Articular cartilage: injury pathways and treatment options

Chondroitin Sulfate and Hyaluronic Acid-Based PolyHIPE Scaffolds for Improved Osteogenesis and Chondrogenesis In Vitro

Osteochondral damage, affecting the articular cartilage and the underlying subchondral bone, presents significant challenges in clinical treatment. Such defects, commonly seen in knee and ankle joints, vary from small localized lesions to larger defects. Current medical therapies encounter several challenges, such as donor shortages, drug side effects, high costs, and rejection problems, often resulting in only temporary relief. Highly porous emulsion-templated polymers (polyHIPEs) offer numerous potential benefits in the fabrication of scaffolds for tissue engineering and regenerative medicine. Polymeric scaffolds synthesized using a high internal phase emulsion (HIPE) technique, called PolyHIPEs, involve polymerizing a continuous phase surrounding a dispersed internal phase to form a solid, foam-like structure. A dense, porous design encourages cell ingrowth, nutrient delivery, and waste disposal from the scaffold, mimicking the cells' natural microenvironment. This study used hydroxyethyl methacrylate (HEMA) and acrylamide (AAM) polyHIPE scaffolds combined with extracellular matrix (ECM) components of the tissue, such as methacrylated hyaluronic acid (MHA) and methacrylated chondroitin sulfate (MCS), to prepare polyHIPE scaffolds. The mouse preosteoblast MC3T3-E1 cells and primary rat chondrocytes (harvested from male Wistar rats) were seeded on the scaffolds and cultured for 21 days to assess the osteogenesis and chondrogenesis in vitro. When compared to the AAM-MHA and AAM-MCS groups at day 21, scaffold groups HEMA-MHA and HEMA-MCS showed a significant rise in alkaline phosphatase (ALP) and calcium content. Chondrogenic markers such as glycosaminoglycan (GAG) and hydroxyproline were also assessed over a 21-day time point. On day 21, it was found that GAG and hydroxyproline production were considerably higher in the HEMA-MHA and HEMA-MCS scaffolds than in the AAM-MHA and AAM-MCS scaffolds. The overall studies showed that polyHIPE monolith scaffolds could favor cell adherence, survival ability, proliferation, differentiation, and ECM formation over 21 days. Thus, incorporating ECM components enhanced osteogenesis and chondrogenesis in vitro and can be further used as tissue repair models.

Ginsenoside Rg1/ADSCs supplemented with hyaluronic acid as the matrix improves rabbit temporomandibular joint osteoarthrosis

OBJECTIVE

To investigate whether and how ginsenoside Rg1/ADSCs supplemented with hyaluronic acid as the matrix can improve rabbit temporomandibular joint osteoarthrosis.

METHOD

Isolate and culture adipose stem cells, measure the activity of differentiated chondrocytes by MTT assay and expression of type II collagen in these cells by immunohistochemistry, in order to evaluate the effect of ginsenoside Rg1 on adipose stem cell proliferation and differentiation into chondrocytes.32 New Zealand white rabbits were randomly divided into four groups: blank group, model group, control group and experimental group, 8 in each group. Osteoarthritis model was established by intra-articular injection of papain. Two weeks after successful model building, medication was given for the rabbits in control group and experimental group. 0.6 mL ginsenoside Rg1/ ADSCs suspension was injected into superior joint space for the rabbits in control group, once a week; 0.6 mL ginsenoside Rg1/ ADSCs complex was injected for the rabbits in experimental group, once a week.

RESULTS

Ginsenoside Rg1 can promote ADSCs-derived chondrocytes' activity and expression of type II collagen. Scanning electron microscopy histology images showed cartilage lesions of the experimental group was significantly improved in comparison with control group.

CONCLUSION

Ginsenoside Rg1 can promote ADSCs differentiate into chondrocytes, and Ginsenoside Rg1/ADSCs supplemented with hyaluronic acid as the matrix can significantly improve rabbit temporomandibular joint osteoarthrosis.

The use of peptides, aptamers, and variable domains of heavy chain only antibodies in tissue engineering and regenerative medicine

Over the years, much research has been focused on the use of small molecules such as peptides or aptamers or more recently on the use of variable antigen-binding domain of heavy chain only antibodies in the field of tissue engineering and regenerative medicine. The use of these molecules originated as an alternative for the larger conventional antibodies, of which most drawbacks are derived from their size and complex structure. In the field of tissue engineering and regenerative medicine, biological functionalities are often conjugated to biomaterials in order to (re-)create an in vivo like situation, especially when bioinert biomaterials are used. Those biomaterials are functionalized with these functionalities for instance for the purpose of cell attachment or cell targeting for targeted drug delivery but also for local enrichment or blocking of ligands such as growth factors or cytokines on the biomaterial surface. In this review, we further refer to peptides, aptamers, and variable antigen-binding domain of heavy chain only antibodies as biological functionalities. Here, we compare these biological functionalities within the field of tissue engineering and regenerative medicine and give an overview of recent work in which these biological functionalities have been explored. We focus on the previously mentioned purposes of the biological functionalities. We will compare structural differences, possible modifications and (chemical) conjugation strategies. In addition, we will provide an overview of biologicals that are, or have been, involved in clinical trials. Finally, we will highlight the challenges of each of these biologicals. STATEMENT OF SIGNIFICANCE: In the field of tissue engineering there is broad application of functionalized biomaterials for cell attachment, targeted drug delivery and local enrichment or blocking of growth factors. This was previously mostly done via conventional antibodies, but their large size and complex structure impose various challenges with respect of retaining biological functionality. Peptides, aptamers and VHHs may provide an alternative solution for the use of conventional antibodies. This review discusses the use of these molecules for biological functionalization of biomaterials. For each of the molecules, their characteristics, conjugation possibilities and current use in research and clinical trials is described. Furthermore, this review sets out the benefits and challenges of using these types of molecules for different fields of application.

Immunohistochemical Analysis of Knee Chondral Defect Repair after Autologous Particulated Cartilage and Platelet-Rich Plasma Treatment in Sheep

This study performs an analysis that will enable the evaluation of the quality, durability, and structure of repaired cartilaginous extracellular matrix tissue using an autologous-based particulated autograft cartilage and platelet-rich plasma treatment (PACI + PRP). A single-blind controlled experiment was conducted on 28 sheep to evaluate the efficacy of the PACI + PRP treatment for cartilage defects. Full-thickness 8 mm diameter defects were created in the weight-bearing area of both knees. The right knees received PACI + PRP. The left knees were treated with Ringer's lactate solution (RLS) or hyaluronic acid (HA) injections. Sheep were euthanized at 9- or 18-months post-surgery. An extensive immunohistochemical analysis was performed to assess collagen types (I, II, III, V, VI, IX, X, XI) and aggrecan positivity. A semiquantitative scoring system provided a detailed evaluation of immunostaining. Collagens and aggrecan scores in the PACI + PRP groups were similar to healthy cartilage. Significant differences were found in collagens associated with matrix maturity (II and V), degradation (IX), structure and mechanics (VI), and hypertrophy (X) between healthy cartilage and RLS- or HA-repaired cartilage. The PACI + PRP treatment advanced the repair cartilage process in chondral defects with mature hyaline cartilage and enhanced the structural and mechanical qualities with better consistent cartilage, less susceptible to degradation and without hypertrophic formation over time.

Proteoglycans in Articular Cartilage and Their Contribution to Chondral Injury and Repair Mechanisms

Proteoglycans are vital components of the extracellular matrix in articular cartilage, providing biomechanical properties crucial for its proper functioning. They are key players in chondral diseases, specifically in the degradation of the extracellular matrix. Evaluating proteoglycan molecules can serve as a biomarker for joint degradation in osteoarthritis patients, as well as assessing the quality of repaired tissue following different treatment strategies for chondral injuries. Despite ongoing research, understanding osteoarthritis and cartilage repair remains unclear, making the identification of key molecules essential for early diagnosis and effective treatment. This review offers an overview of proteoglycans as primary molecules in articular cartilage. It describes the various types of proteoglycans present in both healthy and damaged cartilage, highlighting their roles. Additionally, the review emphasizes the importance of assessing proteoglycans to evaluate the quality of repaired articular tissue. It concludes by providing a visual and narrative description of aggrecan distribution and presence in healthy cartilage. Proteoglycans, such as aggrecan, biglycan, decorin, perlecan, and versican, significantly contribute to maintaining the health of articular cartilage and the cartilage repair process. Therefore, studying these proteoglycans is vital for early diagnosis, evaluating the quality of repaired cartilage, and assessing treatment effectiveness.

Hopes and opportunities of stem cells from human exfoliated deciduous teeth (SHED) in cartilage tissue regeneration

Cartilage lesions are common conditions, affecting elderly and non-athletic populations. Despite recent advances, cartilage regeneration remains a major challenge today. The absence of an inflammatory response following damage and the inability of stem cells to penetrate into the healing site due to the absence of blood and lymph vessels are assumed to hinder joint repair. Stem cell-based regeneration and tissue engineering have opened new horizons for treatment. With advances in biological sciences, especially stem cell research, the function of various growth factors in the regulation of cell proliferation and differentiation has been established. Mesenchymal stem cells (MSCs) isolated from different tissues have been shown to increase into therapeutically relevant cell numbers and differentiate into mature chondrocytes. As MSCs can differentiate and become engrafted inside the host, they are considered suitable candidates for cartilage regeneration. Stem cells from human exfoliated deciduous teeth (SHED) provide a novel and non-invasive source of MSCs. Due to their simple isolation, chondrogenic differentiation potential, and minimal immunogenicity, they can be an interesting option for cartilage regeneration. Recent studies have reported that SHED-derived secretome contains biomolecules and compounds that efficiently promote regeneration in damaged tissues, including cartilage. Overall, this review highlighted the advances and challenges of cartilage regeneration using stem cell-based therapies by focusing on SHED.

Particulate cartilage and platelet-rich plasma treatment for knee chondral defects in sheep

PURPOSE

Articular cartilage is vulnerable to multiple types of damage and it has limited reparative and regenerative capacities due to its absence of vascularity. Although a large number of therapeutic strategies exist to treat chondral defects, they have some limitations, such as fibrocartilage formation. Therefore, the goal of the present study was to evaluate the chondrogenic regenerative properties of an autologous-made matrix of particulated cartilage and platelet-rich plasma (PACI + PRP) implantation for the treatment of full-thickness chondral defects in sheep.

METHODS

A full-thickness 8 mm diameter cartilage defect was created in the weight-bearing area of the medial femoral condyle in both knees of 16 sheep. The right knees of all animals were treated with particulated autograft cartilage implantation and platelet-rich plasma, while the left knees were injected with Ringer's lactate solution or hyaluronic acid. The sheep were killed 9 or 18 months after surgery. Macroscopic evaluations were performed using three different scoring systems, and histopathological evaluations were performed using a modified scoring system based on different scoring systems.

RESULTS

The PACI + PRP groups showed statistically significant differences in the percentage of defect repair and chondrocytes in the newly formed cartilage tissue at 18 months compared to 9 months.

CONCLUSIONS

The results suggest that macroscopic appearance, histological structure and chondrocyte repair were improved when using PACI + PRP treatment for chondral defects, producing an outcome similar to the surrounding healthy cartilage. PACI + PRP is a totally autologous, easy, and unexpensive treatment that can be performed in one-step procedure and is useful as a therapeutic option for knee chondral defects.

Advanced injectable hydrogels for cartilage tissue engineering

The rapid development of tissue engineering makes it an effective strategy for repairing cartilage defects. The significant advantages of injectable hydrogels for cartilage injury include the properties of natural extracellular matrix (ECM), good biocompatibility, and strong plasticity to adapt to irregular cartilage defect surfaces. These inherent properties make injectable hydrogels a promising tool for cartilage tissue engineering. This paper reviews the research progress on advanced injectable hydrogels. The cross-linking method and structure of injectable hydrogels are thoroughly discussed. Furthermore, polymers, cells, and stimulators commonly used in the preparation of injectable hydrogels are thoroughly reviewed. Finally, we summarize the research progress of the latest advanced hydrogels for cartilage repair and the future challenges for injectable hydrogels.

The molecular mechanism research of cartilage calcification induced by osteoarthritis

To explore the molecular mechanism of cartilage calcification induced by osteoarthritis (OA) based on distal-less homeobox gene 5 – alkaline phosphatase – integrin-binding sialoprotein – ecto-nucleotide pyrophosphatase 1 (DLX5-ALPL-IBSP-ENPP1) signal axis. Twenty-four rabbits were selected to build models of cartilage calcification induced by OA and randomly divided into 3 groups. The first group was the normal group whose rabbits were injected into 0.9% saline (0.3 mL), and the second group was model group. The third group was model group whose rabbits were injected into DLX5 antibody by caudal vein. Alizarin red calcium staining was used to analyze calcium deposition of cartilage matrix. Immunohistochemical staining was used to analyze the relative expression levels of proteins DLX5 and ENPP1, and western blot was used to analyze the DLX5, ALPL, IBSP, and ENPP1 expression. Calcium salt precipitation was the most serious, and the calcification area increased in the model group. Although calcified nodules appeared in the anti-DLX5 group, they were relatively few. Immunohistochemical staining analysis showed that the protein DLX5 located in the nucleus and the protein ENPP1 located in the extracellular matrix. Western blot analysis showed that the expressions of proteins DLX5, ALPL, IBSP, and ENPP1 were the highest in OA Model group than that of NC group, followed by anti-DLX5 group. The proteins DLX5, ALPL, IBSP, and ENPP1 can promote cartilage calcification induced by OA based on DLX5-ALPL-IBSP-ENPP1 signal axis.

Beneficial effects of Aucubin on restoration of rabbits with cartilage defect

Osteochondral grafts are suitable materials for repair of articular cartilage defect and plastic and reconstructive surgery. In our study, osteochondral allografts from rabbits were preserved in vitro for 28 days, and chondrocyte death, degradation of collagen and proteoglycan, morphological alterations, and inflammatory reaction were observed in the grafts. Supplementing of Aucubin with 10 or 20 μM in the preservation solution inhibited chondrocyte death, matrix degradation, pathological alterations and inflammation in allografts preserved in vitro, compared with that preserved in standard preservation solution. In addition, after transplantation of 20 μM Aucubin-treated allografts, the osteochondral repair and regeneration of rabbits with knee joint defect were accelerated. In conclusion, Aucubin was beneficial for maintaining chondrocyte viability and normal morphology, and inhibiting inflammatory occurrence in rabbit osteochondral grafts preserved in vitro, and facilitated osteochondral repair and regeneration of rabbits with knee defect. These findings might provide novel insights for preservation of grafts for clinical articular cartilage repair and plastic surgery.

A composite bilayer scaffold functionalized for osteochondral tissue regeneration in rat animal model

Osteochondral defects are defined most typically by damages to both cartilage and subchondral bone tissue. It is challenging to develop bilayered scaffolds that regenerate both of these lineages simultaneously. In the present study, an electrospun bilayer nanofibrous scaffold was designed to repair osteochondral lesions. A nanocomposite of hydroxyapatite, strontium, and reduced graphene oxide were combined with polycaprolactone polymer to fabricate the osteogenic differentiation layer. Additionally, the chondrogenic differentiation layer was also formed using polyethersulfone polymer and benzyl hyaluronan. The physical, mechanical, and chemical properties of the scaffolds were determined, and adipose-derived mesenchymal stem cells were cultured on each layer to evaluate their biocompatibility and differentiation potential. Cell viability, mineralization, alkaline phosphatase enzyme (ALP) expression, and extracellular calcium deposition were measured using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay, alizarin red staining, ALP activity, and calcium deposition. Real-time polymerase chain reaction (PCR) was used to assess the expression levels of osteogenic (Collagen I, Runx II, ALP, Osteocalcin) and chondrogenic (Sox9, Collagen II (Col II), Aggrecan) genes. Finally, the osteochondral scaffold was created by electrospinning these two layers for 2 days. The scaffold was grafted into the osteochondral defect of a Wistar rat's knee. 60 days after surgery, real-time PCR, immunohistochemistry (IHC), and hematoxylin and eosin staining were performed. The expression of chondrogenic and osteogenic genes was increased compared to the control group, as confirmed by real-time PCR. Furthermore, IHC revealed a rise in Col II and Collagen X expression. Finally, in vivo and in vitro studies have shown that the electrospun bilayer scaffold is biocompatible, which facilitates osteochondral healing.

Bionic Biphasic Composite Scaffold with Osteochondrogenic Factors for Regeneration of Full-Thickness Osteochondral Defect

Full-thickness osteochondral defects lack the capability to self-repair owing to their complicated hierarchical structure. At present, clinical treatments including microfracture etc. have shown some efficacy; however, the newborn tissue exhibits...

Effect of Type 1 Collagen Bioactive Material Scaffold on the Recovery of Sports-Caused Cartilage Injury

This study was aim to investigate the effect of type 1 collagen (Col I) bioactive scaffold on regeneration and repair of motor cartilage injury. Fifteen New Zealand rabbits were randomly divided into sham operation group (Sham group, only cartilage was exposed, no defect was made), model group Focal cortical dysplasias (FCD) group, cartilage defect model], and treatment group (Col I group, cartilage defect + Col I bioactive scaffold treatment). The cartilage tissue of each group was detected 16 weeks after the operation. Immunohistochemistry and Western Blot were adopted to detect the expression of cartilage related proteins in each group. The results showed that Col I bioactive scaffold could repair the gross morphology of cartilage defect, promote the regeneration and repair of chondrocytes in defect area, and reduce the mast cells in defect area. Western Blot detection of the expression of signal pathway marker proteins showed that expression of Wnt protein, β-catenin protein, and phosphofructokinase-1 (PFK-1) protein in the FCD group were significantly reduced than Sham group (P < 0.05), while the expression of phosphoenolpyruvate carboxykinase 1 (PEPCK1) protein was significantly increased (P < 0.05). Expression of Wnt protein, β-catenin protein, and PFK-1 protein in Col I group increased significantly versus FCD group (P < 0.05), while the expression of PEPCK1 protein significantly decreased (P < 0.05). In conclusion, Col I bioactive scaffolds could regenerate and repair cartilage defects, and the mechanism may be related to Wnt signaling pathway and glycolysis/gluconeogenesis pathway.

Prospective Outcomes of Cryopreserved Osteochondral Allograft for Patellofemoral Cartilage Defects at Minimum 2-Year Follow-up

OBJECTIVE

To analyze the clinical outcomes, knee function, and activity level of patients after treatment of full-thickness cartilage defects involving the patellofemoral compartment of the knee with cryopreserved osteochondral allograft.

DESIGN

Nineteen patients with cartilage defects involving the patellofemoral compartment were treated. The average age was 31 years (range 15-45 years), including 12 females and 7 males. Patients were prospectively followed using validated clinical outcome measures including Veterans RAND 12-item Health Survey (VR-12), International Knee Documentation Committee (IKDC), Knee Injury and Osteoarthritis Outcome Score (KOOS), and the Tegner activity scale. Graft incorporation was evaluated by magnetic resonance imaging (MRI) or second-look arthroscopy.

RESULTS

The cartilage defects included the patella (n = 16) and the femoral trochlea (n = 3). Mean VR-12 scores increased from 31.6 to 46.3 (P < 0.01), mean IKDC increased from 40.0 to 69.7 (P < 0.01), mean KOOS increased from 53.9 to 80.2 (P < 0.01), and mean Tegner scores increased from 3.0 to 4.9 (P < 0.01), at average follow-up of 41.9 months (range 24-62 months). Of the 3 patients who underwent second-look arthroscopy, all demonstrated a well-incorporated graft. Mean MOCART score for the 6 patients with follow-up MRI was 62.5 (range 25-85). The reoperation rate was 21.1% and 2 patients (12.5%) experienced progressive patellofemoral osteoarthritis requiring conversion to patellofemoral arthroplasty.

CONCLUSION

Patients with unipolar cartilage defects involving the patellofemoral compartment of the knee can have positive outcomes at minimum 2-year follow-up after surgical treatment with a cryopreserved osteochondral allograft when concomitant pathology is also addressed, but the reoperation rate is high and bipolar cartilage lesions may increase the failure rate.

SMURF1 and SMURF2 in Progenitor Cells from Articular Cartilage and Meniscus during Late-Stage Osteoarthritis

OBJECTIVE

The aim of this study was to investigate the roles of SMURF1 and SMURF2 in progenitor cells from the human knee in late-stage osteoarthritis (OA).

DESIGN

We applied immunohistochemistry, immunocytochemistry, RNAi, lentiviral transfection, and Western blot analysis. We obtained chondrogenic progenitor cells (CPCs) from the articular cartilage and meniscus progenitor cells (MPCs) from the nonvascularized part of the meniscus.

RESULTS

SMURF1 and SMURF2 appeared in both osteoarthritic tissues. CPCs and MPCs exhibited comparable amounts of these proteins, which influence the balance between RUNX2 and SOX9. The overexpression of SMURF1 reduced the levels of RUNX2, SOX9, and TGFBR1. The overexpression of SMURF2 also reduced the levels of RUNX2 and TGFBR1, while SOX9 levels were not affected. The knockdown of SMURF1 had no effect on RUNX2, SOX9, or TGFBR1. The knockdown of SMURF2 enhanced RUNX2 and SOX9 levels in CPCs. The respective protein levels in MPCs were not affected.

CONCLUSIONS

This study shows that SMURF1 and SMURF2 are regulatory players for the expression of the major regulator transcription factors RUNX2 and SOX9 in CPCs and MPCs. Our novel findings may help elucidate new treatment strategies for cartilage regeneration.

Effects of unloader bracing on clinical outcomes and articular cartilage regeneration following microfracture of isolated chondral defects: a randomized trial

PURPOSE

To determine whether the use of an unloading brace can increase the thickness of cartilage regenerate after microfracture surgery.

METHODS

This is a randomized (1:1) controlled clinical trial. Twenty-four patients who underwent microfracture between 2012 and 2015 were identified and were randomly assigned to an unloading brace group or a no-brace group. All patients were kept non-weight bearing for the first eight weeks after surgery and then patients in the intervention group began using an unloading brace for an average of 63.9 (SD = 41.6) days to protect clot stability by exerting a varus or valgus force on the knee to decrease the force on the knee's lateral or medial compartment, respectively. Quality of the cartilage repair was assessed with knee magnetic resonance imaging to determine repair tissue thickness (primary outcome), repair tissue volume, and T2 relaxation times at 12 and 24 months after surgery. Clinical outcomes were evaluated with KOOS, Tegner, SF12, and Lysholm questionnaires at six, 12 and 24 months after surgery.

RESULTS

Three patients were lost to follow-up, resulting in 21 patients ultimately analyzed. The unloading brace repair tissue was greater than the no-brace group in volume (26.8 ± 23.7 mm³ vs - 8.4 ± 22.7 mm³, p = 0.005) and thickness (0.2 ± 0.2 mm versus - 0.4 ± 0.3 mm, p = 0.001) at 12 months and in cartilage thickness in the unloading brace group at 24 months (0.4 ± 0.4 mm versus - 0.1 ± 0.3 mm, p = 0.029). There was a positive correlation between wearing the brace longer and improved 6-month KOOS symptom scores (r = 0.82, p = 0.013), 6-month KOOS QOL scores (r = 0.80, p = 0.017), 6-month Tegner scores (r = 0.94, p = 0.002), and Tegner score changes from baseline to 6 months (r = 0.80, p = 0.032).

CONCLUSION

This study found a significant mid-term increase in cartilage repair tissue thickness following unloading bracing in patients recovering from microfracture for isolated chondral defects.

LEVEL OF EVIDENCE

II.

A chondrogenesis induction system based on a functionalized hyaluronic acid hydrogel sequentially promoting hMSC proliferation, condensation, differentiation, and matrix deposition

Hydrogel scaffolds are widely used in cartilage tissue engineering as a natural stem cell niche. In particular, hydrogels based on multiple biological signals can guide behaviors of mesenchymal stem cells (MSCs) during neo-chondrogenesis. In the first phase of this study, we showed that functionalized hydrogels with grafted arginine-glycine-aspartate (RGD) peptides and lower degree of crosslinking can promote the proliferation of human mesenchymal stem cells (hMSCs) and upregulate the expression of cell receptor proteins. Moreover, grafted RGD and histidine-alanine-valine (HAV) peptides in hydrogel scaffolds can regulate the adhesion of the intercellular at an early stage. In the second phase, we confirmed that simultaneous use of HAV and RGD peptides led to greater chondrogenic differentiation compared to the blank control and single-peptide groups. Furthermore, the controlled release of kartogenin (KGN) can better facilitate cell chondrogenesis compared to other groups. Interestingly, with longer culture time, cell condensation was clearly observed in the groups with RGD and HAV peptide. In all groups with RGD peptide, significant matrix deposition was observed, accompanied by glycosaminoglycan (GAG) and collagen (Coll) production. Through in vitro and in vivo experiments, this study confirmed that our hydrogel system can sequentially promote the proliferation, adhesion, condensation, chondrogenic differentiation of hMSCs, by mimicking the cell microenvironment during neo-chondrogenesis.

Co-culture and Mechanical Stimulation on Mesenchymal Stem Cells and Chondrocytes for Cartilage Tissue Engineering

Defects in articular cartilage injury and chronic osteoarthritis are very widespread and common, and the ability of injured cartilage to repair itself is limited. Stem cell-based cartilage tissue engineering provides a promising therapeutic option for articular cartilage damage. However, the application of the technique is limited by the number, source, proliferation, and differentiation of stem cells. The co-culture of mesenchymal stem cells and chondrocytes is available for cartilage tissue engineering, and mechanical stimulation is an important factor that should not be ignored. A combination of these two approaches, i.e., co-culture of mesenchymal stem cells and chondrocytes under mechanical stimulation, can provide sufficient quantity and quality of cells for cartilage tissue engineering, and when combined with scaffold materials and cytokines, this approach ultimately achieves the purpose of cartilage repair and reconstruction. In this review, we focus on the effects of co-culture and mechanical stimulation on mesenchymal stem cells and chondrocytes for articular cartilage tissue engineering. An in-depth understanding of the impact of co-culture and mechanical stimulation of mesenchymal stem cells and chondrocytes can facilitate the development of additional strategies for articular cartilage tissue engineering.

Osteochondritis dissecans (OCD) in Horses - Molecular Background of its Pathogenesis and Perspectives for Progenitor Stem Cell Therapy

Osteochondrosis (osteochondrosis dissecans; OCD) is a disease syndrome of growing cartilage related to different clinical entities such as epiphysitis, subchondral cysts and angular carpal deformities, which occurs in growing animals of all species, including horses. Nowadays, these disorders are affecting increasing numbers of young horses worldwide. As a complex multifactorial disease, OCD is initiated when failure in cartilage canals because of existing ischemia, chondrocyte biogenesis impairment as well as biochemical and genetic disruptions occur. Recently, particular attention have been accorded to the definition of possible relations between OCD and some metabolic disorders; in this way, implication of mitochondrial dysfunctions, endoplasmic reticulum disruptions, oxidative stress or endocrinological affections are among the most considered axes for future researches. As one of the most frequent cause of impaired orthopaedic potential, which may result in a sharp decrease in athletic performances of the affected animals, and lead to the occurrence of complications such as joint fragility and laminitis, OCD remains as one of the primary causes of considerable economic losses in all sections of the equine industry. It would therefore be important to provide more information on the exact pathophysiological mechanism(s) underlying early OC(D) lesions, in order to implement innovative strategies involving the use of progenitor stem cells, which are considered nowadays as a promising approach to regenerative medicine, with the potential to treat numerous orthopaedic disorders, including osteo-degenerative diseases, for prevention and reduction of incidence of the disease, not only in horses, but also in human medicine, as the equine model is already widely accepted by the scientific community and approved by the FDA, for the research and application of cellular therapies in the treatment of human conditions.

The Scaffold-Articular Cartilage Interface: A Combined In Vitro and In Silico Analysis Under Controlled Loading Conditions

The optimal method to integrate scaffolds with articular cartilage has not yet been identified, in part because of our lack of understanding about the mechanobiological conditions at the interface. Our objective was to quantify the effect of mechanical loading on integration between a scaffold and articular cartilage. We hypothesized that increased number of loading cycles would have a detrimental effect on interface integrity. The following models were developed: (i) an in vitro scaffold-cartilage explant system in which compressive sinusoidal loading cycles were applied for 14 days at 1 Hz, 5 days per week, for either 900, 1800, 3600, or 7200 cycles per day and (ii) an in silico inhomogeneous, biphasic finite element model (bFEM) of the scaffold-cartilage construct that was used to characterize interface micromotion, stress, and fluid flow under the prescribed loading conditions. In accordance with our hypothesis, mechanical loading significantly decreased scaffold-cartilage interface strength compared to unloaded controls regardless of the number of loading cycles. The decrease in interfacial strength can be attributed to abrupt changes in vertical displacement, fluid pressure, and compressive stresses along the interface, which reach steady-state after only 150 cycles of loading. The interfacial mechanical conditions are further complicated by the mismatch between the homogeneous properties of the scaffold and the depth-dependent properties of the articular cartilage. Finally, we suggest that mechanical conditions at the interface can be more readily modulated by increasing pre-incubation time before the load is applied, as opposed to varying the number of loading cycles.

Chondrogenic Progenitor Cells Exhibit Superiority Over Mesenchymal Stem Cells and Chondrocytes in Platelet-Rich Plasma Scaffold-Based Cartilage Regeneration

BACKGROUND

Platelet-rich plasma (PRP) has been considered a promising tool for cartilage regeneration. However, increasing evidence has demonstrated the controversial effects of PRP on tissue regeneration, partially due to the unsatisfactory cell source. Chondrogenic progenitor cells (CPCs) have gained increasing attention as a potential cell source due to their self-renewal and multipotency, especially toward the chondrogenic lineage, and, thus, may be an appropriate alternative for cartilage engineering.

PURPOSE

To compare the effects of PRP on CPC, mesenchymal stem cell (MSC), and chondrocyte proliferation, chondrogenesis, and cartilage regeneration.

STUDY DESIGN

Controlled laboratory study.

METHODS

Whole blood samples were obtained from 5 human donors to create PRPs (0, 1000 × 10⁹, and 2000 × 10⁹ platelets per liter). The proliferation and chondrogenesis of CPCs, bone marrow-derived MSCs (BMSCs), and chondrocytes were evaluated via growth kinetic and CCK-8 assays. Immunofluorescence, cytochemical staining, and gene expression analyses were performed to assess chondrogenic differentiation and cartilaginous matrix formation. The in vivo effects of CPCs, BMSCs, and chondrocytes on cartilage regeneration after PRP treatment were measured by use of histopathological, biochemical, and biomechanical techniques in a cartilage defect model involving mature male New Zealand White rabbits (critical size, 5 mm).

RESULTS

The CPCs possessed migration abilities and proliferative capacities superior to those of the chondrocytes, while exhibiting a chondrogenic predisposition stronger than that of the BMSCs. The growth kinetic, CCK-8, cytochemical staining, and biochemical analyses revealed that the CPCs simultaneously displayed a higher cell density than the chondrocytes and stronger chondrogenesis than the BMSCs after PRP stimulation. In addition, the in vivo study demonstrated that the PRP+CPC construct yielded better histological (International Cartilage Repair Society [ICRS] score, mean ± SEM, 1197.2 ± 163.2) and biomechanical (tensile modulus, 1.523 ± 0.194) results than the PRP+BMSC (701.1 ± 104.9, P < .05; 0.791 ± 0.151, P < .05) and PRP+chondrocyte (541.6 ± 98.3, P < .01; 0.587 ± 0.142, P < .01) constructs at 12 weeks after implantation.

CONCLUSION

CPCs exhibit superiority over MSCs and chondrocytes in PRP scaffold-based cartilage regeneration, and PRP+CPC treatment may be a favorable strategy for cartilage repair.

CLINICAL RELEVANCE

These findings provide evidence highlighting the preferable role of CPCs as a cell source in PRP-mediated cartilage regeneration and may help researchers address the problem of unsatisfactory cell sources in cartilage engineering.

Extracellular matrix derived by human umbilical cord-deposited mesenchymal stem cells accelerates chondrocyte proliferation and differentiation potential in vitro

The extracellular matrix (ECM) is a dynamic and intricate three-dimensional (3D) microenvironment with excellent biophysical, biomechanical, and biochemical properties that may directly or indirectly regulate cell behavior, including proliferation, adhesion, migration, and differentiation. Compared with tissue-derived ECM, cell-derived ECM potentially has more advantages, including less potential for pathogen transfer, fewer inflammatory or anti-host immune responses, and a closer resemblance to the native ECM microenvironment. Different types of cell-derived ECM, such as adipose stem cells, synovium-derived stem cells and bone marrow stromal cells, their effects on articular chondrocytes which have been researched. In this study, we aimed to develop a 3D cell culture substrate using decellularized ECM derived from human umbilical cord-derived mesenchymal stem cells (hUCMSCs), and evaluated the effects on articular chondrocytes. We evaluated the morphology and components of hUCMSC-derived ECM using physical and chemical methods. Morphological, histological, immunohistochemical, biochemical, and real-time PCR analyses demonstrated that proliferation and differentiation capacity of chondrocytes using the 3D hUCMSC-derived ECM culture substrate was superior to that using non-coated two-dimensional plastic culture plates. In conclusion, 3D decellularized ECM derived from hUCMSCs offers a tissue-specific microenvironment for in vitro culture of chondrocytes, which not only markedly promoted chondrocyte proliferation but also preserved the differentiation capacity of chondrocytes. Therefore, our findings suggest that a 3D cell-derived ECM microenvironment represents a promising prospect for autologous chondrocyte-based cartilage tissue engineering and regeneration. The hUCMSC-derived ECM as a biomaterial is used for the preparation of scaffold or hybrid scaffold products which need to further study in the future.

Nanofibrous scaffolds for biomedical applications

Tissue engineering is an emergent and very interesting research field, providing potential solutions for a myriad of challenges in healthcare. Fibrous scaffolds specifically have shown promise as an effective tissue engineering method, as their high length-to-width ratio mimics that of extracellular matrix components, which in turn guides tissue formation, promotes cellular adhesion and improves mechanical properties. In this review paper, we discuss in detail both the importance of fibrous scaffolds for the promotion of tissue growth and the different methods to produce fibrous biomaterials to possess favorable and unique characteristics. Here, we focus on the pressing need to develop biomimetic structures that promote an ideal environment to encourage tissue formation. In addition, we discuss different biomedical applications in which fibrous scaffolds can be useful, identifying their importance, relevant aspects, and remaining significant challenges. In conclusion, we provide comments on the future direction of fibrous scaffolds and the best way to produce them, proposed in light of recent technological advances and the newest and most promising fabrication techniques.

hWJECM-Derived Oriented Scaffolds with Autologous Chondrocytes for Rabbit Cartilage Defect Repairing

Previously, we synthesized an articular cartilage extracellular matrix (ECM)-derived oriented scaffold for cartilage tissue engineering, which was biomimetic in terms of structure and biochemical composition. However, the limit resource of the cartilage-derived ECM is a hindrance for its application. In this study, we developed a new material for cartilage tissue engineering-human umbilical cord Wharton's jelly-derived ECM (hWJECM). The hWJECM has an abundant resource and similar biochemistry with cartilage ECM, and the use of it is not associated with ethical controversy. We adopted the method previously used in cartilage ECM-derived oriented scaffold preparation to generate the oriented hWJECM-derived scaffold, and the scaffold properties were tested in vitro and in vivo. The three-dimensional scaffold has a porous and well-oriented structure, with a mean pore diameter of ∼104 μm. Scanning electron microscopy and cell viability staining results demonstrated that the oriented scaffold has good biocompatibility and cell alignment. In addition, we used functional autologous chondrocytes to seed the hWJECM-derived oriented scaffold and tested the efficacy of the cell-scaffold constructs to repair the full-thickness articular cartilage defect in a rabbit model. Defects of 4 mm diameter were generated in the patellar grooves of the femurs of both knees and were implanted with chondrocyte-scaffold constructs (group A) or scaffolds alone (group B); rabbits with untreated defects were used as a control (group C). Six months after surgery, all defects in group A were filled completely with repaired tissue, and most of which were hyaline cartilage. In contrast, the defects in group B were filled partially with repaired tissue, and approximately half of these repaired tissues were hyaline cartilage. The defects in group C were only filled with fibrotic tissue. Histological grading score of group A was lower than those of groups B and C. Quantification of glycosaminoglycan indicated that newly formed cartilage in group A rabbits was comparable with normal cartilage. In conclusion, hWJECM-derived oriented scaffolds loaded with autologous chondrocytes induced cartilage repair in rabbit knees, which was comparable with native cartilage in terms of macroscopic view, microstructure, and biochemical composition.

Silk fibroin/cartilage extracellular matrix scaffolds with sequential delivery of TGF-β3 for chondrogenic differentiation of adipose-derived stem cells

A 3-D scaffold that simulates the microenvironment in vivo for regenerating cartilage is ideal. In this study, we combined silk fibroin and decellularized cartilage extracellular matrix by temperature gradient-guided thermal-induced phase separation to produce composite scaffolds (S/D). Resulting scaffolds had remarkable mechanical properties and biomimeticstructure, for a suitable substrate for attachment and proliferation of adipose-derived stem cells (ADSCs). Moreover, transforming growth factor β3 (TGF-β3) loaded on scaffolds showed a controlled release profile and enhanced the chondrogenic differentiation of ADSCs during the 28-day culture. The S/D scaffold itself can provide a sustained release system without the introduction of other controlled release media, which has potential for commercial and clinical applications. The results of toluidine blue, Safranin O, and immunohistochemical staining and analysis of collagen II expression showed maintenance of a chondrogenic phenotype in all scaffolds after 28-day culture. The most obvious phenomenon was with the addition of TGF-β3. S/D composite scaffolds with sequential delivery of TGF-β3 may mimic the regenerative microenvironment to enhance the chondrogenic differentiation of ADSCs in vitro.

Long-term effects of hydrogen sulfide on the anabolic-catabolic balance of articular cartilage in vitro

Healthy cartilage maintenance relies on an equilibrium among the anabolic and catabolic processes in chondrocytes. With the onset of osteoarthritis (OA), increased interleukin (IL)-1β levels induce an inhibition of the synthesis of extracellular matrix (ECM) proteins, as well as an increase in proteases. This eventually leads to a predominance of the catabolic phenotype and the progressive loss of articular cartilage. Hydrogen sulfide (H₂S) is a small gaseous molecule recognized as the third endogenous gasotransmitter. When administered exogenously, it has shown anti-inflammatory and anti-catabolic properties in several in vitro and in vivo models. Here, OA cartilage disks were co-cultured in vitro with IL-1β (5 ng/ml) and NaSH or GYY4137 (200 or 1000 μM) for 21 days. The ability of these two H₂S-producing compounds to avoid long term extracellular matrix (ECM) destruction was evaluated. We used a glycosaminoglycan (GAG) quantification kit histology and immunohistochemistry (IHC) to evaluate matrix proteins degradation and matrix metalloproteinases (MMP) abundance. Through the GAGs quantification assay, safranin O (S-O) and toluidine blue (TB) stains, and keratan/chondroitin sulfate (KS/ChS) IHCs it was shown that co-stimulation with H₂S-forming reagents effectively avoided GAGs destruction. Both Masson's trichrome (MT) stain and collagen (col) type II IHC, as well as aggrecan (agg) IHC demonstrated that not only were these proteins protected but even promoted, their abundance being higher than in the basal condition. Further, stains also demonstrated that positivity in the inter-territorial and intra-cellular for the different matrix components were rescued, suggesting that NaSH and GYY4137 might also have pro-anabolic effects. In addition, a clear protective effect against the increased MMPs levels was seen, since increased MMP3 and 13 levels were subsequently reduced with the co-stimulation with sulfide compounds. In general, GYY4137 was more effective than NaSH, and increasing the dose improved the results. This study demonstrates that H₂S anti-catabolic effects, which had been previously proven in short-term (24-48 h) in vitro cellular models, are maintained over time directly in OA cartilage tissue.

Enhanced articular cartilage by human mesenchymal stem cells in enzymatically mediated transiently RGDS-functionalized collagen-mimetic hydrogels

Recapitulation of the articular cartilage microenvironment for regenerative medicine applications faces significant challenges due to the complex and dynamic biochemical and biomechanical nature of native tissue. Towards the goal of biomaterial designs that enable the temporal presentation of bioactive sequences, recombinant bacterial collagens such as Streptococcal collagen-like 2 (Scl2) proteins can be employed to incorporate multiple specific bioactive and biodegradable peptide motifs into a single construct. Here, we first modified the backbone of Scl2 with glycosaminoglycan-binding peptides and cross-linked the modified Scl2 into hydrogels via matrix metalloproteinase 7 (MMP7)-cleavable or non-cleavable scrambled peptides. The cross-linkers were further functionalized with a tethered RGDS peptide creating a system whereby the release from an MMP7-cleavable hydrogel could be compared to a system where release is not possible. The release of the RGDS peptide from the degradable hydrogels led to significantly enhanced expression of collagen type II (3.9-fold increase), aggrecan (7.6-fold increase), and SOX9 (5.2-fold increase) by human mesenchymal stem cells (hMSCs) undergoing chondrogenesis, as well as greater extracellular matrix accumulation compared to non-degradable hydrogels (collagen type II; 3.2-fold increase, aggrecan; 4-fold increase, SOX9; 2.8-fold increase). Hydrogels containing a low concentration of the RGDS peptide displayed significantly decreased collagen type I and X gene expression profiles, suggesting a major advantage over either hydrogels functionalized with a higher RGDS peptide concentration, or non-degradable hydrogels, in promoting an articular cartilage phenotype. These highly versatile Scl2 hydrogels can be further manipulated to improve specific elements of the chondrogenic response by hMSCs, through the introduction of additional bioactive and/or biodegradable motifs. As such, these hydrogels have the possibility to be used for other applications in tissue engineering.

Statement of Significance

Recapitulating aspects of the native tissue biochemical microenvironment faces significant challenges in regenerative medicine and tissue engineering due to the complex and dynamic nature of the tissue. The ability to take advantage of, mimic, and modulate cell-mediated processes within novel naturally-derived hydrogels is of great interest in the field of biomaterials to generate constructs that more closely resemble the biochemical microenvironment and functions of native biological tissues such as articular cartilage. Towards this goal, the temporal presentation of bioactive sequences such as RGDS on the chondrogenic differentiation of human mesenchymal stem cells is considered important as it has been shown to influence the chondrogenic phenotype. Here, a novel and versatile platform to recreate a high degree of biological complexity is proposed, which could also be applicable to other tissue engineering and regenerative medicine applications.

Knee donor-site morbidity after mosaicplasty - a systematic review

BACKGROUND

Mosaicplasty has been associated with good short- to long-term results. Nevertheless, the osteochondral harvesting is restricted to the donor-site area available and it may lead to significant donor-site morbidity.

PURPOSE

Provide an overview of donor-site morbidity associated with harvesting of osteochondral plugs from the knee joint in mosaicplasty procedure.

METHODS

Comprehensive search using Pubmed, Cochrane Library, SPORTDiscus and CINAHL databases was carried out through 10th October of 2016. As inclusion criteria, all English-language studies that assessed the knee donor-site morbidity after mosaicplasty were accepted. The outcomes were the description and rate of knee donor-site morbidity, sample's and cartilage defect's characterization and mosaicplasty-related features. Correlation between mosaicplasty features and rate of morbidity was performed. The methodological and reporting quality were assessed according to Coleman's methodology score.

RESULTS

Twenty-one studies were included, comprising a total of 1726 patients, with 1473 and 268 knee and ankle cartilage defects were included. The defect size ranged from 0.85 cm2 to 4.9 cm2 and most commonly 3 or less plugs (averaging 2.9 to 9.4 mm) were used. Donor-site for osteochondral harvesting included margins of the femoral trochlea (condyles), intercondylar notch, patellofemoral joint and upper tibio-fibular joint. Mean donor-site morbidity was 5.9 % and 19.6 % for knee and ankle mosaicplasty procedures, respectively. Concerning knee-to-knee mosaicplasty procedures, the most common donor-site morbidity complaints were patellofemoral disturbances (22 %) and crepitation (31 %), and in knee-to-ankle procedures there was a clear tendency for pain or instability during daily living or sports activities (44 %), followed by patellofemoral disturbances, knee stiffness and persistent pain (13 % each). There was no significant correlation between rate of donor-site morbidity and size of the defect, number and size of the plugs (p > 0.05).

CONCLUSIONS

Osteochondral harvesting in mosaicplasty often results in considerable donor-site morbidity. The donor-site morbidity for knee-to-ankle (16.9 %) was greater than knee-to-knee (5.9 %) mosaicplasty procedures, without any significant correlation between rate of donor-site morbidity and size of the defect, number and size of the plugs. Lack or imcomplete of donor-site morbidity reporting within the mosaicplasty studies is a concern that should be addressed in future studies.

LEVEL OF EVIDENCE

Level IV, systematic review of Level I-IV studies.

Avascular necrosis complicating chondral resurfacing techniques

Autologous chondrocyte implantation (ACI) and mosaicplasty have become established operations used to treat full-thickness chondral lesions in the knee and elsewhere. Although complications of both have been documented, there are no previous reports of avascular necrosis (AVN) complicating these procedures. Awareness of AVN as a complication of ACI might have prompted an earlier diagnosis, with possible non-surgical treatment or more minor surgery being possible. At the very least, an appropriate form of management could have been initiated earlier, so shortening the period of disability and suffering for the patient.

Morphological, genetic and phenotypic comparison between human articular chondrocytes and cultured chondrocytes

Articular cartilage is an avascular and aneural tissue with limited capacity for regeneration. On large articular lesions, it is recommended to use regenerative medicine strategies, like autologous chondrocyte implantation. There is a concern about morphological changes that chondrocytes suffer once they have been isolated and cultured. Due to the fact that there is little evidence that compares articular cartilage chondrocytes with cultured chondrocytes, in this research we proposed to obtain chondrocytes from human articular cartilage, compare them with themselves once they have been cultured and characterize them through genetic, phenotypic and morphological analysis. Knee articular cartilage samples of 10 mm were obtained, and each sample was divided into two fragments; a portion was used to determine gene expression, and from the other portion, chondrocytes were obtained by enzymatic disaggregation, in order to be cultured and expanded in vitro. Subsequently, morphological, genetic and phenotypic characteristics were compared between in situ (articular cartilage) and cultured chondrocytes. Obtained cultured chondrocytes were rounded in shape, possessing a large nucleus with condensed chromatin and a clear cytoplasm; histological appearance was quite similar to typical chondrocyte. The expression levels of COL2A1 and COL10A1 genes were higher in cultured chondrocytes than in situ chondrocytes; moreover, the expression of COL1A1 was almost undetectable on cultured chondrocytes; likewise, COL2 and SOX9 proteins were detected by immunofluorescence. We concluded that chondrocytes derived from adult human cartilage cultured for 21 days do not tend to dedifferentiate, maintaining their capacity to produce matrix and also retaining their synthesis capacity and morphology.

Microfracture in the Hip: Results of a Matched-Cohort Controlled Study With 2-Year Follow-up

BACKGROUND

Microfracture in hip preservation surgery has demonstrated favorable outcomes, but studies with a higher level of evidence assessing microfracture are warranted.

PURPOSE

To assess 2-year outcomes of patients who underwent hip arthroscopy with full-thickness chondral damage treated with microfracture and compare these outcomes with those of a control group from a similar cohort of patients who did not have full-thickness chondral damage and who were not treated with microfracture.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

Between February 2008 and May 2012, prospectively gathered data for patients undergoing microfracture during hip arthroscopy with a 2-year follow-up were reviewed. All patients were assessed pre- and postoperatively at 3 months, 1 year, and 2 years with 4 patient-reported outcome (PRO) instruments. A matched cohort of patients who did not have full-thickness chondral damage and hence did not receive microfracture was selected on a 1:2 ratio. Matching criteria were sex, age within 6 years, workers' compensation status, concomitant labral treatment, and radiographic parameters. Statistical analyses were performed to compare the change in PROs in both groups.

RESULTS

A total of 79 hips were included in the microfracture group and 158 in the control group. There was no significant difference in PRO scores preoperatively between the groups. Both groups demonstrated significant improvement in all postoperative PRO scores at all time points. There was no statistically significant difference in postoperative PRO scores between the microfracture and control groups, except for the visual analog scale (VAS) score at 2 years, which was higher (P = .02) in the microfracture group (mean ± SD, 3.63 ± 2.50) than in the control group (2.82 ± 2.76). Patient satisfaction was 7.2 for the microfracture group and 8.04 for the control group, which was statistically different (P < .05). The mean change in all PRO scores was similar between groups at 3 months and 1 year postoperatively but significantly lower in the microfracture group at 2 years postoperatively. The greatest improvement in both groups was noted at 3 months postoperatively.

CONCLUSION

This study showed that patients undergoing microfracture during hip arthroscopy had equivalent PRO scores compared with the control group at 2 years postoperatively. The change in PRO scores from preoperatively to 2 years postoperatively was significantly lower in the microfracture group compared with the control group. The VAS scores and satisfaction were inferior by 0.81 and 0.84 units, respectively, in the microfracture group compared with the control group, likely due to lack of full-thickness chondral defects in the latter. However, both groups showed significant improvement in all PRO scores after surgery, with no significant difference in final PRO scores.

Potential use of alginate beads as a chondrocyte delivery vehicle and stepwise dissolving porogen in a hydrogel scaffold for cartilage tissue engineering

A chondroitin sulfate (CS)–alginate bead composite gel (CS–ABG) is developed, and which exhibits superiority to aid cartilage regeneration.

Application of an acoustofluidic perfusion bioreactor for cartilage tissue engineering

Cartilage grafts generated using conventional static tissue engineering strategies are characterised by low cell viability, suboptimal hyaline cartilage formation and, critically, inferior mechanical competency, which limit their application for resurfacing articular cartilage defects. To address the limitations of conventional static cartilage bioengineering strategies and generate robust, scaffold-free neocartilage grafts of human articular chondrocytes, the present study utilised custom-built microfluidic perfusion bioreactors with integrated ultrasound standing wave traps. The system employed sweeping acoustic drive frequencies over the range of 890 to 910 kHz and continuous perfusion of the chondrogenic culture medium at a low-shear flow rate to promote the generation of three-dimensional agglomerates of human articular chondrocytes, and enhance cartilage formation by cells of the agglomerates via improved mechanical stimulation and mass transfer rates. Histological examination and assessment of micromechanical properties using indentation-type atomic force microscopy confirmed that the neocartilage grafts were analogous to native hyaline cartilage. Furthermore, in the ex vivo organ culture partial thickness cartilage defect model, implantation of the neocartilage grafts into defects for 16 weeks resulted in the formation of hyaline cartilage-like repair tissue that adhered to the host cartilage and contributed to significant improvements to the tissue architecture within the defects, compared to the empty defects. The study has demonstrated the first successful application of the acoustofluidic perfusion bioreactors to bioengineer scaffold-free neocartilage grafts of human articular chondrocytes that have the potential for subsequent use in second generation autologous chondrocyte implantation procedures for the repair of partial thickness cartilage defects.

Acquiring chondrocyte phenotype from human mesenchymal stem cells under inflammatory conditions

An inflammatory milieu breaks down the cartilage matrix and induces chondrocyte apoptosis, resulting in cartilage destruction in patients with cartilage degenerative diseases, such as rheumatoid arthritis or osteoarthritis. Because of the limited regenerative ability of chondrocytes, defects in cartilage are irreversible and difficult to repair. Mesenchymal stem cells (MSCs) are expected to be a new tool for cartilage repair because they are present in the cartilage and are able to differentiate into multiple lineages of cells, including chondrocytes. Although clinical trials using MSCs for patients with cartilage defects have already begun, its efficacy and repair mechanisms remain unknown. A PubMed search conducted in October 2014 using the following medical subject headings (MeSH) terms: mesenchymal stromal cells, chondrogenesis, and cytokines resulted in 204 articles. The titles and abstracts were screened and nine articles relevant to “inflammatory” cytokines and “human” MSCs were identified. Herein, we review the cell biology and mechanisms of chondrocyte phenotype acquisition from human MSCs in an inflammatory milieu and discuss the clinical potential of MSCs for cartilage repair.

Scaffold-based regeneration of skeletal tissues to meet clinical challenges

The management and reconstruction of damaged or diseased skeletal tissues have remained a significant global healthcare challenge. The limited efficacy of conventional treatment strategies for large bone, cartilage and osteochondral defects has inspired the development of scaffold-based tissue engineering solutions, with the aim of achieving complete biological and functional restoration of the affected tissue in the presence of a supporting matrix. Nevertheless, significant regulatory hurdles have rendered the clinical translation of novel scaffold designs to be an inefficient process, mainly due to the difficulties of arriving at a simple, reproducible and effective solution that does not rely on the incorporation of cells and/or bioactive molecules. In the context of the current clinical situation and recent research advances, this review will discuss scaffold-based strategies for the regeneration of skeletal tissues, with focus on the contribution of bioactive ceramic scaffolds and silk fibroin, and combinations thereof, towards the development of clinically viable solutions.

Effects of immobilization and remobilization on the ankle joint in Wistar rats

A sprained ankle is a common musculoskeletal sports injury and it is often treated by immobilization of the joint. Despite the beneficial effects of this therapeutic measure, the high prevalence of residual symptoms affects the quality of life, and remobilization of the joint can reverse this situation. The aim of this study was to analyze the effects of immobilization and remobilization on the ankle joint of Wistar rats. Eighteen male rats had their right hindlimb immobilized for 15 days, and were divided into the following groups: G1, immobilized; G2, remobilized freely for 14 days; and G3, remobilized by swimming and jumping in water for 14 days, performed on alternate days, with progression of time and a series of exercises. The contralateral limb was the control. After the experimental period, the ankle joints were processed for microscopic analysis. Histomorphometry did not show any significant differences between the control and immobilized/remobilized groups and members, in terms of number of chondrocytes and thickness of the articular cartilage of the tibia and talus. Morphological analysis of animals from G1 showed significant degenerative lesions in the talus, such as exposure of the subchondral bone, flocculation, and cracks between the anterior and mid-regions of the articular cartilage and the synovial membrane. Remobilization by therapeutic exercise in water led to recovery in the articular cartilage and synovial membrane of the ankle joint when compared with free remobilization, and it was shown to be an effective therapeutic measure in the recovery of the ankle joint.

Citrate cross-linked gels with strain reversibility and viscoelastic behavior accelerate healing of osteochondral defects in a rabbit model

Most living tissues are viscoelastic in nature. Self-repair due to the dissipation of energy by reversible bonds prevents the rupture of the molecular backbone in these tissues. Recent studies, therefore, have aimed to synthesize biomaterials that approximate the mechanical performance of biological materials with self-recovery properties. We report an environmentally friendly method for the development of ionotropically cross-linked viscoelastic chitosan gels with a modulus comparable to that of living tissues. The strain recovery property was found to be highest for the gels with the lowest cross-linking density. The force-displacement curve showed significant hysteresis due to the presence of reversible bonds in the cross-linked gels. Nanoindentation studies demonstrated the creep phenomenon for the cross-linked chitosan gels. Creep, hysteresis, and plasticity index confirmed the viscoelastic behavior of the cross-linked gels. The viscoelastic gels were implanted at osteochondral defect sites to assess the tissue regeneration ability. In vivo results demonstrated early cartilage formation and woven bone deposition for defects filled with the gels compared to nontreated defects.

Arthroscopic debridement of unicompartmental arthritis: fact or fiction?

Patients with recurrent or mechanical symptoms of unicompartmental knee arthritis that have failed conservative management are candidates for surgical intervention. Surgical options include debridement, lavage, chondroplasty, bone marrow-stimulating techniques, chondrocyte transfer, and chondrocyte implantation. These techniques have been well studied but it is still unclear which technique is superior. Various factors need to be accounted for when choosing the proper technique; among the factors discussed are the patient's age and the size of the articular cartilage defect.

Increasing the Dose of Autologous Chondrocytes Improves Articular Cartilage Repair: Histological and Molecular Study in the Sheep Animal Model

BACKGROUND

We hypothesized that implanting cells in a chondral defect at a density more similar to that of the intact cartilage could induce them to synthesize matrix with the features more similar to that of the uninjured one.

METHODS

We compared the implantation of different doses of chondrocytes: 1 million (n = 5), 5 million (n = 5), or 5 million mesenchymal cells (n = 5) in the femoral condyle of 15 sheep. Tissue generated by microfracture at the trochlea, and normal cartilage from a nearby region, processed as the tissues resulting from the implantation, were used as references. Histological and molecular (expression of type I and II collagens and aggrecan) studies were performed.

RESULTS

The features of the cartilage generated by implantation of mesenchymal cells and elicited by microfractures were similar and typical of a poor repair of the articular cartilage (presence of fibrocartilage, high expression of type I collagen and a low mRNA levels of type II collagen and aggrecan). Nevertheless, in the samples obtained from tissues generated by implantation of chondrocytes, hyaline-like cartilage, cell organization, low expression rates of type I collagen and high levels of mRNA corresponding to type II collagen and aggrecan were observed. These histological features, show less variability and are more similar to those of the normal cartilage used as control in the case of 5 million cells implantation than when 1 million cells were used.

CONCLUSIONS

The implantation of autologous chondrocytes in type I/III collagen membranes at high density could be a promising tool to repair articular cartilage.

Inhibition of TAK1 and/or JAK can rescue impaired chondrogenic differentiation of human mesenchymal stem cells in osteoarthritis-like conditions

OBJECTIVE

To rescue chondrogenic differentiation of human mesenchymal stem cells (hMSCs) in osteoarthritic conditions by inhibition of protein kinases.

METHODS

hMSCs were cultured in pellets. During early chondrogenic differentiation, these were exposed to osteoarthritic synovium-conditioned medium (OAS-CM), combined with the Janus kinase (JAK)-inhibitor tofacitinib and/or the transforming growth factor β-activated kinase 1 (TAK1)-inhibitor oxozeaenol. To evaluate effects on chondrogenesis, the glycosaminoglycan (GAG) content of the pellets was measured at the time that chondrogenesis was manifest in control cultures. Moreover, mRNA levels of matrix molecules and enzymes were measured during this process, using real-time polymerase chain reaction (RT-PCR). Initial experiments were performed with hMSCs from a fetal donor, and results of these studies were confirmed with hMSCs from adult donors.

RESULTS

Exposure to OAS-CM resulted in pellets with a much lower GAG content, reflecting inhibited chondrogenic differentiation. This was accompanied by decreased mRNA levels of aggrecan, type II collagen, and Sox9, and increased levels of matrix metalloproteinase (MMP)1, MMP3, MMP13, ADAMTS4, and ADAMTS5. Both tofacitinib (JAK-inhibitor) and oxozeaenol (TAK1 inhibitor) significantly increased the GAG content of the pellets in osteoarthritis (OA)-like conditions. The combination of both protein kinase inhibitors showed an additive effect on GAG content. In agreement with this, in the presence of OAS-CM, both tofacitinib and oxozeaenol increased mRNA expression of sox9. The expression of aggrecan and type II collagen was also up-regulated, but this only reached significance for aggrecan after TAK1 inhibition. Both inhibitors decreased the mRNA levels of MMP1, 3, and 13 in the presence of OAS-CM. Moreover, oxozeaenol also significantly down-regulated the mRNA levels of aggrecanases ADAMTS4 and ADAMTS5. When combined, the inhibitors caused additive reduction of OA-induced MMP1 mRNA expression. Counteraction of OAS-CM-induced inhibition of chondrogenesis by these protein kinase inhibitors was confirmed with hMSCs of two different adult donors. Both tofacitinib and oxozeaenol significantly improved GAG content in cell pellets from these adult donors.

CONCLUSIONS

Tofacitinib and oxozeaenol partially prevent the inhibition of chondrogenesis by factors secreted by OA synovium. Their effects are additive. This indicates that these protein kinase inhibitors can potentially be used to improve cartilage formation under the conditions occurring in osteoathritic, or otherwise inflamed, joints.

Effect of treadmill exercise timing on repair of full-thickness defects of articular cartilage by bone-derived mesenchymal stem cells: an experimental investigation in rats

OBJECTIVE

Current medical practice for the treatment of articular cartilage lesions remains a clinical challenge due to the limited self-repair ability of articular cartilage. Both experimental and clinical researches show that moderate exercise can improve articular cartilage repair process. However, optimal timing of moderate exercise is unclear. We aimed to evaluate the effect of timing of moderate treadmill exercise on repair of full-thickness defects of articular cartilage.

DESIGN

Full-thickness cartilage defects were drilled in the patellar groove of bilateral femoral condyles in a total of 40 male SD rats before they were randomly assigned into four even groups. In sedentary control (SED) group, no exercise was given; in 2-week (2W), 4-week (4W) and 8-week groups, moderate treadmill exercise was initiated respectively two, four and eight weeks after operation. Half of the animals were sacrificed at week 10 after operation and half at week 14 after operation. Femoral condyles were harvested for gross observation and histochemical measurement by O'Driscoll scoring system. Collagen type II was detected by immunohistochemistry and mRNA expressions of aggrecan and collagen type II cartilage by RT-PCR.

RESULTS

Both 10 and 14 weeks post-operation, the best results were observed in 4W group and the worst results appeared in 2W group. The histochemistry scores and the expressions of collagen type II and aggrecan were significantly higher in 4W group than that in other three groups (P<0.05).

CONCLUSIONS

Moderate exercise at a selected timing (approximately 4 weeks) after injury can significantly promote the healing of cartilage defects but may hamper the repair process if performed too early while delayed intervention by moderate exercise may reduce its benefits in repair of the defects.

Dual effect of platelet lysate on human articular cartilage: a maintenance of chondrogenic potential and a transient proinflammatory activity followed by an inflammation resolution

Platelet-rich plasma (PRP), a cocktail of platelet growth factors and bioactive proteins, has been proposed as a therapeutic agent to restore damaged articular cartilage. We report the biological effect of the platelet lysate (PL), a PRP derivative, on primary human articular chondrocytes cultured under both physiological and inflammatory conditions. When added to the culture medium, PL induced a strong mitogenic response in the chondrocytes. The in vitro expanded cell population maintained a chondrogenic redifferentiation potential as revealed by micromass culture in vitro and ectopic cartilage formation in vivo. Further, in chondrocytes cultured in the presence of the proinflammatory cytokine interleukin-1α (IL-1α), the PL induced a drastic enhancement of the synthesis of the cytokines IL-6 and IL-8 and of neutrophil-gelatinase associated lipocalin, a lipocalin expressed during chondrocyte differentiation and inflammation. These events were mediated by the p38 MAP kinase and NF-κB pathways. We observed that inflammatory stimuli activated phospo-MAP kinase-activated protein kinase 2, a direct target of p38. The proinflammatory effect of the PL was a transient phenomenon; after an initial upregulation, we observed significant reduction of the NF-κB activity together with the repression of the inflammatory enzyme cyclooxygenase-2. Moreover, the medium of chondrocytes cultured in the simultaneous presence of PL and IL-1α, showed a significant enhancement of the chemoattractant activity versus untreated chondrocytes. Our findings support the concept that the platelet products have a direct beneficial effect on articular chondrocytes and could drive in sequence a transient activation and the resolution of the inflammatory process, thus providing a rational for their use as therapeutic agents in cartilage inflammation and damage.

IL-17 inhibits chondrogenic differentiation of human mesenchymal stem cells

OBJECTIVE

Mesenchymal stem cells (MSCs) can differentiate into cells of mesenchymal lineages, such as osteoblasts and chondrocytes. Here we investigated the effects of IL-17, a key cytokine in chronic inflammation, on chondrogenic differentiation of human MSCs.

METHODS

Human bone marrow MSCs were pellet cultured in chondrogenic induction medium containing TGF-β3. Chondrogenic differentiation was detected by cartilage matrix accumulation and chondrogenic marker gene expression.

RESULTS

Over-expression of cartilage matrix and chondrogenic marker genes was noted in chondrogenic cultures, but was inhibited by IL-17 in a dose-dependent manner. Expression and phosphorylation of SOX9, the master transcription factor for chondrogenesis, were induced within 2 days and phosphorylated SOX9 was stably maintained until day 21. IL-17 did not alter total SOX9 expression, but significantly suppressed SOX9 phosphorylation in a dose-dependent manner. At day 7, IL-17 also suppressed the activity of cAMP-dependent protein kinase A (PKA), which is known to phosphorylate SOX9. H89, a selective PKA inhibitor, also suppressed SOX9 phosphorylation, expression of chondrogenic markers and cartilage matrix, and also decreased chondrogenesis.

CONCLUSIONS

IL-17 inhibited chondrogenesis of human MSCs through the suppression of PKA activity and SOX9 phosphorylation. These results suggest that chondrogenic differentiation of MSCs can be inhibited by a mechanism triggered by IL-17 under chronic inflammation.

A comparative study of the chondrogenic potential between synthetic and natural scaffolds in an in vivo bioreactor

The clinical demand for cartilage tissue engineering is potentially large for reconstruction defects resulting from congenital deformities or degenerative disease due to limited donor sites for autologous tissue and donor site morbidities. Cartilage tissue engineering has been successfully applied to the medical field: a scaffold pre-cultured with chondrocytes was used prior to implantation in an animal model. We have developed a surgical approach in which tissues are engineered by implantation with a vascular pedicle as an in vivo bioreactor in bone and adipose tissue engineering. Collagen type II, chitosan, poly(lactic-co-glycolic acid) (PLGA) and polycaprolactone (PCL) were four commonly applied scaffolds in cartilage tissue engineering. To expand the application of the same animal model in cartilage tissue engineering, these four scaffolds were selected and compared for their ability to generate cartilage with chondrocytes in the same model with an in vivo bioreactor. Gene expression and immunohistochemistry staining methods were used to evaluate the chondrogenesis and osteogenesis of specimens. The result showed that the PLGA and PCL scaffolds exhibited better chondrogenesis than chitosan and type II collagen in the in vivo bioreactor. Among these four scaffolds, the PCL scaffold presented the most significant result of chondrogenesis embedded around the vascular pedicle in the long-term culture incubation phase.