1. Investigación

Rheumatoid arthritis (RA) is a chronic autoimmune disease that causes progressive joint destruction. Despite the advances in the treatment of this condition there remains a clinical need for safe therapies leading to clinical remission. Mesenchymal stem/stromal cells (MSCs) play immunomodulatory and regenerative roles which can be partly mediated by their secretome. In recent years, the important contribution of extracellular vesicles (EVs) to MSC actions has received an increasing interest as a new therapeutic approach. We provide an extensive overview of the immunomodulatory properties of MSC EVs and their effects on articular cells such as fibroblast-like synoviocytes that play a central role in joint destruction. This review discusses the anti-arthritic effects of MSC EVs in vitro and in animal models of RA as well as their potential mechanisms. Recent preclinical data suggest that transfer of non-coding RNAs by MSC EVs regulates key signaling pathways involved in the pathogenesis of RA. We also examine a number of EV modifications for improving their anti-arthritic efficacy and carrier ability for drug delivery.

The use of mesenchymal stem cells constitutes a promising therapeutic approach, as it has shown beneficial effects in different pathologies. Numerous in vitro, pre-clinical, and, to a lesser extent, clinical trials have been published for osteoarthritis. Osteoarthritis is a type of arthritis that affects diarthritic joints in which the most common and studied effect is cartilage degradation. Nowadays, it is known that osteoarthritis is a disease with a very powerful inflammatory component that affects the subchondral bone and the rest of the tissues that make up the joint. This inflammatory component may induce the differentiation of osteoclasts, the bone-resorbing cells. Subchondral bone degradation has been suggested as a key process in the pathogenesis of osteoarthritis. However, very few published studies directly focus on the activity of mesenchymal stem cells on osteoclasts, contrary to what happens with other cell types of the joint, such as chondrocytes, synoviocytes, and osteoblasts. In this review, we try to gather the published bibliography in relation to the effects of mesenchymal stem cells on osteoclastogenesis. Although we find promising results, we point out the need for further studies that can support mesenchymal stem cells as a therapeutic tool for osteoclasts and their consequences on the osteoarthritic joint.

Background: Osteoarthritis (OA) is a joint disease characterized by cartilage degradation, low-grade synovitis and subchondral bone alterations. In the damaged joint, there is a progressive increase of oxidative stress leading to disruption of chondrocyte homeostasis. The modulation of oxidative stress could control the expression of inflammatory and catabolic mediators involved in OA. We have previously demonstrated that extracellular vesicles (EVs) present in the secretome of human mesenchymal stem cells from adipose tissue (AD-MSCs) exert antiinflammatory and anti-catabolic effects in OA chondrocytes. In the current work, we have investigated whether AD-MSC EVs could regulate oxidative stress in OA chondrocytes as well as the possible contribution of peroxiredoxin 6 (Prdx6). Methods: Microvesicles (MV) and exosomes (EX) were isolated from AD-MSC conditioned medium by differential centrifugation with size filtration. The size and concentration of EVs were determined by resistive pulse sensing. OA chondrocytes were isolated from knee articular cartilage of advanced OA patients. 4-Hydroxynonenal adducts, IL-6 and MMP-13 were determined by enzyme-linked immunosorbent assay. Expression of Prdx6 and autophagic markers was assessed by immunofluorescence and Western blotting. Prdx6 was downregulated in AD-MSCs by transfection with a specific siRNA. Results: MV and to a lesser extent EX significantly reduced the production of oxidative stress in OA chondrocytes stimulated with IL-1β. Treatment with MV resulted in a dramatic upregulation of Prdx6. MV also enhanced the expression of autophagy marker LC3B. We downregulated Prdx6 in AD-MSCs by using a specific siRNA and then MV were isolated. These Prdx6-silenced MV failed to modify oxidative stress and the expression of autophagy markers. We also assessed the possible contribution of Prdx6 to the effects of MV on IL-6 and MMP-13 production. The reduction in the levels of both mediators induced by MV was partly reverted after Prdx6 silencing. Conclusion: Our results indicate that EVs from AD-MSCs regulate the production of oxidative stress in OA chondrocytes during inflammation. Prdx6 may mediate the antioxidant and protective effects of MV. The translational potential of this article: This study gives insight into the protective properties of EVs from AD-MSCs in OA chondrocytes. Our findings support the development of novel therapies based on EVs to prevent or treat cartilage degradation.

Adipose tissue represents an abundant source of mesenchymal stem cells (MSC) for therapeutic purposes. Previous studies have demonstrated the anti-inflammatory potential of adipose tissue-derived MSC (ASC). Extracellular vesicles (EV) present in the conditioned medium (CM) have been shown to mediate the cytoprotective effects of human ASC secretome. Nevertheless, the role of EV in the anti-inflammatory effects of mouse-derived ASC is not known. The current study has investigated the influence of mouse-derived ASC CM and its fractions on the response of mouse-derived peritoneal macrophages against lipopolysaccharide (LPS). CM and its soluble fraction reduced the release of pro-inflammatory cytokines, adenosine triphosphate and nitric oxide in stimulated cells. They also enhanced the migration of neutrophils or monocytes, in the absence or presence of LPS, respectively, which is likely related to the presence of chemokines, and reduced the phagocytic response. The anti-inflammatory effect of CM may be dependent on the regulation of toll-like receptor 4 expression and nuclear factor- B activation. Our results demonstrate the antiinflammatory effects of mouse-derived ASC secretome in mouse-derived peritoneal macrophages stimulated with LPS and show that they are not mediated by EV.

Osteoarthritis (OA) is the most common articular disease in adults and has a current prevalence of 12% in the population over 65 years old. This chronic disease causes damage to articular cartilage and synovial joints, causing pain and leading to a negative impact on patients’ function, decreasing quality of life. There are many limitations regarding OA conventional therapies—pharmacological therapy can cause gastrointestinal, renal, and cardiac adverse effects, and some of them could even be a threat to life. On the other hand, surgical options, such as microfracture, have been used for the last 20 years, but hyaline cartilage has a limited regeneration capacity. In recent years, the interest in new therapies, such as cell-based and cell-free therapies, has been considerably increasing. The purpose of this review is to describe and compare bioregenerative therapies’ efficacy for OA, with particular emphasis on the use of mesenchymal stem cells (MSCs) and platelet-rich plasma (PRP). In OA, these therapies might be an alternative and less invasive treatment than surgery, and a more effective option than conventional therapies.

Mesenchymal stem/stromal cells (MSCs) represent a promising therapy for musculoskeletal diseases. There is compelling evidence indicating that MSC e ects are mainly mediated by paracrine mechanisms and in particular by the secretion of extracellular vesicles (EVs). Many studies have thus suggested that EVs may be an alternative to cell therapy with MSCs in tissue repair. In this review, we summarize the current understanding of MSC EVs actions in preclinical studies of (1) immune regulation and rheumatoid arthritis, (2) bone repair and bone diseases, (3) cartilage repair and osteoarthritis, (4) intervertebral disk degeneration and (5) skeletal muscle and tendon repair. We also discuss the mechanisms underlying these actions and the perspectives of MSC EVs-based strategies for future treatments of musculoskeletal disorders.

Dentistry-applied bioceramic materials are ceramic materials that are categorized asbioinert, bioactive and biodegradable. They share a common characteristic of being specificallydesigned to fulfil their function; they are able to act as root canal sealers, cements, root repair or fillingmaterials. Bioactivity is only attributed to those materials which are capable of inducing a desiredtissue response from the host. The aim of this study is to present a systematic review of availableliterature investigating bioactivity of dentistry-applied bioceramic materials towards dental pulp stemcells, including a bibliometric analysis of such a group of studies and a presentation of the parametersused to assess bioactivity, materials studied and a summary of results. The research question, based onthe PICO model, aimed to assess the current knowledge on dentistry-based bioceramic materials byexploring to what extent they express bioactive properties inin vitroassays and animal studies whenexposed to dental pulp stem cells, as opposed to a control or compared to different bioceramic materialcompositions, for their use in the dentin-pulp complex therapy. A systematic search of the literaturewas performed in six databases, followed by article selection, data extraction, and quality assessment.Studies assessing bioactivity of one or more bioceramic materials (both commercially available ornovel/experimental) towards dental pulp stem cells (DPSCs) were included in our review. A total of37 articles were included in our qualitative review. Quantification of osteogenic, odontogenic andangiogenic markers using reverse transcriptase polymerase chain reaction (RT-PCR) is the prevailingmethod used to evaluate bioceramic material bioactivity towards DPSCs in the current investigativestate, followed by alkaline phosphatase (ALP) enzyme activity assays and Alizarin Red Staining(ARS) to assess mineralization potential. Mineral trioxide aggregate and Biodentine are the prevalentreference materials used to compare with newly introduced bioceramic materials. Available literaturecompares a wide range of bioceramic materials for bioactivity, consisting mostly ofin vitroassays.The desirability of this property added to the rapid introduction of new material compositions makesthis subject a clear candidate for future research.Keywords:bioactivity; bioceramic materials; dental pulp stem cells; systematic reviewMaterials2019,12, 1015; doi:10.3390/ma12071015www.mdpi.com/journal/materials Materials2019,12, 10152 of 301. IntroductionWithin the field of biomedical therapeutics, we can highlight the concept of tissue engineeringto refer to the development of procedures and biomaterials that aim to devise new tissues to replacethose damaged, following the principles of cellular and molecular biology and taking as a premise thesearch for “biological solutions for biological problems” [1].In 2007, the American Association of Endodontists adopted the term “regenerative endodontics”to refer to the concept of tissue engineering applied to the restoration of root canal health, in a waythat continuous development of the root and tissues surrounding it is promoted [2].The introduction of the so-called bioceramic materials meant a great advance for this newparadigm in endodontic therapy [3], given their biocompatible nature and excellent physicochemicalproperties [4]. Categorized as bioinert, bioactive and biodegradable [5], dentistry-applied bioceramicmaterials are ceramic materials which share a common characteristic of being specifically designed tofulfil their function; they are able to act as root canal sealers, cements, root repair or filling materials [4].Applied to vital pulp therapy, bioceramic materials can be used in cases of pulp exposition fromtrauma, caries or other mechanical causes, as direct pulp cappers [6].Properties like biocompatibility and bioactivity are to be expected in dentistry-applied bioceramicmaterials for their use in vital pulp therapy [7]. The first one refers to the “ability to perform as asubstrate that will support the appropriate cellular activity, including the facilitation of molecularand mechanical signaling systems, in order to optimize tissue regeneration, without eliciting anyundesirable local or systemic responses in the eventual host” [8], while bioactivity goes even further,and is only attributed to those materials which are capable of inducing a desired tissue responsefrom the host [9] by the use of biomimetic approaches [10]. The term differs depending on the fieldin which it is implemented, being related to the cellular effects induced by biologically active ionsand substances released from biomaterials in the field of tissue engineering, but referred to as thebiomaterial’s capability of forming hydroxyl apatite mineral on its surface bothin vitroandin vivointhe field of biomaterial science [11].Considering these desirable characteristics of bioceramic materials, it seems convenient to analyzethe interaction between human dental pulp stem cells (hDPSCs), which are post-natal stem cellswith mesenchymal stem cell (MSCs)-like characteristics, like auto-renewal ability and multilineagedifferentiation potential [12], and them; as their combined use could mean and advancement in thefield of regenerative endodontics.Cytotoxicity and biocompatibility of a wide range of bioceramic materials towards dental stemcells (DSCs) have been investigated in numerous studies [13–17]; among others. The well-knownPro-Root MTA (Dentsply Tulsa Dental Specialties, Tulsa, OK, USA) has been shown to increaseosteoblast, fibroblast, cementoblast, odontoblast and pulp cell differentiation, but its handling difficultyamong other limitations encourages for a search for alternative materials [13]. Materials like Biodentine(Septodont, Saint Maurdes-Fosses, France) and TheraCal LC (Bisco Inc., Schaumburg, IL, USA) areexamples of bioceramic materials introduced posteriorly in dentistry for their use in vital pulp therapyas blood clot protectors in pulpal revascularization procedures, standing out for their consistency,easier manipulation and tricalcium silicate composition [16].However, to the best of the authors’ knowledge, there has been no effort to sort and summarizestudies analyzing bioactivity of such materials into more homogenous subgroups that would allow foran easier analysis of the evidence.

Chronic musculoskeletal (MSK) pain is one of the most common medical complaintsworldwide and musculoskeletal injuries have an enormous social and economical impact. Currentpharmacological and surgical treatments aim to relief pain and restore function; however,unsatiscactory outcomes are commonly reported. In order to find an accurate treatment to suchpathologies, over the last years, there has been a significantly increasing interest in cellular therapies,such as adipose-derived mesenchymal stem cells (AMSCs). These cells represent a relatively newstrategy in regenerative medicine, with many potential applications, especially regarding MSKdisorders, and preclinical and clinical studies have demonstrated their efficacy in muscle, tendon,bone and cartilage regeneration. Nevertheless, several worries about their safety and side effects atlong-term remain unsolved. This article aims to review the current state of AMSCs therapy in thetreatment of several MSK diseases and their clinical applications in veterinary and human medicine.

The aim of this study was to evaluate the use of serum type II collagen cleavage epitope and serum hyaluronic acid as biomarkers for treatment monitoring in osteoarthritic dogs. For this purpose, a treatment model based on mesenchymal stem cells derived from adipose tissue combined with plasma rich in growth factors was used. This clinical study included 10 dogs with hip osteoarthritis. Both analytes were measured in serum at baseline, just before applying the treatment, and 1, 3, and 6 months after treatment. These results were compared with those obtained from force plate analysis using the same animals during the same study period. Levels of type II collagen cleavage epitope decreased and those of hyaluronic acid increased with clinical improvement objectively verified via force plate analysis, suggesting these two biomarkers could be effective as indicators of clinical development of joint disease in dogs.

The aim of this study was to assess the static posturography in dogs as a useful tool for diagnosis of lameness by means of the use of a pressure platform. For this purpose, a series of different parameters (pressure distribution, area of support, mean pressure, maximum pressure and statokinesiograms) were obtained from five lame dogs with unilateral elbow osteoarthritis treated with plasma rich in growth factors. Data were obtained before and 3 months after treatment, and results were compared with a control group of sound dogs of similar conformation. Significant differences were found in the above mentioned parameters between sound and lame limbs. Improvement after 3 months of treatment was also detected, demonstrating that this multi-parametric technique is an effective and reliable method for the assessment of lameness in dogs.