Transplantation of Adipose Tissue-Derived Mesenchymal Stem Cell (ATMSC) Expressing Alpha-1 Antitrypsin Reduces Bone Loss in Ovariectomized Osteoporosis Mice

Adipokines regulate mesenchymal stem cell osteogenic differentiation

Mesenchymal stem cells (MSCs) can differentiate into various tissue cell types including bone, adipose, cartilage, and muscle. Among those, osteogenic differentiation of MSCs has been widely explored in many bone tissue engineering studies. Moreover, the conditions and methods of inducing osteogenic differentiation of MSCs are continuously advancing. Recently, with the gradual recognition of adipokines, the research on their involvement in different pathophysiological processes of the body is also deepening including lipid metabolism, inflammation, immune regulation, energy disorders, and bone homeostasis. At the same time, the role of adipokines in the osteogenic differentiation of MSCs has been gradually described more completely. Therefore, this paper reviewed the evidence of the role of adipokines in the osteogenic differentiation of MSCs, emphasizing bone formation and bone regeneration.

Alzheimer's Disease and Impaired Bone Microarchitecture, Regeneration and Potential Genetic Links

Alzheimer's Disease (AD) and osteoporosis are both age-related degenerative diseases. Many studies indicate that these two diseases share common pathogenesis mechanisms. In this review, the osteoporotic phenotype of AD mouse models was discussed, and shared mechanisms such as hormonal imbalance, genetic factors, similar signaling pathways and impaired neurotransmitters were identified. Moreover, the review provides recent data associated with these two diseases. Furthermore, potential therapeutic approaches targeting both diseases were discussed. Thus, we proposed that preventing bone loss should be one of the most important treatment goals in patients with AD; treatment targeting brain disorders is also beneficial for osteoporosis.

Human Alpha 1 Antitrypsin Suppresses NF-κB Activity and Extends Lifespan in Adult Drosophila

Human alpha 1 antitrypsin (hAAT) is a multifunctional protein that has been shown to have anti-inflammatory and cellular protective properties. While previous studies demonstrated the antiaging potential of hAAT, the mechanism(s) underlying the antiaging effect remain elusive. In this study, we performed a detailed analysis of transcriptomic data that indicated that NF-κB-targeted genes and NF-κB-regulated pathways were selectively inhibited by hAAT treatment. We further showed that the first detectable impact of hAAT treatment was the inhibition of the nuclear activity of NF-κB. Subsequently, hAAT treatment suppressed the mRNA levels of NF-κB-targeted genes, as well as NF-κB itself (P65 and P50), in human senescent cells. Using Drosophila models, we further examined the impact of hAAT on locomotor activity and endurance. Finally, using an adult-specific promotor, we demonstrated that overexpression of hAAT in the late stage of life significantly extended the lifespan of transgenic flies. These results extend the current understanding of the anti-inflammatory function of hAAT.

EndMT-derived mesenchymal stem cells: a new therapeutic target to atherosclerosis treatment

Cardiovascular diseases, such as coronary artery disease and stroke, are the main threats to human health worldwide. Atherosclerosis, a chronic inflammatory disorder, plays a role as an initiator of all of the above-mentioned diseases. Cell therapy for diseases has attracted widespread attention. Mesenchymal stem cells (MSCs) are a type of stem cell that still exist in adults and have the characteristics of self-renewal ability, pluripotent differentiation potential, immunomodulation, tissue regeneration, anti-inflammation and low immunogenicity. In light of the properties of MSCs, some researchers have begun to target MSCs to create a possible way to alleviate atherosclerosis. Most of these studies are focused on MSC transplantation, injecting MSCs to modulate macrophages, the key inflammatory cell in atherosclerosis plaque. According to recent studies, researchers found that endothelial-to-mesenchymal transition (EndMT) has something to do with atherosclerosis development. A new cell type MSC might also appear during the EndMT process. In this article, we summarize the characteristics of MSCs, the latest progress of MSC research and its application prospects, and in view of the process of EndMT occurring in atherosclerosis, we propose some new ideas for the treatment of atherosclerosis by targeting MSCs.

Inhibition of miRNA-100 facilitates bone regeneration defects of mesenchymal stem cells in osteoporotic mice through the protein kinase B pathway

Osteoporotic patients suffer from bone microstructure damage and are prone to fracture and bone defect. Due to the damage of bone healing ability, the bone repair of osteoporotic patients is usually slow. Here we aimed to explore the function and potential molecular mechanism of miR-100 in osteogenic differentiation ability of bone marrow stem cells (BMSCs). Ovariectomy was performed on mice to induce osteoporosis. BMSCs were extracted from normal and ovariectomized (OVX) mice to examine the effect of microRNA (miR)-100 on BMSC osteogenic differentiation. Hematoxylin and eosin (H&E) staining and safranin O-fast green staining assays were performed on femur tissues to reveal pathological changes. The osteogenic differentiation of BMSCs were determined by Alkaline Phosphatase and Alizarin red staining assays. The results showed that miR-100 expression was significantly upregulated in bone tissues and BMSCs from osteoporotic mice. MiR-100 knockdown partially improved osteogenic function of OVX mice-derived BMSCs. Next, mechanistic target of rapamycin kinase (MTOR) was identified as the target downstream miR-100. MiR-100 deficiency can activate the protein kinase B (AKT)/mTOR pathway. MiR-100 controlled the osteogenic function of BMSCs by the AKT/mTOR pathway. Collectively, our findings demonstrate that inhibition of miR-100 facilitates bone regeneration defects of BMSCs in osteoporotic mice through AKT pathway, indicating that miR-100 might be an effective target for the treatment of osteoporotic mandibular injury and bone defect diseases.

An indispensable tool: Exosomes play a role in therapy for radiation damage

Radiotherapy is one of the three main treatments for tumors. Almost 70% of tumor patients undergo radiotherapy at different periods. Although radiotherapy can enhance the local control rate of tumors and patients' quality of life, normal tissues often show radiation damage following radiotherapy. In recent years, several studies have shown that exosomes could be biomarkers for diseases and be involved in the treatment of radiation damage. Exosomes are nanoscale vesicles containing complex miRNAs and proteins. They can regulate the inflammatory response, enhance the regeneration effect of damaged tissue, and promote the repair of damaged tissues and cells, extending their survival time. In addition, their functions are achieved by paracrine signaling. In this review, we discuss the potential of exosomes as biomarkers and introduce the impact of exosomes on radiation damage in different organs and the hematopoietic system in detail.

Mesenchymal stem cells modifications for enhanced bone targeting and bone regeneration

In pathological bone conditions (e.g., osteoporotic fractures or critical size bone defects), increasing the pool of osteoblast progenitor cells is a promising therapeutic approach to facilitate bone healing. Since mesenchymal stem cells (MSCs) give rise to the osteogenic lineage, a number of clinical trials investigated the potential of MSCs transplantation for bone regeneration. However, the engraftment of transplanted cells is often hindered by insufficient oxygen and nutrients supply and the tendency of MSCs to home to different sites of the body. In this review, we discuss various approaches of MSCs transplantation for bone regeneration including scaffold and hydrogel constructs, genetic modifications and surface engineering of the cell membrane aimed to improve homing and increase cell viability, proliferation and differentiation.

Alpha-1-Antitrypsin Ameliorates Pristane Induced Diffuse Alveolar Hemorrhage in Mice

Diffuse alveolar hemorrhage (DAH) is a fatal complication in patients with lupus. DAH can be induced in B6 mice by an intraperitoneal injection of pristane. Since human alpha-1-antitrypsin (hAAT) is an anti-inflammatory and immuno-regulatory protein, we investigated the protective effect of hAAT against pristane-induced DAH in B6 mice and hAAT transgenic (hAAT-Tg) mice. We first showed that hAAT Tg expression lowers TNF-α production in B cells, as well as CD4+ T cells in untreated mice. Conversely, the frequency of regulatory CD4+CD25+ and CD4+CD25-IL-10+ cells was significantly higher in hAAT-Tg than in B6 mice. This confirmed the anti-inflammatory effect of hAAT that was observed even at steady state. One week after a pristane injection, the frequency of peritoneal Ly6C^hi inflammatory monocytes and neutrophils in hAAT-Tg mice was significantly lower than that in B6 mice. Importantly, pristane-induced DAH was completely prevented in hAAT-Tg mice and this was associated with a modulation of anti- to pro-inflammatory myeloid cell ratio/balance. We also showed that treatment with hAAT decreased the severity of DAH in B6 mice. These results showed for the first time that hAAT has a therapeutic potential for the treatment of DAH.

Stem cells in Osteoporosis: From Biology to New Therapeutic Approaches

Osteoporosis is a systemic disease that affects the skeleton, causing reduction of bone density and mass, resulting in destruction of bone microstructure and increased risk of bone fractures. Since osteoporosis is a disease affecting the elderly and the aging of the world's population is constantly increasing, it is expected that the incidence of osteoporosis and its financial burden on the insurance systems will increase continuously and there is a need for more understanding this condition in order to prevent and/or treat it. At present, available drug therapy for osteoporosis primarily targets the inhibition of bone resorption and agents that promote bone mineralization, designed to slow disease progression. Safe and predictable pharmaceutical means to increase bone formation have been elusive. Stem cell therapy of osteoporosis, as a therapeutic strategy, offers the promise of an increase in osteoblast differentiation and thus reversing the shift towards bone resorption in osteoporosis. This review is focused on the current views regarding the implication of the stem cells in the cellular and physiologic mechanisms of osteoporosis and discusses data obtained from stem cell-based therapies of osteoporosis in experimental animal models and the possibility of their future application in clinical trials.

BM-MSC-derived exosomes alleviate radiation-induced bone loss by restoring the function of recipient BM-MSCs and activating Wnt/β-catenin signaling

Background

Radiotherapy to cancer patients is inevitably accompanied by normal tissue injury, and the bone is one of the most commonly damaged tissues. Damage to bone marrow mesenchymal stem cells (BM-MSCs) induced by radiation is thought to be a major cause of radiation-induced bone loss. Exosomes exhibit great therapeutic potential in the treatment of osteoporosis, but whether exosomes are involved in radiation-induced bone loss has not been thoroughly elucidated to date. The main purpose of this study is to investigate the role of exosomes derived from BM-MSCs in restoring recipient BM-MSC function and alleviating radiation-induced bone loss.

Methods

BM-MSC-derived exosomes were intravenously injected to rats immediately after irradiation. After 28 days, the left tibiae were harvested for micro-CT and histomorphometric analysis. The effects of exosomes on antioxidant capacity, DNA damage repair, proliferation, and cell senescence of recipient BM-MSCs were determined. Osteogenic and adipogenic differentiation assays were used to detect the effects of exosomes on the differentiation potential of recipient BM-MSCs, and related genes were measured by qRT-PCR and Western blot analysis. β-Catenin expression was detected at histological and cytological levels.

Results

BM-MSC-derived exosomes can attenuate radiation-induced bone loss in a rat model that is similar to mesenchymal stem cell transplantation. Exosome-treated BM-MSCs exhibit reduced oxidative stress, accelerated DNA damage repair, and reduced proliferation inhibition and cell senescence-associate protein expression compared with BM-MSCs that exclusively received irradiation. Following irradiation, exosomes promote β-catenin expression in BM-MSCs and restore the balance between adipogenic and osteogenic differentiation.

Conclusions

Our findings indicate that BM-MSC-derived exosomes take effects by restoring the function of recipient BM-MSCs. Therefore, exosomes may represent a promising cell-free therapeutic approach for the treatment of radiation-induced bone loss.

Electronic supplementary material

The online version of this article (10.1186/s13287-018-1121-9) contains supplementary material, which is available to authorized users.

Adipose Stem Cell Translational Applications: From Bench-to-Bedside

During the last five years, there has been a significantly increasing interest in adult adipose stem cells (ASCs) as a suitable tool for translational medicine applications. The abundant and renewable source of ASCs and the relatively simple procedure for cell isolation are only some of the reasons for this success. Here, we document the advances in the biology and in the innovative biotechnological applications of ASCs. We discuss how the multipotential property boosts ASCs toward mesenchymal and non-mesenchymal differentiation cell lineages and how their character is maintained even if they are combined with gene delivery systems and/or biomaterials, both in vitro and in vivo.

Alpha 1 Antitrypsin Gene Therapy Extends the Lifespan of Lupus-Prone Mice

Systemic lupus erythematosus (SLE) is a heterogeneous autoimmune disease characterized by high levels of pathogenic autoantibodies and tissue damage. Multiple studies showed that dendritic cell (DC) activation plays a critical role in SLE pathogenesis. Human alpha 1 antitrypsin (hAAT) is a serine proteinase inhibitor with potent anti-inflammatory and cytoprotective properties. In this study, we first examined the effects of hAAT on the functions of DCs from lupus-prone mice, and we showed that hAAT treatment efficiently inhibited CpG- (TLR9 agonist) induced activation of bone marrow-derived conventional and plasmacytoid DCs as well as the production of pro-inflammatory cytokines. The hAAT treatment also attenuated DC help for B cell proliferation and immunoglobulin M (IgM) production. We next tested the protective effect of hAAT protein and gene therapy using recombinant adeno-associated virus 8 (rAAV8-CB-hAAT) in a spontaneous lupus mouse model, and we showed that both treatments decreased autoantibody levels. Importantly, rAAV8-CB-hAAT did not induce an immune response to its transgene product (hAAT), but it showed more pronounced therapeutic effects in reducing urine protein levels and extending the lifespan of these mice. These results indicate that AAT has therapeutic potential in the treatment of SLE in humans.

Gene Delivery of Alpha-1-Antitrypsin Using Recombinant Adeno-Associated Virus (rAAV)

The challenge for alpha-1-antitrypsin (AAT also known as SERPINA1) gene therapy is to achieve long term and high levels of AAT production. Recombinant adeno-associated virus (rAAV) vector has several advantages for AAT gene delivery including no viral genes in the vector, no requirement of integration for long-term transgene expression, low immunogenicity, and wide tropism. AAV-mediated AAT gene therapy has been developed and tested in animal models for AAT deficiency, type 1 diabetes, rheumatoid arthritis, and osteoporosis. AAV-mediated AAT gene therapy has also been tested in clinical studies and has shown promising results. Here we describe the methods of rAAV-AAT vector construction and production as well as AAT gene delivery through (1) liver-directed, (2) muscle-directed, and (3) mesenchymal stem cell (MSC)-mediated routes. We will also describe methods for the evaluation of AAT expression for each delivery approach.

A bone-targeting drug-delivery system based on Semaphorin 3A gene therapy ameliorates bone loss in osteoporotic ovariectomized mice

Osteoporosis is a serious health problem worldwide. Semaphorins (Sema) have been described as key molecules involved in the cross-talk between bone cells (osteoblasts/osteoclasts). In this study, we investigated whether plasmid containing Sema3a could ameliorate bone loss in an ovariectomized (OVX) mouse model via (AspSerSer)₆, a selectively bone-targeting moiety. Plasmid pcDNA3.1(+)-Sema3a-GFP was fabricated and transfected cells with the plasmid demonstrated statistically higher levels of Sema3A in vitro (p < 0.001). Mice were ovariectomized and injected twice weekly with (AspSerSer)₆-(STR-R8)+pcDNA3.1(+)-Sema3a-GFP for four weeks. The aim of the study was twofold: firstly to design an effective bone-targeting drug-delivery system (AspSerSer)₆. Secondly, the effects of Sem3A gene therapy on bone loss was investigated. Here, the targeting selectivity of pcDNA3.1(+)-Sema3a-GFP via (AspSerSer)₆ to the trabecular bone surface was firstly verified by histological observation of frozen sections and immunofluorescence staining. Then, bone microstructure analysis by Micro-CT indicated significantly less bone loss in mice treated with (AspSerSer)₆-(STR-R8)+pcDNA3.1(+)-Sema3a-GFP compared to the control group (p < 0.05). Furthermore,H&E staining and Safranin O staining of the decalcified sections demonstrated statistically significantly higher bone area/total area in the mice that were injected with (AspSerSer)₆-(STR-R8)+pcDNA3.1(+)-Sema3a-GFP (p < 0.001, p < 0.01,respectively). TRAP staining and immunohistochemistry staining of COL I demonstrated lower numbers of osteoclasts and significantly increased numbers of osteoblasts in the bone-targeting moiety delivering pcDNA3.1(+)-Sema3a-GFP group, when compared to the control group (p < 0.01, p < 0.001,respectively). Together, our findings have identified that, (AspSerSer)₆, a bone-targeting drug-delivery system based on semaphorin3A gene therapy, ameliorated bone loss in osteoporotic ovariectomized mice, by suppressing osteoclastic bone resorption and simultaneously increasing osteoblastic bone formation. Gene therapy by local site-specific Sema3A overexpression might be a potential new strategy for treating osteoporosis and bone defects.

Point Mutation of a Non-Elastase-Binding Site in Human α1-Antitrypsin Alters Its Anti-Inflammatory Properties

Introduction

Human α1-antitrypsin (hAAT) is a 394-amino acid long anti-inflammatory, neutrophil elastase inhibitor, which binds elastase via a sequence-specific molecular protrusion (reactive center loop, RCL; positions 357-366). hAAT formulations that lack protease inhibition were shown to maintain their anti-inflammatory activities, suggesting that some attributes of the molecule may reside in extra-RCL segments. Here, we compare the protease-inhibitory and anti-inflammatory profiles of an extra-RCL mutation (cys232pro) and two intra-RCL mutations (pro357cys, pro357ala), to naïve [wild-type (WT)] recombinant hAAT, in vitro, and in vivo.

Methods

His-tag recombinant point-mutated hAAT constructs were expressed in HEK-293F cells. Purified proteins were evaluated for elastase inhibition, and their anti-inflammatory activities were assessed using several cell-types: RAW264.7 cells, mouse bone marrow-derived macrophages, and primary peritoneal macrophages. The pharmacokinetics of the recombinant variants and their effect on LPS-induced peritonitis were determined in vivo.

Results

Compared to WT and to RCL-mutated hAAT variants, cys232pro exhibited superior anti-inflammatory activities, as well as a longer circulating half-life, despite all three mutated forms of hAAT lacking anti-elastase activity. TNFα expression and its proteolytic membranal shedding were differently affected by the variants; specifically, cys232pro and pro357cys altered supernatant and serum TNFα dynamics without suppressing transcription or shedding.

Conclusion

Our data suggest that the anti-inflammatory profile of hAAT extends beyond direct RCL regions. Such regions might be relevant for the elaboration of hAAT formulations, as well as hAAT-based drugs, with enhanced anti-inflammatory attributes.

Pulsed electromagnetic fields (PEMF) attenuate changes in vertebral bone mass, architecture and strength in ovariectomized mice

Pulsed electromagnetic fields (PEMF) has been investigated as a noninvasive alternative method to prevent bone loss for postmenopausal osteoporosis (OP), and the bone tissue involved in these studies are usually long bones such as femur and tibia in OP patients or rat models. However, few studies have investigated the effects of PEMF on the vertebral bone in mice with OP. This study aimed to investigate whether PEMF preserve lumbar vertebral bone mass, microarchitecture and strength in ovariectomized (OVX) mouse model of OP and its associated mechanisms. Thirty 3-month-old female BALB/c mice were randomly divided into three groups (n=10): sham-operated control (Sham), ovariectomy (OVX), and ovariectomy with PEMF treatment (OVX+PEMF). The OVX+PEMF group was exposed to 15Hz, 1.6 mT PEMF for 8h/day, 7days/week. After 8weeks, the mice were sacrificed. The OVX+PEMF group showed lower body weight gain of mice induced by estrogen deficiency compared with OVX group. Biochemical analysis of serum demonstrated that serum bone formation markers including bone specific alkaline phosphatase (BALP), serum osteocalcin (OCN), osteoprotegerin (OPG) and N-terminal propeptide of type I procollagen (P1NP) were markedly higher in OVX+PEMF group compared with OVX group. Besides, serum bone resorption markers including tartrate-resistant acid phosphatase 5b (TRAP-5b) and C-terminal crosslinked telopeptides of type I collagen (CTX-I) were markedly lower in OVX+PEMF group compared with OVX group. Biomechanical test observed that OVX+PEMF group showed higher compressive maximum load and stiffness of the lumbar vertebrae compared with OVX group. Micro-computed tomography (μCT) and histological analysis of lumbar vertebrae revealed that PEMF partially prevented OVX-induced decrease of trabecular bone mass and deterioration of trabecular bone microarchitecture in lumbar vertebrae. Real-time PCR showed that the canonical Wnt signaling pathway of the lumbar vertebrae, including Wnt3a, LRP5 and β-catenin were markedly up-regulated in OVX+PEMF group compared with OVX group. Moreover, the mRNA expressions of RANKL and OPG were markedly up-regulated in OVX+PEMF group compared with OVX group, whereas no statistical difference in RANKL/OPG mRNA ratio was found between OVX+PEMF group and OVX group. Besides, our study also found that the RANK mRNA expression was down-regulated in OVX+PEMF group compared with OVX group. Taken together, we reported that long-term stimulation with PEMF treatment was able to alleviate lumbar vertebral OP in postmenopausal mice through a combination of increased bone formation and suppressed bone resorption related to regulating the skeletal gene expressions of Wnt3a/LRP5/β-catenin and OPG/RANKL/RANK signaling pathways.

In Vivo Analysis of Alpha-1-Antitrypsin Functions in Autoimmune Disease Models

Alpha-1-antitrypsin (AAT) is a circulating protein, a serpin, with multiple protective functions. Beside the well-known proteinase inhibitory function, which protects the lungs from chronic obstructive pulmonary disease (COPD), many studies have shown that AAT inhibits pro-inflammatory cytokine gene expression and functions. These anti-inflammatory and immune-regulatory properties have led to studies testing the therapeutic effect of AAT in autoimmune disease models. Initially, a study using recombinant adeno-associated viral (rAAV) vector showed that AAT gene therapy prevented type 1 diabetes (T1D) development in a nonobese diabetic (NOD) mouse model. Consequently, several studies confirmed that AAT therapy prevented and reversed T1D. AAT therapy has also been tested and has demonstrated protective effects in a collagen-induced arthritis model and a systemic lupus erythematosus (SLE) mouse model. This chapter describes methods that evaluate AAT functions in autoimmune mouse models.

Adipose-derived stem cell therapies for bone regeneration

INTRODUCTION

Cell-based therapies exploit the heterogeneous and self-sufficient biological environment of stem cells to restore, maintain and improve tissue functions. Adipose-derived stem cells (ASCs) are, to this aim, promising cell types thanks to advantageous isolation procedures, growth kinetics, plasticity and trophic properties. Specifically, bone regeneration represents a suitable, though often challenging, target setting to test and apply ASC-based therapeutic strategies. Areas covered: ASCs are extremely plastic and secrete bioactive peptides that mediate paracrine functions, mediating their trophic actions in vivo. Numerous preclinical studies demonstrated that ASCs improve bone healing. Clinical trials are ongoing to validate the clinical feasibility of these approaches. This review is intended to define the state-of-the-art on ASCs, encompassing the biological features that make them suitable for bone regenerative strategies, and to provide an update on existing preclinical and clinical applications. Expert opinion: ASCs offer numerous advantages over other stem cells in terms of feasibility of clinical translation. Data obtained from in vivo experimentation are encouraging, and clinical trials are ongoing. More robust validations are thus expected to be achieved during the next few years, and will likely pave the way to optimized patient-tailored treatments for bone regeneration.

Alpha-1 antitrypsin inhibits RANKL-induced osteoclast formation and functions

Osteoporosis is a global public health problem affecting more than 200 million people worldwide. We previously showed that treatment with alpha-1 antitrypsin (AAT), a multifunctional protein with anti-inflammatory properties, mitigated bone loss in an ovariectomized mouse model. However, the underlying mechanisms of the protective effect of AAT on bone tissue are largely unknown. In this study, we investigated the effect of AAT on osteoclast formation and function in vitro. Our results showed that AAT dose-dependently inhibited the formation of RANKL (receptor activator of nuclear factor κB ligand) induced osteoclasts derived from mouse bone marrow macrophages/monocyte (BMM) lineage cells and the murine macrophage cell line, RAW 264.7 cells. In order to elucidate the possible mechanisms underlying this inhibition, we tested the effect of AAT on the gene expression of cell surface molecules, transcription factors, and cytokines associated with osteoclast formation. We showed that AAT inhibited M-CSF (macrophage colony-stimulating factor) induced cell surface RANK expression in osteoclast precursor cells. In addition, AAT inhibited RANKL-induced TNF-α production, cell surface CD9 expression, and dendritic cell-specific transmembrane protein (DC-STAMP) gene expression. Importantly, AAT treatment significantly inhibited osteoclast-associated mineral resorption. Together, these results uncovered new mechanisms for the protective effects of AAT and strongly support the notion that AAT has therapeutic potential for the treatment of osteoporosis.