Are Generative Pretrained Transformer 4 Responses to Developmental Dysplasia of the Hip Clinical Scenarios Universal? An International Review.

OBJECTIVE: There is increasing interest in applying artificial intelligence chatbots like generative pretrained transformer 4 (GPT-4) in the medical field. This study aimed to explore the universality of GPT-4 responses to simulated clinical scenarios of developmental dysplasia of the hip (DDH) across diverse global settings. METHODS: Seventeen international experts with more than 15 years of experience in pediatric orthopaedics were selected for the evaluation panel. Eight simulated DDH clinical scenarios were created, covering 4 key areas: (1) initial evaluation and diagnosis, (2) initial examination and treatment, (3) nursing care and follow-up, and (4) prognosis and rehabilitation planning. Each scenario was completed independently in a new GPT-4 session. Interrater reliability was assessed using Fleiss kappa, and the quality, relevance, and applicability of GPT-4 responses were analyzed using median scores and interquartile ranges. Following scoring, experts met in ZOOM sessions to generate Regional Consensus Assessment Scores, which were intended to represent a consistent regional assessment of the use of the GPT-4 in pediatric orthopaedic care. RESULTS: GPT-4's responses to the 8 clinical DDH scenarios received performance scores ranging from 44.3% to 98.9% of the 88-point maximum. The Fleiss kappa statistic of 0.113 (P = 0.001) indicated low agreement among experts in their ratings. When assessing the responses' quality, relevance, and applicability, the median scores were 3, with interquartile ranges of 3 to 4, 3 to 4, and 2 to 3, respectively. Significant differences were noted in the prognosis and rehabilitation domain scores (P < 0.05 for all). Regional consensus scores were 75 for Africa, 74 for Asia, 73 for India, 80 for Europe, and 65 for North America, with the Kruskal-Wallis test highlighting significant disparities between these regions (P = 0.034). CONCLUSIONS: This study demonstrates the promise of GPT-4 in pediatric orthopaedic care, particularly in supporting preliminary DDH assessments and guiding treatment strategies for specialist care. However, effective integration of GPT-4 into clinical practice will require adaptation to specific regional health care contexts, highlighting the importance of a nuanced approach to health technology adaptation. LEVEL OF EVIDENCE: Level IV.

Pulsed electromagnetic fields potentiate the paracrine function of mesenchymal stem cells for cartilage regeneration.

BACKGROUND: The mesenchymal stem cell (MSC) secretome, via the combined actions of its plethora of biologically active factors, is capable of orchestrating the regenerative responses of numerous tissues by both eliciting and amplifying biological responses within recipient cells. MSCs are "environmentally responsive" to local micro-environmental cues and biophysical perturbations, influencing their differentiation as well as secretion of bioactive factors. We have previously shown that exposures of MSCs to pulsed electromagnetic fields (PEMFs) enhanced MSC chondrogenesis. Here, we investigate the influence of PEMF exposure over the paracrine activity of MSCs and its significance to cartilage regeneration. METHODS: Conditioned medium (CM) was generated from MSCs subjected to either 3D or 2D culturing platforms, with or without PEMF exposure. The paracrine effects of CM over chondrocytes and MSC chondrogenesis, migration and proliferation, as well as the inflammatory status and induced apoptosis in chondrocytes and MSCs was assessed. RESULTS: We show that benefits of magnetic field stimulation over MSC-derived chondrogenesis can be partly ascribed to its ability to modulate the MSC secretome. MSCs cultured on either 2D or 3D platforms displayed distinct magnetic sensitivities, whereby MSCs grown in 2D or 3D platforms responded most favorably to PEMF exposure at 2 mT and 3 mT amplitudes, respectively. Ten minutes of PEMF exposure was sufficient to substantially augment the chondrogenic potential of MSC-derived CM generated from either platform. Furthermore, PEMF-induced CM was capable of enhancing the migration of chondrocytes and MSCs as well as mitigating cellular inflammation and apoptosis. CONCLUSIONS: The findings reported here demonstrate that PEMF stimulation is capable of modulating the paracrine function of MSCs for the enhancement and re-establishment of cartilage regeneration in states of cellular stress. The PEMF-induced modulation of the MSC-derived paracrine function for directed biological responses in recipient cells or tissues has broad clinical and practical ramifications with high translational value across numerous clinical applications.

Ascorbate and Iron Are Required for the Specification and Long-Term Self-Renewal of Human Skeletal Mesenchymal Stromal Cells.

The effects of ascorbate on adult cell fate specification remain largely unknown. Using our stepwise and chemically defined system to derive lateral mesoderm progenitors from human pluripotent stem cells (hPSCs), we found that ascorbate increased the expression of mesenchymal stromal cell (MSC) markers, purity of MSCs, the long-term self-renewal and osteochondrogenic capacity of hPSC-MSCs in vitro. Moreover, ascorbate promoted MSC specification in an iron-dependent fashion, but not in a redox-dependent manner. Further studies revealed that iron synergized with ascorbate to regulate hPSC-MSC histone methylation, promote their long-term self-renewal, and increase their osteochondrogenic capacity. We found that one of the histone demethylases affected by ascorbate, KDM4B, was necessary to promote the specification of hPSC-MSCs. This mechanistic understanding led to the metabolic optimization of hPSC-MSCs with an extended lifespan in vitro and the ability to fully repair cartilage defects upon transplantation in vivo. Our results highlight the importance of ascorbate and iron metabolism in adult human cell fate specification.

Enhancing the Efficacy of Stem Cell Therapy with Glycosaminoglycans.

Human mesenchymal stem cell (hMSC) therapy offers significant potential for osteochondral regeneration. Such applications require their ex vivo expansion in media frequently supplemented with fibroblast growth factor 2 (FGF2). Particular heparan sulfate (HS) fractions stabilize FGF2-FGF receptor complexes. We show that an FGF2-binding HS variant (HS8) accelerates the expansion of freshly isolated bone marrow hMSCs without compromising their naivety. Importantly, the repair of osteochondral defects in both rats and pigs is improved after treatment with HS8-supplemented hMSCs (MSCHS8), when assessed histologically, biomechanically, or by MRI. Thus, supplementing hMSC culture media with an HS variant that targets endogenously produced FGF2 allows the elimination of exogenous growth factors that may adversely affect their therapeutic potency.

A Heparan Sulfate Device for the Regeneration of Osteochondral Defects.

IMPACT STATEMENT: Repairing damaged joint cartilage remains a significant challenge. Treatment involving microfracture, tissue grafting, or cell therapy provides some benefit, but seldom regenerates lost articular cartilage. Providing a point-of-care solution that is cell and tissue free has the potential to transform orthopedic treatment for such cases. Glycosaminoglycans such as heparan sulfate (HS) are well suited for this purpose because they provide a matrix that enhances the prochondrogenic activities of growth factors normally found at sites of articular damage. In this study, we show the potential of a novel HS device, which is free of exogenous cells or growth factors, in regenerating osteochondral defects.

A roundtable on responsible innovation with autologous stem cells in Australia, Japan and Singapore.

We report on a roundtable event hosted in Singapore that sought to identify some of the ethical and regulatory challenges in translating autologous cell-based interventions, particularly those claiming to involve stem cells, into safe and effective therapies and to propose some solutions to encourage responsible innovation with these products. Challenges are identified in the three areas of cell manufacturing and processing, innovative uses of autologous cells in clinical practice and standards of evidence. Proposed solutions are discussed within a co-operative model of statutory laws and regulations that can enable product development with autologous cells and professional codes and standards that can encourage ethical conduct in clinical practice. Future research should be directed toward establishing regional networks for the development of internationally consistent standards in manufacturing and ethical codes of conduct for innovating with stem cells, and other autologous cells, and fostering ongoing exchange between jurisdictions.

Patellar tracking should be taken into account when measuring radiographic parameters for recurrent patellar instability.

PURPOSE: To date, many radiographic parameters on patellar instability have their measurements taken statically, and have not been studied in various degrees of flexion according to the patellar tracking. There are also limited data regarding the use of these parameters in predicting recurrent patellar dislocation. The current study aims to review the radiographic parameters of the patellofemoral joint in different degrees of knee flexion and to correlate them with the presence of recurrent instability. METHODS: A 10-year retrospective study was conducted on all patients who had computed tomography patellar-tracking scan done for patellar instability when aged 18 years or younger. The computed tomography patellar-tracking scans were performed with the knee in extension, 10° flexion, and 20° flexion. The axial radiographic parameters were evaluated at the patellar equator, roman arch, and distal patellar pole. Sagittal and coronal parameters were noted. Radiographic parameters were then correlated with recurrent patellar instability. RESULTS: The femoral sulcus angle and trochlear groove depth at the distal patellar pole in 10° knee flexion (p value 0.04 and 0.03, respectively) and patellar equator in 20° knee flexion (p value 0.02 and 0.03, respectively) had the most significant clinical correlations with recurrent instability on multivariate analysis. Other radiographic parameters found to have significant clinical correlation on univariate analysis include the patellar tilt angle, congruence angle, femoral sulcus angle, trochlear groove depth, and Wiberg's classification. CONCLUSIONS: As per the knee dynamics, axial radiographic parameters had the most significant correlation with recurrent patellar instability when measured at the distal patellar pole in 10° knee flexion and at the patellar equator in 20° knee flexion. Future axial radiographic evaluation of patellofemoral instability should then be performed at these degrees of knee flexion and axial cuts. Trochlear dysplasia, as measured by the femoral sulcus angle and trochlear groove depth, was the most significant predictor of recurrent patellar instability in the skeletally immature. Wiberg's classification was also a novel factor found to have clinical correlation with patellofemoral instability. LEVEL OF EVIDENCE: III.

Concise Review: Multifaceted Characterization of Human Mesenchymal Stem Cells for Use in Regenerative Medicine.

Mesenchymal stem cells (MSC) hold great potential for regenerative medicine because of their ability for self-renewal and differentiation into tissue-specific cells such as osteoblasts, chondrocytes, and adipocytes. MSCs orchestrate tissue development, maintenance and repair, and are useful for musculoskeletal regenerative therapies to treat age-related orthopedic degenerative diseases and other clinical conditions. Importantly, MSCs produce secretory factors that play critical roles in tissue repair that support both engraftment and trophic functions (autocrine and paracrine). The development of uniform protocols for both preparation and characterization of MSCs, including standardized functional assays for evaluation of their biological potential, are critical factors contributing to their clinical utility. Quality control and release criteria for MSCs should include cell surface markers, differentiation potential, and other essential cell parameters. For example, cell surface marker profiles (surfactome), bone-forming capacities in ectopic and orthotopic models, as well as cell size and granularity, telomere length, senescence status, trophic factor secretion (secretome), and immunomodulation, should be thoroughly assessed to predict MSC utility for regenerative medicine. We propose that these and other functionalities of MSCs should be characterized prior to use in clinical applications as part of comprehensive and uniform guidelines and release criteria for their clinical-grade production to achieve predictably favorable treatment outcomes for stem cell therapy. Stem Cells Translational Medicine 2017;6:2173-2185.

Role of High Tibial Osteotomy in Cartilage Regeneration - Is Correction of Malalignment Mandatory for Success?

Malalignment of the knee can cause debilitating symptoms such as pain, resulting in a decline in function and mobility. Surgical options that exist to address this problem include realignment osteotomies and joint replacements. Realignment osteotomies are the more appropriate options in certain patient populations, especially with regard to age and level of activity. Since a high tibial osteotomy (HTO) was first used to manage malalignment of the knee and osteoarthritis, different techniques involving the use of specialized implants have been developed and further refined to good effect. There has also since been much research into the field of cartilage restoration techniques, both as a standalone treatment option and as an adjunct to a realignment osteotomy. This review attempts to detail the origin and the evolution of HTO, particularly in regard to combining this tried and tested procedure with adjunct cartilage restoration techniques, and the overall patient outcomes. A literature search on PubMed was performed, and articles pertaining to the outcomes of the use of an HTO and cartilage restoration techniques were reviewed. The literature in this field indicates good outcomes in terms of objective measurements of cartilage regeneration (such as arthroscopic visualization and magnetic resonance imaging evaluation) and subjective patient outcome scoring systems (such as the International Knee Documentation Committee and Lysholm scores) with a realignment osteotomy alone, and studies have shown that patient outcomes can be further improved with the use of a cartilage restoration procedure as an adjunct.

Enhancement of mesenchymal stem cell chondrogenesis with short-term low intensity pulsed electromagnetic fields.

Pulse electromagnetic fields (PEMFs) have been shown to recruit calcium-signaling cascades common to chondrogenesis. Here we document the effects of specified PEMF parameters over mesenchymal stem cells (MSC) chondrogenic differentiation. MSCs undergoing chondrogenesis are preferentially responsive to an electromagnetic efficacy window defined by field amplitude, duration and frequency of exposure. Contrary to conventional practice of administering prolonged and repetitive exposures to PEMFs, optimal chondrogenic outcome is achieved in response to brief (10 minutes), low intensity (2 mT) exposure to 6 ms bursts of magnetic pulses, at 15 Hz, administered only once at the onset of chondrogenic induction. By contrast, repeated exposures diminished chondrogenic outcome and could be attributed to calcium entry after the initial induction. Transient receptor potential (TRP) channels appear to mediate these aspects of PEMF stimulation, serving as a conduit for extracellular calcium. Preventing calcium entry during the repeated PEMF exposure with the co-administration of EGTA or TRP channel antagonists precluded the inhibition of differentiation. This study highlights the intricacies of calcium homeostasis during early chondrogenesis and the constraints that are placed on PEMF-based therapeutic strategies aimed at promoting MSC chondrogenesis. The demonstrated efficacy of our optimized PEMF regimens has clear clinical implications for future regenerative strategies for cartilage.

Outcome of Patellar Tendon Versus 4-Strand Hamstring Tendon Autografts for Anterior Cruciate Ligament Reconstruction: A Systematic Review and Meta-analysis of Prospective Randomized Trials.

PURPOSE: To compare clinical outcomes of anterior cruciate ligament (ACL) reconstruction and investigate whether the clinical results of 4-strand hamstring tendon (HT) reconstruction are still inferior to that of the patellar tendon (PT). METHODS: We performed a comprehensive systematic review and meta-analysis of the English literature on PubMed, Scopus, Web of Science, and the Cochrane register for papers that compared clinical outcomes of PT versus HT for ACL reconstruction. Outcome measures analyzed included rate of rerupture, KT-1000, International Knee Documentation Committee grade, Lachman, pivot shift, Lysholm score, Tegner Activity Scale, anterior knee pain, and discomfort on kneeling. RESULTS: We included 19 studies from an initial 1,168 abstracts for the systematic review, and, eventually, 19 studies were included in the meta-analysis. The study population consisted of a total of 1784 patients. The average follow-up duration was 58.8 months. We found significant differences in favor of the HT technique in the domains of anterior knee pain, kneeling pain, and restriction in the range of active extension ("extension deficit"). We found no differences between the PT and HT technique in terms of rerupture rate. There were no clinically significant differences for the outcomes of Lysholm score and Tegner Activity Scale as well as the KT-1000 side-to-side at maximum manual force. CONCLUSIONS: Contemporary 4-strand HT ACL reconstruction is comparable with the PT technique in terms of clinical stability and postoperative functional status across most parameters studied. The HT technique carries lower risk of postoperative complications such as anterior knee pain, kneeling discomfort, and extension deficit. Primary ACL reconstruction using the 4-strand HT technique achieves clinical results that are comparable with the PT technique with significantly less postoperative complications. LEVEL OF EVIDENCE: Level I, systemic review and meta-analysis of Level I studies.

Affinity Selection of FGF2-Binding Heparan Sulfates for Ex Vivo Expansion of Human Mesenchymal Stem Cells.

The future of human mesenchymal stem cells (hMSCs) as a successful cell therapy relies on bioprocessing strategies to improve the scalability of these cells without compromising their therapeutic ability. The culture-expansion of hMSCs can be enhanced by supplementation with growth factors, particularly fibroblast growth factor 2 (FGF2). The biological activity of FGF2 is controlled through interactions with heparan sulfate (HS) that facilitates ligand-receptor complex formation. We previously reported on an FGF2-interacting HS variant (termed HS2) isolated from embryonic tissue by anionic exchange chromatography that increased the proliferation and potency of hMSCs. Here, we detail the isolation of an FGF2 affinity-purified HS variant (HS8) using a scalable platform technology previously employed to generate HS variants with increased affinity for BMP-2 or VEGF165 . This process used a peptide sequence derived from the heparin-binding domain of FGF2 as a substrate to affinity-isolate HS8 from a commercially available source of porcine mucosal HS. Our data show that HS8 binds to FGF2 with higher affinity than to FGF1, FGF7, BMP2, PDGF-BB, or VEGF165 . Also, HS8 protects FGF2 from thermal destabilization and increases FGF signaling and hMSC proliferation through FGF receptor 1. Long-term supplementation of cultures with HS8 increased both hMSC numbers and their colony-forming efficiency without adversely affecting the expression of hMSC-related cell surface antigens. This strategy further exemplifies the utility of affinity-purifying HS variants against particular ligands important to the stem cell microenvironment and advocates for their addition as adjuvants for the culture-expansion of hMSCs destined for cellular therapy. J. Cell. Physiol. 232: 566-575, 2017. © 2016 Wiley Periodicals, Inc.

The Combined Effect of Substrate Stiffness and Surface Topography on Chondrogenic Differentiation of Mesenchymal Stem Cells.

Stem cell differentiation is guided by contact with the physical microenvironment, influence by both topography and mechanical properties of the matrix. In this study, the combined effect of substratum nano-topography and mechanical stiffness in directing mesenchymal stem cell (MSC) chondrogenesis was investigated. Three polyesters of varying stiffness were thermally imprinted to create nano-grating or pillar patterns of the same dimension. The surface of the nano-patterned substrate was coated with chondroitin sulfate (CS) to provide an even surface chemistry, with cell-adhesive and chondro-inductive properties, across all polymeric substrates. The surface characteristic, mechanical modulus, and degradation of the CS-coated patterned polymeric substrates were analyzed. The cell morphology adopted on the nano-topographic surfaces were accounted by F-actin distribution, and correlated to the cell proliferation and chondrogenic differentiation outcomes. Results show that substratum stiffness and topographical cues affected MSC morphology and aggregation, and influenced the phenotypic development at the earlier stage of chondrogenic differentiation. Hyaline-like cartilage with middle/deep zone cartilage characteristics was generated on softer pillar surface, while on stiffer nano-pillar material MSCs showed potential to generate constituents of hyaline/fibro/hypertrophic cartilage. Fibro/superficial zone-like cartilage could be derived from nano-grating of softer stiffness, while stiffer nano-grating resulted in insignificant chondrogenesis. This study demonstrates the possibility of refining the phenotype of cartilage generated from MSCs by manipulating surface topography and material stiffness.

Long-term Follow-up of Pulmonary Function and Scoliosis in Patients With Duchenne's Muscular Dystrophy and Spinal Muscular Atrophy.

BACKGROUND: Spine surgery for neuromuscular scoliosis in patients with Duchenne's Muscular Dystrophy (DMD) and Spinal Muscular Atrophy (SMA) remained controversial. This study aimed to review the long-term results of spine surgery and its effect on pulmonary function in these patients. METHODS: A retrospective review was conducted for the above patients who had undergone surgery from 1990 to 2006 in a tertiary hospital. Their yearly lung function tests, clinical records, and x-ray films before and after surgery were reviewed. All patients had at least 2 lung function tests performed before surgery and at least 3 lung function tests performed after surgery. Records of perioperative pulmonary infections that resulted in hospital admissions were also retrieved from the hospital computer system. RESULTS: Forty patients were reviewed: 29 with DMD, 11 with SMA. The mean follow-up period was 11.6 years. For patients with DMD, the mean correction of Cobb's angle from surgery was 34.1 degrees. The rate of decline of the predicted forced vital capacity preoperatively was 7.80% per year, and was reduced to 4.26% per year postoperatively (P<0.001). For patients with SMA, the mean correction of Cobb's angle from surgery was 44.1 degrees. The rate of decline of the predicted forced vital capacity preoperatively was 5.31% per year, and was reduced to 1.77% per year postoperatively (P<0.001). For both DMD and SMA patients, the difference between the rate of preoperative and postoperative pulmonary infections that resulted in hospital admission were, however, not significant (P=0.433 and 0.452, respectively). CONCLUSIONS: Scoliosis surgery in patients with DMD and SMA results in a long-term decreased rate of decline in pulmonary function over a follow-up period of more than 10 years. The level of the apical vertebrae of the scoliosis did not demonstrate a significant trend on the pulmonary function. The frequency of chest infections did not improve by scoliosis surgery. LEVEL OF SIGNIFICANCE: Level III­Retrospective study.

Aarhus Regenerative Orthopaedics Symposium (AROS).

The combination of modern interventional and preventive medicine has led to an epidemic of ageing. While this phenomenon is a positive consequence of an improved lifestyle and achievements in a society, the longer life expectancy is often accompanied by decline in quality of life due to musculoskeletal pain and disability. The Aarhus Regenerative Orthopaedics Symposium (AROS) 2015 was motivated by the need to address regenerative challenges in an ageing population by engaging clinicians, basic scientists, and engineers. In this position paper, we review our contemporary understanding of societal, patient-related, and basic science-related challenges in order to provide a reasoned roadmap for the future to deal with this compelling and urgent healthcare problem.

Effect of heparin on the biological properties and molecular signature of human mesenchymal stem cells.

Chronic use of heparin as an anti-coagulant for the treatment of thrombosis or embolism invokes many adverse systemic events including thrombocytopenia, vascular reactions and osteoporosis. Here, we addressed whether adverse effects might also be directed to mesenchymal stem cells that reside in the bone marrow compartment. Harvested human bone marrow-derived mesenchymal stem cells (hMSCs) were exposed to varying doses of heparin and their responses profiled. At low doses (<200 ng/ml), serial passaging with heparin exerted a variable effect on hMSC proliferation and multipotentiality across multiple donors, while at higher doses (≥ 100 µg/ml), heparin supplementation inhibited cell growth and increased both senescence and cell size. Gene expression profiling using cDNA arrays and RNA-seq analysis revealed pleiotropic effects of low-dose heparin on signaling pathways essential to hMSC growth and differentiation (including the TGFß/BMP superfamily, FGFs, and Wnts). Cells serially passaged in low-dose heparin possess a donor-dependent gene signature that reflects their altered phenotype. Our data indicate that heparin supplementation during the culturing of hMSCs can alter their biological properties, even at low doses. This warrants caution in the application of heparin as a culture supplement for the ex vivo expansion of hMSCs. It also highlights the need for careful evaluation of the bone marrow compartment in patients receiving chronic heparin treatment.

Establishing criteria for human mesenchymal stem cell potency.

This study sought to identify critical determinants of mesenchymal stem cell (MSC) potency using in vitro and in vivo attributes of cells isolated from the bone marrow of age- and sex-matched donors. Adherence to plastic was not indicative of potency, yet capacity for long-term expansion in vitro varied considerably between donors, allowing the grouping of MSCs from the donors into either those with high-growth capacity or low-growth capacity. Using this grouping strategy, high-growth capacity MSCs were smaller in size, had greater colony-forming efficiency, and had longer telomeres. Cell-surface biomarker analysis revealed that the International Society for Cellular Therapy (ISCT) criteria did not distinguish between high-growth capacity and low-growth capacity MSCs, whereas STRO-1 and platelet-derived growth factor receptor alpha were preferentially expressed on high-growth capacity MSCs. These cells also had the highest mean expression of the mRNA transcripts TWIST-1 and DERMO-1. Irrespective of these differences, both groups of donor MSCs produced similar levels of key growth factors and cytokines involved in tissue regeneration and were capable of multilineage differentiation. However, high-growth capacity MSCs produced approximately double the volume of mineralized tissue compared to low-growth capacity MSCs when assessed for ectopic bone-forming ability. The additional phenotypic criteria presented in this study when combined with the existing ISCT minimum criteria and working proposal will permit an improved assessment of MSC potency and provide a basis for establishing the quality of MSCs prior to their therapeutic application.

Evidence-based status of osteochondral cylinder transfer techniques: a systematic review of level I and II studies.

PURPOSE: Our purpose was to examine the Level I and II evidence for the use of osteochondral cylinder transfer technique (OCT) for cartilage repair. METHODS: A literature search was carried out for Level I and II evidence studies on cartilage repair using the PubMed database. All the studies that involved OCT were identified. Only Level I and II studies that compared OCT to other modalities of treatment such as microfracture (MF) and autologous chondrocyte implantation (ACI) were selected. RESULTS: A total of 8 studies matched the selection criteria with 2 Level I and 6 Level II studies. Four studies compared OCT with MF, 3 compared OCT with ACI, and one compared all 3 techniques. Of 3 studies, 4 came from a single center. Mean age of patients ranged from 24 to 33 years, and mean follow-up ranged from 9 to 124 months. The studies from the single center showed superior results from OCT over MF, especially in younger patients, with one study having long-term follow-up of 10 years. They also showed an earlier return to sports. The size of the lesions were small (average < 3 cm(2)). The 4 other independent studies did not show any difference between OCT and ACI, with one study showing inferior outcome in the OCT group. Magnetic resonance imaging (MRI) showed good osseous integration of the osteochondral plugs to the subchondral bone. Histologic examination showed that there was hyaline cartilage in the transplanted osteochondral plugs but no hyaline cartilage between the plugs. CONCLUSIONS: From the studies of a single center, OCT had an advantage over MF in younger patients with small chondral lesions. Comparison of outcomes between OCT and ACI showed no significant difference in 2 studies and contrasting results in another 2 studies. There was insufficient evidence for long-term results for OCT. LEVEL OF EVIDENCE: Level II, systematic review of Level I and II studies.

Substrate topography determines the fate of chondrogenesis from human mesenchymal stem cells resulting in specific cartilage phenotype formation.

To reproduce a complex and functional tissue, it is crucial to provide a biomimetic cellular microenvironment that not only incorporates biochemical cues, but also physical features including the nano-topographical patterning, for cell/matrix interaction. We developed spatially-controlled nano-topography in the form of nano-pillar, nano-hole and nano-grill on polycaprolactone surface via thermal nanoimprinting. The effects of chondroitin sulfate-coated nano-topographies on cell characteristics and chondrogenic differentiation of human mesenchymal stem cell (MSC) were investigated. Our results show that various nano-topographical patterns triggered changes in MSC morphology and cytoskeletal structure, affecting cell aggregation and differentiation. Compared to non-patterned surface, nano-pillar and nano-hole topography enhanced MSC chondrogenesis and facilitated hyaline cartilage formation. MSCs experienced delayed chondrogenesis on nano-grill topography and were induced to fibro/superficial zone cartilage formation. This study demonstrates the sensitivity of MSC differentiation to surface nano-topography and highlights the importance of incorporating topographical design in scaffolds for cartilage tissue engineering. From the clinical editor: These authors have developed spatially-controlled nano-topography in the form of nano-pillar, nano-hole and nano-grill on polycaprolactone surface via thermal nanoimprinting, and the effects of chondroitin sulfate-coated nano-topographies on cell characteristics and chondrogenic differentiation of human mesenchymal stem cells (MSC) were investigated. It has been concluded that MSC differentiation is sensitive to surface nano-topography, and certain nano-imprinted surfaces are more useful than others for cartilage tissue engineering.