Cartilage Repair With Autologous Bone Marrow Mesenchymal Stem Cell Transplantation: Review of Preclinical and Clinical Studies

Decellularized laser micro-patterned osteochondral implants exhibit zonal recellularization and self-fixing for osteochondral regeneration in a goat model

Background

Osteochondral regeneration has long been recognized as a complex and challenging project in the field of tissue engineering. In particular, reconstructing the osteochondral interface is crucial for determining the effectiveness of the repair. Although several artificial layered or gradient scaffolds have been developed recently to simulate the natural interface, the functions of this unique structure have still not been fully replicated. In this paper, we utilized laser micro-patterning technology (LMPT) to modify the natural osteochondral "plugs" for use as grafts and aimed to directly apply the functional interface unit to repair osteochondral defects in a goat model.

Methods

For in vitro evaluations, the optimal combination of LMPT parameters was confirmed through mechanical testing, finite element analysis, and comparing decellularization efficiency. The structural and biological properties of the laser micro-patterned osteochondral implants (LMP-OI) were verified by measuring the permeability of the interface and assessing the recellularization processes. In the goat model for osteochondral regeneration, a conical frustum-shaped defect was specifically created in the weight-bearing area of femoral condyles using a customized trephine with a variable diameter. This unreported defect shape enabled the implant to properly self-fix as expected.

Results

The micro-patterning with the suitable pore density and morphology increased the permeability of the LMP-OIs, accelerated decellularization, maintained mechanical stability, and provided two relative independent microenvironments for subsequent recellularization. The LMP-OIs with goat's autologous bone marrow stromal cells in the cartilage layer have securely integrated into the osteochondral defects. At 6 and 12 months after implantation, both imaging and histological assessments showed a significant improvement in the healing of the cartilage and subchondral bone.

Conclusion

With the natural interface unit and zonal recellularization, the LMP-OI is an ideal scaffold to repair osteochondral defects especially in large animals.

The translational potential of this article

These findings suggest that such a modified xenogeneic osteochondral implant could potentially be explored in clinical translation for treatment of osteochondral injuries. Furthermore, trimming a conical frustum shape to the defect region, especially for large-sized defects, may be an effective way to achieve self-fixing for the implant.

Autologous Mesenchymal Stromal Cells Immobilized in Plasma-Based Hydrogel for the Repair of Articular Cartilage Defects in a Large Animal Model

The treatment of cartilage defects in trauma injuries and degenerative diseases represents a challenge for orthopedists. Advanced mesenchymal stromal cell (MSC)-based therapies are currently of interest for the repair of damaged cartilage. However, an approved system for MSC delivery and maintenance in the defect is still missing. This study aimed to evaluate the effect of autologous porcine bone marrow MSCs anchored in a commercially available polyglycolic acid-hyaluronan scaffold (Chondrotissue®) using autologous blood plasma-based hydrogel in the repair of osteochondral defects in a large animal model. The osteochondral defects were induced in twenty-four minipigs with terminated skeletal growth. Eight animals were left untreated, eight were treated with Chondrotissue® and eight received Chondrotissue® loaded with MSCs. The animals were terminated 90 days after surgery. Macroscopically, the untreated defects were filled with newly formed tissue to a greater extent than in the other groups. The histological evaluations showed that the defects treated with Chondrotissue® and Chondrotissue® loaded with pBMSCs contained a higher amount of hyaline cartilage and a lower amount of connective tissue, while untreated defects contained a higher amount of connective tissue and a lower amount of hyaline cartilage. In addition, undifferentiated connective tissue was observed at the edges of defects receiving Chondrotissue® loaded with MSCs, which may indicate the extracellular matrix production by transplanted MSCs. The immunological analysis of the blood samples revealed no immune response activation by MSCs application. This study demonstrated the successful and safe immobilization of MSCs in commercially available scaffolds and defect sites for cartilage defect repair.

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.

Low-intensity pulsed ultrasound promotes mesenchymal stem cell transplantation-based articular cartilage regeneration via inhibiting the TNF signaling pathway

BACKGROUND

Mesenchymal stem cell (MSC) transplantation therapy is highly investigated for the regenerative repair of cartilage defects. Low-intensity pulsed ultrasound (LIPUS) has the potential to promote chondrogenic differentiation of MSCs. However, its underlying mechanism remains unclear. Here, we investigated the promoting effects and mechanisms underlying LIPUS stimulation on the chondrogenic differentiation of human umbilical cord mesenchymal stem cells (hUC-MSCs) and further evaluated its regenerative application value in articular cartilage defects in rats.

METHODS

LIPUS was applied to stimulate cultured hUC-MSCs and C28/I2 cells in vitro. Immunofluorescence staining, qPCR analysis, and transcriptome sequencing were used to detect mature cartilage-related markers of gene and protein expression for a comprehensive evaluation of differentiation. Injured articular cartilage rat models were established for further hUC-MSC transplantation and LIPUS stimulation in vivo. Histopathology and H&E staining were used to evaluate the repair effects of the injured articular cartilage with LIPUS stimulation.

RESULTS

The results showed that LIPUS stimulation with specific parameters effectively promoted the expression of mature cartilage-related genes and proteins, inhibited TNF-α gene expression in hUC-MSCs, and exhibited anti-inflammation in C28/I2 cells. In addition, the articular cartilage defects of rats were significantly repaired after hUC-MSC transplantation and LIPUS stimulation.

CONCLUSIONS

Taken together, LIPUS stimulation could realize articular cartilage regeneration based on hUC-MSC transplantation due to the inhibition of the TNF signaling pathway, which is of clinical value for the relief of osteoarthritis.

Targeted therapy in Coronavirus disease 2019 (COVID-19): Implication from cell and gene therapy to immunotherapy and vaccine

Severe acute respiratory syndrome Coronavirus 2 (SARS-CoV-2) is a highly pathogenic and transmissible virus. Infection caused by SARS-CoV-2 known as Coronavirus disease 2019 (COVID-19) can be severe, especially among high risk populations affected of underlying medical conditions. COVID-19 is characterized by the severe acute respiratory syndrome, a hyper inflammatory syndrome, vascular injury, microangiopathy and thrombosis. Antiviral drugs and immune modulating methods has been evaluated. So far, a particular therapeutic option has not been approved for COVID-19 and a variety of treatments have been studied for COVID-19 including, current treatment such as oxygen therapy, corticosteroids, antiviral agents until targeted therapy and vaccines which are diverse in each patient and have various outcomes. According to the findings of different in vitro and in vivo studies, some novel approach such as gene editing, cell based therapy, and immunotherapy may have significant potential in the treatment of COVID-19. Based on these findings, this paper aims to review the different strategies of treatment against COVID-19 and provide a summary from traditional and newer methods in curing COVID-19.

YY1-induced lncRNA XIST inhibits cartilage differentiation of BMSCs by binding with TAF15 to stabilizing FUT1 expression

Introduction

The functional roles and mechanism of the XIST in osteoarthritis and the chondrogenic differentiation of BMSCs were clarified.

Methods

The expression levels of XIST, TAF15, FUT1 and YY1 were detected through quantitative RT-PCR. The protein expression of Sox9, ACAN, COL2A1 and FUT1 were detected by western blot and immunohistochemistry. The damage of cartilage tissue was detected by HE staining, and Safranin O-fast green. Alcian-Blue and Alizarin red S staining were performed to evaluate BMSCs chondrogenic differentiation. The relationship between XIST and TAF15, XIST and TAF15 were analyzed by RNA immunoprecipitation assay. Luciferase reporter assays and chromatin immunoprecipitation were performed to detect the interaction relationship between XIST and YY1. In addition, osteoarthritis mice were built to assess the function of XIST in vivo.

Results

The levels of XIST, TAF15 and FUT1 were upregulated in cartilage tissues from osteoarthritis patient. The level of XIST was decreased in BMSCs during chondrogenic differentiation. XIST overexpression inhibited the chondrogenic differentiation of BMSCs. Moreover, silencing of FUT1 reversed the effects of XIST overexpression on BMSCs chondrogenic differentiation. Mechanistically, in BMSCs, YY1 induced the expression of XIST in BMSCs, and XIST regulated FUT1 mRNA stability through targeting TAF15. Furthermore, silencing of XIST alleviated the symptoms of cartilage injury in OA mice.

Conclusion

Taken together, these results suggested that YY1 induced XIST was closely related to the chondrogenic differentiation of BMSCs and the progression of osteoarthritis by TAF15/FUT1 axis, and may be a new OA therapeutic target.

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XIST and TAF15 expression were upregulated in osteoarthritis.

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Overexpression of XIST suppressed the chondrogenic differentiation of BMSCs.

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XIST regulated BMSCs chondrogenic differentiation through enhancing FUT1 mRNA stability via TAF15.

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XIST silencing relieved cartilage damage in OA mice.

Methods of Modification of Mesenchymal Stem Cells and Conditions of Their Culturing for Hyaline Cartilage Tissue Engineering

The use of mesenchymal stromal cells (MSCs) for tissue engineering of hyaline cartilage is a topical area of regenerative medicine that has already entered clinical practice. The key stage of this procedure is to create conditions for chondrogenic differentiation of MSCs, increase the synthesis of hyaline cartilage extracellular matrix proteins by these cells and activate their proliferation. The first such works consisted in the indirect modification of cells, namely, in changing the conditions in which they are located, including microfracturing of the subchondral bone and the use of 3D biodegradable scaffolds. The most effective methods for modifying the cell culture of MSCs are protein and physical, which have already been partially introduced into clinical practice. Genetic methods for modifying MSCs, despite their effectiveness, have significant limitations. Techniques have not yet been developed that allow studying the effectiveness of their application even in limited groups of patients. The use of MSC modification methods allows precise regulation of cell culture proliferation, and in combination with the use of a 3D biodegradable scaffold, it allows obtaining a hyaline-like regenerate in the damaged area. This review is devoted to the consideration and comparison of various methods used to modify the cell culture of MSCs for their use in regenerative medicine of cartilage tissue.

Second-look arthroscopic cartilage status is related to intermediate-term outcomes after medial opening-wedge high tibial osteotomy

AIMS

To determine the relationship between articular cartilage status and clinical outcomes after medial opening-wedge high tibial osteotomy (MOHTO) for medial compartmental knee osteoarthritis at intermediate follow-up.

METHODS

We reviewed 155 patients (155 knees) who underwent MOHTO from January 2008 to December 2016 followed by second-look arthroscopy with a mean 5.3-year follow-up (2.0 to 11.7). Arthroscopic findings were assessed according to the International Cartilage Repair Society (ICRS) Cartilage Repair Assessment (CRA) grading system. Patients were divided into two groups based on the presence of normal or nearly normal quality cartilage in the medial femoral condyle: good (second-look arthroscopic) status (ICRS grade I or II; n = 70), and poor (second-look arthroscopic) status (ICRS grade III or IV; n = 85) groups at the time of second-look arthroscopy. Clinical outcomes were assessed using the International Knee Documentation Committee (IKDC) score, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and 36-Item Short Form survey.

RESULTS

Significant improvements in all clinical outcome categories were found between the preoperative and second-look arthroscopic assessments in both groups (p < 0.001). At the latest follow-up, the mean IKDC and WOMAC scores in the good status group further improved compared with those at the time of second-look arthroscopic surgery (p < 0.001), which was not shown in the poor status group. The mean IKDC (good status, 72.8 (SD 12.5); poor status, 64.7 (SD 12.1); p = 0.002) and mean WOMAC scores (good status, 15.7 (SD 10.8); poor status, 21.8 (SD 13.6); p = 0.004) significantly differed between both groups at the latest follow-up. Moreover, significant correlations were observed between ICRS CRA grades and IKDC scores (negative correlation; p < 0.001) and WOMAC scores (positive correlation; p < 0.001) at the latest follow-up. Good cartilage status was found more frequently in knees with the desired range of 2° to 6° valgus correction than in those with corrections outside this range (p = 0.019).

CONCLUSION

Second-look arthroscopic cartilage status correlated with clinical outcomes after MOHTO at intermediate-term follow-up, despite the relatively small clinical differences between groups. Cite this article: Bone Joint J 2021;103-B(11):1686-1694.

Introduction of Cells into Porous Poly-l-Lactic Acid Scaffolds Using Impregnation Techniques

Porous materials containing cells-prepared via cell seeding on scaffolds or gelation of cell-containing solutions-have been widely studied to investigate tissue regeneration and three-dimensional cultures. However, these methods cannot introduce cells into porous materials that have low water absorption or scaffolds that require cytotoxic solvents or processes for their production. In this study, first, three different impregnation treatments conditions (vacuum, pressure, and vacuum pressure impregnation: VPI) were applied to cell suspensions to evaluate the effect of each treatment on cells. Following all three treatments, fibroblasts adhered to the cell culture dish and proliferated in the same manner as untreated cells, which confirmed that the three impregnation treatments did not affect cell function. Second, cells were introduced into a poly-l-lactic acid (PLA) scaffold, which has low water absorption, using the same impregnation treatments. The PLA scaffolds subjected to the three impregnation treatments that exhibited a significantly greater amount of DNA than those subjected to immersion treatments and showed increasing amounts of DNA in the order vacuum treatment > VPI treatment > pressure treatment. Furthermore, the amount of DNA in the vacuum-treated and VPI-treated PLA scaffolds increased on the first, third, and fifth days of culture, and it was confirmed that the cells introduced into the PLA scaffolds proliferated. These results suggest that vacuum and VPI treatments may be useful methods for introducing cells into porous materials.

Nanosecond pulsed electric fields enhance mesenchymal stem cells differentiation via DNMT1-regulated OCT4/NANOG gene expression

Background

Multiple strategies have been proposed to promote the differentiation potential of mesenchymal stem cells (MSCs), which is the fundamental property in tissue formation and regeneration. However, these strategies are relatively inefficient that limit the application. In this study, we reported a novel and efficient strategy, nanosecond pulsed electric fields (nsPEFs) stimulation, which can enhance the trilineage differentiation potential of MSCs, and further explained the mechanism behind.

Methods

We used histological staining to screen out the nsPEFs parameters that promoted the trilineage differentiation potential of MSCs, and further proved the effect of nsPEFs by detecting the functional genes. In order to explore the corresponding mechanism, we examined the expression of pluripotency genes and the methylation status of their promoters. Finally, we targeted the DNA methyltransferase which was affected by nsPEFs.

Results

The trilineage differentiation of bone marrow-derived MSCs was significantly enhanced in vitro by simply pre-treating with 5 pulses of nsPEFs stimulation (energy levels as 10 ns, 20 kV/cm; 100 ns, 10 kV/cm), due to that the nsPEFs demethylated the promoters of stem cell pluripotency genes OCT4 and NANOG through instantaneous downregulation of DNA methylation transferase 1 (DNMT1), thereby increasing the expression of OCT4 and NANOG for up to 3 days, and created a treatment window period of stem cells.

Conclusions

In summary, nsPEFs can enhance MSCs differentiation via the epigenetic regulation and could be a safe and effective strategy for future stem cell application.

Intra-articular xenogeneic mesenchymal stem cell-based therapy increases CD4+CD25+ cells in synovial fluid

Osteoarthritis (OA) is a chronic joint disease afflicting a substantial portion of the world's population with no currently available cure. Mesenchymal stem cell (MSC)-based therapies have been observed to have a mild beneficial effect in OA but the mechanism behind their action remains unclear. This study aimed to identify the lymphocytic response to a xenogeneic human umbilical cord-derived MSC-based cell therapy. A unilateral medial meniscal release model was employed in an ovine model of post-traumatic OA, with the contralateral limb employed as the control. A dose of 1.0 × 10⁷ MSCs was administered to a subset of the OA group as well as to a normal sham-operated group. Synovial fluid was aspirated periodically for 13 weeks for flow cytometry analysis. At the termination of the study the stifle joints were collected and analyzed for potential pathologic changes. Cell therapy induced a transient influx of CD4⁺ leukocytes; there was a similar significant increase in the proportion of CD4⁺CD25⁺ and CD4⁺CD25^hi leukocytes in response to cell therapy, the latter being a subset that may be composed of regulatory T cells. There was no significant effect of the cell therapy treatment on the proportion of synovial fluid-derived CD8⁺ cells or BAQ44A⁺ B cells. iNOS expression of intimal lining macrophages was evident but reduced in the cell therapy OA group suggesting macrophage phenotype transformation. There were no inflammatory or histological changes that could be attributed to the cell therapy. Cell therapy induced chemotaxis of CD4⁺ cells to the joint but these cells were not associated with pathological changes, despite their expression of activation markers (CD25⁺).

In situ repair abilities of human umbilical cord-derived mesenchymal stem cells and autocrosslinked hyaluronic acid gel complex in rhesus monkeys with intrauterine adhesion

Increasing occurrence of moderate to severe intrauterine adhesion (IUA) is seriously affecting the quality of human life. The aim of the study was to establish IUA models in nonhuman primates and to explore the dual repair effects of human umbilical cord-derived mesenchymal stem cells (huMSCs) loaded on autocrosslinked hyaluronic acid gel (HA-GEL) on endometrial damage and adhesion. Here, we recorded the menstrual cycle data in detail with uterine cavities observed and endometrial tissues detected after intervention, and the thicker endometria, decreased amount of fibrotic formation, increased number of endometrium glands, etc., suggested that both HA-GEL and huMSC/HA-GEL complexes could partially repair IUA caused by mechanical injury, but huMSC/HA-GEL complex transplantation had notable dual repair effects: a reliable antiadhesion property and the promotion of endometrial regeneration.

Phenotype changes of subchondral plate osteoblasts based on a rat model of ovariectomy-induced osteoarthritis

Background

Osteoarthritis (OA) is prevalent in postmenopausal women. Subchondral bone in ovariectomized (OVX) rats might play a more important role in cartilage degeneration compared with other types of OA. How subchondral osteoblast changes in OVX rats is still unclear. Understanding of osteoblast changes obtained from OVX subchondral bone might be helpful to clarify pathogenesis of OVX-OA.

Methods

Female Sprague-Dawley rats were randomly divided into two groups: Sham (n=20) and OVX (n=20). Serum levels of Alkaline phosphatase (ALP) and C-telopeptide of type I collagen (CTX-I) were measured every one or two weeks. All rats were executed at week 9 post surgery. The weight of rats and the wet weight of uterus were assessed. Micro-computed Tomography (micro-CT) was used to analyze the knee microstructure, and toluidine blue staining was employed to evaluate cartilage erosion. Subchondral osteoblast proliferation ability by cell counting kit-8 assay, osteogenic genes expressions by reverse transcription polymerase chain reaction (RT-PCR), differentiation and mineralization ability by ALP staining and alizarin red staining were evaluated and compared between Sham and OVX.

Results

Ovariectomy induced significant increases of serum ALP and CTX-I as early as at week 2. At week 9 after surgery, the body weight of OVX rats was significantly increased, and uterus weight of OVX rats was remarkably decreased. OVX rats demonstrated significant subchondral bone change and cartilage erosion compared with Sham rats. mRNA levels of early markers of osteogenic differentiation (ALP, type I collagen, Runx2) were enhanced in OVX rats, but the late marker (osteocalcin) was not significantly different. ALP activity of osteoblasts increased, but the mineralization capacity decreased in OVX rats.

Conclusions

Subchondral osteoblasts in OVX rats exhibited different proliferation, differentiation and mineralization abilities from normal counterparts.

Histone ChIP-Seq identifies differential enhancer usage during chondrogenesis as critical for defining cell-type specificity

Epigenetic mechanisms are known to regulate gene expression during chondrogenesis. In this study, we have characterized the epigenome during the in vitro differentiation of human mesenchymal stem cells (hMSCs) into chondrocytes. Chromatin immunoprecipitation followed by next‐generation sequencing (ChIP‐seq) was used to assess a range of N‐terminal posttranscriptional modifications (marks) to histone H3 lysines (H3K4me3, H3K4me1, H3K27ac, H3K27me3, and H3K36me3) in both hMSCs and differentiated chondrocytes. Chromatin states were characterized using histone ChIP‐seq and cis‐regulatory elements were identified in chondrocytes. Chondrocyte enhancers were associated with chondrogenesis‐related gene ontology (GO) terms. In silico analysis and integration of DNA methylation data with chondrogenesis chromatin states revealed that enhancers marked by histone marks H3K4me1 and H3K27ac were de‐methylated during in vitro chondrogenesis. Similarity analysis between hMSC and chondrocyte chromatin states defined in this study with epigenomes of cell‐types defined by the Roadmap Epigenomics project revealed that enhancers are more distinct between cell‐types compared to other chromatin states. Motif analysis revealed that the transcription factor SOX9 is enriched in chondrocyte enhancers. Luciferase reporter assays confirmed that chondrocyte enhancers characterized in this study exhibited enhancer activity which may be modulated by DNA methylation and SOX9 overexpression. Altogether, these integrated data illustrate the cross‐talk between different epigenetic mechanisms during chondrocyte differentiation.

Efficacy of autologous bone marrow mesenchymal stem cells in the treatment of knee osteoarthritis and their effects on the expression of serum TNF-α and IL-6

OBJECTIVE

To investigate the clinical efficacy of autologous bone marrow mesenchymal stem cell (BMSC) transplantation in the treatment of knee osteoarthritis (OA) and its effect on the expression of serum TNF-α and IL-6.

METHODS

The clinical data of 86 patients with knee OA treated in the Shanghai East Hospital Tongji University from March 2015 to March 2017 were analyzed retrospectively. Observation group (treated with intraarticular injection of autologous BMSC); Control group (treated with arthroscopic debridement and injected with sodium hyaluronate). The patients were followed up for 1 year after treatment, the clinical efficacy was evaluated by the Lysholm Knee Scale (Lysholm), Visual analog scale (VAS), and the expression of serum TNF-α and IL-6 was detected by ELISA.

RESULTS

The expression of TNF-α and IL-6 at 6 and 12 months after surgery was significantly lower than that before surgery (P<0.05).

CONCLUSIONS

The Lysholm score and total effective rate of knee OA patients underwent BMSC transplantation are better than that of joint debridement, while the VAS score was lower than that of joint debridement. Meanwhile, BMSC transplantation seems to reduce the postoperative inflammatory reaction.

The Manufacture of GMP-Grade Bone Marrow Stromal Cells with Validated In Vivo Bone-Forming Potential in an Orthopedic Clinical Center in Brazil

In vitro-expanded bone marrow stromal cells (BMSCs) have long been proposed for the treatment of complex bone-related injuries because of their inherent potential to differentiate into multiple skeletal cell types, modulate inflammatory responses, and support angiogenesis. Although a wide variety of methods have been used to expand BMSCs on a large scale by using good manufacturing practice (GMP), little attention has been paid to whether the expansion procedures indeed allow the maintenance of critical cell characteristics and potency, which are crucial for therapeutic effectiveness. Here, we described standard procedures adopted in our facility for the manufacture of clinical-grade BMSC products with a preserved capacity to generate bone in vivo in compliance with the Brazilian regulatory guidelines for cells intended for use in humans. Bone marrow samples were obtained from trabecular bone. After cell isolation in standard monolayer flasks, BMSC expansion was subsequently performed in two cycles, in 2- and 10-layer cell factories, respectively. The average cell yield per cell factory at passage 1 was of 21.93 ± 12.81 × 106 cells, while at passage 2, it was of 83.05 ± 114.72 × 106 cells. All final cellular products were free from contamination with aerobic/anaerobic pathogens, mycoplasma, and bacterial endotoxins. The expanded BMSCs expressed CD73, CD90, CD105, and CD146 and were able to differentiate into osteogenic, chondrogenic, and adipogenic lineages in vitro. Most importantly, nine out of 10 of the cell products formed bone when transplanted in vivo. These validated procedures will serve as the basis for in-house BMSC manufacturing for use in clinical applications in our center.

Equivalent 10-Year Outcomes After Implantation of Autologous Bone Marrow-Derived Mesenchymal Stem Cells Versus Autologous Chondrocyte Implantation for Chondral Defects of the Knee

BACKGROUND

The use of bone marrow-derived mesenchymal stem cells (BMSCs) in cartilage repair procedures circumvents some of the limitations of autologous chondrocyte implantation (ACI), but long-term outcomes for this newer procedure are lacking. The authors previously reported comparable outcomes for the 2 procedures at 2-year follow-up.

PURPOSE/HYPOTHESIS

The purpose was to compare the long-term clinical outcomes of ACI versus BMSCs. It was hypothesized that there would be no significant difference between the groups in terms of patient-reported outcome scores and safety outcomes at 10-year follow-up.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

Seventy-two patients who underwent either ACI or BMSC implantation-matched in terms of age and lesion site- were followed up to a median of at least 10 years. Patients were assessed with the 36-item Short Form Health Survey (SF-36), the International Knee Documentation Committee knee evaluation form, the Lysholm Knee Score, and the Tegner Activity Scale. In addition, information was obtained regarding any additional surgical procedures as well as safety data, with particular attention to infection and tumor formation.

RESULTS

There was an improvement in all patient-reported outcomes scores apart from the Mental Component Summary of the SF-36 after cartilage repair surgery. There was no significant difference in any of the patient-reported outcomes between cohorts at any time point. Six and 5 patients in the ACI and BMSC groups, respectively, underwent subsequent surgical procedures, including 1 total knee replacement in the BMSC group. None of the patients in either group developed any deep infection or tumor within the follow-up period.

CONCLUSION

BMSC implantation used for the treatment of chondral defects of the knee appears to result in equivalent clinical outcomes to first-generation ACI at up to 10 years, with no apparent increased tumor formation risk.

A Mini-Review: The Therapeutic Potential of Bone Marrow Mesenchymal Stem Cells and Relevant Signaling Cascades

Bone marrow mesenchymal stem cells (BMSCs) characterized multi-directional differentiation, low immunogenicity and high portability, serve as ideal "seed cells" in ophthalmological disease therapy. Therefore, in this mini-review, we examined the recent literature concerning the potential application of BMSCs for the treatment of ophthalmological disease, that includes: the cellular activity of BMSCs transplantation, migration and homing, as well as the immuno-modulatory and antiinflammatory effects of BMSCs and signaling involved. Each aspect is complementary to the others and together these aspects promoted further understanding of the potential use of BMSCs in treating ophthalmological diseases.

Therapeutic effect of transplantation of human bone marrow‑derived mesenchymal stem cells on neuron regeneration in a rat model of middle cerebral artery occlusion

Human bone marrow-derived mesenchymal stromal cells (hBMSCs) have been revealed to be beneficial for the regeneration of tissues and cells in several diseases. The present study aimed to elucidate the mechanisms underlying the effect of hBMSC transplantation on neuron regeneration in a rat model of middle cerebral artery occlusion (MCAO). The hBMSCs were isolated, cultured and identified. A rat model of MCAO was induced via the modified Longa method. Neurological severity scores (NSS) were adopted for the evaluation of neuronal function in the model rats after cell transplantation. Next, the expression levels of nestin, β-III-tubulin (β-III-Tub), glial fibrillary acidic protein (GFAP), HNA and neuronal nuclear antigen (NeuN) were examined, as well as the positive expression rates of human neutrophil alloantigen (HNA), nestin, NeuN, β-III-Tub and GFAP. The NSS, as well as the mRNA and protein expression of nestin, decreased at the 1st, 2nd, 4 and 8th weeks, while the mRNA and protein expression of NeuN, β-III-Tub and GFAP increased with time. In addition, after treatment, the MCAO rats showed decreased NSS and mRNA and protein expression of nestin, but elevated mRNA and protein expression of NeuN, β-III-Tub and GFAP at the 2nd, 4 and 8th weeks, and decreased positive expression of HNA and nestin with enhanced expression of NeuN, β-III-Tub and GFAP. Therefore, the present findings demonstrated that hBMSC transplantation triggered the formation of nerve cells and enhanced neuronal function in a rat model of MCAO.

Transplantation of autologous bone marrow-derived mesenchymal stem cells under arthroscopic surgery with microfracture versus microfracture alone for articular cartilage lesions in the knee: A multicenter prospective randomized control clinical trial

Introduction

To investigate the efficacy of the transplantation of autologous bone marrow-derived mesenchymal stem cells (BMSCs) under arthroscopy with microfracture (MFX) compared with microfracture alone.

Methods

Eleven patients with a symptomatic articular cartilage defect of the knee were included in the study. They were randomized to receive BMSCs with MFX (cell-T group, n=7) or MFX alone (control group, n=4). Clinical results were evaluated using International Knee Documentation committee (IKDC) knee evaluation questionnaires and the Knee Injury and Osteoarthritis Outcome Score (KOOS) before and 48 weeks after surgery. Quantitative and qualitative assessments of repair tissue were carried out at 48 weeks by T2 mapping of magnetic resonance images (MRIs) and the magnetic resonance observation of cartilage repair tissue (MOCART) scoring system with follow-up MRI.

Results

No significant differences between preoperative and postoperative IKDC and KOOS were observed in the cell-T or control group. However, forty-eight weeks after surgery, the cell-T group showed a trend for a greater KOOS QOL score compared with the control group (79.4 vs. 39.1, respectively; P=0.07). The T2 value did not differ significantly between the two groups, but the mean MOCART score was significantly higher in the cell-T group than in the control group (P=0.02).

Conclusions

Compared with MFX alone, BMSC transplantation with MFX resulted in better postoperative healing of the cartilage and subchondral bone as determined by the MOCART score. Clinically, BMSC transplantation with MFX gave a higher KOOS QOL score after 48 weeks.

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This is the first prospective randomized clinical trial between BMSCs with MFX and MFX alone.

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BMSCs with MFX showed a trend for a greater KOOS QOL score compared with MFX alone.

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BMSCs with MFX resulted in better healing of the cartilage by the MOCART score.

Emerging therapeutic agents in osteoarthritis

Osteoarthritis (OA) is the most common joint disorder and a leading cause of disability. Current treatments for OA can improve symptoms but do not delay the progression of disease. In the last years, much effort has been devoted to developing new treatments for OA focused on pain control, inflammatory mediators or degradation of articular tissues. Although promising results have been obtained in ex vivo studies and animal models of OA, few of these agents have completed clinical trials. Available clinical data support the interest of nerve growth factor as a target in pain control as well as the disease-modifying potential of inhibitors of Wnt signaling or catabolic enzymes such as aggrecanases and cathepsin K, and anabolic strategies like fibroblast growth factor-18 or cellular therapies. Carefully controlled studies in patients selected according to OA phenotypes and with a long follow-up will help to confirm the relevance of these new approaches as emerging therapeutic treatments in OA.

In Vitro and In Vivo Comparison of Different Types of Rabbit Mesenchymal Stem Cells for Cartilage Repair

Objective

Systematic studies indicate a growing number of clinical studies that use mesenchymal stem cells (MSCs) for the treatment of cartilage lesions. The current experimental and preclinical study aims to comparatively evaluate the potential of MSCs from a variety of tissues for the treatment of cartilage defect in rabbit’s knee which has not previously been reported.

Materials and Methods

In this experimental study, MSCs isolated from bone marrow (BMMSCs), adipose (AMSCs), and ears (EMSCs) of rabbits and expanded under in vitro culture. The growth rate and differentiation ability of MSCs into chondrocyte and the formation of cartilage pellet were investigated by drawing the growth curve and real-time polymerase chain reaction (RT-PCR), respectively. Then, the critical cartilage defect was created on the articular cartilage (AC) of the rabbit distal femur, and MSCs in collagen carrier were transplanted. The studied groups were as the control (only defect), sham (defect with scaffold), BMMSCs in the scaffold, EMSCs in the scaffold, and EMSCs in the scaffold with cartilage pellets. Histological and the gene expression analysis were performed following the transplantation.

Results

Based on our comparative in vitro investigation, AMSCs possessed the highest growth rate, as well as the lowest chondrogenic differentiation potential. In this context, MSCs of the ear showed a significantly higher growth rate and cartilage differentiation potential than those of bone marrow tissue (P<0.05). According to our in vivo assessments, BMMSC- and EMSC-seeded scaffolds efficiently improved the cartilage defect 4 weeks post-transplantation, while no improvement was observed in the group contained the cartilage pellets.

Conclusion

It seems that the ear contains MSCs that promote cartilage regeneration as much as the conventional MSCs from the bone marrow. Considering a high proliferation rate and easy harvesting of MSCs of the ear, this finding could be of value for the regenerative medicine.

Superoxide dismutase 3 facilitates the chondrogenesis of bone marrow-derived mesenchymal stem cells

Articular cartilage defects are considered a major clinical problem because they cannot heal by themselves. To date, bone marrow-derived mesenchymal stem cells (BMSCs)-based therapy has been widely applied for cartilage repair. However, fibrocartilage was often generated after BMSC therapy; therefore, there is an urgent need to stimulate and maintain BMSCs chondrogenic differentiation. The specific role of superoxide dismutase 3 (SOD3) in chondrogenesis is unknown; therefore, the present study aimed to clarify whether SOD3 could facilitate the chondrogenic differentiation of BMSCs. We first evaluated SOD3 protein levels during chondrogenesis of BMSCs using plate cultures. We then tested whether SOD3 could facilitate chondrogenesis of BMSCs using knockdown or overexpression experiments. Increased SOD3 protein levels were observed during BMSCs chondrogenesis. SOD3 knockdown inhibited collagen type II alpha 1 chain (COL2A1), aggrecan (ACAN), and SRY-box 9 (SOX9) expression. Overexpression of SOD3 increased the levels of chondrogenesis markers (COL2A1, ACAN, and SOX9). Elevated superoxide anions were observed when SOD3 was knocked down. We concluded that SOD3 could facilitate chondrogenesis of BMSCs to improve cartilage regeneration.

Evaluation of the effects of the combination of BMP-2-modified BMSCs and PRP on cartilage defects

Articular cartilage is avascular and aneural, and has limited capacity for self-regeneration when injured. Tissue engineering has emerged as a promising approach in repairing cartilage defects. To improve the therapy of cartilage healing, the present study investigated the efficacy of the combination of lentivirus-mediated bone morphogenetic protein-2 (BMP2) in bone marrow-derived stromal cells (BMSCs) and platelet-rich plasma (PRP) on cartilage and bone healing in a cartilage defect model using the rabbit knee. The BMSCs were harvested from New Zealand rabbits and transduced with lentivirus carrying BMP-2. Standard bone defects were introduced in the femoral groove of patellofemoral joints of 48 New Zealand rabbits. The cartilage defects were subjected to synthetic scaffold mosaicplasty with chitosan/silk fibroin/nanohydroxyapatite particles tri-component scaffolds soaked in BMSCs and PRP. After 16 weeks, the tissue specimens were assessed by micro-computed tomography (micro-CT) and macroscopic examination. The results showed that lentivirus-mediated BMP-2 and PRP increased the cell viability of the BMSCs, induced the expression of associated genes and enhanced osteogenic differentiation in vitro. In vivo, the expression of BMP-2 was observed for 16 weeks. The combination of BMP-2 and PRP treatment led to optimal results, compared with the other groups on micro-CT and gross observations. The results of the present study present a novel therapy using the lentivirus-mediated BMP-2 gene together with PRP for cartilage healing.

Application of adult mesenchymal stem cells in bone and vascular tissue engineering

Tissue engineering is a very promising field of regenerative medicine. Life expectancy has been increasing, and tissue replacement is increasingly needed in patients suffering from various degenerative disorders of the organs. The use of adult mesenchymal stem cells (e.g. from adipose tissue or from bone marrow) in tissue engineering seems to be a promising approach for tissue replacements. Clinical applications can make direct use of the large secretome of these cells, which can have a positive influence on other cells around. Another advantage of adult mesenchymal stem cells is the possibility to differentiate them into various mature cells via appropriate culture conditions (i.e. medium composition, biomaterial properties, and dynamic conditions). This review is focused on current and future ways to carry out tissue replacement of damaged bones and blood vessels, especially with the use of suitable adult mesenchymal stem cells as a potential source of differentiated mature cells that can later be used for tissue replacement. The advantages and disadvantages of different stem cell sources are discussed, with a main focus on adipose-derived stem cells. Patient factors that can influence later clinical applications are taken into account.

Type III Transforming Growth Factor-β Receptor RNA Interference Enhances Transforming Growth Factor β3-Induced Chondrogenesis Signaling in Human Mesenchymal Stem Cells

The type III transforming growth factor-β (TGF-β) receptor (TβRIII), a coreceptor of the TGF-β superfamily, is known to bind TGF-βs and regulate TGF-β signaling. However, the regulatory roles of TβRIII in TGF-β-induced mesenchymal stem cell (MSC) chondrogenesis have not been explored. The present study examined the effect of TβRIII RNA interference (RNAi) on TGF-β3-induced human MSC (hMSC) chondrogenesis and possible signal mechanisms. A lentiviral expression vector containing TβRIII small interfering RNA (siRNA) (SiTβRIII) or a control siRNA (SiNC) gene was constructed and infected into hMSCs. The cells were cultured in chondrogenic medium containing TGF-β3 or control medium. TβRIII RNAi significantly enhanced TGF-β3-induced chondrogenic differentiation of hMSCs, the ratio of type II (TβRII) to type I (TβRI) TGF-β receptors, and phosphorylation levels of Smad2/3 as compared with cells infected with SiNC. An inhibitor of the TGF-β signal, SB431542, not only inhibited TβRIII RNAi-stimulated TGF-β3-mediated Smad2/3 phosphorylation but also inhibited the effects of TβRIII RNAi on TGF-β3-induced chondrogenic differentiation. These results demonstrate that TβRIII RNAi enhances TGF-β3-induced chondrogenic differentiation in hMSCs by activating TGF-β/Smad2/3 signaling. The finding points to the possibility of modifying MSCs by TβRIII knockdown as a potent future strategy for cell-based cartilage tissue engineering.

Anti-inflammatory effect of hesperidin enhances chondrogenesis of human mesenchymal stem cells for cartilage tissue repair

Background

Articular cartilage diseases are considered a major health problem, and tissue engineering using human mesenchymal stem cells (MSCs) have been shown as a promising solution for cartilage tissue repair. Hesperidin is a flavonoid extract from citrus fruits with anti-inflammatory properties. We aimed to investigate the effect of hesperidin on MSCs for cartilage tissue repair. MSCs were treated by hesperidin, and colony formation and proliferation assays were performed to evaluate self-renewal ability of MSCs. Alcian blue staining and Sox9 expression were measured to evaluate chondrogenesis of MSCs. Secretion of pro-inflammatory cytokines IFN-γ, IL-2, IL-4 and IL-10, and expression of nuclear factor kappa B (NF-κB) subunit p65 were also assessed.

Results

Hesperidin improved self-renewal ability and chondrogenesis of MSCs, inhibited secretion of pro-inflammatory cytokines IFN-γ, IL-2, IL-4 and IL-10, and suppressed the expression of p65. Overexpression of p65 was able to reverse the hesperidin inhibited secretions of pro-inflammatory cytokines, and abolish the enhancing effect of hesperidin on chondrogenesis of MSCs.

Conclusion

Hesperidin could serve as a therapeutic agent to effectively enhance chondrogenesis of human MSCs by inhibiting inflammation to facilitate cartilage tissue repair.

Injections for Knee Osteoarthritis: Corticosteroids, Viscosupplementation, Platelet-Rich Plasma, and Autologous Stem Cells

This article reviews the benefits of corticosteroid, viscosupplementation, platelet-rich plasma, and autologous mesenchymal stem cell injections for the treatment of patients with knee osteoarthritis. Integrating injections into both clinical and surgical practices is complicated given existing health insurance reimbursement policies. This review describes the outcomes associated with these interventions and appropriate methods of navigating the existing reimbursement pathways to help providers implement these treatments into their practices.

Combating Osteoarthritis through Stem Cell Therapies by Rejuvenating Cartilage: A Review

Knee osteoarthritis (OA) is a chronic degenerative disorder which could be distinguished by erosion of articular cartilage, pain, stiffness, and crepitus. Not only aging-associated alterations but also the metabolic factors such as hyperglycemia, dyslipidemia, and obesity affect articular tissues and may initiate or exacerbate the OA. The poor self-healing ability of articular cartilage due to limited regeneration in chondrocytes further adversely affects the osteoarthritic microenvironment. Traditional and current surgical treatment procedures for OA are limited and incapable to reverse the damage of articular cartilage. To overcome these limitations, cell-based therapies are currently being employed to repair and regenerate the structure and function of articular tissues. These therapies not only depend upon source and type of stem cells but also on environmental conditions, growth factors, and chemical and mechanical stimuli. Recently, the pluripotent and various multipotent mesenchymal stem cells have been employed for OA therapy, due to their differentiation potential towards chondrogenic lineage. Additionally, the stem cells have also been supplemented with growth factors to achieve higher healing response in osteoarthritic cartilage. In this review, we summarized the current status of stem cell therapies in OA pathophysiology and also highlighted the potential areas of further research needed in regenerative medicine.

Translational Application of Microfluidics and Bioprinting for Stem Cell-Based Cartilage Repair

Cartilage defects can impair the most elementary daily activities and, if not properly treated, can lead to the complete loss of articular function. The limitations of standard treatments for cartilage repair have triggered the development of stem cell-based therapies. In this scenario, the development of efficient cell differentiation protocols and the design of proper biomaterial-based supports to deliver cells to the injury site need to be addressed through basic and applied research to fully exploit the potential of stem cells. Here, we discuss the use of microfluidics and bioprinting approaches for the translation of stem cell-based therapy for cartilage repair in clinics. In particular, we will focus on the optimization of hydrogel-based materials to mimic the articular cartilage triggered by their use as bioinks in 3D bioprinting applications, on the screening of biochemical and biophysical factors through microfluidic devices to enhance stem cell chondrogenesis, and on the use of microfluidic technology to generate implantable constructs with a complex geometry. Finally, we will describe some new bioprinting applications that pave the way to the clinical use of stem cell-based therapies, such as scaffold-free bioprinting and the development of a 3D handheld device for the in situ repair of cartilage defects.

Allogeneic Umbilical Cord-Derived Mesenchymal Stem Cells as a Potential Source for Cartilage and Bone Regeneration: An In Vitro Study

Umbilical cord (UC) may represent an attractive cell source for allogeneic mesenchymal stem cell (MSC) therapy. The aim of this in vitro study is to investigate the chondrogenic and osteogenic potential of UC-MSCs grown onto tridimensional scaffolds, to identify a possible clinical relevance for an allogeneic use in cartilage and bone reconstructive surgery. Chondrogenic differentiation on scaffolds was confirmed at 4 weeks by the expression of sox-9 and type II collagen; low oxygen tension improved the expression of these chondrogenic markers. A similar trend was observed in pellet culture in terms of matrix (proteoglycan) production. Osteogenic differentiation on bone-graft-substitute was also confirmed after 30 days of culture by the expression of osteocalcin and RunX-2. Cells grown in the hypertrophic medium showed at 5 weeks safranin o-positive stain and an increased CbFa1 expression, confirming the ability of these cells to undergo hypertrophy. These results suggest that the UC-MSCs isolated from minced umbilical cords may represent a valuable allogeneic cell population, which might have a potential for orthopaedic tissue engineering such as the on-demand cell delivery using chondrogenic, osteogenic, and endochondral scaffold. This study may have a clinical relevance as a future hypothetical option for allogeneic single-stage cartilage repair and bone regeneration.

Repair of articular cartilage and subchondral defects in rabbit knee joints with a polyvinyl alcohol/nano-hydroxyapatite/polyamide 66 biological composite material

Background

This study sought to prepare a new PVA/n-HA/PA66 composite to investigate the repair of articular cartilage and subchondral defects in rabbit knee joints.

Methods

A 5 × 5 × 5 mm-sized defect was created in the patellofemoral joints of 72 healthy adult New Zealand rabbits. The rabbits were then randomly divided into three groups (n = 24): PVA/n-HA+PA66 group, polyvinyl alcohol (PVA) group, and control (untreated) group. Cylindrical PVA/n-HA+PA66, 5 × 5 mm, comprised an upper PVA layer and a lower n-HA+PA66 layer. Macroscopic and histological evaluations were performed at 4, 8, 12, and 24 weeks, postoperatively. Type II collagen was measured by immunohistochemical staining. The implant/cartilage and bone interfaces were observed by scanning electron microscopy.

Results

At 24 weeks postoperatively, the lower PVA/n-HA+PA66 layer became surrounded by cartilage, with no obvious degeneration. In the PVA group, an enlarged space was observed between the implant and the host tissue that had undergone degeneration. In the control group, the articular cartilage had become calcified. In the PVA/n-HA+PA66 group, positive type II collagen staining was observed between the composite and the surrounding cartilage and on the implant surface. In the PVA group, positive staining was slightly increased between the PVA and the surrounding cartilage, but reduced on the PVA surface. In the control group, reduced staining was observed throughout. Scanning electron microscopy showed increased bone tissue in the lower n-HA+PA66 layer that was in close approximation with the upper PVA layer of the composite. In the PVA group, the bone tissue around the material had receded, and in the control group, the defect was filled with bone tissue, while the superior aspect of the defect was filled with disordered, fibrous tissue.

Conclusion

The diphase biological composite material PVA/n-HA+PA66 exhibits good histocompatibility and offers a satisfactory substitute for articular cartilage and subchondral bone.

Emerging potential of gene silencing approaches targeting anti-chondrogenic factors for cell-based cartilage repair

The field of cartilage repair has exponentially been growing over the past decade. Here, we discuss the possibility to achieve satisfactory regeneration of articular cartilage by means of human mesenchymal stem cells (hMSCs) depleted of anti-chondrogenic factors and implanted in the site of injury. Different types of molecules including transcription factors, transcriptional co-regulators, secreted proteins, and microRNAs have recently been identified as negative modulators of chondroprogenitor differentiation and chondrocyte function. We review the current knowledge about these molecules as potential targets for gene knockdown strategies using RNA interference (RNAi) tools that allow the specific suppression of gene function. The critical issues regarding the optimization of the gene silencing approach as well as the delivery strategies are discussed. We anticipate that further development of these techniques will lead to the generation of implantable hMSCs with enhanced potential to regenerate articular cartilage damaged by injury, disease, or aging.

Hypothermia inhibits the proliferation of bone marrow-derived mesenchymal stem cells and increases tolerance to hypoxia by enhancing SUMOylation

Hypothermia therapy has a positive effect on patients with severe brain injury. Recent studies have shown that mild hypothermia increases the survival of bone marrow-derived mesenchymal stem cells (BMSCs) in a hypoxic environment; however, the underlying mechanisms are not yet fully understood. Small ubiquitin-like modifiers (SUMOs) are sensitive to temperature stress reactions and are considered to exert a protective effect. In this study, we examined the protective effects of hypothermia on BMSCs in terms of SUMO protein modification. First, we found that mild hypothermia inhibited the proliferation and differentiation of BMSCs and increased cell tolerance to a hypoxic environment. Second, hypothermia significantly increased the levels of SUMO modification of multiple proteins in BMSCs. The knockdown of SUMO1/2/3 induced the rapid aging of the BMSCs, while the inhibition of the SUMO-conjugating enzyme, Ubc9, reduced cell proliferation and increased the proportion of BMSCs differentiating into nerve cells. Moreover, the tolerance of BMSCs to the hypoxic environment was significantly decreased. Lastly, we investigated 4 reported SUMO target proteins, anti-proliferating cell nuclear antigen, octamer-binding transcription factor 4, p53 and hypoxia-inducible factor-1α, to confirm that SUMO modification was indeed involved in maintaining the proliferation, inhibiting differentiation and enhancing the resistance of BMSCs against adverse conditions. Taken together, our results indicate that the SUMO pathway is involved in the response to hypothermic stress, and that SUMOylation may be an important protective mechanism against hypothermia for the survival of BMSCs under unfavorable conditions.

Effects of mechanical loading on human mesenchymal stem cells for cartilage tissue engineering

Today, articular cartilage damage is a major health problem, affecting people of all ages. The existing conventional articular cartilage repair techniques, such as autologous chondrocyte implantation (ACI), microfracture, and mosaicplasty, have many shortcomings which negatively affect their clinical outcomes. Therefore, it is essential to develop an alternative and efficient articular repair technique that can address those shortcomings. Cartilage tissue engineering, which aims to create a tissue-engineered cartilage derived from human mesenchymal stem cells (MSCs), shows great promise for improving articular cartilage defect therapy. However, the use of tissue-engineered cartilage for the clinical therapy of articular cartilage defect still remains challenging. Despite the importance of mechanical loading to create a functional cartilage has been well demonstrated, the specific type of mechanical loading and its optimal loading regime is still under investigation. This review summarizes the most recent advances in the effects of mechanical loading on human MSCs. First, the existing conventional articular repair techniques and their shortcomings are highlighted. The important parameters for the evaluation of the tissue-engineered cartilage, including chondrogenic and hypertrophic differentiation of human MSCs are briefly discussed. The influence of mechanical loading on human MSCs is subsequently reviewed and the possible mechanotransduction signaling is highlighted. The development of non-hypertrophic chondrogenesis in response to the changing mechanical microenvironment will aid in the establishment of a tissue-engineered cartilage for efficient articular cartilage repair.

The potential of induced pluripotent stem cells as a tool to study skeletal dysplasias and cartilage-related pathologic conditions

The development of induced pluripotent stem cells (iPSCs) technology has opened up new horizons for development of new research tools especially for skeletal dysplasias, which often lack human disease models. Regenerative medicine and tissue engineering could be the next areas to benefit from refinement of iPSC methods to repair focal cartilage defects, while applications for osteoarthritis (OA) and drug screening have evolved rather slowly. Although the advances in iPSC research of skeletal dysplasias and repair of focal cartilage lesions are not directly relevant to OA, they can be considered to pave the way to future prospects and solutions to OA research, too. The same problems which face the present cell-based treatments of cartilage injuries concern also the iPSC-based ones. However, established iPSC lines, which have no genomic aberrations and which efficiently differentiate into extracellular matrix secreting chondrocytes, could be an invaluable cell source for cell transplantations in the future. The safety issues concerning the recipient risks of teratoma formation and immune response still have to be solved before the potential use of iPSCs in cartilage repair of focal cartilage defects and OA.

Microfracture combined with functional pig peritoneum-derived acellular matrix for cartilage repair in rabbit models

Due to avascular and hypocellular nature of cartilage, repair of articular cartilage defects within synovial joints still poses a significant clinical challenge. To promote neocartilage properties, we established a functional scaffold named APM-E7 by conjugating a bone marrow-derived mesenchymal stem cell (BM-MSC) affinity peptide (E7) onto the acellular peritoneum matrix (APM). During in vitro culture, the APM-E7 scaffold can support better proliferation as well as better differentiation into chondrocytes of BM-MSCs. After implanting into cartilage defects in rabbits for 24weeks, compared with microfracture and APM groups, the APM-E7 scaffolds exhibited superior quality of neocartilage without transplant rejection, according to general observations, histological assessment, synovial fluid analysis, magnetic resonance imaging (MRI) and nanomechanical properties. This APM-E7 scaffold provided a scaffold for cell attachment, which was crucial for cartilage regeneration. Overall, the APM-E7 is a promising biomaterial with low immunogenicity for one-step cartilage repair by promoting autologous connective tissue progenitor (CTP) attachment.

STATEMENT OF SIGNIFICANCE

We report the one-step transplantation of functional acellular peritoneum matrix (APM-E7) with specific mesenchymal stem cell recruitment to repair rabbit cartilage injury. The experimental results illustrated that the APM-E7 scaffold was successfully fabricated, which could specifically recruit MSCs and fill the cartilage defects in the femoral trochlear of rabbits at 24weeks post-surgery. The repaired tissue was hyaline cartilage, which exhibited ideal mechanical stability. The APM-E7 biomaterial could provide scaffold for MSCs and improve cell homing, which are two key factors required for cartilage tissue engineering, thereby providing new insights into cartilage tissue engineering.

SMAD3 and SMAD4 have a more dominant role than SMAD2 in TGFβ-induced chondrogenic differentiation of bone marrow-derived mesenchymal stem cells

To improve cartilage formation by bone marrow-derived mesenchymal stem cells (BMSCs), the signaling mechanism governing chondrogenic differentiation requires better understanding. We previously showed that the transforming growth factor-β (TGFβ) receptor ALK5 is crucial for chondrogenesis induced by TGFβ. ALK5 phosphorylates SMAD2 and SMAD3 proteins, which then form complexes with SMAD4 to regulate gene transcription. By modulating the expression of SMAD2, SMAD3 and SMAD4 in human BMSCs, we investigated their role in TGFβ-induced chondrogenesis. Activation of TGFβ signaling, represented by SMAD2 phosphorylation, was decreased by SMAD2 knockdown and highly increased by SMAD2 overexpression. Moreover, TGFβ signaling via the alternative SMAD1/5/9 pathway was strongly decreased by SMAD4 knockdown. TGFβ-induced chondrogenesis of human BMSCs was strongly inhibited by SMAD4 knockdown and only mildly inhibited by SMAD2 knockdown. Remarkably, both knockdown and overexpression of SMAD3 blocked chondrogenic differentiation. Chondrogenesis appears to rely on a delicate balance in the amount of SMAD3 and SMAD4 as it was not enhanced by SMAD4 overexpression and was inhibited by SMAD3 overexpression. Furthermore, this study reveals that TGFβ-activated phosphorylation of SMAD2 and SMAD1/5/9 depends on the abundance of SMAD4. Overall, our findings suggest a more dominant role for SMAD3 and SMAD4 than SMAD2 in TGFβ-induced chondrogenesis of human BMSCs.

Repair Potential of Matrix-Induced Bone Marrow Aspirate Concentrate and Matrix-Induced Autologous Chondrocyte Implantation for Talar Osteochondral Repair: Patterns of Some Catabolic, Inflammatory, and Pain Mediators

OBJECTIVE

The low regenerative potential of cartilage contributed to the development of different cell therapies aimed to improve the clinical outcome in young patients with Osteochondral Lesions of the Talus (OLT). This study is designed to assess the regenerative potential of autologous matrix-induced Bone Marrow Aspirate Concentrate (mBMAC) and matrix-induced Autologous Chondrocyte Implantation (mACI) evaluating, on a small number of osteochondral biopsies, the expression of some catabolic, inflammatory, and pain mediators.

DESIGN

Twenty-two patients with OLT were analyzed in this study; 7 were treated with mACI and 15 with mBMAC. Informed consent was obtained from all the patients. Clinical assessments were performed pre-operatively and at 12, 24, and 36 months after surgery using the American Orthopedic Foot and Ankle Society (AOFAS). Histology and immunohistochemistry were used to assess cartilage repair at 24 months. Data were analyzed using non-parametric Wilcoxon-Mann-Whitney and Spearman tests.

RESULTS

A remarkable improvement in AOFAS score was noticed for both treatments up to 36 months; however, patients treated with mACI reported the best AOFAS score. Various degrees of tissue remodeling were observed by histological analysis for both cell strategies. However, mBMAC treatment showed a higher expression of some fibrous and hypertrophic markers compared to mACI group. A mild positivity for nerve growth factor, as pain mediator, was noticed for both treatments.M.

CONCLUSIONS

Our findings demonstrated the best histological and clinical results following mACI treatment since different fibrotic and hypertrophic features were evident in the mBMAC group at 24-month follow-up.

Acid ceramidase and the treatment of ceramide diseases: The expanding role of enzyme replacement therapy

Ceramides are a diverse group of sphingolipids that play important roles in many biological processes. Acid ceramidase (AC) is one key enzyme that regulates ceramide metabolism. Early research on AC focused on the fact that it is the enzyme deficient in the rare genetic disorder, Farber Lipogranulomatosis. Recent research has revealed that deficiency of the same enzyme is responsible for a rare form of spinal muscular atrophy associated with myoclonic epilepsy (SMA-PME). Due to their diverse role in biology, accumulation of ceramides also has been implicated in the pathobiology of many other common diseases, including infectious lung diseases, diabetes, cancers and others. This has revealed the potential of AC as a therapy for many of these diseases. This review will focus on the biology of AC and the potential role of this enzyme in the treatment of human disease.

Mesenchymal stem cells (MSCs) as skeletal therapeutics - an update

Mesenchymal stem cells hold the promise to treat not only several congenital and acquired bone degenerative diseases but also to repair and regenerate morbid bone tissues. Utilizing MSCs, several lines of evidences advocate promising clinical outcomes in skeletal diseases and skeletal tissue repair/regeneration. In this context, both, autologous and allogeneic cell transfer options have been utilized. Studies suggest that MSCs are transplanted either alone by mixing with autogenous plasma/serum or by loading onto repair/induction supportive resorb-able scaffolds. Thus, this review is aimed at highlighting a wide range of pertinent clinical therapeutic options of MSCs in the treatment of skeletal diseases and skeletal tissue regeneration. Additionally, in skeletal disease and regenerative sections, only the early and more recent preclinical evidences are discussed followed by all the pertinent clinical studies. Moreover, germane post transplant therapeutic mechanisms afforded by MSCs have also been conversed. Nonetheless, assertive use of MSCs in the clinic for skeletal disorders and repair is far from a mature therapeutic option, therefore, posed challenges and future directions are also discussed. Importantly, for uniformity at all instances, term MSCs is used throughout the review.

Mesenchymal stem cell therapy for osteoarthritis

The versatility of mesenchymal stem cells (MSCs) as a treatment modality has landed it another repair target: osteoarthritis, a crippling cartilage disease that frequently afflicts the aged population. Through many studies, this newly discovered method has been shown to significantly alleviate the pain experienced by osteoarthritic patients. Notwithstanding the effectiveness of MSCs in this regard, varying degrees of success rates have also been reported, which is probably attributable to the different approaches adopted in harnessing MSCs' therapeutic value. Accordingly, it is pertinent to understand the contributory factors like MSC type, dosage, size of osteoarthritic lesion, MSC carrier, and mode of infusion, which would be briefly discussed in this review.

Activin Receptor-Like Kinase Receptors ALK5 and ALK1 Are Both Required for TGFβ-Induced Chondrogenic Differentiation of Human Bone Marrow-Derived Mesenchymal Stem Cells

Introduction

Bone marrow-derived mesenchymal stem cells (BMSCs) are promising for cartilage regeneration because BMSCs can differentiate into cartilage tissue-producing chondrocytes. Transforming Growth Factor β (TGFβ) is crucial for inducing chondrogenic differentiation of BMSCs and is known to signal via Activin receptor-Like Kinase (ALK) receptors ALK5 and ALK1. Since the specific role of these two TGFβ receptors in chondrogenesis is unknown, we investigated whether ALK5 and ALK1 are expressed in BMSCs and whether both receptors are required for chondrogenic differentiation of BMSCs.

Materials & Methods

ALK5 and ALK1 gene expression in human BMSCs was determined with RT-qPCR. To induce chondrogenesis, human BMSCs were pellet-cultured in serum-free chondrogenic medium containing TGFβ1. Chondrogenesis was evaluated by aggrecan and collagen type IIα1 RT-qPCR analysis, and histological stainings of proteoglycans and collagen type II. To overexpress constitutively active (ca) receptors, BMSCs were transduced either with caALK5 or caALK1. Expression of ALK5 and ALK1 was downregulated by transducing BMSCs with shRNA against ALK5 or ALK1.

Results

ALK5 and ALK1 were expressed in in vitro-expanded as well as in pellet-cultured BMSCs from five donors, but mRNA levels of both TGFβ receptors did not clearly associate with chondrogenic induction. TGFβ increased ALK5 and decreased ALK1 gene expression in chondrogenically differentiating BMSC pellets. Neither caALK5 nor caALK1 overexpression induced cartilage matrix formation as efficient as that induced by TGFβ. Moreover, short hairpin-mediated downregulation of either ALK5 or ALK1 resulted in a strong inhibition of TGFβ-induced chondrogenesis.

Conclusion

ALK5 as well as ALK1 are required for TGFβ-induced chondrogenic differentiation of BMSCs, and TGFβ not only directly induces chondrogenesis, but also modulates ALK5 and ALK1 receptor signaling in BMSCs. These results imply that optimizing cartilage formation by mesenchymal stem cells will depend on activation of both receptors.

Cartilage Defect Treatments: With or without Cells? Mesenchymal Stem Cells or Chondrocytes? Traditional or Matrix-Assisted? A Systematic Review and Meta-Analyses

Articular cartilage defects have been addressed by using multiple strategies. In the last two decades, promising new strategies by using assorted scaffolds and cell sources to induce tissue regeneration have emerged, such as autologous chondrocyte implantation (ACI) and mesenchymal stem cell implantation (MSCI). However, it is still controversial in the clinical strategies when to choose these treatments. Thus, we conducted a systematic review and meta-analyses to compare the efficacy and safety of different cartilage treatments. In our study, 17 studies were selected to compare different treatments for cartilage defects. The results of meta-analyses indicated that cell-based cartilage treatments showed significant better efficacy than cell-free treatments did (OR: 4.27, 95% CI: 2.19–8.34; WMD: 10.11, 95% CI: 2.69–16.53). Another result indicated that MACT had significant better efficacy than traditional ACI did (OR: 0.49, 95% CI: 0.30–0.82). Besides, the incidence of graft hypertrophy of MACT was slightly lower than that of traditional ACI (OR: 2.43, 95% CI: 1.00–5.94). Current data showed that the cell-based treatments and MACT are better options for cartilage treatments, but more well-designed comparative studies are still needed to enhance our understanding of different treatments for cartilage defects.

Effect of the direct injection of bone marrow mesenchymal stem cells in hyaluronic acid and bone marrow stimulation to treat chondral defects in the canine model

Introduction

The purpose of this study was to assess the direct injection of bone marrow-derived mesenchymal stem cells (BMSCs) suspended in hyaluronic acid (HA) combined with drilling as a treatment for chondral defects in a canine model.

Methods

Tibial bone marrow was aspirated, and BMSCs were isolated and cultured. One 8.0-mm diameter chondral defect was created in the femoral groove, and nine 0.9-mm diameter holes were drilled into the defect. BMSCs (2.14 × 10⁷ cells) suspended in HA were injected into the defect. HA alone was injected into a similar defect on the contralateral knee as a control. Animals were sacrificed at 3 and 6 months.

Results

Although the percentage of coverage assessed macroscopically was significantly better at 6 months than at 3 months in both the BMSC (p = 0.02) and control (p = 0.001) groups, there were no significant differences in the International Cartilage Repair Society grades. The Wakitani histological score was significantly better at 6 months than at 3 months in the BMSC and control groups. While the control defects were mostly filled with fibrocartilage, several of the defects in the BMSC group contained hyaline-like cartilage. The mean Wakitani scores of the BMSC group improved from 7.0 ± 1.0 at 3 months to 4.6 ± 0.9 at 6 months, and those of the control group improved from 9.4 ± 1.2 to 6.0 ± 0.6. The BMSC group showed significantly better regeneration than the control group at 3 months (p = 0.04), but the difference at 6 months was not significant (p = 0.06).

Conclusions

The direct injection of BMSCs in HA combined with drilling enhanced cartilage regeneration.

High Tibial Osteotomy in Combination With Chondrogenesis After Stem Cell Therapy: A Histologic Report of 8 Cases

PURPOSE

To histologically evaluate the quality of articular cartilage regeneration from the medial compartment after arthroscopic subchondral drilling followed by postoperative intra-articular injections of autologous peripheral blood stem cells (PBSCs) and hyaluronic acid with concomitant medial open-wedge high tibial osteotomy (HTO) in patients with varus deformity of the knee joint.

METHODS

Eight patients with varus deformity of the knee joint underwent arthroscopic subchondral drilling of International Cartilage Repair Society (ICRS) grade 4 bone-on-bone lesions of the medial compartment with concomitant HTO. These patients were part of a larger pilot study in which 18 patients underwent the same procedure. PBSCs were harvested and cryopreserved preoperatively. At 1 week after surgery, 8 mL of PBSCs was mixed with 2 mL of hyaluronic acid and injected intra-articularly into the knee joint; this was repeated once a week for 5 consecutive weeks. Three additional intra-articular injections were administered weekly at intervals of 6, 12, and 18 months postoperatively. Informed consent was obtained at the time of hardware removal for opportunistic second-look arthroscopy and chondral biopsy. Biopsy specimens were stained with H&E, safranin O, and immunohistochemical staining for type I and II collagen. Specimens were graded using the 14 components of the ICRS Visual Assessment Scale II, and a total score was obtained.

RESULTS

Second-look arthroscopy showed satisfactory healing of the regenerated cartilage. Histologic analysis showed significant amounts of proteoglycan and type II collagen. The total ICRS Visual Assessment Scale II histologic scores comparing the regenerated articular cartilage (mean, 1,274) with normal articular cartilage (mean, 1,340) indicated that the repair cartilage score approached 95% of the normal articular cartilage score. There were no infections, delayed unions, or nonunions.

CONCLUSIONS

Chondrogenesis with stem cells in combination with medial open-wedge HTO for varus deformity correction of the knee joint regenerates cartilage that closely resembles the native articular cartilage.

LEVEL OF EVIDENCE

Level IV, therapeutic case series.

The Challenge and the Promise of Bone Marrow Cells for Human Cartilage Repair

The cartilage repair potential of bone marrow-derived stem cells has been well described. Harnessing this potential for human articular cartilage repair remains challenging. Accessing bone marrow repair cells through marrow stimulation techniques such as microfracture is readily achieved with generally good but inconsistent results. Animal and human studies show feasibility for ex vivo processing of bone marrow to isolate, concentrate, and culture mesenchymal stem cells. Nevertheless, it has been difficult to show consistent and clinically meaningful improvement using bone marrow cell preparations above what has been achieved with microfracture. Consequently, microfracture continues to be the simplest and most commonly used method to enhance repair of focal articular cartilage defects. Emerging preclinical work in the equine model suggests a role for enhancing marrow-stimulation techniques through the use of natural scaffolds such as autologous platelet enriched fibrin as well as optimization of joint biology through localized gene therapy to support cartilage repair. In contrast to joint replacement where inert materials of known mechanical properties are used, host biology determines the relative success, failure, and durability of cartilage repair. As such, development of personalized strategies to improve the quality and durability of bone marrow cell-based articular cartilage repair represent exciting new areas of inquiry. Continued advances in stem cell biology, scaffold technologies, and methods to delineate and enhance host biology, both systemically and within the joint, hold promise for harnessing the full power of bone marrow cells to facilitate cartilage repair and regeneration.

On the genealogy of tissue engineering and regenerative medicine

In this article, we identify and discuss a timeline of historical events and scientific breakthroughs that shaped the principles of tissue engineering and regenerative medicine (TERM). We explore the origins of TERM concepts in myths, their application in the ancient era, their resurgence during Enlightenment, and, finally, their systematic codification into an emerging scientific and technological framework in recent past. The development of computational/mathematical approaches in TERM is also briefly discussed.