteoarthritis is a complex pain state that includes both nociceptive and neuropathic mechanisms. Currently, the therapeutic approaches for osteoarthritis are limited as no drugs are available to control the disease progression and the analgesic treatment has restricted efficacy. Increasing evidence from preclinical studies supports the interest of the endocannabinoid system as an emerging therapeutic target for osteoarthritis pain. Indeed, pharmacological studies have shown the anti-nociceptive effects of cannabinoids in different rodent models of osteoarthritis, and compelling evidence suggests an active participation of the endocannabinoid system in the pathophysiology of this disease. The ubiquitous distribution of cannabinoid receptors, together with the physiological role of the endocannabinoid system in the regulation of pain, inflammation and even joint function further support the therapeutic interest of cannabinoids for osteoarthritis. However, limited clinical evidence has been provided to support this therapeutic use of cannabinoids, despite the promising preclinical data. This review summarizes the promising results that have been recently obtained in support of the therapeutic value of cannabinoids for osteoarthritis management.

Updates in biological therapies for knee injuries: full thickness cartilage defect

Full thickness cartilage defect might occur at different ages, but a focal defect is a major concern in the knee of young athletes. It causes impairment and does not heal by itself. Several techniques were described to treat symptomatic full thickness cartilage defect. Recently, several advances were described on the known techniques of microfracture, osteochondral allograft, cell therapy, and others. This article brings an update of current literature on these well-described techniques for full thickness cartilage defect.

Functional cartilage repair capacity of de-differentiated, chondrocyte- and mesenchymal stem cell-laden hydrogels in vitro

OBJECTIVE

The long-term performance of cell-seeded matrix-based cartilage constructs depends on (1) the development of sufficient biomechanical properties, and (2) lateral integration with host tissues, both of which require cartilage-specific matrix deposition within the scaffold. In this study, we have examined the potential of tissue-engineered cartilage analogs developed using different cell types, i.e., mesenchymal stem cells (MSCs) vs chondrocytes and de-differentiated chondrocytes, in an established "construct in cartilage ring" model.

DESIGN

Cell-laden constructs of differentiated chondrocytes, de-differentiated chondrocytes after two, five or eight population doublings, and MSCs were either implanted into a native cartilage ring immediately after fabrication (immature group) or pre-treated for 21 days in a transforming growth factor-β3 (TGF-β3) containing medium prior to implantation. After additional culture for 28 days in a serum-free, chemically defined medium, the extent of lateral integration, and biochemical and biomechanical characteristics of the implants as hybrid constructs were assessed.

RESULTS

The quality of integration, the amount of accumulated cartilage-specific matrix components and associated biomechanical properties were found to be highest when using differentiated chondrocytes. De-differentiation of chondrocytes negatively impacted the properties of the implants, as even two population doublings of the chondrocytes in culture significantly lowered cartilage repair capacity. In contrast, MSCs showed chondrogenic differentiation with TGF-β3 pre-treatment and superior integrational behavior.

CONCLUSIONS

Chondrocyte expansion and de-differentiation impaired the cell response, resulting in inferior cartilage repair in vitro. With TGF-β3 pre-treatment, MSCs were able to undergo sustained chondrogenic differentiation and exhibited superior matrix deposition and integration compared to de-differentiated chondrocytes.

Significant increase in Young's modulus of ATDC5 cells during chondrogenic differentiation induced by PAMPS/PDMAAm double-network gel: comparison with induction by insulin

A double-network (DN) gel, which was composed of poly(2-acrylamido-2-methylpropanesulfonic acid) and poly(N,N'-dimethyl acrylamide) (PAMPS/PDMAAm), has the potential to induce chondrogenesis both in vitro and in vivo. The present study investigated the biomechanical and biological responses of chondrogenic progenitor ATDC5 cells cultured on the DN gel. ATDC5 cells were cultured on a polystyrene surface without insulin (Culture 1) and with insulin (Culture 2), and on the DN gel without insulin (Culture 3). The cultured cells were evaluated using micropipette aspiration for cell Young's modulus and qPCR for gene expression of chondrogenic and actin organization markers on days 3, 7 and 14. On day 3, the cells in Culture 3 formed nodules, in which the cells exhibited an actin cortical layer inside them, and gene expression of type-II collagen, aggrecan, and SOX9 was significantly higher in Culture 3 than Cultures 1 and 2 (p<0.05). Young's modulus in Culture 3 was significantly higher than that in Culture 1 throughout the testing period (p<0.05) and that in Culture 2 on day 14 (p<0.01). There was continuous expression of actin organization markers in Culture 3. This study highlights that the cells on the DN gel increased the modulus and mRNA expression of chondrogenic markers at an earlier time point with a greater magnitude compared to those on the polystyrene surface with insulin. This study also demonstrates a possible strong interrelation among alteration of cell mechanical properties, changes in actin organization and the induction of chondrogenic differentiation.

Development of hybrid scaffolds using ceramic and hydrogel for articular cartilage tissue regeneration

The regeneration of articular cartilage consisting of hyaline cartilage and hydrogel scaffolds has been generally used in tissue engineering. However, success in in vivo studies has been rarely reported. The hydrogel scaffolds implanted into articular cartilage defects are mechanically unstable and it is difficult for them to integrate with the surrounding native cartilage tissue. Therefore, it is needed to regenerate cartilage and bone tissue simultaneously. We developed hybrid scaffolds with hydrogel scaffolds for cartilage tissue and with ceramic scaffolds for bone tissue. For in vivo study, hybrid scaffolds were press-fitted into osteochondral tissue defects in a rabbit knee joints and the cartilage tissue regeneration in blank, hydrogel scaffolds, and hybrid scaffolds was compared. In 12th week after implantation, the histological and immunohistochemical analyses were conducted to evaluate the cartilage tissue regeneration. In the blank and hydrogel scaffold groups, the defects were filled with fibrous tissues and the implanted hydrogel scaffolds could not maintain their initial position; in the hybrid scaffold group, newly generated cartilage tissues were morphologically similar to native cartilage tissues and were smoothly connected to the surrounding native tissues. This study demonstrates hybrid scaffolds containing hydrogel and ceramic scaffolds can provide mechanical stability to hydrogel scaffolds and enhance cartilage tissue regeneration at the defect site.

In vitro isolation and cultivation of human chondrocytes for osteoarthritis renovation

The purpose of this study was to evaluate the repair effects of chondrocytes that were cultured in vitro on osteoarthritis (OA). Chondrocytes were isolated from fetal rabbits and cultured in Biosilon microcarriers. Sixty rabbits were randomly divided into three groups equally (blank group, model group, treatment group). The rabbit knee OA model was established by inducing papain. Rabbits in the treatment group were injected with the chondrocytes that were cultured in vitro. Hematoxylin-eosin (HE) staining and gross morphologic observation were conducted. Expression level of cytokines such as IL-1bβ, IL-6, and TNF-α in cartilage synovial cells was also analyzed by an ELISA assay. The cultured chondrocyte was validated by a positive stain of type II collagen and vimentin by immunofluorescence. Compared to the model group, the articular cartilage of the rabbit knee in the treatment group showed a normal color, smooth surface, and none of malacia and coloboma. HE staining indicated that the articular surface of the treatment group tended to be smooth and flat; the matrix stained tinge and the cartilage destruction and fiber hyperplasia of the synovia were lightened. The expression levels of IL-1bβ, IL-6, and TNF-α also declined in the treatment group. OA symptoms were improved by treating with chondrocytes. In summary, the animal experiment in the present study indicated that chondrocyte injection played an active effect on renovation of OA.

Human Infrapatellar Fat Pad-Derived Stromal Cells Have More Potent Differentiation Capacity Than Other Mesenchymal Cells and Can Be Enhanced by Hyaluronan

The microenvironment plays an important role in the homing in and differentiation of stem cells to repair injured tissue. Infrapatellar fat pad stromal cells (IFPSCs) are a promising source of such cells for the repair of articular injury-induced degeneration. This study investigated the chemotaxis of IFPSCs to chondrocytes and the effect of hyaluronan (HA) on the biological and regenerative properties of IFPSCs. The IFPSCs were obtained from patients undergoing arthroscopy and cultured via a standard 2-week culture protocol that yielded more than 10 million cells on passage 3. The results showed that the IFPSCs had a higher capacity for chondrogenic differentiation than mesenchymal cells from body fat, bone marrow, and Wharton's jelly of the umbilical cord. The IFPSCs cultured on 25% or 50% HA showed better osteogenic and adipogenic capabilities than those without HA or with 75% HA (p < 0.001). Cultures of the IFPSCs on 25% HA had a fourfold increase in chondrogenic differentiation compared to cultures without HA, which was better than with 50% and 75% HA (p < 0.05). Cell proliferation was not affected by the presence of HA. In conclusion, IFPSCs have a strong potential for chondrogenic regeneration, which can even be augmented in a 25% HA microenvironment.

In Situ Recruitment of Human Bone Marrow-Derived Mesenchymal Stem Cells Using Chemokines for Articular Cartilage Regeneration

Bone marrow-derived mesenchymal stem cells (BMSCs) are a good cell source for regeneration of cartilage as they can migrate directly to the site of cartilage injury and differentiate into articular chondrocytes. Articular cartilage defects do not heal completely due to the lack of chondrocytes or BMSCs at the site of injury. In this study, the chemotaxis of BMSCs toward chemokines, which may give rise to a complete regeneration of the articular cartilage, was investigated. CCR2, CCR4, CCR6, CXCR1, and CXCR2 were expressed in normal BMSCs and were increased significantly upon treatment with proinflammatory cytokines. BMSC migration was increased by MIP-3α and IL-8 more than by MCP-1 or SDF-1α. IL-8 and MIP-3α significantly enhanced the chemotaxis of BMSCs compared with MCP-1, SDF-1α, or PBS. Human BMSC recruitment to transplanted scaffolds containing either IL-8 or MIP-3α significantly increased in vivo compared to scaffolds containing PBS. Furthermore, IL-8- and MIP-3α-containing scaffolds enhanced tissue regeneration of an osteochondral defect site in beagle knee articular cartilage. Therefore, this study suggests that IL-8 and MIP-3α are the candidates that induce the regeneration of damaged articular cartilage.

Intra-articular administration of hyaluronic acid increases the volume of the hyaline cartilage regenerated in a large osteochondral defect by implantation of a double-network gel

Implantation of PAMPS/PDMAAm double-network (DN) gel can induce hyaline cartilage regeneration in the osteochondral defect. However, it is a problem that the volume of the regenerated cartilage tissue is gradually reduced at 12 weeks. This study investigated whether intra-articular administration of hyaluronic acid (HA) increases the volume of the cartilage regenerated with the DN gel at 12 weeks. A total of 48 rabbits were used in this study. A cylindrical osteochondral defect created in the bilateral femoral trochlea was treated with DN gel (Group DN) or left without any implantation (Group C). In both Groups, we injected 1.0 mL of HA in the left knee, and 1.0 mL of saline solution in the right knee. Quantitative histological evaluations were performed at 2, 4, and 12 weeks, and PCR analysis was performed at 2 and 4 weeks after surgery. In Group DN, the proteoglycan-rich area was significantly greater in the HA-injected knees than in the saline-injected knees at 12 weeks (P = 0.0247), and expression of type 2 collagen, aggrecan, and Sox9 mRNAs was significantly greater in the HA-injected knees than in the saline-injected knees at 2 weeks (P = 0.0475, P = 0.0257, P = 0.0222, respectively). The intra-articular administration of HA significantly enhanced these gene expression at 2 weeks and significantly increased the volume of the hyaline cartilage regenerated by implantation of a DN gel at 12 weeks. This information is important to develop an additional method to increase the volume of the hyaline cartilage tissue in a potential cartilage regeneration strategy using the DN gel.

BMP activation and Wnt-signalling affect biochemistry and functional biomechanical properties of cartilage tissue engineering constructs

OBJECTIVES

Bone morphogenetic protein (BMP-) and Wnt-signalling play crucial roles in cartilage homeostasis. Our objective was to investigate whether activation of the BMP-pathway or stimulation of Wnt-signalling cascades effectively enhances cartilage-specific extracellular matrix (ECM) accumulation and functional biomechanical parameters of chondrocyte-seeded tissue engineering (TE)-constructs.

DESIGN

Articular chondrocytes were cultured in collagen-type-I/III-matrices over 6 weeks to create a biomechanical standard curve. Effects of stimulation with 100 ng/mL BMP-4/-7 heterodimer or 10 mM lithium chloride (LiCl) on ECM-deposition was quantified and characterized histologically. Biomechanical parameters were determined by the Very Low Rubber Hardness (VLRH) method and under confined compression stress relaxation.

RESULTS

BMP-4/-7 treatment resulted in stronger collagen type-II staining and significantly enhanced glycosaminoglycan (GAG) deposition (3.2-fold; *P < 0.01) correlating with improved hardness (∼1.7-fold; *P = 0.001) reaching 83% of native cartilage values after 28 days, a value not reached before 9 weeks without stimulation. LiCl treatment enhanced VLRH slightly, but significantly (∼1.3-fold; *P = 0.016) with a trend to more ECM-deposition. BMP-4/-7 treatment significantly enhanced the E Modulus (105.7 ± 34.1 kPa; *P = 0.000001) compared to controls (8.0 ± 4.2 kPa). Poisson's ratio was significantly improved by BMP-4/-7 treatment (0.0703 ± 0.0409; *P = 0.013) vs controls (0.0432 ± 0.0284) and a significantly lower permeability (5.8 ± 2.1056 × 10(-14) m4/N.s; *P = 0.00001) was detected compared to untreated scaffolds (4.4 ± 3.1289 × 10(-13) m4/N.s).

CONCLUSIONS

While Wnt-activation is less effective, BMP-4/-7 heterodimer stimulation approximated native cartilage features in less than 50% of standard culture time representing a promising strategy for functional cartilage TE to improve biomechanical parameters of engineered cartilage.

Clinical rehabilitation guidelines for matrix-induced autologous chondrocyte implantation on the tibiofemoral joint

Autologous chondrocyte implantation (ACI) has become an established technique for the repair of full-thickness chondral defects in the knee. Matrix-induced ACI (MACI) is the third and current generation of this surgical technique, and, while postoperative rehabilitation following MACI aims to restore normal function in each patient as quickly as possible by facilitating a healing response without overloading the repair site, current published guidelines appear conservative, varied, potentially outdated, and often based on earlier ACI surgical techniques. This article reviews the existing evidence-based literature pertaining to cell loading and postoperative rehabilitation following generations of ACI. Based on this information, in combination with the technical benefits provided by third-generation MACI in comparison to its surgical predecessors, we present a rehabilitation protocol for patients undergoing MACI in the tibiofemoral joint that has now been implemented for several years by our institution in patients with MACI, with good clinical outcomes.

The effect of platelet-rich plasma on osteochondral defects treated with mosaicplasty

PURPOSE

This study investigated the efficacy of platelet-rich plasma (PRP) on articular surfaces on which the mosaicplasty technique was performed. Our hypothesis was that PRP can accelerate the osseointegration process and enhance the quality of articular integrity after the mosaicplasty procedure.

METHODS

Standard defects were created in the femoral groove of both patellofemoral joints of 12 New Zealand rabbits. PRP solution was placed inside the defect before fixation of the osteochondral autografts and injected inside the involved joint after capsular closure of the tested knees. The contralateral knees served as the control sides. The animals were euthanized three or six weeks after mosaicplasty, and both limbs were assessed according to Pineda's histological grading scale. Significance level was set at p ≤ 0.05 a priori, and the Mann-Whitney U test was used for statistical analysis.

RESULTS

Histologic findings at the interface between the transferred autograft and the original cartilage revealed better integration of the adjacent surfaces in the mosaicplasty with PRP group three weeks after the procedure; the difference was significant (p < 0.05). However, no significant difference in the transition zone was observed between the groups six weeks after the experiment (p = 0.59).

CONCLUSIONS

Our animal model showed that adjunctive use of PRP produced a better healing response and resulted in superior histological scores after three weeks compared with the mosaicplasty-only procedure. Interpretation of our results is important in terms of rapid return to previous activity levels. Thus, application of PRP can represent a valid therapeutic option for improving the efficacy of mosaicplasty by stimulating the local healing response.