Autologous Chondrocyte Implantation: Past, Present, and Future

An injectable and degradable heterogeneous microgel assembly capable of forming a "micro-nest group" for cell condensation and cartilage regeneration

Cell condensation, linking the migration and chondrogenic differentiation of MSCs, plays a crucial role in cartilage development. Current cartilage repair strategies are inadequately concerned with this process, leading to a suboptimal quality of regenerated cartilage. Inspired by the "nest flocks" structure of Social Weavers, a degradable heterogeneous microgel assembly (F/S-MA) is developed, which can release SDF-1, to form a "micro-nest group" structure and bond with HAV peptides to promote cell recruitment, condensation and chondrogenic differentiation. First, slow-degrading microgels (S-microgels) grafted with HAV peptides and fast-degrading microgels (F-microgels) loaded with SDF-1 are fabricated by an amidation reaction and Schiff base reaction, respectively. They employ sulfhydryl-modified gelatin as assembling agents to form F/S-MA through a thiol-ene reaction, exhibiting injectability, tissue adhesion, and microporosity. F-microgels undergo rapid degradation, leading to the release of SDF-1 and the formation of a "micro-nest group" in F/S-MA. Consequently, F/S-MA exhibits cell recruitment ability, meanwhile facilitating BMSC condensation through the synergistic effects of the "micro-nest group" and HAV peptides. In vitro experiments prove that F/S-MA enhances the expression of cell-condensation-related markers, ultimately upregulating the secretion of cartilage matrix. Animal experiments show that F/S-MA optimizes the quality of regenerated cartilage by improving cell recruitment and condensation. F/S-MA enhances cell condensation through structural and component design, which will provide new insights for cartilage regeneration.

Equine Musculoskeletal Pathologies: Clinical Approaches and Therapeutical Perspectives-A Review

Musculoskeletal injuries such as equine osteoarthritis, osteoarticular defects, tendonitis/desmitis, and muscular disorders are prevalent among sport horses, with a fair prognosis for returning to exercise or previous performance levels. The field of equine medicine has witnessed rapid and fruitful development, resulting in a diverse range of therapeutic options for musculoskeletal problems. Staying abreast of these advancements can be challenging, prompting the need for a comprehensive review of commonly used and recent treatments. The aim is to compile current therapeutic options for managing these injuries, spanning from simple to complex physiotherapy techniques, conservative treatments including steroidal and non-steroidal anti-inflammatory drugs, hyaluronic acid, polysulfated glycosaminoglycans, pentosan polysulfate, and polyacrylamides, to promising regenerative therapies such as hemoderivatives and stem cell-based therapies. Each therapeutic modality is scrutinized for its benefits, limitations, and potential synergistic actions to facilitate their most effective application for the intended healing/regeneration of the injured tissue/organ and subsequent patient recovery. While stem cell-based therapies have emerged as particularly promising for equine musculoskeletal injuries, a multidisciplinary approach is underscored throughout the discussion, emphasizing the importance of considering various therapeutic modalities in tandem.

Cell Therapy Approaches for Articular Cartilage Regeneration

Articular cartilage is a common cartilage type found in a multitude of joints throughout the human body. However, cartilage is limited in its regenerative capacity. A range of methods have been employed to aid adults under the age of 45 with cartilage defects, but other cartilage pathologies such as osteoarthritis are limited to non-steroidal anti-inflammatory drugs and total joint arthroplasty. Cell therapies and synthetic biology can be utilized to assist not only cartilage defects but have the potential as a therapeutic approach for osteoarthritis as well. In this review, we will cover current cell therapy approaches for cartilage defect regeneration with a focus on autologous chondrocyte implantation and matrix autologous chondrocyte implantation. We will then discuss the potential of stem cells for cartilage repair in osteoarthritis and the use of synthetic biology to genetically engineer cells to promote cartilage regeneration and potentially reverse osteoarthritis.

Application of human platelet lysate in chondrocyte expansion promotes chondrogenic phenotype and slows senescence progression via BMP-TAK1-p38 pathway

Osteoarthritis (OA) is one of the most common musculoskeletal degenerative. OA treatments are aiming to slow down disease progression; however, lack of cartilage regeneration efficacy. Autologous chondrocyte implantation (ACI) is a promising cartilage-regeneration strategy that uses human articular chondrocytes (HACs) as cellular materials. However, the unreadiness of HACs from prolonged expansion, cellular senescence, and chondrogenic dedifferentiation occurred during conventional expansion, thus, minimizing the clinical efficacy of ACI. We aimed to examine the effects of a human platelet lysate (HPL) as an alternative human-derived HAC medium supplement to overcome the limitations of conventional expansion, and to explain the mechanism underlying the effects of HPL. During passages 2-4 (P2-P4), HPL significantly increased HAC proliferation capacities and upregulated chondrogenic markers. Simultaneously, HPL significantly reduced HAC senescence compared with conventional condition. HACs treated with LDN193189 exhibited a reduction in proliferation capacity and chondrogenic marker expression, whereas the HAC senescence increased slightly. These findings indicated involvement of BMP-2 signaling transduction in the growth-assistive, anti-senescent, and chondrogenic-inductive properties of HPL, which demonstrated its beneficial effects for application as HAC medium supplement to overcome current expansion limitations. Finally, our findings support the roles of platelets in platelet-rich plasma as a promising treatment for patients with OA.

Current and Novel Therapeutics for Articular Cartilage Repair and Regeneration

Articular cartilage repair is a sophisticated process that has is being recently investigated. There are several different approaches that are currently reported to promote cartilage repair, like cell-based therapies, biologics, and physical therapy. Cell-based therapies involve the using stem cells or chondrocytes, which make up cartilage, to promote the growth of new cartilage. Biologics, like growth factors, are also being applied to enhance cartilage repair. Physical therapy, like exercise and weight-bearing activities, can also be used to promote cartilage repair by inducing new cartilage growth and improving joint function. Additionally, surgical options like osteochondral autograft, autologous chondrocyte implantation, microfracture, and others are also reported for cartilage regeneration. In the current literature review, we aim to provide an up-to-date discussion about these approaches and discuss the current research status.

Sericin-reinforced dual-crosslinked hydrogel for cartilage defect repair

Articular cartilage is essential for normal daily joint function activities. However, it is difficult for articular cartilage to repair itself after injury due to the lack of nerves and blood vessels, so an effective cartilage repair method is necessary. As a three-dimensional polymer network structure with high water content, hydrogel is a good candidate material for cartilage repair, and it is also a research hotspot in the treatment of cartilage injury. Here, a porous dual-crosslinked hydrogel containing sodium alginate (SA) and silk sericin (SS) was designed for in situ repair of cartilage damage. The degradation rate of the hydrogel was regulated by changing the content of SS to match the rate of cartilage regeneration. The hydrogel had excellent mechanical properties (compressive strength≈245 kPa, compressibility≈60%), high water content (85%-88%) and porosity(>20%), and when the content of SS is 1%, the scaffold has the best comprehensive performance. Existing excellent cytocompatibility, the scaffold can promote the adhesion and proliferation of chondrocytes while reducing inflammatory cell infiltration. The cartilage defect repair experiments in vivo showed that artificial cartilage was formed at 4 weeks with molecular structure similar to natural cartilage. It is expected to be applied to clinical cartilage repair through the dual-crosslinked three-dimensional cartilage scaffold.

Perspective in Achieving Stratified Articular Cartilage Repair Using Zonal Chondrocytes

Articular cartilage is composed of superficial, medial, and deep zones, which endow the tissue with biphasic mechanical properties to withstand shearing force and compressional loading. The tissue has very limited self-healing capacity once it is damaged due to its avascular nature. To prevent the early onset of osteoarthritis, surgical intervention is often needed to repair the injured cartilage. Current noncell-based and cell-based treatments focus on the regeneration of homogeneous cartilage to achieve bulk compressional properties without recapitulating the zonal matrix and mechanical properties, and often oversight in aiding cartilage integration between host and repair cartilage. It is hypothesized that achieving zonal architecture in articular cartilage tissue repair could improve the structural and mechanical integrity and thus the life span of the regenerated tissue. Engineering stratified cartilage constructs using zonal chondrocytes have been hypothesized to improve the functionality and life span of the regenerated tissues. However, stratified articular cartilage repair has yet to be realized to date due to the lack of an efficient zonal chondrocyte isolation method and an expansion platform that would allow both cell propagation and phenotype maintenance. Various attempts and challenges in achieving stratified articular cartilage repair in a clinical setting are evaluated. In this review, different perspectives on achieving stratified articular cartilage repair using zonal chondrocytes are described. The effectiveness of different zonal chondrocyte isolation and zonal chondrocyte phenotype maintenance methodologies during expansion are compared, with the focus on recent advancements in zonal chondrocyte isolation and expansion that could present a possible strategy to overcome the limitation of applying zonal chondrocytes to facilitate zonal architecture development in articular cartilage regeneration. Impact Statement The zonal properties of articular cartilage contribute to the biphasic mechanical properties of the tissues. Recapitulation of the zonal architecture in regenerated articular cartilage has been hypothesized to improve the mechanical integrity and life span of the regenerated tissue. This review provides a comprehensive discussion on the current state of research relevant to achieving stratified articular cartilage repair using zonal chondrocytes from different perspectives. This review further elaborates on a zonal chondrocyte production pipeline that can potentially overcome the current clinical challenges and future work needed to realize stratified zonal chondrocyte implantation in a clinical setting.

Effects of Electrical Stimulation on Articular Cartilage Regeneration with a Focus on Piezoelectric Biomaterials for Articular Cartilage Tissue Repair and Engineering

There is increasing evidence that chondrocytes within articular cartilage are affected by endogenous force-related electrical potentials. Furthermore, electrical stimulation (ES) promotes the proliferation of chondrocytes and the synthesis of extracellular matrix (ECM) molecules, which accelerate the healing of cartilage defects. These findings suggest the potential application of ES in cartilage repair. In this review, we summarize the pathogenesis of articular cartilage injuries and the current clinical strategies for the treatment of articular cartilage injuries. We then focus on the application of ES in the repair of articular cartilage in vivo. The ES-induced chondrogenic differentiation of mesenchymal stem cells (MSCs) and its potential regulatory mechanism are discussed in detail. In addition, we discuss the potential of applying piezoelectric materials in the process of constructing engineering articular cartilage, highlighting the important advances in the unique field of tissue engineering.

Loose Body Versus Trochlear Biopsy Matrix-Induced Autologous Chondrocyte Implantation (MACI) MOCART Scores and IKDC Reported Outcomes in Pediatric Patients

BACKGROUND

Matrix-induced autologous chondrocyte implantation (MACI) has shown promising results in the treatment of osteochondral lesions of the knee. A recent study showed similar viability comparing chondrocytes harvested from the intercondylar notch compared to those harvested from osteochondral loose bodies. However, there is limited evidence assessing how these different biopsies perform clinically. The goal of this study was to compare both radiographic and patient-reported outcomes in patients with patellar and femoral osteochondral lesions treated with MACI using either a standard intercondylar notch biopsy or an osteochondral loose body biopsy.

METHODS

A retrospective study was performed on all pediatric autologous chondrocyte implantation procedures performed from 2014 to 2017 at a single institution. Patients were divided into 2 groups: one group had cartilage derived from a standard intercondylar notch biopsy (n=9) and the other group had cartilage derived from an osteochondral loose body found within the ipsilateral knee (n=10). At a minimum of 1-year postimplantation, magnetic resonance imagings of the operative knee were performed and the Magnetic Resonance Observation of Cartilage Repair Tissue Knee Score (MOCART 2.0) knee score was used to assess the integrity and quality of the cartilage repair tissue. Interclass correlation coefficients were calculated between the 2 groups. International Knee Documentation Committee (IKDC) outcome scores were determined at a minimum 2 years post-implantation.

RESULTS

The interclass correlation coefficient between three independent examiners for the MOCART scoring was excellent at 0.94. With regards to the MOCART score, the loose body group had an insignificant 17-point lower median score at 63 [interquartile range (IQR): 58 to 89] compared to the intercondylar group at 80 (IQR: 65 to 90) ( P =0.15). There was no difference in IKDC scores with the loose body group having a median score of 82 (IQR: 65 to 95) and the intercondylar group having a median score of 84 (IQR: 53 to 99) ( P =0.90).

CONCLUSION

These results demonstrate that osteochondral loose bodies can be used as viable harvest site in MACI procedures with no difference in functional and radiographic outcomes at 2 years postimplantation. This may limit both short and long-term donor site morbidity.

LEVEL OF EVIDENCE

Level III-retrospective comparative study.

Biological Reconstruction of Localized Full-Thickness Cartilage Defects of the Knee: A Systematic Review of Level 1 Studies with a Minimum Follow-Up of 5 Years

OBJECTIVE

The objective of this study was to evaluate the best available mid- to long-term evidence of surgical procedures for the treatment of localized full-thickness cartilage defects of the knee.

DESIGN

Systematic review using Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines of Level 1 randomized clinical trials (RCTs), meta-analyses of RCTs and systematic reviews with a minimum follow-up of 5 years. Data extracted included patient demographics, defect characteristics, clinical and radiological outcomes, as well as treatment failures.

RESULTS

Six RCTs and 3 Level 1 systematic reviews were included. Two RCTs compared microfracture (MFx) to periosteum-covered autologous chondrocyte implantation (ACI-P), 1 to matrix-associated ACI (M-ACI) and 2 to osteochondral autograft transplantation (OAT). One study compared OAT to collagen membrane covered ACI (ACI-C). The 3 Level 1 systematic reviews/meta-analyses assessed the outcome of MFx, OAT, and various ACI methods in RCTs. OAT showed significantly better outcomes compared with MFx. In the 2 RCTs comparing ACI-P and MFx, no significant differences in clinical outcomes were seen, whereas significantly better outcomes were reported for M-ACI versus MFx in 1 study including patients with larger defects (5 cm²), and for ACI-C versus OAT in terms of Cincinnati Score. Higher failure rates were reported for MFx compared with OAT and for OAT compared with ACI-C, while no significant differences in failure rates were observed for ACI-P compared to MFx.

CONCLUSION

Restorative cartilage procedures (ACI-C or M-ACI and OAT) are associated with better long-term clinical outcomes including lower complication and failure rates when compared with reparative techniques (MFx). Among the restorative procedures, OAT seems to be inferior to ACI especially in larger defects after longer follow-up periods.

LEVEL OF EVIDENCE

Level I: Systematic review of Level I studies.

Third-Generation Autologous Chondrocyte Implantation (Cells Cultured Within Collagen Membrane) Is Superior to Microfracture for Focal Chondral Defects of the Knee Joint: Systematic Review and Meta-analysis

PURPOSE

To systematically review randomized controlled trials to compare clinical outcomes of microfracture (MFx) versus third-generation autologous chondrocyte implantation (ACI) for the treatment of focal chondral defects (FCDs) of the knee joint.

METHODS

A systematic review was performed by searching PubMed, Cochrane Library, and EMBASE to locate randomized controlled trials comparing minimum 2-year clinical outcomes of patients undergoing MFx versus third-generation ACI for FCDs of the knee joint. The search terms used were: "knee" AND "microfracture" AND "autologous chondrocyte" AND "randomized." Patients were evaluated based on treatment failure rates, magnetic resonance imaging, International Cartilage Repair Society scores, and patient-reported outcome scores (Lysholm, Tegner, Knee Injury and Osteoarthritis Outcome Score, modified Cincinnati Knee Rating System, 12-item Short Form Health Survey Physical and Mental, and the EuroQol 5 Dimensions Visual Analog Scale score).

RESULTS

Six studies (5 Level I, 1 Level II) met inclusion criteria, including a total of 238 patients undergoing MFx and 274 undergoing ACI. Two studies had an overlapping cohort of patients and therefore the study with longer follow-up was used in all analyses. The average follow-up among patients ranged from 2.0 years to 6.0 years. Average lesion size ranged from 1.8 cm² to 5.0 cm². Treatment failure ranged from 0% to 1.8% in the ACI group and 2.5% to 8.3% in the MFx group. In 4 studies, ACI patients demonstrated significantly greater improvement in multiple Knee Injury and Osteoarthritis Outcome Score subscores compared with MFx. In 2 studies, patients who received ACI demonstrated significantly greater improvement in the Tegner score compared to MFx, and 1 study showed significantly greater improvement in the Lysholm and ICRS scores for ACI compared with MFx.

CONCLUSIONS

At short-term follow-up, third-generation ACI demonstrates a lower failure rate and greater improvement in patient-reported outcomes compared with MFx for FCDs of the knee joint.

LEVEL OF EVIDENCE

II, systematic review of Levels I-II studies.

Anterior Knee Pain: State of the Art

Anterior knee pain (AKP) is one of the most common conditions to bring active young patients to a sports injury clinic. It is a heterogeneous condition related to multiple causative factors. Compared to the general population, there appears to be a higher risk of development of patellofemoral osteoarthritis in patients with AKP. AKP can be detrimental to the patient’s quality of life and, in the larger context, significantly burdens the economy with high healthcare costs. This study aims to present a comprehensive evaluation of AKP to improve clinical daily practice. The causes of AKP can be traced not only to structures within and around the knee, but also to factors outside the knee, such as limb malalignment, weakness of specific hip muscle groups, and core and ligamentous laxity. Hence, AKP warrants a pointed evaluation of history and thorough clinical examination, complemented with relevant radiological investigations to identify its origin in the knee and its cause. Conservative management of the condition achieves good results in a majority of patients with AKP. Surgical management becomes necessary only when it is deemed to provide benefit—when the patient has well-characterized structural abnormalities of the knee or limb that correlate with the AKP clinically or in situations where the patient does not obtain significant or sustained relief from symptoms. AKP has a multifactorial etiology. The treatment strategy must be individualized to the patient based on the patient profile and specific cause identified. Hence, treatment of AKP warrants a pointed evaluation of history and thorough clinical examination complemented with relevant radiological investigations to identify the condition’s origin and its cause. A holistic approach focused on the patient as a whole will ensure a good clinical outcome, as much as a focus on the joint as the therapeutic target.

The multifaced role of HtrA1 in the development of joint and skeletal disorders

HtrA1 (High temperature requirement A1) family proteins include four members, widely conserved from prokaryotes to eukaryotes, named HtrA1, HtrA2, HtrA3 and HtrA4. HtrA1 is a serine protease involved in a variety of biological functions regulating many signaling pathways degrading specific components and playing key roles in many human diseases such as neurodegenerative disorders, pregnancy complications and cancer. Due to its role in the breakdown of many ExtraCellular Matrix (ECM) components of articular cartilage such as fibronectin, decorin and aggrecan, HtrA1 encouraged many researches on studying its role in several skeletal diseases (SDs). These studies were further inspired by the fact that HtrA1 is able to regulate the signaling of one of the most important cytokines involved in SDs, the TGFβ-1. This review aims to summarize the data currently available on the role of HtrA1 in skeletal diseases such as Osteoporosis, Rheumatoid Arthritis, Osteoarthritis and Intervertebral Disc Degeneration (IDD). The use of HtrA1 as a marker of frailty in geriatric medicine would represent a powerful tool for identifying older individuals at risk of developing skeletal disorders, evaluating an appropriate intervention to improve quality care in these people avoiding or improving age-related SDs in the elderly population.

[Surgical treatment of focal cartilage defects in the knee : Indications, techniques, modifications and results]

The treatment strategies for focal cartilage damage in the knee are multifarious. For established procedures, such as microfracturing (MFX), autologous matrix-induced chondrogenesis (AMIC), osteochondral transplantation (OCT) and autologous chondrocyte transplantation (ACT), well-founded, partly comparative long-term studies and overlapping size-dependent differential indications are available. Innovative cell sources, the utilization of biological scaffolds as well as biologic agents and various combinations, have recently become the focus of scientific attention; however, high regulatory demands are restricting their use in Germany. The success of every procedure is dependent on the appropriate indications, the treatment of comorbidities, such as axis deviations or ligamentous instability, the surgeon's experience and an adequate follow-up treatment.

Strategies for Articular Cartilage Repair and Regeneration

Articular cartilage is an avascular tissue, with limited ability to repair and self-renew. Defects in articular cartilage can induce debilitating degenerative joint diseases such as osteoarthritis. Currently, clinical treatments have limited ability to repair, for they often result in the formation of mechanically inferior cartilage. In this review, we discuss the factors that affect cartilage homeostasis and function, and describe the emerging regenerative approaches that are informing the future treatment options.

Failures, Reoperations, and Improvement in Knee Symptoms Following Matrix-Assisted Autologous Chondrocyte Transplantation: A Meta-Analysis of Prospective Comparative Trials

OBJECTIVE

Though multiple high-level comparative studies have been performed for matrix-assisted autologous chondrocyte transplantation (MACT), quantitative reviews synthesizing best-available clinical evidence on the topic are lacking.

DESIGN

A meta-analysis was performed of prospective randomized or nonrandomized comparative studies utilizing MACT. A total of 13 studies reporting 13 prospective trials (9 randomized, 5 nonrandomized) were included (658 total study participants at weighted mean 3.1 years follow-up, range 1-7.5 years).

RESULTS

Reporting and methodological quality was moderate according to mean Coleman (59.4 SD 7.6), Delphi (3.0 SD 2.1), and MINORS (Methodological Index For Non-Randomized Studies) scores (20.2 SD 1.6). There was no evidence of small study or reporting bias. Effect sizes were not correlated with reporting quality, financial conflict of interest, sample size, year of publication, or length of follow-up (P > 0.05). Compared to microfracture, MACT had greater improvement in International Knee Documentation Committee (IKDC)-subjective and Knee Injury and Osteoarthritis Outcome Pain Subscale Score (KOOS)-pain scores in randomized studies (P < 0.05). Accelerated weight-bearing protocols (6 or 8 weeks) resulted in greater improvements in IKDC-subjective and KOOS-pain scores than standard protocols (8 or 11 weeks) for MACT in randomized studies (P < 0.05) with insufficient nonrandomized studies for pooled analysis.

CONCLUSIONS

Compared to microfracture, MACT has no increased risk of clinical failure and superior improvement in patient-reported outcome scores. Compared to MACT with standardized postoperative weight-bearing protocols, accelerated weight-bearing protocols have no increased risk of clinical failure and show superior improvement in patient-reported outcome scores. There is limited evidence regarding MACT compared to first-generation autologous chondrocyte implantation, mosaicplasty, and mesenchymal stem cell therapy without compelling differences in outcomes.

Cellular alterations and crosstalk in the osteochondral joint in osteoarthritis and promising therapeutic strategies

Osteoarthritis (OA) is a joint disorder involving cartilage degeneration and subchondral bone sclerosis. The bone-cartilage interface is implicated in OA pathogenesis due to its susceptibility to mechanical and biological factors. The crosstalk between cartilage and the underlying subchondral bone is elevated in OA due to multiple factors, such as increased vascularization, porosity, microcracks and fissures. Changes in the osteochondral joint are traceable to alterations in chondrocytes and bone cells (osteoblasts, osteocytes and osteoclasts). The phenotypes of these cells can change with the progression of OA. Aberrant intercellular communications among bone cell-bone cell and bone cell-chondrocyte are of great importance and might be the factors promoting OA development. An appreciation of cellular phenotypic changes in OA and the mechanisms by which these cells communicate would be expected to lead to the development of targeted drugs with fewer side effects.

[Surgical treatment of focal cartilage defects in the knee : Indications, techniques, modifications and results]

The treatment strategies for focal cartilage damage in the knee are multifarious. For established procedures, such as microfracturing (MFX), autologous matrix-induced chondrogenesis (AMIC), osteochondral transplantation (OCT) and autologous chondrocyte transplantation (ACT), well-founded, partly comparative long-term studies and overlapping size-dependent differential indications are available. Innovative cell sources, the utilization of biological scaffolds as well as biologic agents and various combinations, have recently become the focus of scientific attention; however, high regulatory demands are restricting their use in Germany. The success of every procedure is dependent on the appropriate indications, the treatment of comorbidities, such as axis deviations or ligamentous instability, the surgeon's experience and an adequate follow-up treatment.

Chondromalacia patellae: current options and emerging cell therapies

Chondromalacia patellae (CMP), also known as runner’s knee, typically occurs in young patients, which is characterized by anterior knee pain (AKP) that is associated with visible changes in patellar cartilage. The initial pathological changes include cartilage softening, swelling, and edema. CMP is caused by several factors, including trauma, increased cartilage vulnerability, patellofemoral instability, bony anatomic variations, abnormal patellar kinematics, and occupation hazards. CMP may be reversible or may progress to develop patellofemoral osteoarthritis. Quadriceps wasting, patellofemoral crepitus, and effusion are obvious clinical indications. Additionally, radiological examinations are also necessary for diagnosis. Magnetic resonance imaging (MRI) is a non-invasive diagnostic method, which holds a promise in having the unique ability to potentially identify cartilage lesions. Modalities are conventionally proposed to treat cartilage lesions in the PF joint, but none have emerged as a gold standard, neither to alleviated symptoms and function nor to prevent OA degeneration. Recently, researchers have been focused on cartilage-targeted therapy. Various efforts including cell therapy and tissue emerge for cartilage regeneration exhibit as the promising regime, especially in the application of mesenchymal stem cells (MSCs). Intra-articular injections of variously sourced MSC are found safe and beneficial for treating CMP with improved clinical parameters, less invasiveness, symptomatic relief, and reduced inflammation. The mechanism of MSC injection remains further clinical investigation and is tremendously promising for CMP treatment. In this short review, etiology, MRI diagnosis, and treatment in CMP, especially the treatment of the cell-based therapies, are reviewed.

Hyaluronic Acid Supplement as a Chondrogenic Adjuvant in Promoting the Therapeutic Efficacy of Stem Cell Therapy in Cartilage Healing

The main aim of this study is to investigate the therapeutic efficacy of direct intra-articular injection of bone-marrow-derived stem/stromal cells (BMSCs) and the adjuvant role of hyaluronic acid (HA) in facilitating rabbit articular cartilage repair. First, rabbit BMSCs were treated with a medium containing different concentrations of HA. Later, HA’s influence on BMSCs’ CD44 expression, cell viability, extracellular glycosaminoglycan (GAG) synthesis, and chondrogenic gene expression was evaluated during seven-day cultivation. For the in vivo experiment, 24 rabbits were used for animal experiments and 6 rabbits were randomly allocated to each group. Briefly, chondral defects were created at the medial femoral condyle; group 1 was left untreated, group 2 was injected with HA, group 3 was transplanted with 3 × 10⁶ BMSCs, and group 4 was transplanted with 3 × 10⁶ BMSCs suspended in HA. Twelve weeks post-treatment, the repair outcome in each group was assessed and compared both macroscopically and microscopically. Results showed that HA treatment can promote cellular CD44 expression. However, the proliferation rate of BMSCs was downregulated when treated with 1 mg/mL (3.26 ± 0.03, p = 0.0002) and 2 mg/mL (2.61 ± 0.04, p = 0.0001) of HA compared to the control group (3.49 ± 0.05). In contrast, 2 mg/mL (2.86 ± 0.3) of HA treatment successfully promoted normalized GAG expression compared to the control group (1.88 ± 0.06) (p = 0.0009). The type II collagen gene expression of cultured BMSCs was significantly higher in BMSCs treated with 2 mg/mL of HA (p = 0.0077). In the in vivo experiment, chondral defects treated with combined BMSC and HA injection demonstrated better healing outcomes than BMSC or HA treatment alone in terms of gross grading and histological scores. In conclusion, this study helps delineate the role of HA as a chondrogenic adjuvant in augmenting the effectiveness of stem-cell-based injection therapy for in vivo cartilage repair. From a translational perspective, the combination of HA and BMSCs is a convenient, ready-to-use, and effective formulation that can improve the therapeutic efficacy of stem-cell-based therapies.

Non-viral Gene Therapy for Osteoarthritis

Strategies for delivering nucleic acids into damaged and diseased tissues have been divided into two major areas: viral and non-viral gene therapy. In this mini-review article we discuss the application of gene therapy for the treatment of osteoarthritis (OA), one of the most common forms of arthritis. We focus primarily on non-viral gene therapy and cell therapy. We briefly discuss the advantages and disadvantages of viral and non-viral gene therapy and review the nucleic acid transfer systems that have been used for gene delivery into articular chondrocytes in cartilage from the synovial joint. Although viral gene delivery has been more popular due to its reported efficiency, significant effort has gone into enhancing the transfection efficiency of non-viral delivery, making non-viral approaches promising tools for further application in basic, translational and clinical studies on OA. Non-viral gene delivery technologies have the potential to transform the future development of disease-modifying therapeutics for OA and related osteoarticular disorders. However, further research is needed to optimize transfection efficiency, longevity and duration of gene expression.

3D printed gelatin/hydroxyapatite scaffolds for stem cell chondrogenic differentiation and articular cartilage repair

The hUCB-MSC-laden 3D printed gelatin/HAP scaffold effectively repairs knee cartilage defects in a pig model.

Clinical and Radiological Outcomes After Autologous Matrix-Induced Chondrogenesis Versus Microfracture of the Knee: A Systematic Review and Meta-analysis With a Minimum 2-Year Follow-up

Background:

Microfracture (MFx) is the most common procedure for treating chondral lesions in the knee; however, initial improvements decline after 2 years. Autologous matrix-induced chondrogenesis (AMIC) may overcome this shortcoming by combining MFx with collagen scaffolds. However, the outcomes of AMIC and MFx in the knee have not been compared.

Purpose:

To compare the clinical and radiological outcomes of AMIC and MFx over a minimum 2-year follow-up.

Study Design:

Systematic review; Level of evidence, 4.

Methods:

A systematic search of the MEDLINE, Embase, and Cochrane Library databases identified studies of patients who underwent AMIC or MFx and that reported validated clinical outcome measure and/or radiological evaluation findings at a follow-up of ≥2 years. There were 2 reviewers who performed study selection, a risk of bias assessment, and data extraction.

Results:

Overall, 29 studies were included in this systematic review. The mean improvement on the Lysholm score, Tegner activity scale, and visual analog scale for pain did not differ significantly between the 2 procedures. The mean improvement on the International Knee Documentation Committee (IKDC) subjective score was significantly greater in the AMIC (45.9 [95% CI, 36.2-55.5]) than in the MFx (27.2 [95% CI, 23.3-31.1]) group (P < .001). In addition, the mean magnetic resonance observation of cartilage repair tissue score was significantly higher in the AMIC (69.3 [95% CI, 55.1-83.5]) versus MFx (41.0 [95% CI, 27.3-54.7]) group (P = .005), and the mean adequate defect filling rate on magnetic resonance imaging scans was significantly better in the AMIC (77.3% [95% CI, 66.7%-87.9%]) versus MFx (47.9% [95% CI, 29.2%-66.6%]) group (P = .008) (odds ratio, 1.58 [95% CI, 1.07-2.33]).

Conclusion:

No significant differences in clinical outcomes, except for the IKDC subjective score, were found between the AMIC and MFx groups. Greater improvement in IKDC subjective scores and magnetic resonance imaging findings were seen in patients treated with AMIC compared with MFx at a minimum 2-year follow-up.

An Off-the-Shelf Tissue Engineered Cartilage Composed of Optimally Sized Pellets of Cartilage Progenitor/Stem Cells

Articular cartilage focal lesion remains an intractable challenge in sports medicine, and autologous chondrocytes' implantation (ACI) is one of the most commonly utilized treatment modality for this ailment. However, the current ACI technique requires two surgical steps which increases patients' morbidity and incurs additional medical costs. In the present study, we developed a one-step cryopreserved off-the-shelf ACI tissue-engineered (TE) cartilage by seeding pellets of spheroidal cartilage stem/progenitor cells (CSPCs) on a silk scaffold. The pellets were developed through a hanging-drop method, and the incubation time of 1 day could efficiently produce spheroidal pellets without any adverse influence on the cell activity. The pellet size was also optimized. Under chondrogenic induction, pellets consisting of 40 000 CSPCs were found to exhibit the most abundant cartilage matrix deposition and the highest mRNA expression levels of SOX9, aggrecan, and COL2A1, as compared with pellets consisting of 10 000, 100 000, or 200 000 CSPCs. Scaffolds seeded with CSPCs pellets containing 40 000 cells could be preserved in liquid nitrogen with the viability, migration, and chondrogenic ability remaining unaffected for as long as 3 months. When implanted in a rat trochlear cartilage defect model for 3 months, the ready-to-use, cryopreserved TE cartilage yielded fully cartilage reconstruction, which was comparable with the uncryopreserved control. Hence, our study provided preliminary data that our off-the-shell TE cartilage with optimally sized CSPCs pellets seeded within silk scaffolds exhibited strong cartilage repair capacity, which provided a convenient and promising one-step surgical approach to ACI.

Enzyme-Cross-linked Gelatin Hydrogel Enriched with an Articular Cartilage Extracellular Matrix and Human Adipose-Derived Stem Cells for Hyaline Cartilage Regeneration of Rabbits

Hyaline cartilage regeneration remains clinically challenging. In this study, microbial transglutaminase was used to cross-link gelatin. The articular cartilage extracellular matrix (cECM), mainly comprising collagen type II and glycosaminoglycans (GAGs), which can support chondrogenesis, was enclosed in this enzyme-catalyzed hydrogel. After human adipose-derived stem cells (hASCs) were encapsulated in the hydrogel enriched with the cECM, the results demonstrated that the enzymatic cross-linking reaction is of low cytotoxicity. Moreover, the stem cells showed great proliferation and chondrogenic differentiation potential in the hydrogel. Most importantly, we assessed the therapeutic effects of applying a hydrogel enriched with the cECM and hASCs to repair a full-thickness osteochondral defect. At 8 weeks after surgery, the GCC group (hydrogel encapsulating cells and the cECM) exhibited a smooth articular surface with transparent new hyaline-like tissue macroscopically. According to histological analysis, inflammatory responses were hardly observed, and sound chondrocytes were aligned in the newly formed chondral layer. In addition, the GCC group exhibited significant improvement in the GAG content between weeks 4 and 8. In summary, the implantation of a gelatin hydrogel enriched with the cECM and hASCs could facilitate the hyaline cartilage regeneration significantly in rabbit knee joint models.

Respective stemness and chondrogenic potential of mesenchymal stem cells isolated from human bone marrow, synovial membrane, and synovial fluid

BACKGROUND

MSCs isolated from bone marrow (BM-MSCs) have well-established chondrogenic potential, but MSCs derived from the synovial membrane (SM-MSCs) and synovial fluid (SF-MSCs) are thought to possess superior chondrogenicity. This study aimed to compare the in vitro immunophenotype and trilineage and chondrogenic potential of BM-MSCs to SM-MSCs and SF-MSCs.

METHODS

MSCs were isolated from bone marrow (BM-MSCs), synovial membrane (SM-MSCs), and synovial fluid (SF-MSCs) extracted from the hips (BM) and knees (SM and SF) of advanced OA patients undergoing arthroplasty. Flow cytometric analysis was used at P2 to evaluate cell stemness. The trilinear differentiation test was performed at P2. At P3, MSC-seeded collagen sponges were cultured in chondrogenic medium for 28 days. Chondrogenic gene expression was quantified by qRT-PCR. Finally, the implants were stained to assess the deposition of proteoglycans and type II collagen.

RESULTS

Despite variability, the immunophenotyping of BM-MSCs, SM-MSCs, and SF-MSCs was quite similar. All cell types were positive for the expression of stem cell markers and negative for exclusion markers. Additionally, chondrogenic differentiation and hypertrophy were more pronounced in BM-MSCs (ACAN, SOX9, COL2B, and COL10A) than in SF-MSCs, with SM-MSCs having intermediate characteristics. Concerning matrix synthesis, the three cell types were equipotent in terms of GAG content, while BM-MSC ECM synthesis of type II collagen was superior.

CONCLUSIONS

Chondrogenic MSCs are easily collected from SM and SF in advanced human OA, but in vitro chondrogenesis that is superior to age-matched BM-MSCs should not be expected. However, due to intra-articular priming, SF-MSCs did not overexpress hypertrophic gene.

[Technique of all arthroscopic autologous chondrocyte implantation (ACI) for the treatment of cartilage defects in the knee]

OBJECTIVE

All arthroscopic treatment of deep cartilage defects in the knee for reconstruction of the articular surface.

INDICATIONS

Focal cartilage defects of the knee (ICRS ≥ grade 3) from a size of 2.5 cm² and more.

CONTRAINDICATIONS

Osteoarthritis (Kellgren-Lawrence > grade 2), osseus defect situation, cartilage lesion of the opposing articular surfaces (ICRS > grade 2), instability, malalignment (>3-4°), inflammatory joint diseases.

SURGICAL TECHNIQUE

First procedure (cell harvesting): Treatment of additional pathologies, preparation of the cartilage defect, harvesting of osteochondral cylinders for cell culture. Second procedure (cell implantation): Dry arthroscopy, cleaning and drying of the already prepared defect, implantation of the in situ crosslinking cartilage cell suspension.

POSTOPERATIVE MANAGEMENT

First procedure (cell harvesting): Early functional treatment with weight bearing as tolerated. Second procedure (cell implantation): No drains, extension brace for 4 days, then free range of motion, partial weight bearing for 4 weeks in patellofemoral implantation and for 8 weeks in tibiofemoral implantation, continuous passive motion beginning in postoperative week 2, cycling from postoperative week 9.

RESULTS

In the literature, results for ACI in the knee are reported to be good, especially for larger cartilage defects. Arthroscopic techniques should lead to a decrease of complications and perioperative morbidity. No technique-specific complications occurred in our cohort. From 2012-2015, 98 patients were treated using the above mentioned technique, whereby 62 patients were retrospectively evaluated after 31.0 ± 14.8 (12.5-61.4) months. In 15 patients (28%) additional procedures were performed (7 anterior cruciate ligament reconstructions, 3 correction osteotomies and 5 medial patellofemoral ligament reconstructions). Average cartilage defect size was 4.7 ± 2.8 cm², in 18 patients (29%) more than one cartilage defect was treated. The subjective IKDC and total KOOS scores resulted in 66 ± 10 and 73 ± 19 points.

Assessment of Cartilage Growth After Biopsy of Osteochondral Loose Bodies in Adolescent Knees for Use in Autologous Chondrocyte Implantation

BACKGROUND

The goal of this study is to determine whether harvested cartilage from an osteochondral loose body maintains the same viability for implantation as cartilage harvested from the traditional locations within the adolescent knee for autologous chondrocyte implantation (ACI).

METHODS

A retrospective study was performed on all ACI procedures performed from 2014 to 2017 at a single institution. Biopsies were derived from 2 groups: osteochondral loose body verses the intercondylar notch. The viability, yield, identity, potency, and density were obtained from each sample in addition to basic demographics and concomitant injuries. A total of 12 patients with osteochondral loose bodies 14.6 (SD=2.9) and 20 patients 13.6 (SD=3.3) with intercondylar notch biopsies were evaluated for the study.

RESULTS

In the microscopic and histologic comparison, there was no significant difference in viability: 94% in the loose bodies and 93% in the intercondylar notch groups, identity: 7.4 d5L versus 6.3 d5L, or yield. Minimum yield is presented as different units in Carticel (1.2×10 cells/vial) and matrix-induced ACI (>8500 relative fluorescent units) products; however, there was no difference between groups and all samples were above the acceptable limit. Minimum identity value is recorded as d5L> -2.00 and all samples were above this limit. In addition, no sample had signs of contamination or endotoxin in either group.

CONCLUSION

These results demonstrate an alternative method for obtaining cartilage biopsies in ACI procedures that may limit short-term and long-term donor site morbidity.

LEVEL OF EVIDENCE

Level III.

Prior Surgery Negatively Affects Cell Culture Identity in Patients Undergoing Autologous Chondrocyte Implantation

BACKGROUND

Recently, a cell identity assay has been introduced to evaluate the identity of cultured chondrocytes before autologous chondrocyte implantation (ACI), which was shown to be associated with graft survival after ACI.

PURPOSE

To identify the influence of several patient- and lesion-specific factors on cell identity and viability assays.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

A total of 187 patients with second-generation ACI were included in this study. Patient and lesion characteristics, cell viability, cell identity, and biopsy specimen weight were recorded for each patient. A binomial logistic regression model was utilized to determine patient-specific predictive factors for cell product quality.

RESULTS

The implanted ACI cell products showed a cell viability of 93% ± 2.4% (mean ± SD; range, 84-98) with an identity score of 5.8 ± 2.1 (range, -0.08 to 9.46). Patients with multiple previous surgical procedures on the index knee had significantly lower cell identity scores when compared with patients without previous surgery (odds ratio = 0.31; 95% CI, 0.16-0.59; P < .001). Patients without surgical history had significantly higher cell identity scores than patients with 1 and ≥2 previous surgical procedures on the index knee (6.32 vs 5.32 vs 5.05; P = .006 and P < .001, respectively). Cell viability was not predicted by any preoperative variable (P > .05). Cell identity and viability were not associated with each other or with biopsy specimen weight (P > .05).

CONCLUSION

Cartilage biopsy specimens from patients with ≥1 previous surgical procedures resulted in implants with lower cell identity scores when compared with patients without previous operations. None of the other patient- or lesion-specific factors were correlated, specifically biopsy specimen weight.

Inflammation-Modulating Hydrogels for Osteoarthritis Cartilage Tissue Engineering

Osteoarthritis (OA) is the most common form of the joint disease associated with age, obesity, and traumatic injury. It is a disabling degenerative disease that affects synovial joints and leads to cartilage deterioration. Despite the prevalence of this disease, the understanding of OA pathophysiology is still incomplete. However, the onset and progression of OA are heavily associated with the inflammation of the joint. Therefore, studies on OA treatment have sought to intra-articularly deliver anti-inflammatory drugs, proteins, genes, or cells to locally control inflammation in OA joints. These therapeutics have been delivered alone or increasingly, in delivery vehicles for sustained release. The use of hydrogels in OA treatment can extend beyond the delivery of anti-inflammatory components to have inherent immunomodulatory function via regulating immune cell polarization and activity. Currently, such immunomodulatory biomaterials are being developed for other applications, which can be translated into OA therapy. Moreover, anabolic and proliferative levels of OA chondrocytes are low, except initially, when chondrocytes temporarily increase anabolism and proliferation in response to structural changes in their extracellular environment. Therefore, treatments need to restore matrix protein synthesis and proliferation to healthy levels to reverse OA-induced damage. In conjugation with injectable and/or adhesive hydrogels that promote cartilage tissue regeneration, immunomodulatory tissue engineering solutions will have robust potential in OA treatment. This review describes the disease, its current and future immunomodulatory therapies as well as cartilage-regenerative injectable and adhesive hydrogels.

Editorial Commentary: Autologous Chondrocyte Implantation Versus Microfracture for Knee Articular Cartilage Repair: We Should Focus on the Latest Autologous Chondrocyte Implantation Techniques

The clinical efficacy of autologous chondrocyte implantation (ACI) versus microfracture (MFx) for repair of articular cartilage lesions in the knee has gained significant attention in the orthopaedic sports medicine community in recent years. Bone marrow stimulation with MFx often is considered a first-line treatment option, given the ease and low cost of the procedure, as well as the good short-term outcomes. However, multiple studies have recently shown the outcomes of knee MFx to worsen after 5 years postoperatively, particularly for larger lesions. Because of this, ACI has been proposed as a first-line rather than salvage procedure for focal chondral defects in the knee. Although it is important to understand the differences in clinical outcomes between ACI and MFx at mid-term follow-up, longer-term outcomes need to be further investigated. In addition, it may be more appropriate to focus on the comparison of MFx with newer-generation techniques of chondrocyte implantation matrix-associated ACI rather than a collation of historical 2-step ACI using periosteum and newer techniques.

Arthroscopic autologous chondrocyte implantation in the knee with an in situ crosslinking matrix: minimum 4-year clinical results of 15 cases and 1 histological evaluation

PURPOSE

To clinically evaluate an arthroscopic autologous chondrocyte implantation (ACI) technique with an in situ crosslinking matrix for the treatment of full thickness cartilage defects of the knee and to present histological results of a graft cartilage biopsy obtained after 1.5 years.

METHODS

Fifteen cases of arthroscopic autologous chondrocyte implantation in the knee performed between November 2011 and October 2012 were included in the study. Medical charts and operational reports were screened and the patients were contacted after 0.8 ± 0.3 years (0.4-1.3) and 4.3 ± 0.3 years (4.0-4.8) to asses subjective IKDC and re-operation. The Tegner activity scale was collected at the second follow-up time point. Subjective IKDC response rates were assessed at both follow-up time points.

RESULTS

The first and second follow-up was completed by all 15 patients (100%). The subjective IKDC scores showed a significant improvement (pre-operative 44.5 ± 15.9, first follow-up 71.1 ± 15.9, p < 0.001, second follow-up 72.6 ± 17.3, p < 0.001). The overall response rate was 66.7% (n = 10) at follow-up one and two. There were no significant differences in pre-injury (4, range 1-9) and follow-up two (4, range 2-7) Tegner activity scales (p = n.s.). Two patients required re-operation in the index knee, not related to the ACI procedure. No complication related to the ACI or the implantation technique occurred. The histological results showed excellent cartilage regeneration.

CONCLUSION

Arthroscopic ACI using an in situ crosslinking matrix is a safe and reliable treatment option for full-thickness cartilage defects of the knee.

Redifferentiated Chondrocytes in Fibrin Gel for the Repair of Articular Cartilage Lesions

BACKGROUND

Autologous chondrocyte implantation, which uses passaged chondrocytes, commonly leads to the formation of fibrocartilage. When chondrocytes are passaged to increase cell numbers, they lose their phenotype and ability to form hyaline cartilage. The use of transforming growth factor β (TGFβ) to redifferentiate passaged chondrocytes has been validated in vitro; however, it is unknown if redifferentiated chondrocytes will enhance defect repair when implanted in vivo. Furthermore, fibrin gel is used in orthopaedic surgery as a fixative and scaffold and could be an appropriate carrier to enhance retention of cells in the repair site.

PURPOSE

To investigate if passaged redifferentiated chondrocytes in fibrin gel have the ability to form cartilage tissue and if these redifferentiated cells will enhance the formation of hyaline cartilage in vivo when implanted into critical-size osteochondral defects.

STUDY DESIGN

Controlled laboratory study.

METHODS

Rabbit and human chondrocytes were serially passaged twice in monolayer culture. Twice-passaged cells were used directly (dedifferentiated) or redifferentiated in high-density culture with TGFβ3. Dedifferentiated or redifferentiated cells were mixed with fibrin gel to form fibrin clots, which were cultured in vitro to assess the use of fibrin gel as a scaffold or implanted in vivo in a critical-size osteochondral defect in New Zealand White rabbit knee joints. Rabbits were sacrificed 6 weeks after implantation, and tissues were assessed histologically and by immunohistochemistry.

RESULTS

Redifferentiation of passaged chondrocytes by means of 3-dimensional culture in the presence of TGFβ3 improved the formation of cartilaginous tissues in vitro, and culture in fibrin gel did not affect the cell phenotype. Implantation of dedifferentiated cells in vivo resulted in fibrocartilaginous repair tissues. Redifferentiated chondrocyte implants resulted in granulation tissues containing the hyaline cartilage marker collagen type 2.

CONCLUSION

Redifferentiated chondrocytes will maintain their chondrogenic differentiation in fibrin clots. Implanted redifferentiated chondrocytes show a different reparative response than dedifferentiated chondrocytes and do not appear to enhance repair at an early time point. Another study of longer duration is required to assess tissue maturation over time.

CLINICAL RELEVANCE

Redifferentiation of passaged chondrocytes with TGFβ3 before implantation does not improve defect repair in the first 6 weeks.

Image-Guided Chondrocyte Harvesting for Autologous Chondrocyte Implantation: Initial Feasibility Study with Human Cadaver and Pilot Clinical Experience

Background:

Autologous chondrocyte implantation (ACI), a promising modality for repairing full-thickness cartilage defects, requires 2 consecutive arthroscopic procedures for chondrocyte harvesting and implantation. In the present study, we assessed the feasibility and efficacy of image-guided chondrocyte harvesting as an alternative to arthroscopic biopsy.

Methods:

We induced full-thickness cartilage defects in 10 human cadaveric knees. Computed tomographic arthrography (CTA) was performed following the intra-articular administration of Omnipaque 350 to measure the diameters of the induced cartilage defects. Subsequently, 2 independent operators conducted CTA-guided chondrocyte harvesting (from the medial and lateral trochlear ridges) in each knee. The time for chondrocyte harvesting, accuracy (distance between the predefined target on CTA and the final insertion site of the needle), and number of needle readjustments were recorded. In the institutional review board-approved clinical study, informed consent was obtained and chondrocyte harvesting was performed both with use of a conventional arthroscopic biopsy method and with use of a needle through an arthroscopy access site in 10 subjects for whom ACI was indicated. The samples were processed and cultured blindly, and the quantity and quality of the samples were determined.

Results:

CTA measurements of full-thickness cartilage defects showed high to perfect absolute agreement and consistency when compared with direct measurements (overall interclass correlation coefficient, 0.933 to 0.983; p < 0.05). For both operators, image-guided chondrocyte harvesting from the lateral ridge was more accurate (p = 0.007 and 0.040) and faster (p = 0.056 and 0.014) in comparison with harvesting from the medial ridge. In the clinical study, no significant difference was observed for the growth index of samples between the needle-harvest and conventional methods (p = 0.897).

Conclusions:

CTA can be used for precise measurement of full-thickness cartilage defects. Image-guided chondrocyte harvesting is a viable alternative to traditional arthroscopic biopsy for ACI.

Clinical Relevance:

We recognize the current pivotal role of arthroscopic biopsy, as a part of ACI, for chondrocyte harvesting as well as for delineating the nature of the lesion. However, on the basis of our results, image-guided chondrocyte retrieval may obviate the need for arthroscopic biopsy in some patients in the future.

PTH decreases in vitro human cartilage regeneration without affecting hypertrophic differentiation

Regenerated cartilage formed after Autologous Chondrocyte Implantation may be of suboptimal quality due to postulated hypertrophic changes. Parathyroid hormone-related peptide, containing the parathyroid hormone sequence (PTHrP 1–34), enhances cartilage growth during development and inhibits hypertrophic differentiation of mesenchymal stromal cells (MSCs) and growth plate chondrocytes. This study aims to determine the possible anabolic and/or hypertrophic effect of PTH on human articular chondrocytes. Healthy human articular cartilage-derived chondrocytes (n = 6 donors) were cultured on type II collagen-coated transwells with/without 0.1 or 1.0 μM PTH from day 0, 9, or 21 until the end of culture (day 28). Extracellular matrix production, (pre)hypertrophy and PTH signaling were assessed by RT-qPCR and/or immunohistochemistry for collagen type I, II, X, RUNX2, MMP13, PTHR1 and IHH and by determining glycosaminoglycan production and DNA content. The Bern score assessed cartilage quality by histology. Regardless of the concentration and initiation of supplementation, PTH treatment significantly decreased DNA and glycosaminoglycan content and reduced the Bern score compared with controls. Type I collagen deposition was increased, whereas PTHR1 expression and type II collagen deposition were decreased by PTH supplementation. Expression of the (pre)hypertrophic markers MMP13, RUNX2, IHH and type X collagen were not affected by PTH. In conclusion, PTH supplementation to healthy human articular chondrocytes did not affect hypertrophic differentiation, but negatively influenced cartilage quality, the tissues’ extracellular matrix and cell content. Although PTH may be an effective inhibitor of hypertrophic differentiation in MSC-based cartilage repair, care may be warranted in applying accessory PTH treatment due to its effects on articular chondrocytes.

Preservation of Knee Articular Cartilage

Hyaline articular cartilage is critical for the normal functioning of the knee joint. Untreated focal cartilage defects have the potential to rapidly progress to diffuse osteoarthritis. Over the last several decades, a variety of interventions aiming at preserving articular cartilage and preventing osteoarthritis have been investigated. Reparative cartilage procedures, such as microfracture, penetrate the subchondral bone plate in effort to fill focal cartilage defects with marrow elements and stimulate fibrocartilaginous repair. In contrast, restorative cartilage procedures aim to replace the defective articular surface with autologous or allogeneic hyaline cartilage. This review focuses on the preservation of articular cartilage, and discusses the current reparative and restorative surgical techniques available for treating focal cartilage defects.

Cartilage Defect Treatment Using High-Density Autologous Chondrocyte Implantation: Two-Year Follow-up

OBJECTIVE

The aim of this work was to study the short- and mid-term effectiveness and safety of high-density autologous chondrocyte implantation (HD-ACI) in the first 50 patients with knee cartilage damage treated in our unit.

DESIGN

Fifty consecutive patients with cartilage lesions (Outerbridge grade III-IV) in the knee treated with HD-ACI were included in this study. Chondrocytes were isolated from a nonbearing cartilage area biopsy and were cultured until 40 to 50 million cells were obtained. Five million chondrocytes per cm² of a porcine collagen type I/III membrane were implanted covering the defect. Procedure effectiveness was assessed by evaluating pain, swelling, and range of mobility (flexion and extension) at 6-, 12-, and 24-month follow-up. The International Knee Documentation Committee (IKDC) subjective evaluation form was used to evaluate symptoms and functions of the knee.

RESULTS

The percentage of patients with pain and swelling decreased progressively in the following visits, with differences being statistically significant ( P < 0.001 and P = 0.040, respectively). IKDC scores improved progressively throughout the 24-month follow-up ( P < 0.001). Thus, the mean IKDC score improvement was 26.3 points (95% confidence interval [CI] = 18.2-34.4 points) at 12 months and 31.0 points (95% CI = 22.9-39 points) at 24 months. No significant differences were found when performing extension ( P = 0.112). Flexion significantly improved by 25.1° at 24-month follow-up ( P = 0.013).

CONCLUSIONS

HD-ACI is a safe and effective technique for the treatment of cartilage defects, improving clinical and subjective perception of knee functionality. These preliminary results encourage future studies comparing this technique with traditional ACI.

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

BACKGROUND

Treating articular cartilage lesions is clinically challenging. However, whether the addition of autologous platelet-rich plasma (PRP) to bioimplants along with early rehabilitation exercise provides therapeutic effects and regenerates the osteochondral defect remains uninvestigated.

HYPOTHESIS

The addition of PRP to a polylactic-co-glycolic acid (PLGA) scaffold along with continuous passive motion (CPM) in osteochondral defects may offer beneficial in situ microenvironment changes to facilitate hyaline cartilage and subchondral bone tissue repair.

STUDY DESIGN

Controlled laboratory study.

METHODS

In 26 rabbits, 52 critical osteochondral defects were created in bilateral femoral trochlear grooves. The rabbits were allocated to 1 of the following 3 groups: PRP gel (PG group), PRP + PLGA scaffold (PP group), and PRP + PLGA scaffold + CPM (PPC group). At 4 and 12 weeks after surgery, the specimens were assessed by a macroscopic examination, a histological evaluation with immunohistochemical staining, and micro-computed tomography.

RESULTS

The PPC group exhibited the most favorable therapeutic outcomes in terms of hyaline cartilage regeneration. At week 4, the PPC group exhibited significantly higher levels of glycosaminoglycan (GAG) and collagen (COL) II and modest increases in COL I, matrix metalloproteinase-3 (MMP-3), and inflammatory cells with tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6). At week 12, the PPC group had significantly higher tissue repair scores, corresponding to a sound articular cartilage surface and chondrocyte and collagen arrangement. This group demonstrated restored hyaline cartilage and mineralized bone volume per tissue volume, which had an integrating structure in the repair site. However, the PG and PP groups exhibited mainly fibrous tissue and fibrocartilage, corresponding to higher expressions of COL I, TNF-α, IL-6, and MMP-3.

CONCLUSION

PRP with a PLGA graft along with early CPM exercise is promising for the repair of osteochondral defects in rabbit knee joints.

CLINICAL RELEVANCE

This study demonstrates the efficacy of a triad therapy involving the addition of PRP to bioimplants along with early CPM intervention for hyaline cartilage and subchondral regeneration. However, PRP alone (with or without PLGA implants) is limited to osteochondral defect repair without significant regeneration.

[Research progress of rehabilitation after autologous chondrocyte implantation on knee]

Objective

To summarize the research progress of rehabilitation after autologous chondrocyte implantation (ACI).

Methods

The literature related to basic science and clinical practice about rehabilitation after ACI in recent years was searched, selected, and analyzed.

Results

Based on the included literature, the progress of the graft maturation consists of proliferation phase (0-6 weeks), transition phase (6-12 weeks), remodeling phase (12-26 weeks), and maturation phase (26 weeks-2 years). To achieve early protection, stimulate the maturation, and promote the graft-bone integrity, rehabilitation protocol ought to be based on the biomechanical properties at different phases. Weight-bearing program, range of motion (ROM), and options or facilities of exercise are importance when considering a rehabilitation program.

Conclusion

It has been proved that the patients need a program with an increasingly progressive weight-bearing and ROM in principles of rehabilitation after ACI. Specific facilities can be taken at a certain phase. Evidences extracted in the present work are rather low and the high-quality and controlled trials still need to improve the rehabilitation protocol.

Patellofemoral Cartilage Repair

Purpose of Review

This review provides an overview of well-established and newly developed cartilage repair techniques for cartilage defects in the patellofemoral joint (PFJ). An algorithm will be presented for approaching cartilage defects considering the distinct anatomy of both the patellar and trochlear articular surfaces.

Recent Findings

Recent studies on cartilage repair in the PFJ have demonstrated improved outcomes in an attempt to delay or obviate the need for arthroplasty, and improve symptoms in young patients. While autologous chondrocyte implantation shows good and excellent outcomes for chondral lesions, osteochondral defects are adequately addressed with osteochondral allograft transplantation. In case of patellar malalignment, concomitant tibial tubercle osteotomy can significantly improve outcomes. Particulated cartilage and bone marrow aspirate concentrate are potential new alternative treatments for cartilage repair, currently in early clinical studies.

Summary

Due to the frequency of concomitant anatomic abnormalities in the PFJ, a thorough clinical examination combined with careful indication for each procedure in each individual patient combined with meticulous surgical technique is central to achieve satisfying outcomes. Additional comparative studies of cartilage repair procedures, as well as investigation of newer techniques, are needed.

Mesenchymal stem cell-derived extracellular matrix enhances chondrogenic phenotype of and cartilage formation by encapsulated chondrocytes in vitro and in vivo

Mesenchymal stem cell derived extracellular matrix (MSC-ECM) is a natural biomaterial with robust bioactivity and good biocompatibility, and has been studied as a scaffold for tissue engineering. In this investigation, we tested the applicability of using decellularized human bone marrow derived MSC-ECM (hBMSC-ECM) as a culture substrate for chondrocyte expansion in vitro, as well as a scaffold for chondrocyte-based cartilage repair. hBMSC-ECM deposited by hBMSCs cultured on tissue culture plastic (TCP) was harvested, and then subjected to a decellularization process to remove hBMSCs. Compared with chondrocytes grown on TCP, chondrocytes seeded onto hBMSC-ECM exhibited significantly increased proliferation rate, and maintained better chondrocytic phenotype than TCP group. After being expanded to the same cell number and placed in high-density micromass cultures, chondrocytes from the ECM group showed better chondrogenic differentiation profile than those from the TCP group. To test cartilage formation ability, composites of hBMSC-ECM impregnated with chondrocytes were subjected to brief trypsin treatment to allow cell-mediated contraction, and folded to form 3-dimensional chondrocyte-impregnated hBMSC-ECM (Cell/ECM constructs). Upon culture in vitro in chondrogenic medium for 21 days, robust cartilage formation was observed in the Cell/ECM constructs. Similarly prepared Cell/ECM constructs were tested in vivo by subcutaneous implantation into SCID mice. Prominent cartilage formation was observed in the implanted Cell/ECM constructs 14 days post-implantation, with higher sGAG deposition compared to controls consisting of chondrocyte cell sheets. Taken together, these findings demonstrate that hBMSC-ECM is a superior culture substrate for chondrocyte expansion and a bioactive matrix potentially applicable for cartilage regeneration in vivo.

STATEMENT OF SIGNIFICANCE

Current cell-based treatments for focal cartilage defects face challenges, including chondrocyte dedifferentiation, need for xenogenic scaffolds, and suboptimal cartilage formation. We present here a novel technique that utilizes adult stem cell-derived extracellular matrix, as a culture substrate and/or encapsulation scaffold for human adult chondrocytes, for the repair of cartilage defects. Chondrocytes cultured in stem cell-derived matrix showed higher proliferation, better chondrocytic phenotype, and improved redifferentiation ability upon in vitro culture expansion. Most importantly, 3-dimensional constructs formed from chondrocytes folded within stem cell matrix manifested excellent cartilage formation both in vitro and in vivo. These findings demonstrate the suitability of stem cell-derived extracellular matrix as a culture substrate for chondrocyte expansion as well as a candidate bioactive matrix for cartilage regeneration.

Microfracture Versus Autologous Chondrocyte Implantation for Articular Cartilage Lesions in the Knee: A Systematic Review of 5-Year Outcomes

BACKGROUND

Microfracture (MFx) and autologous chondrocyte implantation (ACI) are 2 surgical treatment options used to treat articular cartilage injuries of the knee joint.

PURPOSE

To compare the midterm to long-term clinical outcomes of MFx versus ACI for focal chondral defects of the knee.

STUDY DESIGN

Systematic review.

METHODS

A systematic review was performed by searching PubMed, the Cochrane Library, and Embase to locate studies (level of evidence I-III) comparing the minimum average 5-year clinical outcomes of patients undergoing MFx versus ACI. Search terms used were "knee," "microfracture," "autologous chondrocyte implantation," and "autologous chondrocyte transplantation." Patients were evaluated based on treatment failure rates, magnetic resonance imaging, and patient-reported outcome scores (Lysholm, Knee Injury and Osteoarthritis Outcome Score [KOOS], and Tegner scores).

RESULTS

Five studies (3 level I evidence, 2 level II evidence) were identified that met the inclusion criteria, including a total of 210 patients (211 lesions) undergoing MFx and 189 patients (189 lesions) undergoing ACI. The average follow-up among all studies was 7.0 years. Four studies utilized first-generation, periosteum-based ACI (P-ACI), and 1 study utilized third-generation, matrix-associated ACI (M-ACI). Treatment failure occurred in 18.5% of patients undergoing ACI and 17.1% of patients undergoing MFx ( P = .70). Lysholm and KOOS scores were found to improve for both groups across studies, without a significant difference in improvement between the groups. The only significant difference in patient-reported outcome scores was found in the 1 study using M-ACI in which Tegner scores improved to a significantly greater extent in the ACI group compared with the MFx group ( P = .003).

CONCLUSION

Patients undergoing MFx or first/third-generation ACI for articular cartilage lesions in the knee can be expected to experience improvement in clinical outcomes at midterm to long-term follow-up without any significant difference between the groups.

A 3D-Printed PLCL Scaffold Coated with Collagen Type I and Its Biocompatibility

Scaffolds play an important role in tissue engineering and their structure and biocompatibility have great influence on cell behaviors. In this study, poly(l-lactide-co-ε-caprolactone) (PLCL) scaffolds were printed by a 3D printing technology, low-temperature deposition manufacturing (LDM), and then PLCL scaffolds were treated by alkali and coated with collagen type I (COLI). The scaffolds were characterized by scanning electron microscopy (SEM), porosity test, mechanical test, and infrared spectroscopy. The prepared PLCL and PLCL-COLI scaffolds had three-dimensional (3D) porous structure and they not only have macropores but also have micropores in the deposited lines. Although the mechanical property of PLCL-COLI was slightly lower than that of PLCL scaffold, the hydrophilicity of PLCL-COLI was significantly enhanced. Rabbit articular chondrocytes were extracted and were identified as chondrocytes by toluidine blue staining. To study the biocompatibility, the chondrocytes were seeded on scaffolds for 1, 3, 5, 7, and 10 days. MTT assay showed that the proliferation of chondrocytes on PLCL-COLI scaffold was better than that on PLCL scaffold. And the morphology of cells on PLCL-COLI after 1-day culture was much better than that on PLCL. This 3D-printed PLCL scaffold coated with COLI shows a great potential application in tissue engineering.

Sporting Activity Is Reduced 11 Years After First-Generation Autologous Chondrocyte Implantation in the Knee Joint

BACKGROUND

Little is known about long-term sporting activity after periosteal autologous chondrocyte implantation (ACI-P) and its correlation to clinical, morphological, and ultrastructural cartilage characteristics on magnetic resonance imaging (MRI).

PURPOSE

To evaluate long-term sporting activity after ACI-P and to correlate with clinical and MRI findings.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Patients who underwent ACI-P for isolated cartilage defects of the knee joint between 1997 and 2001 were analyzed for sporting ability for 3 different time points: lifetime until the onset of pain, the year before ACI-P, and 11 years (range, 9.0-13.4 years) postoperatively. Sporting activity was assessed and patients' level of activity scaled using standardized questionnaires. MRI scans of the affected knee joint at follow-up were analyzed using the MOCART (magnetic resonance observation of cartilage repair tissue) score and T2 mapping.

RESULTS

Seventy of 86 patients (81% follow-up rate) consisting of 25 female and 45 male patients, with a mean age of 33.3 ± 10.2 years at the time of surgery, mean defect size of 6.5 ± 4.0 cm², and 1.17 treated defects per patient, agreed to participate in the study at a mean 10.9 ± 1.1 years after ACI-P. Fifty-nine patients (69% of total; 84% of follow-up) agreed to MRI, allowing the complete evaluation of 71 transplant sites. Before the onset of symptoms (lifetime), 95.7% of patients played a mean 6.0 sporting activities at a competitive level. In the year before ACI-P, 81.4% of patients played a mean 3.4 sporting activities in 2.4 sessions during 5.4 hours per week at a recreational level. At follow-up, 82.9% of the patients played a mean 3.0 sporting activities in 1.8 sessions during 3.0 hours per week at a recreational level. In contrast to objective factors, 65.6% of the patients felt that their subjective sporting ability had improved or strongly improved after ACI-P, whereas 12.9% felt that their situation had declined or strongly declined, and 21.4% stated that their sporting ability had undergone no change because of surgery. Factors of sporting activity correlated significantly with clinical long-term outcomes. MRI analysis with a mean repair tissue T2 relaxation time of 35.2 milliseconds and mean MOCART score of 44.9 showed no conclusive significant correlation to sporting activity. Level of performance was the only sporting activity factor to show a weak correlation with subgroups of the MOCART score.

CONCLUSION

The premorbid level of sporting and recreational activities cannot be achieved 11 years after ACI-P. The MRI results determined at this time point did not conclusively correlate with long-term sporting activity.

Biomechanical evaluation of novel ultrasound-activated bioresorbable pins for the treatment of osteochondral fractures compared to established methods

BACKGROUND

Osteochondral injuries often lead to osteoarthritis of the affected joint. All established systems for refixation of osteochondral defects show certain disadvantages. To address the problem of reduced stability in resorbable implants, ultrasound-activated pins were developed. By ultrasound-activated melting of the tip of these implants, a more secure anchoring is assumed.

MATERIALS AND METHODS

The aim of the study was to investigate if ultrasound-activated pins can provide secure fixation of osteochondral fragments compared to screws and conventional resorbable pins. In a biomechanical laboratory setting, osteochondral fragments of the medial femoral condyle of sheep were refixated with ultrasound-activated pins [US fused poly(L-lactide-co-D,L-lactide) (PLDLLA) pins], polydioxanone (PDA) pins and conventional titanium screws. Anchoring forces of the different fixation methods were examined, registered and compared concerning shear force and tensile force.

RESULTS

Concerning the pull out test, the US fused PLDLLA pins and titanium screws (~122 N and ~203 N) showed comparable good results, while the PDA pins showed significantly lower anchoring forces (~18 N). Examination of shear forces showed a significantly higher anchoring of the screws (~248 N) than the US fused PLDLLA pins (~218 N). Nevertheless, the US fused PLDLLA pins could significantly outperform the PDA pins (~68 N) concerning shear forces.

CONCLUSION

The US fused PLDLLA pins demonstrated a comparable anchorage to the fixation with screws, but were free from the disadvantages of metal implants, i.e. the need for implant removal. The PDA pin application showed inferior biomechanical properties.

A comparative assessment of adipose-derived stem cells from subcutaneous and visceral fat as a potential cell source for knee osteoarthritis treatment

The intra‐articular injection of adipose‐derived stem cells (ASCs) is a novel potential therapy for patients with osteoarthritis (OA). However, the efficacy of ASCs from different regions of the body remains unknown. This study investigated whether ASCs from subcutaneous or visceral adipose tissue provide the same improvement of OA. Mouse and human subcutaneous and visceral adipose tissue were excised for ASC isolation. Morphology, proliferation, surface markers and adipocyte differentiation of subcutaneous ASCs (S‐ASCs) and visceral ASCs (V‐ASCs) were analysed. A surgically induced rat model of OA was established, and 4 weeks after the operation, S‐ASCs, V‐ASCs or phosphate‐buffered saline (PBS, control) were injected into the articular cavity. Histology, immunohistochemistry and gene expression analyses were performed 6 weeks after ASC injection. The ability of ASCs to differentiate into chondrocytes was assessed by in vitro chondrogenesis, and the immunosuppressive activity of ASCs was evaluated by co‐culturing with macrophages. The proliferation of V‐ASCs was significantly greater than that of S‐ASCs, but S‐ASCs had the greater adipogenic capacity than V‐ASCs. In addition, the infracted cartilage treated with S‐ASCs showed significantly greater improvement than cartilage treated with PBS or V‐ASCs. Moreover, S‐ASCs showed better chondrogenic potential and immunosuppression in vitro. Subcutaneous adipose tissue is an effective cell source for cell therapy of OA as it promotes stem cell differentiation into chondrocytes and inhibits immunological reactions.