FGF2 induces RANKL gene expression as well as IL1β regulated MHC class II in human bone marrow-derived mesenchymal progenitor stromal cells

Sarcopenic obesity and osteoporosis: Research progress and hot spots

Sarcopenic obesity (SO) and osteoporosis (OP) are associated with aging and obesity. The pathogenesis of SO is complex, including glucolipid and skeletal muscle metabolic disorders caused by inflammation, insulin resistance, and other factors. Growing evidence links muscle damage to bone loss. Muscle-lipid metabolism disorders of SO disrupt the balance between bone formation and bone resorption, increasing the risk of OP. Conversely, bones also play a role in fat and muscle metabolism. In the context of aging and obesity, the comprehensive review focuses on the effects of mechanical stimulation, mesenchymal stem cells (MSCs), chronic inflammation, myokines, and adipokines on musculoskeletal, at the same time, the impact of osteokines on muscle-lipid metabolism were also analyzed. So far, exercise combined with diet therapy is the most effective strategy for increasing musculoskeletal mass. A holistic treatment of musculoskeletal diseases is still in the preliminary exploration stage. Therefore, this article aims to improve the understanding of musculoskeletal -fat interactions in SO and OP, explores targets that can provide holistic treatment for SO combined with OP, and discusses current limitations and challenges. We hope to provide relevant ideas for developing specific therapies and improving disease prognosis in the future.

Expression of HLA-DR by mesenchymal stromal cells in the platelet lysate era: an obsolete release criterion for MSCs?

BACKGROUND

According to the definition of the International Society for Cell and Gene Therapy (ISCT), mesenchymal stromal cells (MSCs) do not express HLA-DR. This phenotypic marker as a release criterion for clinical use was established at a time when MSCs were expanded in fetal bovine serum (FBS)-containing media. Replacement of FBS with platelet lysate (PLs) as a medium supplement induced a significantly higher fraction of MSCs to express MHC class II antigens.

METHODS

As this raised concerns that such MSCs may play the role of antigen-presenting cells for T cells, in the current study, we studied major factors that may induce HLA-DR on MSCs by means of flow cytometry and real-time polymerase chain reaction. The immunomodulatory potential of MSCs was assessed by a mixed lymphocyte reaction.

RESULTS

Our results demonstrated that a very low percentage of generated and expanded MSCs in FBS express HLA-DR (median: 1.1%, range: 0.3-22%) compared to MSCs generated and expanded in PLs (median: 28.4%, range: 3.3-73.7%). Analysis of the cytokine composition of ten PLs showed a significant positive correlation between the levels of IL-1β, IL-4, IL-10, IL-17, bFGF and expression of HLA-DR, in contrast to no correlation with the age of MSC donors and HLA-DR (r = 0.21). Both MSCs expressing low and high levels of HLA-DR expressed class II transactivator (CIITA), a master gene coding for these molecules. Our results demonstrate for the first time that MSCs with constitutively high levels of HLA-DR also express moderate levels of indoleamine 2,3-dioxygenase (IDO). Treatment of MSCs with multiple doses of TGF-β1 at passage 0 (P0) and passage 1 (P1) completely abrogated HLA-DR and IDO expression. In contrast, treatment of MSCs with a single dose of TGF-β1 after P0 only partially reduced the expression of HLA-DR and CIITA. Remarkably, increased expression of HLA-DR on MSCs that constitutively express high levels of this antigen after overnight incubation with IFN-γ was rather unaffected by incubation with TGF-β1. However, treatment of MSCs with TGF-β1 for 24 h completely abrogated constitutive expression of IDO.

CONCLUSIONS

Irrespective of HLA-DR expression at the population level, all MSC preparations significantly inhibited the proliferation of stimulated peripheral blood mononuclear cells, indicating that HLA-DR represents an obsolete release marker for the clinical use of MSCs.

TNF-α and IFN-γ Participate in Improving the Immunoregulatory Capacity of Mesenchymal Stem/Stromal Cells: Importance of Cell-Cell Contact and Extracellular Vesicles

Mesenchymal stem/stromal cells (MSCs) have an immunoregulatory capacity and have been used in different clinical protocols requiring control of the immune response. However, variable results have been obtained, mainly due to the effect of the microenvironment on the induction, increase, and maintenance of MSC immunoregulatory mechanisms. In addition, the importance of cell–cell contact for MSCs to efficiently modulate the immune response has recently been highlighted. Because these interactions would be difficult to achieve in the physiological context, the release of extracellular vesicles (EVs) and their participation as intermediaries of communication between MSCs and immune cells becomes relevant. Therefore, this article focuses on analyzing immunoregulatory mechanisms mediated by cell contact, highlighting the importance of intercellular adhesion molecule-1 (ICAM-1) and the participation of EVs. Moreover, the effects of tumor necrosis factor-alpha (TNF-α) and interferon-gamma (IFN-γ), the main cytokines involved in MSC activation, are examined. These cytokines, when used at the appropriate concentrations and times, would promote increases in the expression of immunoregulatory molecules in the cell and allow the acquisition of EVs enriched with these molecules. The establishment of certain in vitro activation guidelines will facilitate the design of conditioning protocols to obtain functional MSCs or EVs in different pathophysiological conditions.

Human Bone Marrow Mesenchymal Stem/Stromal Cells Exposed to an Inflammatory Environment Increase the Expression of ICAM-1 and Release Microvesicles Enriched in This Adhesive Molecule: Analysis of the Participation of TNF-α and IFN-γ

Bone marrow mesenchymal stem/stromal cells (BM-MSCs) have immunoregulatory capacity; therefore, they have been used in different clinical protocols in which it is necessary to decrease the immune response. This capacity is mainly regulated by TNF-α and IFN-γ, and it has been observed that cell-cell contact, mainly mediated by ICAM-1, is important for MSCs to carry out efficient immunoregulation. Therefore, in the present work, we analyzed the effect of TNF-α alone or in combination with IFN-γ on the expression of ICAM-1. Besides, given the importance of cell contact in the immunoregulatory function of MSCs, we analyzed whether these cells release ICAM-1⁺ microvesicles (MVs). Our results show for the first time that TNF-α is capable of increasing the early expression of ICAM-1 in human BM-MSCs. Also, we observed that TNF-α and IFN-γ have a synergistic effect on the increase in the expression of ICAM-1. Furthermore, we found that BM-MSCs exposed to an inflammatory environment release MVs enriched in ICAM-1 (MVs-ICAM-1^high). The knowledge generated in this study will contribute to the improvement of in vitro conditioning protocols that favor the therapeutic effect of these cells or their products.

FGF/FGFR signaling in health and disease

Growing evidences suggest that the fibroblast growth factor/FGF receptor (FGF/FGFR) signaling has crucial roles in a multitude of processes during embryonic development and adult homeostasis by regulating cellular lineage commitment, differentiation, proliferation, and apoptosis of various types of cells. In this review, we provide a comprehensive overview of the current understanding of FGF signaling and its roles in organ development, injury repair, and the pathophysiology of spectrum of diseases, which is a consequence of FGF signaling dysregulation, including cancers and chronic kidney disease (CKD). In this context, the agonists and antagonists for FGF-FGFRs might have therapeutic benefits in multiple systems.

RIPK1 suppresses apoptosis mediated by TNF and caspase-3 in intervertebral discs

BACKGROUND

Low back pain has become a serious social and economic burden and the leading cause of disability worldwide. Among a variety of pathophysiological triggers, intervertebral disc (IVD) degeneration plays a primary underlying role in causing such pain. Specifically, multiple independent endplate changes have been implicated in the initiation and progression of IVD degeneration.

METHODS

In this study, we built a signaling network comprising both well-characterized IVD pathology-associated proteins as well as some potentially correlated proteins that have been associated with one or more of the currently known pathology-associated proteins. We then screened for the potential IVD degeneration-associated proteins using patients' normal and degenerative endplate specimens. Short hairpin RNAs for receptor interacting serine/threonine kinase 1 (RIPK1) were constructed to examine the effects of RIPK1 knockdown in primary chondrocyte cells and in animal models of caudal vertebra intervertebral disc degeneration in vivo.

RESULTS

RIPK1 was identified as a potential IVD degeneration-associated protein based on IVD pathology-associated signaling networks and the patients' degenerated endplate specimens. Construction of the short hairpin RNAs was successful, with short-term RIPK1 knockdown triggering inflammation in the primary chondrocytes, while long-term knockdown triggered apoptosis through cleavage of the caspase 3 pathway, down-regulated NF-κB and mitogen-activating protein kinase (MAPK)s cascades, and decreased cell survival and inflammation. Animal models of caudal vertebra intervertebral disc degeneration further demonstrated that apoptosis was induced by up-regulation of tumor necrosis factor (TNF) accompanied by down-regulation of NF-κB and MAPKs cascades that are dependent on caspase and RIPK1.

CONCLUSIONS

These results provide proof-of-concept for developing novel therapies to combat IVD degeneration through interfering with RIPK1-mediated apoptosis signaling pathways especially in patients with RIPK1 abnormality.

Mesenchymal Progenitors Derived from Different Locations in Long Bones Display Diverse Characteristics

Mesenchymal progenitors within bone marrow have multiple differentiation potential and play an essential role in the maintenance of adult skeleton homeostasis. Mesenchymal progenitors located in bone regions other than the bone marrow also display bone-forming properties. However, owing to the differences in each distinct microenvironment, the mesenchymal characteristics of skeletal progenitor cells within different regions of long bones may show some differences. In order to clearly elucidate these differences, we performed a comparative study on mesenchymal progenitors from different regions of long bones. Here, we isolated mesenchymal progenitors from the periosteum, endosteum, and bone marrow of rat long bones. The three groups exhibited similar cellular morphologies and expressed the typical surface markers associated with mesenchymal stem cells. Interestingly, after cell proliferation assays and bidirectional differentiation analysis, periosteal mesenchymal progenitors showed a higher proliferative ability and adipogenic differentiation potential. In contrast, endosteal mesenchymal progenitors were more prone to osteogenic differentiation. Using in vitro osteoclast culture systems, conditioned media from different mesenchymal progenitor cultures were used to induce osteoclastic differentiation. Osteoclast formation was found to be significantly promoted by the secretion of RANKL and IL-6 by endosteal progenitors. Overall, our results provide strong evidence for the importance of selecting the appropriate source of skeletal progenitors for applications in future skeleton regeneration therapies.

Expression of inflammatory cytokines in mesenchymal stromal cells is sensitive to culture conditions and simple cell manipulations

BACKGROUND

Mesenchymal stromal cells (MSCs) can be used in several clinical applications. While MSCs are frequently cultured in fetal bovine serum for in vitro experimentation, human serum supplements are required for cells to be used in patients. Here we show how different human serum supplements and in vitro manipulations used during the cell culture impact on MSC proliferation rate and expression of inflammatory molecules.

METHODS

MSCs were cultured in medium supplemented with human plasma or serum combined with human platelet lysate (PL) and/or basic fibroblast growth factor (FGF2). Real time RT-PCR and western blot were used to assess expression of inflammatory cytokines.

RESULTS

Serum with addition of FGF2 gave the fastest proliferation rate. However, serum with FGF2 also increased expression of genes encoding inflammatory cytokines. The most favorable expansion condition for chondrogenic differentiation and inhibition of cartilage matrix degrading enzymes was plasma supplemented with PL and FGF2. Detachment of cells using trypsin gave considerable upregulation of inflammatory cytokine mRNAs which lasted for up to 24 h, with concomitant increase in protein levels. Even the gentle act of changing medium led to upregulation of cytokine mRNA, caused by addition of fresh serum.

DISCUSSION

Different culture conditions and simple cell manipulation influence proliferation rate and expression of inflammatory genes. Supplementing culture medium with allogeneic AB serum and FGF2 during monolayer expansion supported cell expansion better than other supplements, but also induced the highest levels of inflammatory cytokines and gave inferior results for chondrogenic differentiation. The importance of the composition of the culture medium and even gentle in vitro manipulation of the cells should be taken into account in the planning of procedures using in vitro expanded MSCs.

Geraniin inhibits TNF-α-induced impairments of osteogenesis through NF-κB and p38 MAPK signalling pathways in bone marrow stem cells

Objective

To study the effect and mechanism of geraniin on the osteogenesis of tumour necrosis factor-alpha (TNF-α)-induced bone marrow-derived mesenchymal stem cells (BMSCs).

Methods

BALB/c mice aged 4–6 weeks were used to collect BMSC. Methyl thiazol tetrazolium assay and lactate dehydrogenase assay were used to analyse the effect of geraniin on the TNF-α-induced impairments of osteogenesis in BMSCs. BMSCs were stained using Oil red to measure the osteogenesis. Real-time reverse transcription PCR and western blot analysis were used to analyse the expression of RunX2 and Osx miRNA, and expression of NF-κB, IкB-α and p38 MAPK protein in BMSCs.

Results

2.5 µM geraniin significantly inhibited TNF-α-induced BMSCs cytotoxicity. 2.5 µM geraniin significantly reduced the expression of RunX2 and Osx miRNA in TNF-α-induced BMSCs. 2.5 µM geraniin suppressed the expression of NF-κB and p38 MAPK protein and promoted the expression of IкB-α protein in the TNF-α-induced BMSCs.

Conclusion

Geraniin inhibits TNF-α-induced impairments of osteogenesis through NF-κB/IкB-α and p38 MAPK signalling pathways in BMSCs.

Murine Rankl-/- Mesenchymal Stromal Cells Display an Osteogenic Differentiation Defect Improved by a RANKL-Expressing Lentiviral Vector

Autosomal recessive osteopetrosis (ARO) is a severe bone disease characterized by increased bone density due to impairment in osteoclast resorptive function or differentiation. Hematopoietic stem cell transplantation is the only available treatment; however, this therapy is not effective in RANKL-dependent ARO, since in bone this gene is mainly expressed by cells of mesenchymal origin. Of note, whether lack of RANKL production might cause a defect also in the bone marrow (BM) stromal compartment, possibly contributing to the pathology, is unknown. To verify this possibility, we generated and characterized BM mesenchymal stromal cell (BM-MSC) lines from wild type and Rankl^-/- mice, and found that Rankl^-/- BM-MSCs displayed reduced clonogenicity and osteogenic capacity. The differentiation defect was significantly improved by lentiviral transduction of Rankl^-/- BM-MSCs with a vector stably expressing human soluble RANKL (hsRANKL). Expression of Rankl receptor, Rank, on the cytoplasmic membrane of BM-MSCs pointed to the existence of an autocrine loop possibly activated by the secreted cytokine. Based on the close resemblance of RANKL-defective osteopetrosis in humans and mice, we expect that our results are also relevant for RANKL-dependent ARO patients. Data obtained in vitro after transduction with a lentiviral vector expressing hsRANKL would suggest that restoration of RANKL production might not only rescue the defective osteoclastogenesis of this ARO form, but also improve a less obvious defect in the osteoblast lineage, thus possibly achieving higher benefit for the patients, when the approach is translated to clinics. Stem Cells 2017;35:1365-1377.

Stem cell transplantation and mesenchymal cells to treat autoimmune diseases

Since the start of the international stem cell transplantation project in 1997, over 2000 patients have received a haematopoietic stem cell transplant (HSCT), mostly autologous, as treatment for a severe autoimmune disease, the majority being multiple sclerosis (MS), systemic sclerosis (SSc) and Crohn's disease. There was an overall 85% 5-year survival and 43% progression-free survival. Around 30% of patients in all disease subgroups had a complete response, often durable despite full immune reconstitution. In many cases, e.g. systemic sclerosis, morphological improvement such as reduction of skin collagen and normalization of microvasculature was documented, beyond any predicted known effects of intense immunosuppression alone. It is hoped that the results of the three running large prospective randomized controlled trials will allow modification of the protocols to reduce the high transplant-related mortality which relates to regimen intensity, age of patient, and comorbidity. Mesenchymal stromal cells (MSC), often incorrectly called stem cells, have been the intense focus of in vitro studies and animal models of rheumatic and other diseases over more than a decade. Despite multiple plausible mechanisms of action and a plethora of positive in vivo animal studies, few randomised controlled clinical trials have demonstrated meaningful clinical benefit in any condition so far. This could be due to confusion in cell product terminology, complexity of clinical study design and execution or agreement on meaningful outcome measures. Within the rheumatic diseases, SLE and rheumatoid arthritis (RA) have received most attention. Uncontrolled multiple trial data from over 300 SLE patients have been published from one centre suggesting a positive outcome; one single centre comparative study in 172 RA was positive. In addition, small numbers of patients with Crohn's disease, multiple sclerosis, primary Sjögren's disease, polymyositis/dermatomyositis and type II diabetes mellitus have received MSC therapeutically. The possible reasons for this apparent mismatch between expectation and clinical reality will be discussed.

Pharmacological Therapy in the Heart as an Alternative to Cellular Therapy: A Place for the Brain Natriuretic Peptide?

The discovery that stem cells isolated from different organs have the ability to differentiate into mature beating cardiomyocytes has fostered considerable interest in developing cellular regenerative therapies to treat cardiac diseases associated with the loss of viable myocardium. Clinical studies evaluating the potential of stem cells (from heart, blood, bone marrow, skeletal muscle, and fat) to regenerate the myocardium and improve its functional status indicated that although the method appeared generally safe, its overall efficacy has remained modest. Several issues raised by these studies were notably related to the nature and number of injected cells, as well as the route and timing of their administration, to cite only a few. Besides the direct administration of cardiac precursor cells, a distinct approach to cardiac regeneration could be based upon the stimulation of the heart's natural ability to regenerate, using pharmacological approaches. Indeed, differentiation and/or proliferation of cardiac precursor cells is controlled by various endogenous mediators, such as growth factors and cytokines, which could thus be used as pharmacological agents to promote regeneration. To illustrate such approach, we present recent results showing that the exogenous administration of the natriuretic peptide BNP triggers “endogenous” cardiac regeneration, following experimental myocardial infarction.

Mesenchymal stromal cells and rheumatic disorders

Mesenchymal stromal cells (MSC), often incorrectly called stem cells, have been the intense focus of in vitro studies and animal models of rheumatic and other diseases over more than a decade. Despite multiple plausible mechanisms of action and a plethora of positive in vivo animal studies, few randomised controlled clinical trials have demonstrated meaningful clinical benefit in any condition so far. This could be due to confusion in cell product terminology, complexity of clinical study design and execution or agreement on meaningful outcome measures. It could also indicate that MSC as currently employed are ineffective. Within the rheumatic diseases, SLE, rheumatoid arthritis (RA) and osteoarthritis (OA) have received most attention. Uncontrolled multiple trial data from over 300 SLE patients have been published from one centre suggesting a positive outcome; one single centre comparative study in 172 RA was positive and no human studies have compared intra-articular MSC therapy to non-MSC techniques for osteoarthritis in the absence of surgery. Two randomised studies suggested benefit from the addition of bone marrow derived MSC and peripheral blood mononuclear cells added to surgical "standard of care" in knee OA and knee focal cartilage defects, respectively. The possible reasons for this apparent mismatch between expectation and clinical reality will be discussed.