The Necessity of a Systematic Approach for the Use of MSCs in the Clinical Setting

Human Mesenchymal Stem Cells and Innovative Scaffolds for Bone Tissue Engineering Applications

Stem cell-based therapy is a significant topic in regenerative medicine, with a predominant role being played by human mesenchymal stem cells (hMSCs). The hMSCs have been shown to be suitable in regenerative medicine for the treatment of bone tissue. In the last few years, the average lifespan of our population has gradually increased. The need of biocompatible materials, which exhibit high performances, such as efficiency in bone regeneration, has been highlighted by aging. Current studies emphasize the benefit of using biomimetic biomaterials, also known as scaffolds, for bone grafts to speed up bone repair at the fracture site. For the healing of injured bone and bone regeneration, regenerative medicine techniques utilizing a combination of these biomaterials, together with cells and bioactive substances, have drawn a great interest. Cell therapy, based on the use of hMSCs, alongside materials for the healing of damaged bone, has obtained promising results. In this work, several aspects of cell biology, tissue engineering, and biomaterials applied to bone healing/regrowth will be considered. In addition, the role of hMSCs in these fields and recent progress in clinical applications are discussed. Impact Statement The restoration of large bone defects is both a challenging clinical issue and a socioeconomic problem on a global scale. Different therapeutic approaches have been proposed for human mesenchymal stem cells (hMSCs), considering their paracrine effect and potential differentiation into osteoblasts. However, different limitations are still to be overcome in using hMSCs as a therapeutic opportunity in bone fracture repair, including hMSC administration methods. To identify a suitable hMSC delivery system, new strategies have been proposed using innovative biomaterials. This review provides an update of the literature on hMSC/scaffold clinical applications for the management of bone fractures.

Culturing Adipose-Derived Stem Cells Under Serum-Free Conditions

Growing adipose-derived stem cells (ADSC) in serum-free conditions is important as it represents a way of expanding multipotent cells in a clinical grade medium. Most cultured ADSC are expanded and tested in serum-containing media, which can pose significant health risks if these cells were used in clinical applications. Moreover, cells grown in serum-free conditions behave very different than those cultured in serum-containing media. Here, we present a technique to culture adipose-derived stem cells in serum-free conditions. The methods described in this chapter were optimized for ovine ADSC. The appropriate optimization should be done for other cell lines.

Effect and mechanism of human umbilical cord mesenchymal stem cells in treating allergic rhinitis in mice

A model of allergic rhinitis (AR) in BALB/c mice was established and evaluated to provide experimental subjects for further research. Preparation of human umbilical cord mesenchymal stem cells (hUCMSCs), including isolation, expansion culture, passaging, cryopreservation, and preparation of cell suspensions, provided materials for experimental research and clinical treatment. The mouse AR model was established by ovalbumin (OVA) intraperitoneal injection and the nasal stimulation induction method, and the model had a good effect and high repeatability. GFP-labeled hUCMSCs had good effects and were stable cells that could be used for tracking in animals. Transplantation of hUCMSCs by intraperitoneal and tail vein injections had a specific effect on the AR model of mice, and tail vein injection had a better effect. Tracking of hUCMSCs in vivo showed that the three groups of mice had the greatest number of hUCMSCs in the nose at week 2. The mouse AR model was used to evaluate the efficacy of hUCMSC transplantation via multiple methods for AR. The distribution of hUCMSCs in vivo was tracked by detecting green fluorescent protein (GFP), and the treatment mechanism of hUCMSCs was elucidated. This study provides technical methods and a theoretical basis for the clinical application of hUCMSCs.

Osteoblastogenesis Alters Small RNA Profiles in EVs Derived from Bone Marrow Stem Cells (BMSCs) and Adipose Stem Cells (ASCs)

Multipotent stem cells (MSCs) are used in various therapeutic applications based on their paracrine secretion activity. Here, we set out to identify and characterize the paracrine factors released during osteoblastogenesis, with a special focus on small non-coding RNAs released in extracellular vesicles (EVs). Bone marrow stem cells (BMSCs) and adipose stem cells (ASCs) from healthy human donors were used as representatives of MSCs. We isolated EVs secreted before and after induction of osteoblastic differentiation and found that the EVs contained a specific subset of microRNAs (miRNAs) and tRNA-derived small RNAs (tsRNA) compared to their parental cells. Osteoblastic differentiation had a larger effect on the small RNA profile of BMSC-EVs relative to ASC-EVs. Our data showed that EVs from different MSC origin exhibited distinct expression profiles of small RNA profiles when undergoing osteoblastogenesis, a factor that should be taken into consideration for stem cell therapy.

Adult Stem Cells for Bone Regeneration and Repair

The regeneration of bone fractures, resulting from trauma, osteoporosis or tumors, is a major problem in our super-aging society. Bone regeneration is one of the main topics of concern in regenerative medicine. In recent years, stem cells have been employed in regenerative medicine with interesting results due to their self-renewal and differentiation capacity. Moreover, stem cells are able to secrete bioactive molecules and regulate the behavior of other cells in different host tissues. Bone regeneration process may improve effectively and rapidly when stem cells are used. To this purpose, stem cells are often employed with biomaterials/scaffolds and growth factors to accelerate bone healing at the fracture site. Briefly, this review will describe bone structure and the osteogenic differentiation of stem cells. In addition, the role of mesenchymal stem cells for bone repair/regrowth in the tissue engineering field and their recent progress in clinical applications will be discussed.

Intra-articular administration of peripheral blood stem cells with platelet-rich plasma regenerated articular cartilage and improved clinical outcomes for knee chondral lesions

PURPOSE

To determine whether intra-articular injections of peripheral blood stem cells improved the regeneration of articular cartilage in patients with osteochondral knee injuries.

METHODS

This prospective study included 20 patients with grade 3b knee osteochondral lesions who underwent knee arthroscopies. All were white, and all had performed physical activity at least five times a week. International Knee Documentation Committee (IKDC) and visual analog scale scores were recorded before surgery, six months and one year after surgery, and then yearly until five years after surgery. Magnetic resonance imaging scans were obtained six months preoperatively and then yearly and were evaluated by musculoskeletal radiologists blinded to the patient data. Tissue repair was quantified using the International Cartilage Repair Society morphologic score system. Unpaired t-tests were used for comparisons between the time points.

RESULTS

The mean preoperative IKDC score was 50.5 (42-61). At the six-month follow-up, the mean values were 60.79 (P = 0.32) and 90.97. At the six-month follow-up, the mean values were 70.8 (P = 0.043). At the end of the five-year follow-up, the IKDC was 82.2 (P = 0.024). At five-year follow-up, the visual analog scale score was 1.1 (P = 0.0018). The main morphologic score system score was 3.2 preoperatively and 9.7 ± 1.6 at five-year follow-up (P = 0.0021). No infection, tumors, or synovitis were reported at the end of the follow-up.

CONCLUSIONS

Intra-articular peripheral blood stem cells with platelet-rich plasma regenerated articular cartilage and improved clinical outcomes for knee chondral lesions at five years of follow-up.

Biomarkers of bone healing induced by a regenerative approach based on expanded bone marrow-derived mesenchymal stromal cells

BACKGROUND

Safety and feasibility of a regenerative strategy based on the use of culture-expanded mesenchymal stromal cells (MSCs) have been investigated in phase 2 trials for the treatment of nonunion and osteonecrosis of the femoral head (ONFH). As part of the clinical study, we aimed to evaluate if bone turnover markers (BTMs) could be useful for predicting the regenerative ability of the cell therapy product.

MATERIALS AND METHODS

The bone defects of 39 patients (nonunion: n = 26; ONFH: n = 13) were treated with bone marrow-derived MSCs, expanded using a clinical-grade protocol and combined with biphasic calcium phosphate before implantation. Bone formation markers, bone-resorption markers and osteoclast regulatory proteins were measured before treatment (baseline) and after 12 and 24 weeks from surgery. At the same time-points, clinical and radiological controls were performed to evaluate the bone-healing progression.

RESULTS

We found that C-Propeptide of Type I Procollagen (CICP) and C-terminal telopeptide of type-I collagen (CTX) varied significantly, not only over time, but also according to clinical results. In patients with a good outcome, CICP increased and CTX decreased, and this trend was observed in both nonunion and ONFH. Moreover, collagen biomarkers were able to discriminate healed patients from non-responsive patients with a good diagnostic accuracy.

DISCUSSION

CICP and CTX could be valuable biomarkers for monitoring and predicting the regenerative ability of cell products used to stimulate the repair of refractory bone diseases. To be translated in a clinical setting, these results are under validation in a currently ongoing phase 3 clinical trial.

Cell therapy induced regeneration of severely atrophied mandibular bone in a clinical trial

Background

Autologous grafting, despite some disadvantages, is still considered the gold standard for reconstruction of maxillofacial bone defects. The aim of this study was to evaluate bone regeneration using bone marrow-derived mesenchymal stromal cells (MSCs) in a clinical trial, a less invasive approach than autologous bone grafting. This comprehensive clinical trial included subjects with severe mandibular ridge resorption.

Methods

The study included 11 subjects aged 52–79 years with severe mandibular ridge resorption. Bone marrow cells were aspirated from the posterior iliac crest and plastic adherent cells were expanded in culture medium containing human platelet lysate. The MSCs and biphasic calcium phosphate granules as scaffolds were inserted subperiosteally onto the resorbed alveolar ridge. After 4–6 months of healing, new bone formation was assessed clinically and radiographically, as were safety and feasibility. Bone at the implant site was biopsied for micro-computed topography and histological analyses and dental implants were placed in the newly regenerated bone. Functional outcomes and patient satisfaction were assessed after 12 months.

Results

The bone marrow cells, expanded in vitro and inserted into the defect together with biphasic calcium phosphate granules, induced significant new bone formation. The regenerated bone volume was adequate for dental implant installation. Healing was uneventful, without adverse events. The patients were satisfied with the esthetic and functional outcomes. No side effects were observed.

Conclusions

The results of this comprehensive clinical trial in human subjects confirm that MSCs can successfully induce significant formation of new bone, with no untoward sequelae. Hence, this novel augmentation procedure warrants further investigation and may form the basis of a valid treatment protocol, challenging the current gold standard.

Trial registration

EudraCT, 2012-003139-50. Registered on 21 August 2013. ClinicalTrials.gov, NCT 02751125. Registered on 26 April 2016.

Growing Adipose-Derived Stem Cells Under Serum-Free Conditions

Growing adipose-derived stem cells (ADSC) in serum-free conditions is important as it represents a way of expanding multipotent cells in a clinical grade medium. Most cultured ADSC are expanded and tested in serum-containing media, which can pose significant health risks if these cells were used in clinical applications. Moreover, cells grown in serum-free conditions behave significantly different than those cultured in serum-containing media. Here, we present a technique to culture adipose-derived stem cells in serum-free conditions. The methods described in this chapter were optimized for ovine ADSC. The appropriate optimization should be done for other cell lines.

Current clinical evidence for the use of mesenchymal stem cells in articular cartilage repair

INTRODUCTION

Articular cartilage is renowned for its poor intrinsic capacity for repair. Current treatments for osteoarthritis are limited in their ability to reliably restore the native articular cartilage structure and function. Mesenchymal stem cells (MSCs) present an attractive treatment option for articular cartilage repair, with a recent expansion of clinical trials investigating their use in patients.

AREAS COVERED

This paper provides a current overview of the clinical evidence on the use of MSCs in articular cartilage repair.

EXPERT OPINION

The article demonstrates robust clinical evidence that MSCs have significant potential for the regeneration of hyaline articular cartilage in patients. The majority of clinical trials to date have yielded significantly positive results with minimal adverse effects. However the clinical research is still in its infancy. The optimum MSC source, cell concentrations, implantation technique, scaffold, growth factors and rehabilitation protocol for clinical use are yet to be identified. A larger number of randomised control trials are required to objectively compare the clinical efficacy and long-term safety of the various techniques. As the clinical research continues to evolve and address these challenges, it is likely that MSCs may become integrated into routine clinical practice in the near future.

Comprehensive transcriptomic and proteomic characterization of human mesenchymal stem cells reveals source specific cellular markers

Mesenchymal stem cells (MSC) are multipotent cells with great potential in therapy, reflected by more than 500 MSC-based clinical trials registered with the NIH. MSC are derived from multiple tissues but require invasive harvesting and imply donor-to-donor variability. Embryonic stem cell-derived MSC (ESC-MSC) may provide an alternative, but how similar they are to ex vivo MSC is unknown. Here we performed an in depth characterization of human ESC-MSC, comparing them to human bone marrow-derived MSC (BM-MSC) as well as human embryonic stem cells (hESC) by transcriptomics (RNA-seq) and quantitative proteomics (nanoLC-MS/MS using SILAC). Data integration highlighted and validated a central role of vesicle-mediated transport and exosomes in MSC biology and also demonstrated, through enrichment analysis, their versatility and broad application potential. Particular emphasis was placed on comparing profiles between ESC-MSC and BM-MSC and assessing their equivalency. Data presented here shows that differences between ESC-MSC and BM-MSC are similar in magnitude to those reported for MSC of different origin and the former may thus represent an alternative source for therapeutic applications. Finally, we report an unprecedented coverage of MSC CD markers, as well as membrane associated proteins which may benefit immunofluorescence-based applications and contribute to a refined molecular description of MSC.

In vivo bone regeneration on titanium devices using serum-free grown adipose-derived stem cells, in a sheep femur model

AIM

The aim of this study was to investigate the capacity of adipose-derived stem cells (ADSC), grown in serum-free conditions, to regenerate bone around titanium discs with different titanium surfaces.

MATERIAL AND METHODS

Ovine ADSC (oADSC) were isolated from seven sheep and cultured using serum-free and osteogenic conditions. Prior to in vivo testing, the growth and osteogenic behaviour of these cells were analysed in vitro using cell proliferation and extracellular matrix mineralisation assays. The bone regenerative capacity of autologous oADSC was evaluated in vivo on titanium discs in a sheep femur epicondyle model. Machined (MTi) and alumina-blasted (ABTi) titanium discs were used. Bone regeneration within the defects was evaluated after 1 month using histology and histomorphometry. PKH26 cell-tracking dye was used to verify the persistence of oADSC in the surgical wound.

RESULTS

oADSC sourced from five of seven sheep differentiated into osteoblast-like cells. Cellular proliferation was reduced only for osteogenically induced oADSC (oOS-ADSC) grown on ABTi, compared to non-induced oADSC grown on ABTi and tissue culture polystyrene (P = 0.03 and 0.02 respectively). There was no significant difference for in vitro mineralisation assays comparing oADSC with oOS-ADSC, regardless of implant surface type. oADSC labelled with PKH26 were detected 1 month after surgery within the defect. There was no difference in bone regeneration between the bone defects treated with oADSC vs. just blood clot.

CONCLUSION

After 1-month healing, the use of autologous oADSC did not improve bone regeneration in defects containing titanium devices with different surfaces.

Transplantation of mesenchymal stem cells carrying the human receptor activity-modifying protein 1 gene improves cardiac function and inhibits neointimal proliferation in the carotid angioplasty and myocardial infarction rabbit model

Although transplanting mesenchymal stem cells (MSCs) can improve cardiac function and contribute to endothelial recovery in a damaged artery, natural MSCs may induce neointimal hyperplasia by directly or indirectly acting on vascular smooth muscle cells (VSMCs). Receptor activity-modifying protein 1 (RAMP1) is the component and the determinant of ligand specificity of calcitonin gene-related peptide (CGRP). It is recently reported that CGRP and its receptor involve the proliferation and the apoptosis in vivo and in vitro, and the exogenous RAMP1 enhances the antiproliferation effect of CGRP in VSMCs. Here, we investigated the effects of MSCs overexpressing the human receptor activity-modifying protein 1 (hRAMP1) on heart function and artery repair in rabbit models of myocardial infarction (MI) reperfusion and carotid artery injury. MSCs transfected with a recombinant adenovirus containing the hRAMP1 gene (EGFP-hRAMP1-MSCs) were injected into the rabbit models via the ear vein at 24 h after carotid artery injury and MI 7 days post-EGFP-hRAMP1-MSC transplantation. The cells that expressed both enhance green fluorescent protein (EGFP) and CD31 were detected in the neointima of the damaged artery via immunofluorescence. EGFP-hRAMP1 expression was observed in the injured artery and infarcted myocardium by western blot analysis, confirming that the engineered MSCs targeted the injured artery and infarcted myocardium and expressed hRAMP1 protein. Compared with the EGFP-MSCs group, the EGFP-hRAMP1-MSCs group had a significantly smaller infarcted area and improved cardiac function by 28 days after cell transplantation, as detected by triphenyltetrazolium chloride staining and echocardiography. Additionally, arterial hematoxylin-eosin staining revealed that the area of the neointima and the area ratio of intima/media were significantly decreased in the EGFP-hRAMP1-MSCs group. An immunohistological study showed that the expression of α-smooth muscle antigen and proliferating cell nuclear antigen in the neointima cells of the carotid artery of the EGFP-hRAMP1-MSCs group was approximately 50% lower than that of the EGFP-MSCs group, suggesting that hRAMP1 expression may inhibit VSMCs proliferation within the neointima. Therefore, compared with natural MSCs, EGFP-hRAMP1-engineered MSCs improved infarcted heart function and endothelial recovery from artery injury more efficiently, which will provide valuable information for the development of MSC-based therapy.

Recent advances in mesenchymal stem cell immunomodulation: the role of microvesicles

Mesenchymal stem cells are the most widely used cell phenotype for therapeutic applications, the main reasons being their well-established abilities to promote regeneration of injured tissues and to modulate immune responses. Efficacy was reported in the treatment of several animal models of inflammatory and autoimmune diseases and, in clinical settings, for the management of disorders such as GVHD, systemic lupus erythematosus, multiple sclerosis, and inflammatory bowel disease. The effects of mesenchymal stem cells are believed to be largely mediated by paracrine signals, and several secreted molecules have been identified as contributors to the net biological effect. Recently, it has been recognized that bioactive molecules can be shuttled from cell to cell packed in microvesicles, tiny portions of cytoplasm surrounded by a membrane. Coding and noncoding RNAs are also carried in such microvesicles, transferring relevant biological activity to target cells. Several reports indicate that the regenerative effect of mesenchymal stem cells can be reproduced by microvesicles isolated from their culture medium. More recent evidence suggests that the immunomodulatory effects of mesenchymal stem cells are also at least partially mediated by secreted microvesicles. These findings allow better understanding of the mechanisms involved in cell-to-cell interaction and may have interesting implications for the development of novel therapeutic tools in place of the parent cells.