Update on mesenchymal stem cell therapies for cartilage disorders

Mesenchymal Stem Cells and Tissue Bioengineering Applications in Sheep as Ideal Model

The most common technologies in tissue engineering include growth factor therapies; metal implants, such as titanium; 3D bioprinting; nanoimprinting for ceramic/polymer scaffolds; and cell therapies, such as mesenchymal stem cells (MSCs). Cell therapy is a promising alternative to organ grafts and transplants in the treatment of numerous musculoskeletal diseases. MSCs have increasingly been used in generative medicine due to their specialized self-renewal, immunomodulation, multiplication, and differentiation properties. To further expand the potential of these cells in tissue repair, significant efforts are currently dedicated to the production of biomaterials with desirable short- and long-term biophysical properties that can aid the differentiation and expansion of MSCs. Biomaterials support MSC differentiation by modulating their characteristics, such as composition, mechanical properties, porosity, and topography. This review aimed to describe recent MSC approaches, including those associated with biomaterials, from experimental, clinical, and preclinical studies with sheep models.

The Research Progress of Exosomes in Osteoarthritis, With Particular Emphasis on the Therapeutic Effect

Exosomes participate in many physiological and pathological processes by regulating cell-to-cell communication. This affects the etiology and development of diseases, such as osteoarthritis (OA). Although exosomes in the OA tissue microenvironment are involved in the progression of OA, exosomes derived from therapeutic cells represent a new therapeutic strategy for OA treatment. Recent studies have shown that exosomes participate in OA treatment by regulating the proliferation, apoptosis, inflammation, and extracellular matrix synthesis of chondrocytes. However, studies in this field are scant. This review summarizes the therapeutic properties of exosomes on chondrocytes in OA and their underlying molecular mechanisms. We also discuss the challenges and prospects of exosome-based OA treatment.

Mesenchymal Stem Cells in the Treatment of Cartilage Defects of the Knee: A Systematic Review of the Clinical Outcomes

BACKGROUND

Osteochondral lesions are a common clinical problem and their management has been historically challenging. Mesenchymal stem cells have the potential to differentiate into chondrocytes and thus restore hyaline cartilage to the defect, theoretically improving clincal outcomes in these patients. They can also be harvested with minimal donor site morbidity.

PURPOSE

To assess the clinical and functional outcomes of mesenchymal stem cell implantation to treat isolated osteochondral defects of the knee. A secondary purpose is to assess the quality of the current available evidence as well as the radiological and histological outcomes. We also reviewed the cellular preparation and operative techniques for implantation.

STUDY DESIGN

Systematic review.

METHODS

A comprehensive literature search of 4 databases was carried out: CINAHL, Embase, MEDLINE, and PubMed. We searched for clinical studies reporting the outcomes on a minimum of 5 patients with at least 12 months of follow-up. Clinical, radiological, and histological outcomes were recorded. We also recorded demographics, stem cell source, culture technique, and operative technique. Methodological quality of each study was assessed using the modified Coleman methodology score, and risk of bias for the randomized controlled studies was assessed using the Cochrane Collaboration tool.

RESULTS

Seventeen studies were found, encompassing 367 patients. The mean patient age was 35.1 years. Bone marrow was the most common source of stem cells utilized. Mesenchymal stem cell therapy consistently demonstrated good short- to medium-term outcomes in the studies reviewed with no serious adverse events being recorded. There was significant heterogeneity in cell harvesting and preparation as well as in the reporting of outcomes.

CONCLUSION

Mesenchymal stem cells demonstrated a clinically relevant improvement in outcomes in patients with osteochondral defects of the knee. More research is needed to establish an optimal treatment protocol, long-term outcomes, and superiority over other therapies.

REGISTRATION

CRD42020179391 (PROSPERO).

Mesenchymal Stem Cell-Derived Exosomes and Their Therapeutic Potential for Osteoarthritis

Exosomes are nano-sized vesicles (50-150 nm in diameter) that contain nucleic acids (e.g., microRNA and messenger RNA), functional proteins, and bioactive lipids. They are secreted by various types of cells, including B cells, T cells, reticulocytes, dendritic cells, mast cells, epithelial cells, and mesenchymal stem cells (MSCs). They perform a wide variety of functions, including the repair of damaged tissues, regulation of immune responses, and reduction in inflammation. When considering the limitations of MSCs, including issues in standardization and immunogenicity, MSC-derived exosomes have advantages such as small dimensions, low immunogenicity, and lack of requirement for additional procedures for culture expansion or delivery. MSC-derived exosomes have shown outstanding therapeutic effects through chondro-protective and anti-inflammatory properties. MSC-derived exosomes may enable a new therapeutic paradigm for the treatment of osteoarthritis. However, further research is needed to prove their clinical effectiveness and feasibility.

Human bone marrow-derived mesenchymal stem cells from different bone sources: a panorama

Regenerative medicine is a promising field in orthopaedic surgery. Although surgical treatments can produce excellent outcomes and may be the best choice for some patients, regenerative medicine can provide with more minimally-invasive treatment options. Mesenchymal stem cells (MSCs) are multipotent cells and are highly capable to differentiate into osteocytes or chondrocytes, while they can be isolated from different bone sources. The bone marrow aspiration from the posterior iliac crest appears to be preferred, as it provided a modestly higher concentration of nucleated cells [(25.1-54.7)×10⁶ cells/mL]. MSCs are also easily obtained from other bone sources, such as humerus, femur, tibia, vertebral body or calcaneus and have their content ranges between 5.8×10⁶ and 38.7×10⁶ nucleated cells. Although, they present a wide range of documented nucleated cells, they can be cultivated and expanded in vitro in multiple cell types, avoiding a second surgical site while preventing post-operative pain and the possible risk for infection. Thus, they represent a promising and encouraging treatment option in orthopaedic surgery.

Distal-Less Homeobox 5 Is a Therapeutic Target for Attenuating Hypertrophy and Apoptosis of Mesenchymal Progenitor Cells

Chondrocyte hypertrophy is a hallmark of osteoarthritis (OA) pathology. In the present study, we elucidated the mechanism underlying the relationship between the hypertrophy/apoptotic phenotype and OA pathogenesis in bone marrow-derived mesenchymal stem cells (BM-MSCs) via gene targeting of distal-less homeobox 5 (DLX5). Our primary objectives were (1) to determine whether DLX5 is a predictive biomarker of cellular hypertrophy in human osteoarthritic tissues; (2) To determine whether modulating DLX5 activity can regulate cell hypertrophy in mesenchymal stem/progenitor cells from marrow and cartilage. Whole transcriptome sequencing was performed to identify differences in the RNA expression profile between human-cartilage-derived mesenchymal progenitors (C-PCs) and bone-marrow-derived mesenchymal progenitors (BM-MSCs). Ingenuity Pathway Analysis (IPA) software was used to compare molecular pathways known to regulate hypertrophic terminal cell differentiation. RT-qPCR was used to measure DLX5 and hypertrophy marker COL10 in healthy human chondrocytes and OA chondrocytes. DLX5 was knocked down or overexpressed in BM-MSCs and C-PCs and RT-qPCR were used to measure the expression of hypertrophy/terminal differentiation markers following DLX5 modulation. Apoptotic cell activity was characterized by immunostaining for cleaved caspase 3/7. We demonstrate that DLX5 and downstream hypertrophy markers were significantly upregulated in BM-MSCs, relative to C-PCs. DLX5 and COL10 were also significantly upregulated in cells from OA knee joint tissues, relative to normal non-arthritic joint tissues. Knocking down DLX5 in BM-MSCs inhibited cell hypertrophy and apoptotic activity without attenuating their chondrogenic potential. Overexpression of DLX5 in C-PCs stimulated hypertrophy markers and increased apoptotic cell activity. Modulating DLX5 activity regulates cell hypertrophy and apoptosis in BM-MSCs and C-PCs. These findings suggest that DLX5 is a biomarker of OA changes in human knee joint tissues and confirms the DLX5 mechanism contributes to hypertrophy and apoptosis in BM-MSCs.

Epidural Fat-Derived Mesenchymal Stem Cell: First Report of Epidural Fat-Derived Mesenchymal Stem Cell

STUDY DESIGN

Experimental study.

PURPOSE

To determine whether epidural fat (EF) tissue contains mesenchymal stem cells (MSC).

OVERVIEW OF LITERATURE

Spine surgeons are unaware of the contents of EF tissue and the reason for its presence between the ligamentum flavum and the dura mater; therefore, EF tissues are routinely eliminated during surgical procedures. However, EF removal causes certain postoperative problems, such as post-laminectomy syndrome. We hypothesized that the EF tissue may play a significant supportive role for the neural structures and other nearby conditions.

METHODS

EF tissues were obtained from consenting patients (n=3) during posterior decompression surgery of the lumbar spine. The primary cells were isolated and cultured as per previously described methods with some modifications, and the cell morphology and cumulation were examined. Thereafter, reverse transcription-polymerase chain reaction (RT-PCR), a fluorescence-activated cell sorting (FACS) analysis, and differentiation potency for differentiation into osteoblasts, chondroblasts, and adipocytes were investigated to identify whether the cells derived from EF are MSC.

RESULTS

The cells from the EF tissue had a fibroblast or neuron-like morphology that persisted until the senescence at p18. MSCspecific genes, such as OCT4, SOX2, KLF4, MYC, and GAPDH were expressed in the RT-PCR study, while MSC-specific surface markers such as CD105, CD90, and CD73 were exhibited in the FACS analysis. The differentiation properties of EF-MSC for differentiation into the three types of cells (osteoblast, chondroblast, and adipocyte) were also confirmed.

CONCLUSIONS

Based on the cell culture, FACS analysis, RT-PCR analysis, and differentiation potent outcomes, all the features of the cells corresponded to MSC. This is the first study to identify EF-MSC derived from the EF tissue.

Preclinical safety study of a combined therapeutic bone wound dressing for osteoarticular regeneration

The extended life expectancy and the raise of accidental trauma call for an increase of osteoarticular surgical procedures. Arthroplasty, the main clinical option to treat osteoarticular lesions, has limitations and drawbacks. In this manuscript, we test the preclinical safety of the innovative implant ARTiCAR for the treatment of osteoarticular lesions. Thanks to the combination of two advanced therapy medicinal products, a polymeric nanofibrous bone wound dressing and bone marrow-derived mesenchymal stem cells, the ARTiCAR promotes both subchondral bone and cartilage regeneration. In this work, the ARTiCAR shows 1) the feasibility in treating osteochondral defects in a large animal model, 2) the possibility to monitor non-invasively the healing process and 3) the overall safety in two animal models under GLP preclinical standards. Our data indicate the preclinical safety of ARTiCAR according to the international regulatory guidelines; the ARTiCAR could therefore undergo phase I clinical trial.

Arthroplasty is the main clinical option for the treatment of osteoarticular lesions, but has limited efficacy. Here, the authors use a wound dressing with autologous mesenchymal stromal cells, functionalised for local BMP2 delivery, and show feasibility and safety in standardised preclinical tests in animal models, suggesting suitability for use in clinical trials.

Non-thermal atmospheric pressure plasma is an excellent tool to activate proliferation in various mesoderm-derived human adult stem cells

Adult stem cells are capable of self-renewal and differentiation into specific cell types in tissues and have high potential for stem cell therapy. Mesenchymal and hematopoietic stem cells are easily attainable from the human body and have become applicable tools for adult stem cell therapy. However, there are still technical barriers for the application of mesenchymal and hematopoietic stem cells for therapy, such as the small number of cell populations, high risk of contamination, and loss of their stemness properties in vitro. In our previous study, we showed that non-thermal atmospheric pressure plasma (NTAPP) promoted the proliferation of adipose tissue-derived stem cells (ASCs) by 1.6-fold on average, while maintaining their stemness. Here, we examined the feasibility of NTAPP as a tool to activate the proliferation of mesenchymal and hematopoietic stem cells in vitro without affecting their stem cell characteristics. NTAPP increased the proliferation of bone marrow-derived stem cells (BM-MSCs) and hematopoietic stem cells (HSCs) by 1.8- and 2-fold, respectively, when compared to that of untreated cells. As observed in ASCs, NTAPP exposure also activated the expression of stem cell-specific surface markers, CD44 and CD105, by 5-fold in BM-MSCs, when compared to that in unexposed control cells in a low glucose medium with a low concentration of basic fibroblast growth factor (b-FGF). In addition, NTAPP exposure highly augmented the mRNA expression of well-known pluripotent genes for stemness, such as Oct4, Sox2, and Nanog in ASCs and BM-MSCs when compared to that in unexposed control cells. When cell cycle progression was examined, the G1-S shift was accelerated, and expression of PCNA was increased in NTAPP-exposed ASCs when compared to that in untreated control cells, suggesting that NTAPP activated G1-S transition. Taken together, these results demonstrated that NTAPP activated the proliferation of various mesodermal-derived human adult stem cells by accelerating the G1-S transition while maintaining their pluripotency and stemness, strongly suggesting that NTAPP can be an efficient tool for expanding the population of various adult stem cells in vitro for medical applications.

[Osteogenic differentiation of bone marrow mesenchymal stem cells induced by gene-loaded lipopolysaccharide-amine nanopolymersomes]

Objective

To investigate the ability of gene-loaded lipopolysaccharide-amine nanopolymersomes (LNPs) in inducing osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) by in vitro gene transfection, where LNPs were used as a non-viral cationic carrier, and their properties were optimized during synthesis.

Methods

LNPs were synthesized by a graft-copolymerization method, and the effects of different pH environments during synthesis on physicochemical properties of LNPs and LNPs/plasmid of bone morphogenetic protein 2-green fluorescent protein (pBMP-2-GFP) complexes were explored. Then, optimized LNPs with maximum transfection efficiency and safe cytotoxicity in rat BMSCs were identified by cytotoxicity and transfection experiments in vitro. Thereafter, the optimized LNPs were used to mediate pBMP-2-GFP to transfect rat BMSCs, and the influences of LNPs/pBMP-2-GFP on osteogenic differentiation of BMSCs were evaluated by monitoring the cell morphology, concentration of BMP-2 protein, activity of alkaline phosphatase (ALP), and the formation of calcium nodules.

Results

The nitrogen content, particle size, and zeta potential of LNPs synthesized at pH 8.5 were lower than those of the other pH groups, with the lowest cytotoxicity (96.5%±1.4%) and the highest transfection efficiency (98.8%±0.1%). After transfection treatment, within the first 4 days, BMSCs treated by LNPs/pBMP-2-GFP expressed BMP-2 protein significantly higher than that treated by Lipofectamine2000 (Lipo)/pBMP-2-GFP, polyethylenimine 25K/pBMP-2-GFP, and the blank (non-treated). At 14 days after transfection, ALP activity in BMSCs treated by LNPs/pBMP-2-GFP was higher than that treated by Lipo/pBMP-2-GFP and the blank, comparable to that induced by osteogenic medium; with alizarin red staining, visible calcium nodules were found in BMSCs treated by LNPs/pBMP-2-GFP or osteogenic medium, but absent in BMSCs treated by Lipo/pBMP-2-GFP or the blank with apoptosis. At 21 days after transfection, transparent massive nodules were discovered in BMSCs treated by LNPs/pBMP-2-GFP, and BMSCs exhibited the morphologic features of osteoblasts.

Conclusion

LNPs synthesized at pH 8.5 has optimal transfection efficiency and cytotoxicity, they can efficiently mediate pBMP-2-GFP to transfect BMSCs, and successfully induce their directional osteogenic differentiation, whose inducing effect is comparable to the osteogenic medium. The results suggest that gene transfection mediated by LNPs may be a convenient and effective strategy in inducing directional differentiation of stem cells.