Resveratrol enhances proliferation and osteoblastic differentiation in human mesenchymal stem cells via ER-dependent ERK1/2 activation

Phytochemicals impact on osteogenic differentiation of mesenchymal stem cells

Medicinal plants have always been utilized for the prevention and treatment of the spread of different diseases all around the world. To name some traditional medicine that has been used over centuries, we can refer to phytochemicals such as naringin, icariin, genistein, and resveratrol gained from plants. Osteogenic differentiation and mineralization of stem cells can be the result of specific bioactive compounds from plants. One of the most appealing choices for therapy can be mesenchymal stem cells (MSCs) because it has a great capability of self-renewal and differentiation into three descendants, namely, endoderm, mesoderm, and ectoderm. Stem cell gives us the glad tidings of great advances in tissue regeneration and transplantation field for treatment of diseases. Using plant bioactive phytochemicals also holds tremendous promises in treating diseases such as osteoporosis. The purpose of the present review article thus is to investigate what are the roles and consequences of phytochemicals on osteogenic differentiation of MSCs.

Resveratrol Rescue Indoxyl Sulfate-Induced Deterioration of Osteoblastogenesis via the Aryl Hydrocarbon Receptor /MAPK Pathway

Indoxyl sulfate (IS), a uremic toxin derived from dietary tryptophan metabolism by the gut microbiota, is an endogenous aryl hydrocarbon receptor (AhR) agonist and a key player in bone remodeling. Resveratrol (RSV), an AhR antagonist, plays a protective role in shielding against AhR ligands. Our study explored the impact of IS on osteoblast differentiation and examined the possible mechanism of IS in controlling the expression of osteoblastogenesis markers through an in-depth investigation of AhR signaling. In vivo, we found histological architectural disruption of the femoral bones in 5/6 nephrectomies of young adult IS exposed mice, including reduced Runx2 antigen expression. RSV improved the diaphysis architecture, Runx2 expression, and trabecular quality. In vitro data suggest that IS at 500 and 1000 μM disturbed osteoblastogenesis through suppression of the ERK and p38 mitogen-activated protein kinase (MAPK) pathways, which were found to be downstream of AhR. RSV proved to ameliorate the anti-osteoblastogenic effects of IS through the inhibition of AhR and downstream signaling. Taken together, we demonstrated that the IS/AhR/MAPK signaling pathway plays a crucial role in the inhibition of osteoblastogenesis, and RSV has a potential therapeutic role in reversing the IS-induced decline in osteoblast development and suppressing abnormal bone turnover in chronic kidney disease patients.

Bone marrow fat: friend or foe in people with diabetes mellitus?

Global trends in the prevalence of overweight and obesity put the adipocyte in the focus of huge medical interest. This review highlights a new topic in adipose tissue biology, namely the emerging pathogenic role of fat accumulation in bone marrow (BM). Specifically, we summarize current knowledge about the origin and function of BM adipose tissue (BMAT), provide evidence for the association of excess BMAT with diabetes and related cardiovascular complications, and discuss potential therapeutic approaches to correct BMAT dysfunction. There is still a significant uncertainty about the origins and function of BMAT, although several subpopulations of stromal cells have been suggested to have an adipogenic propensity. BM adipocytes are higly plastic and have a distinctive capacity to secrete adipokines that exert local and endocrine functions. BM adiposity is abundant in elderly people and has therefore been interpreted as a component of the whole-body ageing process. BM senescence and BMAT accumulation has been also reported in patients and animal models with Type 2 diabetes, being more pronounced in those with ischaemic complications. Understanding the mechanisms responsible for excess and altered function of BMAT could lead to new treatments able to preserve whole-body homeostasis.

The Stemness of Human Ovarian Granulosa Cells and the Role of Resveratrol in the Differentiation of MSCs-A Review Based on Cellular and Molecular Knowledge

Ovarian Granulosa Cells (GCs) are known to proliferate in the developing follicle and undergo several biochemical processes during folliculogenesis. They represent a multipotent cell population that has been differentiated to neuronal cells, chondrocytes, and osteoblasts in vitro. However, progression and maturation of GCs are accompanied by a reduction in their stemness. In the developing follicle, GCs communicate with the oocyte bidirectionally via gap junctions. Together with neighboring theca cells, they play a crucial role in steroidogenesis, particularly the production of estradiol, as well as progesterone following luteinization. Many signaling pathways are known to be important throughout the follicle development, leading either towards luteinization and release of the oocyte, or follicular atresia and apoptosis. These signaling pathways include cAMP, PI3K, SMAD, Hedgehog (HH), Hippo and Notch, which act together in a complex manner to control the maturation of GCs through regulation of key genes, from the primordial follicle to the luteal phase. Small molecules such as resveratrol, a phytoalexin found in grapes, peanuts and other dietary constituents, may be able to activate/inhibit these signaling pathways and thereby control physiological properties of GCs. This article reviews the current knowledge about granulosa stem cells, the signaling pathways driving their development and maturation, as well as biological activities of resveratrol and its properties as a pro-differentiation agent.

Norepinephrine Inhibits the Proliferation of Human Bone Marrow-Derived Mesenchymal Stem Cells via β2-Adrenoceptor-Mediated ERK1/2 and PKA Phosphorylation

Bone marrow-derived mesenchymal stem cells (BMSCs) represent an alternative to chondrocytes to support cartilage regeneration in osteoarthritis (OA). The sympathetic neurotransmitter norepinephrine (NE) has been shown to inhibit their chondrogenic potential; however, their proliferation capacity under NE influence has not been studied yet. Therefore, we used BMSCs obtained from trauma and OA donors and compared the expression of adrenergic receptors (AR). Then, BMSCs from both donor groups were treated with NE, as well as with combinations of NE and α1-, α2- or β1/2-AR antagonists (doxazosin, yohimbine or propranolol). Activation of AR-coupled signaling was investigated by analyzing ERK1/2 and protein kinase A (PKA) phosphorylation. A similar but not identical subset of ARs was expressed in trauma (α2B-, α2C- and β2-AR) and OA BMSCs (α2A-, α2B-, and β2-AR). NE in high concentrations inhibited the proliferation of both trauma and OA BMCSs significantly. NE in low concentrations did not influence proliferation. ERK1/2 as well as PKA were activated after NE treatment in both BMSC types. These effects were abolished only by propranolol. Our results demonstrate that NE inhibits the proliferation and accordingly lowers the regenerative capacity of human BMSCs likely via β2-AR-mediated ERK1/2 and PKA phosphorylation. Therefore, targeting β2-AR-signaling might provide novel OA therapeutic options.

The effects of 17 Beta-Estradiol primed mesenchymal stem cells on the biology of co-cultured neutrophil

OBJECTIVES

Mesenchymal stem cells (MSCs) can influence immune effector cells. It is proved that MSCs respond to various Toll-like receptor (TLR) ligands, which could ultimately result in changes in their immunomodulatory effects. Neutrophils play an essential role in the first line defense system and their function can be regulated by MSCs. Estrogen is a female hormone that contributes to sex differences in several immune-related diseases. With regard to the stated facts, this research aims to elucidate the effects of estrogen treatment on the ability of TLR4-primed MSCs to regulate neutrophil functions.

METHODS

Following isolation and characterization, MSCs were stimulated with LPS as a TLR4 ligand and subsequently incubated with different concentrations (0, 10, 20 and 40 nM) of estrogen for 48 hrs. Then, MSCs were co-cultured with neutrophils to investigate the vitality and function of the co-cultured neutrophils.

RESULTS

Our results indicated that TLR4-primed MSCs could decrease the viability and neutral red uptake potential of co-cultured neutrophils. Furthermore, neutrophils co-cultured with TLR4-primed MSCs exhibited a decrease in the respiratory burst intensity after being challenged with opsonized yeast. Interestingly, treating TLR4-primed MSCs with estrogen reversed the observed alterations in neutrophil functions.

CONCLUSION

It appears that estrogen can alter the interaction between MSCs and neutrophils.

Nanoencapsulated dietary polyphenols for cancer prevention and treatment: successes and challenges

Many dietary polyphenols have been investigated for their therapeutic potential either as single agents or in combinations. Despite the significant anticancer potential of these polyphenols in in vitro cell culture and in vivo animal models, their clinical applications have been limited because of challenges such as ineffective systemic delivery, stability and low bioavailability. Nanoencapsulation of these polyphenols could prolong circulation, improve localization, enhance efficacy and reduce the chances of multidrug resistance. This review summarized the use of various polyphenols especially epigallocatechin gallate, quercetin, curcumin and resveratrol as nanoformulations for cancer prevention and treatment. Despite some success, more research is warranted to design a nanoencapsulated combination of polyphenols, effective in in vitro, in vivo and human systems.

Resveratrol inhibits adipocyte differentiation and cellular senescence of human bone marrow stromal stem cells

Bone marrow adipose tissue (BMAT) is a unique adipose depot originating from bone marrow stromal stem cells (BMSCs) and regulates bone homeostasis and energy metabolism. An increased BMAT volume is observed in several conditions e.g. obesity, type 2 diabetes, osteoporosis and is known to be associated with bone fragility and increased risk for fracture. Therapeutic approaches to decrease the accumulation of BMAT are clinically relevant. In a screening experiment of natural compounds, we identified Resveratrol (RSV), a plant-derived antioxidant mediating biological effects via sirtuin- related mechanisms, to exert significant effects of BMAT formation. Thus, we examined in details the effects RSV on adipocytic and osteoblastic differentiation of tolermerized human BMSCs (hBMSC-TERT). RSV (1.0 μM) enhanced osteoblastic differentiation and inhibited adipocytic differentiation of hBMSC-TERT when compared with control and Sirtinol (Sirtuin inhibitor). Global gene expression profiling and western blot analysis revealed activation of a number of signaling pathways including focal adhesion kinase (FAK). Pharmacological inhibition of FAK using (PF-573228) and AKT inhibitor (LY-294002) (5μM), diminished RSV-induced osteoblast differentiation. In addition, RSV reduced the levels of senescence-associated secretory phenotype (SASP), gene markers associated with senescence (P53, P16, and P21), intracellular ROS levels and increased gene expression of enzymes protecting cells from oxidative damage (HMOX1 and SOD3). In vitro treatment of primary hBMSCs from aged patients characterized with high adipocytic and low osteoblastic differentiation ability with RSV, significantly enhanced osteoblast and decreased adipocyte formation when compared to hBMSCs from young donors. RSV targets hBMSCs and inhibits adipogenic differentiation and senescence-associated phenotype and thus a potential agent for treating conditions of increased BMAT formation.

Polyphenols from grape pomace induce osteogenic differentiation in mesenchymal stem cells

Polyphenols are increasingly investigated for the treatment of periodontitis and research on their use in dental biomaterials is currently being conducted. Grape pomace extracts are a rich source of polyphenols. In the present study, the polyphenols of two different types of grape pomace were characterized and identified by high-performance liquid chromatography-diode array detector, and the effect of polyphenol-rich grape pomace extracts on mesenchymal stem cell (MSC) osteogenic differentiation was investigated. Solid-liquid extraction was used to recover polyphenols from red and white grape pomace. The two extracts have been characterized through the phenolic content and antioxidant power. Human MSCs (hMSCs) from the bone marrow were cultured both with and without given amounts (10 or 20 µg/ml) of the obtained pomace extracts. Their effects on cell differentiation were evaluated by reverse transcription-quantitative polymerase chain reaction, compared with relevant controls. Results showed that both pomace extracts, albeit different in phenolic composition and concentration, induced multiple effects on hMSC gene expression, such as a decreased receptor activator of nuclear factor κ-B ligand/osteoprotegerin ratio and an enhanced expression of genes involved in osteoblast differentiation, thus suggesting a shift of hMSCs towards osteoblast differentiation. The obtained results provided data in favor of the exploitation of polyphenol properties from grape pomace extracts as complementary active molecules for dental materials and devices for bone regeneration in periodontal defects.

Potential Adverse Effects of Resveratrol: A Literature Review

Due to its health benefits, resveratrol (RE) is one of the most researched natural polyphenols. Resveratrol's health benefits were first highlighted in the early 1990s in the French paradox study, which opened extensive research activity into this compound. Ever since, several pharmacological activities including antioxidant, anti-aging, anti-inflammatory, anti-cancerous, anti-diabetic, cardioprotective, and neuroprotective properties, were attributed to RE. However, results from the available human clinical trials were controversial concerning the protective effects of RE against diseases and their sequelae. The reason for these conflicting findings is varied but differences in the characteristics of the enrolled patients, RE doses used, and duration of RE supplementation were proposed, at least in part, as possible causes. In particular, the optimal RE dosage capable of maximizing its health benefits without raising toxicity issues remains an area of extensive research. In this context, while there is a consistent body of literature on the protective effects of RE against diseases, there are relatively few reports investigating its possible toxicity. Indeed, toxicity and adverse effects were reported following consumption of RE; therefore, extensive future studies on the long-term effects, as well as the in vivo adverse effects, of RE supplementation in humans are needed. Furthermore, data on the interactions of RE when combined with other therapies are still lacking, as well as results related to its absorption and bioavailability in the human body. In this review, we collect and summarize the available literature about RE toxicity and side effects. In this process, we analyze in vitro and in vivo studies that have addressed this stilbenoid. These studies suggest that RE still has an unexplored side. Finally, we discuss the new delivery methods that are being employed to overcome the low bioavailability of RE.

Resveratrol rescues TNF‑α‑induced inhibition of osteogenesis in human periodontal ligament stem cells via the ERK1/2 pathway

Periodontitis is a common inflammatory disorder affecting the tissues surrounding the teeth, which can lead to the destruction of periodontal tissue and tooth loss. Resveratrol, a natural phytoalexin, exerts multiple biological effects. For example, its anti-inflammatory activity has been widely studied for the treatment of inflammatory bowel disease for a number of years. However, its effect on bone repair and new bone formation in an inflammatory microenvironment is not well understood. Accordingly, the effect of resveratrol on inflammation-affected human periodontal ligament stem cells (hPDLSCs) requires further investigation. In the present study, the effect of tumor necrosis factor-α (TNF-α), resveratrol, or the combination of both on the osteogenic differentiation of hPDLSCs, as well as the underlying mechanisms involved, were investigated. Cell Counting Kit-8 assay, alkaline phosphatase staining, Alizarin red staining, Oil Red O staining, reverse transcription-quantitative PCR and western blotting were used in the present study. It was demonstrated that resveratrol enhanced hPDLSC osteogenesis and reversed the inhibitory effects of TNF-α on this process. Further mechanistic studies indicated that resveratrol exerted anti-inflammatory activity by activating the ERK1/2 pathway, decreasing the secretion of interleukin (IL)-6 and IL-8 induced by TNF-α, and enhancing hPDLSCs osteogenesis. The present study suggested that resveratrol may be a novel and promising therapeutic choice for periodontitis.

Small molecules for mesenchymal stem cell fate determination

Mesenchymal stem cells (MSCs) are adult stem cells harboring self-renewal and multilineage differentiation potential that are capable of differentiating into osteoblasts, adipocytes, or chondrocytes in vitro, and regulating the bone marrow microenvironment and adipose tissue remodeling in vivo. The process of fate determination is initiated by signaling molecules that drive MSCs into a specific lineage. Impairment of MSC fate determination leads to different bone and adipose tissue-related diseases, including aging, osteoporosis, and insulin resistance. Much progress has been made in recent years in discovering small molecules and their underlying mechanisms control the cell fate of MSCs both in vitro and in vivo. In this review, we summarize recent findings in applying small molecules to the trilineage commitment of MSCs, for instance, genistein, medicarpin, and icariin for the osteogenic cell fate commitment; isorhamnetin, risedronate, and arctigenin for pro-adipogenesis; and atractylenolides and dihydroartemisinin for chondrogenic fate determination. We highlight the underlying mechanisms, including direct regulation, epigenetic modification, and post-translational modification of signaling molecules in the AMPK, MAPK, Notch, PI3K/AKT, Hedgehog signaling pathways etc. and discuss the small molecules that are currently being studied in clinical trials. The target-based manipulation of lineage-specific commitment by small molecules offers substantial insights into bone marrow microenvironment regulation, adipose tissue homeostasis, and therapeutic strategies for MSC-related diseases.

The application of resveratrol to mesenchymal stromal cell-based regenerative medicine

Currently, the transplantation of mesenchymal stromal cells (MSCs) has emerged as an effective strategy to protect against tissue and organ injury. MSC transplantation also serves as a promising therapy for regenerative medicine, while poor engraftment and limited survival rates are major obstacles for its clinical application. Although multiple studies have focused on investigating chemicals to improve MSC stemness and differentiation in vitro and in vivo, there is still a shortage of effective and safe agents for MSC-based regenerative medicine. Resveratrol (RSV), a nonflavonoid polyphenol phytoalexin with a stilbene structure, was first identified in the root extract of white hellebore and is also found in the roots of Polygonum cuspidatum, and it is widely used in traditional Chinese medicine. RSV is a natural agent that possesses great therapeutic potential for protecting against acute or chronic injury in multiple tissues as a result of its antioxidative, anti-inflammatory, and anti-cancer properties. According to its demonstrated properties, RSV may improve the therapeutic effects of MSCs via enhancing their survival, self-renewal, lineage commitment, and anti-aging effects. In this review, we concluded that RSV significantly improved the preventive and therapeutic effects of MSCs against multiple diseases. We also described the underlying mechanisms of the effects of RSV on the survival, self-renewal, and lineage commitment of MSCs in vitro and in vivo. Upon further clarification of the potential mechanisms of the effects of RSV on MSC-based therapy, MSCs may be able to be more widely used in regenerative medicine to promote recovery from tissue injury.

Natural Compounds as a Strategy to Optimize "In Vitro" Expansion of Stem Cells

The efficient use of stem cells for transplantation is often limited by the relatively low number of stem cells collected. The ex vivo expansion of human stem cells for clinical use is a potentially valuable approach to increase stem cell number. Currently, most of the procedures used to expand stem cells are carried out using a 21% oxygen concentration, which is about 4- to 10-fold greater than the concentration characteristic of their natural niches. Hyperoxia might cause oxidative stress with a deleterious effect on the physiology of cultured stem cells. In this review, we investigate and critically examine the available information on the ability of natural compounds to counteract hyperoxia-induced damage in different types of stem cells ex vivo. In particular, we focused on proliferation and stemness maintenance in an attempt to draw up useful indications to define new culture media with a promoting activity on cell expansion in vitro.

Autophagy drives osteogenic differentiation of human gingival mesenchymal stem cells

BACKGROUND/AIM

Autophagy is a macromolecular degradation process playing a pivotal role in the maintenance of stem-like features and in the morpho-functional remodeling of the tissues undergoing differentiation. In this work we investigated the involvement of autophagy in the osteogenic differentiation of mesenchymal stem cells originated from human gingiva (HGMSC).

METHODS

To promote the osteogenic differentiation of HGMSCs we employed resveratrol, a nutraceutical known to modulate autophagy and cell differentiation, together with osteoblastic inductive factors. Osteoblastic differentiation and autophagy were monitored through western blotting and immunofluorescence staining of specific markers.

RESULTS

We show that HGMSCs can differentiate into osteoblasts when cultured in the presence of appropriate factors and that resveratrol accelerates this process by up-regulating autophagy. The prolonged incubation with dexamethasone, β-glycerophosphate and ascorbic acid induced the osteogenic differentiation of HGMSCc with increased expression of autophagy markers. Resveratrol (1 μM) alone elicited a less marked osteogenic differentiation yet it greatly induced autophagy and, when added to the osteogenic differentiation factors, it provoked a synergistic effect. Resveratrol and osteogenic inductive factors synergistically induced the AMPK-BECLIN-1 pro-autophagic pathway in differentiating HGMSCs, that was thereafter downregulated in osteoblastic differentiated cells. Pharmacologic inhibition of BECLIN-1-dependent autophagy precluded the osteogenic differentiation of HGMSCs.

CONCLUSIONS

Autophagy modulation is instrumental for osteoblastic differentiation of HGMSCs. The present findings can be translated into the regenerative cell therapy of maxillary / mandibular bone defects.

Enhancement of Mesenchymal Stem Cell-Driven Bone Regeneration by Resveratrol-Mediated SOX2 Regulation

Mesenchymal stem cells (MSCs) are an attractive cell source for regenerative medicine. However, MSCs age rapidly during long-term ex vivo culture and lose their therapeutic potential before they reach effective cell doses (ECD) for cell therapy. Thus, a prerequisite for effective MSC therapy is the development of cell culture methods to preserve the therapeutic potential during long-term ex vivo cultivation. Resveratrol (RSV) has been highlighted as a therapeutic candidate for bone disease. Although RSV treatment has beneficial effects on bone-forming cells, in vivo studies are lacking. The current study showed that long-term (6 weeks from primary culture date)-cultured MSCs with RSV induction retained their proliferative and differentiation potential despite reaching ECD. The mechanism of RSV action depends entirely on the SIRT1-SOX2 axis in MSC culture. In a rat calvarial defect model, RSV induction significantly improved bone regeneration after MSC transplantation. This study demonstrated an example of efficient MSC therapy for treating bone defects by providing a new strategy using the plant polyphenol RSV.

A Review on the Effect of Plant Extract on Mesenchymal Stem Cell Proliferation and Differentiation

Stem cell has immense potential in regenerative cellular therapy. Mesenchymal stem cells (MSCs) can become a potential attractive candidate for therapy due to its remarkable ability of self-renewal and differentiation into three lineages, i.e., ectoderm, mesoderm, and endoderm. Stem cell holds tremendous promises in the field of tissue regeneration and transplantation for disease treatments. Globally, medicinal plants are being used for the treatment and prevention of a variety of diseases. Phytochemicals like naringin, icariin, genistein, and resveratrol obtained from plants have been extensively used in traditional medicine for centuries. Certain bioactive compounds from plants increase the rate of tissue regeneration, differentiation, and immunomodulation. Several studies show that bioactive compounds from plants have a specific role (bioactive mediator) in regulating the rate of cell division and differentiation through complex signal pathways like BMP2, Runx2, and Wnt. The use of plant bioactive phytochemicals may also become promising in treating diseases like osteoporosis, neurodegenerative disorders, and other tissue degenerative disorders. Thus, the present review article is aimed at highlighting the roles and consequences of plant extracts on MSCs proliferation and desired lineage differentiations.

Aging and lineage allocation changes of bone marrow skeletal (stromal) stem cells

Aging is associated with decreased bone mass and accumulation of bone marrow adipocytes. Both bone forming osteoblastic cells and bone marrow adipocytes are derived from a stem cell population within the bone marrow stroma called bone marrow stromal (skeletal or mesenchymal) stem cells (BMSC). In the present review, we provide an overview, based on the current literature, regarding the physiological aging processes that cause changes in BMSC lineage allocation, enhancement of adipocyte and defective osteoblast differentiation, leading to gradual exhaustion of stem cell regenerative potential and defects in bone tissue homeostasis and metabolism. We discuss strategies to preserve the "youthful" state of BMSC, to reduce bone marrow age-associated adiposity, and to counteract the overall negative effects of aging on bone tissues with the aim of decreasing bone fragility and risk of fractures.

Short-Term Protocols to Obtain Insulin-Producing Cells from Rat Adipose Tissue: Signaling Pathways and In Vivo Effect

Studies using mesenchymal stromal cells (MSCs) as a source of insulin-secreting cells (IPCs) are a promising path in the pursuit for diabetes therapy. Here, we investigate three short-term differentiation protocols in order to generate IPCs from autologous adipose-derived stromal cells (ADSCs) with an expressive insulin-secreting profile in vitro and in vivo, as well as the signaling pathways involved in the chosen differentiation protocols. We extracted and cultured ADSCs and differentiated them into IPCs, using three different protocols with different inductors. Afterwards, the secretory profile was analyzed and IPCs differentiated in exendin-4/activin A medium, which presented the best secretory profile, was implanted in the kidney subcapsular region of diabetic rats. All protocols induced the differentiation, but media supplemented with exendin-4/activin A or resveratrol induced the expression and secretion of insulin more efficiently, and only the exendin-4/activin-A-supplemented medium generated an insulin secretion profile more like β-cells, in response to glucose. The PI3K/Akt pathway seems to play a negative role in IPC differentiation; however, the differentiation of ADSCs with exendin-4/activin A positively modulated the p38/MAPK pathway. Resveratrol medium activated the Jak/STAT3 pathway and generated IPCs apparently less sensitive to insulin and insulin-like receptors. Finally, the implant of IPCs with the best secretory behavior caused a decrease in hyperglycemia after one-week implantation in diabetic rats. Our data provide further information regarding the generation of IPCs from ADSCs and strengthen evidence to support the use of MSCs in regenerative medicine, specially the use of exendin-4/activin A to produce rapid and effectively IPCs with significant in vivo effects.

Advance on Resveratrol Application in Bone Regeneration: Progress and Perspectives for Use in Oral and Maxillofacial Surgery

The natural polyphenol Resveratrol (RSV) claims numerous positive effects on health due to the well documented biological effects demonstrating its potential as a disease-preventing agent and as adjuvant for treatment of a wide variety of chronic diseases. Since several studies, both in vitro and in vivo, have highlighted the protective bone aptitude of RSV both as promoter of osteoblasts' proliferation and antagonist of osteoclasts' differentiation, they could be interesting in view of applications in the field of dentistry and maxillofacial surgery. This review has brought together experimental findings on the use of RSV in the regeneration of bone tissue comprising also its application associated with scaffolds and non-transfusional hemocomponents.

Resveratrol attenuates hydrogen peroxide-induced aging through upregulation of autophagy in human umbilical vein endothelial cells

PURPOSE

Resveratrol (RESV; trans-3,5,4'-trihydroxystilbene) has emerged as a potential new therapeutic for age-related atherosclerotic diseases. However, the effect of RESV on cellular aging and its underlying mechanisms remain unknown. Therefore, the aim of this study was to examine whether RESV can delay cellular aging through upregulation of autophagy.

MATERIALS AND METHODS

Human umbilical endothelial vein cells (HUVECs) were divided into four groups: the control group, and the hydrogen peroxide (H2O2) alone, H2O2 + RESV pretreatment, and H2O2 + 3-methyladenine (3-MA) + RESV pretreatment intervention groups. The cell viability was evaluated by a cell counting kit-8 assay. Superoxide dismutase (SOD) activity and intracellular reactive oxygen species (ROS) levels were tested using commercial kits. Senescence-related β-galactosidase activities were detected by immunohistochemical staining. The expression levels of aging-related and autophagy-related markers, including phosphorylated Rb (p-Rb), LC3, and p62, with or without RESV were measured by Western blotting.

RESULTS

Pretreatment with 10 µM RESV increased the cell viability and SOD levels. The remarkably higher positive rate of senescence-associated β-galactosidase and increased intracellular ROS levels in the H2O2 treatment group were reversed by treatment with 10 µM RESV. As compared to the H2O2 treatment group, 10 µM RESV could upregulate autophagy through the regulation of p-Rb, LC3, and p62 levels. The anti-aging effect of RESV via an autophagy regulation mechanism was further confirmed by the suppression of these effects with 3-MA treatment.

CONCLUSION

RESV may reverse and delay the aging process of HUVECs via upregulation of autophagy and could be a candidate therapeutic for age-related atherosclerotic diseases.

Atypical antipsychotics induce human osteoblasts apoptosis via Wnt/β-catenin signaling

Background

There is evidence that atypical antipsychotics (APs) increase risk of osteoporosis in schizophrenia patients, however the mechanism is unclear. The aim of the study was to explore the molecular mechanisms about Wnt/β-catenin signal pathway underlying the osteal side effects of APs.

Methods

We cultured human osteoblast cell line hFob1. 19 (OB) treatments with olanzapine, risperidone, amisulpride, aripiprazole or resveratrol in vitro. OB cells viability was detected by cell viability assay. OB cells apoptosis was analyzed by flow cytometry (FCM). Further apoptosis-related marker and β-catenin expression was analyzed by Western blot and Immunofluorescence analysis.

Results

Compared with the control group, proliferation of OB cells decreased and apoptosis rates of OB cells increased significantly in APs group (p < 0.05). There were a reduced level of Bcl-2, Mcl-1 (antiapoptotic marker) and an elevated level of Bax, Cleaved-Caspase3 (proapoptotic marker) in APs group (p < 0.05). Simultaneously, β-catenin expression decreased in cytoplasm and nucleus (p < 0.05). Compared with the just APs group, the apoptosis rates decreased and β-catenin expression increased significantly in resevratrol combined with APs group (p < 0.05). Correlation analysis showed positive correlation between β-catenin expression and the apoptotic rate in OB cells (r = − 0.515, p < 0.05).

Conclusions

APs cause OB cells apoptosis relating to Wnt/β-catenin signaling while resevratrol could reverse this phenomenon. Our study could lay the foundation for overcoming the APs-induced osteal side effects to improve the life quality of schizophrenia patients.

Exercise and resveratrol increase fracture resistance in the 3xTg-AD mouse model of Alzheimer's disease

Background

Alzheimer’s disease (AD) and osteoporosis are progressive diseases that affect the elderly population. Both conditions are associated with fracture risk that is greater than twice that of the healthy population. Resveratrol and exercise are two treatments that have been linked with attenuation of age-related diseases, including the risk of bone fractures. In this study, we test the hypothesis that these treatments improve fracture resistance in a mouse model representative of the AD condition.

Methods

Three-month-old male 3xTg-AD mice were treated for 4 months with resveratrol or exercise or both combined, and compared with wild type mice. Exercise training was performed on a treadmill at 15 m/min for 45 min/day, 5 days/week. Resveratrol was given at 4 g/kg diet in the form of pellets. Three-point bending, cross-sectional geometric, and fluorescence analyses were conducted on tibias and compared by treatment group.

Results

Tibias of 3xTg mice exhibited signs of diminished bone quality and fracture under less force than age-matched wild type mice (P < 0.05). Treatment with both resveratrol and exercise improved indicators of fracture resistance and bone quality in AD mice to levels comparable to that of wild type mice (P < 0.05).

Conclusions

The 3xTg mouse model of AD is at elevated risk for limb bone fracture compared to wild type controls. Treatment with resveratrol, exercise, or both in combination improves fracture resistance and cross-sectional geometric indicators of bone strength.

Ethyl acetate and n-butanol fraction of Cissus quadrangularis promotes the mineralization potential of murine pre-osteoblast cell line MC3T3-E1 (sub-clone 4)

In a sequel to investigate osteogenic potential of ethanolic extract of Cissus quadrangularis (CQ), the present study reports the osteoblast differentiation and mineralization potential of ethyl acetate (CQ-EA) and butanol (CQ-B) extracts of CQ on mouse pre-osteoblast cell line MC3T3-E1 (sub-clone 4) with an objective to isolate an antiosteoporotic compound. Growth curve, proliferation, and viability assays showed that both the extracts were nontoxic to the cells even at high concentration (100 µg/ml). The cell proliferation was enhanced at low concentrations (0.1 µg/ml and 1 µg/ml) of both the extracts. They also upregulated the osteoblast differentiation and mineralization processes in MC3T3-E1 cells as reflected by expression profile of osteoblast marker genes such as RUNX2, Osterix, Collagen (COL1A1), Alkaline Phosphatase (ALP), Integrin-related Bone Sialoprotein (IBSP), Osteopontin (OPN), and Osteocalcin (OCN). CQ-EA treatment resulted in early differentiation and mineralization as compared with the CQ-B treatment. These findings suggest that low concentrations of CQ-EA and CQ-B have proliferative and osteogenic properties. CQ-EA, however, is more potent osteogenic than CQ-B.

Oxidative Stress in Mesenchymal Stem Cell Senescence: Regulation by Coding and Noncoding RNAs

SIGNIFICANCE

Mesenchymal stem cells (MSCs), adult stem cells with the potential of differentiation into mesodermal lineages, play an important role in tissue homeostasis and regeneration. In different organs, a subpopulation of MSCs is located near the vasculature and possibly represents the original source of lineage-committed mesenchymal progenitors. Recent Advances: The plasticity and immune characteristics of MSCs render them a preferential tool for regenerative cell therapy.

CRITICAL ISSUES

The culture expansion needed before MSC transplantation is associated with cellular senescence. Moreover, accelerated senescence of the total and perivascular MSC pool has been observed in humans and mouse models of premature aging disorders. MSC dysfunction is acknowledged as a culprit for the aging-associated degeneration of mesodermal tissues, but the underlying epigenetic pathways remain elusive. This article reviews current understanding of mechanisms impinging on MSC health, including oxidative stress, Nrf2-antioxidant responsive element activity, sirtuins, noncoding RNAs, and PKCs.

FUTURE DIRECTIONS

We provide evidence that epigenetic profiling of MSCs is utilitarian to the prediction of therapeutic outcomes. In addition, strategies that target oxidative stress-associated mechanisms represent promising approaches to counteract the detrimental effect of age and senescence in MSCs.-Antioxid. Redox Signal. 29, 864-879.

Enhanced articular cartilage regeneration with SIRT1-activated MSCs using gelatin-based hydrogel

To investigate the functional effects of resveratrol (RSV) on mesenchymal stem cells (MSCs), we treated MSCs with RSV continuously during ex vivo expansion. MSCs were continuously treated with RSV from passage (P) 0 to P5. A proliferative capacity of RSV-treated MSCs was higher than that of non-treated MSCs and similar with P1-MSCs. Continuous treatment of RSV on MSCs increased the stemness and inhibited the senescence. During chondrogenic differentiation in vitro, RSV-treated MSCs had higher differentiation potential and reduced hypertrophic maturation, which are limitations for hyaline cartilage formation. The histological analysis of micromass demonstrated increased chondrogenic differentiation potential. We further explored the therapeutic effectiveness of this method in a rabbit osteochondral defect model. A rabbit osteochondral defect model was established to investigate the hyaline cartilage regeneration potential of RSV-treated MSCs. Moreover, the cartilage regeneration potential of RSV-treated MSCs was greater than that of untreated MSCs. The expression levels of chondrogenic markers increased and those of hypertrophic markers decreased in RSV-treated MSCs compared with untreated MSCs. Sustained treatment of RSV on MSCs during ex vivo expansion resulted in the maintenance of stemness and enhanced chondrogenic differentiation potential. Consequentially, highly efficient MSCs promoted superior hyaline cartilage regeneration in vivo. This novel treatment method provides a basis for cell-based tissue engineering.

Plants and Their Bioactive Constituents in Mesenchymal Stem Cell-Based Periodontal Regeneration: A Novel Prospective

Periodontitis is a common chronic inflammatory disease, which causes the destruction of both the soft and mineralized tissues. However, current treatments such as bone graft materials, barrier membranes, and protein products all have difficulties in regenerating the complete periodontal tissue structure. Stem cell-based tissue engineering has now emerged as one of the most effective treatments for the patients suffering from periodontal diseases. Plants not only can be substrates for life processes, but also contain hormones or functional molecules. Numbers of preclinical studies have revealed that products from plant can be successfully applied in modulating proliferation and differentiation of human mesenchymal stem cells. Plant-derived substances can induce stem cells osteogenic differentiation, and they also possess angiogenic potency. Furthermore, in the field of tissue engineering, plant-derived compounds or plant extracts can be incorporated with biomaterials or utilized as biomaterials for cell transplantation. So it is speculated that botanical products may become a new perspective in stem cell-based periodontal regeneration. However, the lack of achieving predict clinical efficacy and quality control has been the major impediment to its extensive application. This review gives an overview of the prospect of applying different plant-derived substances in various human mesenchymal stem cells-based periodontal regeneration.

Demethylbelamcandaquinone B (Dmcq B) Is the Active Compound of Marantodes pumilum var. alata (Blume) Kuntze with Osteoanabolic Activities

Phytoestrogens have attracted considerable attention for their potential in the prevention of postmenopausal osteoporosis. Recently, a phytoestrogen-rich herbal plant, Marantodes pumilum var. alata (Blume) Kuntze was reported to protect against bone loss in ovariectomized rat. However, the bioactive compound responsible for these effects and the underlying mechanism were not known. Through bioassay-guided isolation, demethylbelamcandaquinone B (Dmcq B) was isolated and identified from Marantodes pumilum var. alata leaf extract. In terms of its bone anabolic effects, Dmcq B was at par with 17β-estradiol (E2), in promoting the proliferation, differentiation and mineralization of osteoblast cells. Dmcq-B increased early differentiation markers, collagen content and enzymatic ALP activity. It was demonstrated to regulate BMP2 signaling pathway which further activated the transcription factor, osterix. Subsequently, Dmcq B was able to increase the osteocalcin expression which promoted matrix mineralization as evidenced by the increase in calcium deposition. Dmcq B also reduced the protein level of receptor activator of NF-κβ ligand (RANKL) and promoted osteoprotegerin (OPG) protein expression by osteoblast cells, therefore hastening bone formation rate by decreasing RANKL/OPG ratio. Moreover, Dmcq B was able to increase ER expression, postulating its phytoestrogen property. As the conclusion, Dmcq B is the active compound isolated from Marantodes pumilum var. alata leaves, regulating osteoanabolic activities potentially through the BMP2 and ER signaling pathways.

Evaluating the Effect of Resveratrol on the Healing of Extraction Sockets in Cyclosporine A-Treated Rats

PURPOSE

The objective of this study was to investigate the effects of resveratrol on alveolar socket healing after tooth extraction in normal and cyclosporin A (CsA)-treated rats.

MATERIALS AND METHODS

Seventy-two female Sprague-Dawley rats were separated into 4 groups of 18. Group 1 was injected with a placebo solution intraperitoneally. Group 2 was injected with resveratrol (10 μmol/kg) intraperitoneally. Groups 3 and 4 were injected with CsA (10 mg/kg) subcutaneously for 8 days once daily before tooth extraction. Next, the teeth were extracted and CsA injection continued until the animals were sacrificed. Eight days after commencing the CsA injections, group 4 was injected with resveratrol while continuing with CsA injections. Nine rats from each group were sacrificed on days 14 and 28, and sections were examined to assess the degree of inflammation, formation of connective tissue, and new bone formation. Immunohistochemical analysis was used to evaluate the alveolar socket healing process using osteocalcin and osteopontin markers. A P value less than .05 was considered significant.

RESULTS

There was more new bone formation in group 2 than in the other 3 groups on day 14 after tooth extraction (P < .05), and there was more new bone formation in group 2 than in groups 3 and 4 on day 28 after extraction (P < .05). Based on the immunohistochemical assessment, the amount of osteocalcin and osteopontin labeling was greater in group 2 compared with the other 3 groups on day 14 (P < .05); however, on day 28 after extraction, it was greater in group 4 compared with group 3 (P < .05).

CONCLUSIONS

Resveratrol improves alveolar socket healing in normal and CsA-treated rats. Resveratrol also increases levels of osteocalcin and osteopontin in normal and CsA-treated rats. These results suggest that this natural compound is useful for alveolar socket healing after tooth extraction.

Beneficial Effects of Concentrated Growth Factors and Resveratrol on Human Osteoblasts In Vitro Treated with Bisphosphonates

Bisphosphonates are primary pharmacological agents against osteoclast-mediated bone loss and widely used in the clinical practice for prevention and treatment of a variety of skeletal conditions, such as low bone density and osteogenesis imperfecta, and pathologies, such as osteoporosis, malignancies metastatic to bone, Paget disease of bone, multiple myeloma, and hypercalcemia of malignancy. However, long-term bisphosphonate treatment is associated with pathologic conditions including osteonecrosis of the jaw, named BRONJ, which impaired bone regeneration process. Clinical management of BRONJ is controversy and one recent approach is the use of platelet concentrates, such as Concentrated Growth Factors, alone or together with biomaterials or antioxidants molecules, such as resveratrol. The aim of the present study was to investigate the in vitro effects of Concentrated Growth Factors and/or resveratrol on the proliferation and differentiation of human osteoblasts, treated or not with bisphosphonates. Human osteoblasts were stimulated for 3 days in complete medium and for 21 days in mineralization medium. At the end of the experimental period, the in vitro effect on osteoblast proliferation and differentiation was evaluated using different techniques such as MTT, ELISA for the quantification/detection of osteoprotegerin and bone morphogenetic protein-2, immunohistochemistry for sirtuin 1 and collagen type I, and the Alizarin Red S staining for the rate of mineralization. Results obtained showed that Concentrated Growth Factors and/or resveratrol significantly increased osteoblast proliferation and differentiation and that the cotreatment with Concentrated Growth Factors and resveratrol had a protective role on osteoblasts treated with bisphosphonates. In conclusion, these data suggest that this approach could be promised in the clinical management of BRONJ.

Enhanced proliferation and differentiation of HO-1 gene-modified bone marrow-derived mesenchymal stem cells in the acute injured kidney

The aim of the present study was to investigate the effect of heme oxygenase-1 (HO-1) overexpression on the survival and differentiation ability of bone marrow‑derived mesenchymal stem cells (BMSCs) in the acute kidney injury (AKI) microenvironment. HO-1-BMSCs and enhanced green fluorescent protein (eGFP)-BMSCs were constructed. Rat ischemia/reperfusion (I/R)‑AKI-kidney homogenate supernatant was prep-ared to treat the BMSCs, eGFP-BMSCs and HO-1-BMSCs in vitro. In the AKI microenvironment, the HO-1-BMSCs exhibited a smaller proportion of cells at the G0/G1 phase, and a larger proportion of cells expressing proliferating cell nuclear antigen (PCNA) and cytokeratin 18 (CK18). Phosphorylated protein kinase B (Akt) and extracellular signal‑regulated kinase (ERK) protein levels were observed to be increased in the HO-1-BMSCs compared with the BMSCs. LY294002 and PD98059 each inhibited the above effects. BMSCs, eGFP-BMSCs and HO-1-BMSCs were implanted into an I/R-AKI rat model. The proportions of PCNA+ BMSCs and CK18+ BMSCs were higher in the HO-1-BMSCs group compared with the BMSCs group, which resulted in a decreased acute tubular necrosis score and improved renal function for the AKI rats. In conclusion, the enhanced proliferation and differentiation of HO-1-BMSCs suggest the beneficial effects of such cells in the BMSC-based therapy of AKI. The mechanism underlying these effects may involve the stimulation of Akt and ERK signaling.

Effect of olive oil phenolic compounds on osteoblast differentiation

BACKGROUND

Osteoporosis is a skeletal disorder characterized by compromised bone strength that predisposes individuals to an increased risk of fracture. Previous in vivo and in vitro studies have reported that phenolic compounds present in extra virgin olive oil have a beneficial effect on osteoblasts in terms of increase cell proliferation. The aim of this study was to determine whether phenolic compounds present in olive oil could modify the expression of cell differentiation markers on osteoblasts.

STUDY DESIGN

An in vitro experimental design was performed using MG-63 osteoblasts cell line.

METHODS

MG63 cells were exposed to different doses of luteolin, apigenin, or p-coumaric, caffeic or ferulic acid. Alkaline phosphatase (ALP) was evaluated by spectrophotometry and antigen expression (cluster of differentiation [CD] 54, CD80, CD86 and HLA-DR) by flow cytometry.

RESULTS

At 24 hour, treated groups showed an increased ALP and modulated antigen profile, with respect to the nontreated group.

CONCLUSION

These results demonstrate that the phenolic compounds studied induce cell maturation in vitro, increasing ALP synthesis and reducing the expression of antigens involved in immune functions of the osteoblast which would improve bone density.

Resveratrol counteracts bone loss via mitofilin-mediated osteogenic improvement of mesenchymal stem cells in senescence-accelerated mice

Rational: Senescence of mesenchymal stem cells (MSCs) and the related functional decline of osteogenesis have emerged as the critical pathogenesis of osteoporosis in aging. Resveratrol (RESV), a small molecular compound that safely mimics the effects of dietary restriction, has been well documented to extend lifespan in lower organisms and improve health in aging rodents. However, whether RESV promotes function of senescent stem cells in alleviating age-related phenotypes remains largely unknown. Here, we intend to investigate whether RESV counteracts senescence-associated bone loss via osteogenic improvement of MSCs and the underlying mechanism.

Methods: MSCs derived from bone marrow (BMMSCs) and the bone-specific, senescence-accelerated, osteoblastogenesis/osteogenesis-defective mice (the SAMP6 strain) were used as experimental models. In vivo application of RESV was performed at 100 mg/kg intraperitoneally once every other day for 2 months, and in vitro application of RESV was performed at 10 μM. Bone mass, bone formation rates and osteogenic differentiation of BMMSCs were primarily evaluated. Metabolic statuses of BMMSCs and the mitochondrial activity, transcription and morphology were also examined. Mitofilin expression was assessed at both mRNA and protein levels, and short hairpin RNA (shRNA)-based gene knockdown was applied for mechanistic experiments.

Results: Chronic intermittent application of RESV enhances bone formation and counteracts accelerated bone loss, with RESV improving osteogenic differentiation of senescent BMMSCs. Furthermore, in rescuing osteogenic decline under BMMSC senescence, RESV restores cellular metabolism through mitochondrial functional recovery via facilitating mitochondrial autonomous gene transcription. Molecularly, in alleviating senescence-associated mitochondrial disorders of BMMSCs, particularly the mitochondrial morphological alterations, RESV upregulates Mitofilin, also known as inner membrane protein of mitochondria (Immt) or Mic60, which is the core component of the mitochondrial contact site and cristae organizing system (MICOS). Moreover, Mitofilin is revealed to be indispensable for mitochondrial homeostasis and osteogenesis of BMMSCs, and that insufficiency of Mitofilin leads to BMMSC senescence and bone loss. More importantly, Mitofilin mediates resveratrol-induced mitochondrial and osteogenic improvements of BMMSCs in senescence.

Conclusion: Our findings uncover osteogenic functional improvements of senescent MSCs as critical impacts in anti-osteoporotic practice of RESV, and unravel Mitofilin as a novel mechanism mediating RESV promotion on mitochondrial function in stem cell senescence.

Long-Term High-Dose Resveratrol Supplementation Reduces Bone Mass and Fracture Strength in Rats

Resveratrol (RSV) is a natural polyphenolic compound. A recent study suggests a positive effect on BMD in men; however, the underlying changes in microstructure and strength remain unknown. We aimed to investigate the effects of RSV on the skeleton in hindlimb-immobilized and non-immobilized rats. Seventy-two female Wistar rats were divided into six groups. Two baseline (BSL) groups underwent short-term diet intervention for 4 weeks before sacrifice [phytoestrogen-deficient diet (PD) (BSL + PD) or RSV diet (600 mg/kg body weight/day) (BSL + RSV)]. Four groups were injected in the right hindlimb with botulinum toxin (BTX) (immobilized) or saline (non-immobilized), and fed either PD diet or RSV diet 4 weeks pre-injection and 6 weeks post-injection before sacrifice (BTX + PD, BTX + RSV, PD, and RSV, respectively). DXA, µCT, dynamic histomorphometry, and mechanical tests were performed. Short-term RSV treatment did not affect bone parameters, whereas long-term RSV exposure had a consistent negative impact on non-immobilized rats (RSV vs. PD); whole femoral aBMD (p = 0.01) and distal femoral metaphyseal Tb.N (p = 0.01), Tb.Sp (p = 0.02), and BV/TV (p = 0.07). At the femoral mid-diaphysis, RSV increased periosteal resorption (p = 0.01) and increased endosteal formation (p = 0.02), while mineralization was unaffected. In addition, RSV reduced femoral mid-diaphyseal three-point bending strength (p = 0.03) and stiffness (p = 0.04). BTX-induced immobilization resulted in significant bone loss and reduced bone strength; however, RSV supplementation was unable to prevent this. In conclusion, long-term high-dose RSV reduced bone mass and fracture strength and did not prevent immobilization-induced bone loss in rats.

Estrogen/ERα signaling axis participates in osteoblast maturation via upregulating chromosomal and mitochondrial complex gene expressions

Estrogen deficiency usually leads to bone loss and osteoporosis in postmenopausal women. Osteoblasts play crucial roles in bone formation. However, osteoblast functions are influenced by mitochondrial bioenergetic conditions. In this study, we investigated the roles of the estrogen and estrogen receptor alpha (ERα) axis in mitochondrial energy metabolism and subsequent osteoblast mineralization. Exposure of rat calvarial osteoblasts to estradiol caused substantial improvements in alkaline phosphatase activities and cell calcification. In parallel, treatment of human osteoblast-like U2OS cells, derived from a female osteosarcoma patient, with estradiol specifically augmented ERα levels. Sequentially, estradiol stimulated translocation of ERα to nuclei in human osteoblasts and induced expressions of genomic respiratory chain complex NDUFA10, UQCRC1, cytochrome c oxidase (COX)8A, COX6A2, COX8C, COX6C, COX6B2, COX412, and ATP12A genes. Concurrently, estradiol stimulated translocation of ERα to mitochondria from the cytoplasm. A bioinformatic search found the existence of four estrogen response elements in the 5’-promoter region of the mitochondrial cox i gene. Interestingly, estradiol induced COX I mRNA and protein expressions in human osteoblasts or rat calvarial osteoblasts. Knocking-down ERα translation concurrently downregulated estradiol-induced COX I mRNA expression. Consequently, exposure to estradiol led to successive increases in the mitochondrial membrane potential, the mitochondrial enzyme activity, and cellular adenosine triphosphate levels. Taken together, this study showed the roles of the estradiol/ERα signaling axis in improving osteoblast maturation through upregulating the mitochondrial bioenergetic system due to induction of definite chromosomal and mitochondrial complex gene expressions. Our results provide novel insights elucidating the roles of the estrogen/ERα alliance in regulating bone formation.

Molecular signaling mechanisms behind polyphenol-induced bone anabolism

For millennia, in the different cultures all over the world, plants have been extensively used as a source of therapeutic agents with wide-ranging medicinal applications, thus becoming part of a rational clinical and pharmacological investigation over the years. As bioactive molecules, plant-derived polyphenols have been demonstrated to exert many effects on human health by acting on different biological systems, thus their therapeutic potential would represent a novel approach on which natural product-based drug discovery and development could be based in the future. Many reports have provided evidence for the benefits derived from the dietary supplementation of polyphenols in the prevention and treatment of osteoporosis. Polyphenols are able to protect the bone, thanks to their antioxidant properties, as well as their anti-inflammatory actions by involving diverse signaling pathways, thus leading to bone anabolic effects and decreased bone resorption. This review is meant to summarize the research works performed so far, by elucidating the molecular mechanisms of action of polyphenols in a bone regeneration context, aiming at a better understanding of a possible application in the development of medical devices for bone tissue regeneration.

Beneficial effect of resveratrol on phenotypic features and activity of osteoarthritic osteoblasts

Background

Osteoarthritis (OA) is a complex disease, which affects multiple tissues, namely the subchondral bone, articular cartilage and synovial membrane. Alterations of the subchondral bone include an increased, yet under mineralized osteoid matrix, abnormal osteoblast cell phenotype including elevated alkaline phosphatase (ALP) activity, increased release of osteocalcin (OC) and transforming growth factor β-1 (TGF-β1). Previous studies have demonstrated an inhibition of the canonical Wnt signaling (cWnt) pathway in OA osteoblasts (Ob). As resveratrol (RSV) has been shown to upregulate the Wnt signaling pathway in different cell systems, we hypothesized that RSV could be beneficial for OA Ob.

Method

We prepared primary human Ob using the subchondral bone plate of tibial plateaus of OA patients undergoing total knee arthroplasty, or tibial plateaus of normal individuals at autopsy. Sirtuin 1 (Sirt1) expression in normal and OA subchondral bone tissue was evaluated by immunohistochemical analysis. Expression of genes was evaluated by qRT-PCR and protein production by western blot analysis. ALP activity and osteocalcin secretion were evaluated respectively with substrate hydrolysis and enzyme immunoassay. Mineralization levels were evaluated with alizarin red staining. Wnt/β-catenin signaling was evaluated by target gene expression using the TOPflash TCF/lef luciferase reporter assay and intracellular signaling using β-catenin levels in western blot analysis. Extracellular signal-regulated kinase (Erk)1/2 and the Smad1/5/8 pathways were evaluated by western blot analysis.

Results

Sirt1 expression and production were reduced in OA subchondral bone tissue compared to normal tissue. RSV upregulated Sirt1 and its activity, and reduced the expression of leptin. RSV increased Erk1/2 phosphorylation in OA Ob; however, it had no effect on Smad 1/5/8 phosphorylation. RSV had little effect on cell proliferation and only slightly affected the Bax/Bcl2 ratio. The expression of Runx2/Cbfa1 and peroxisome proliferator-activated receptor (PPAR)γ were not affected by increasing doses of RSV. The endogenous increased ALP activity and OC release observed in OA Ob compared to normal Ob were partly corrected only for ALP at high RSV levels but not for OC release. In contrast, RSV increased the mineralization of OA Ob. Moreover, whereas Wnt3a stimulates the Wnt/β-catenin pathway in these cells, RSV further increased the response to Wnt3a.

Conclusion

These data indicate that RSV promotes Sirt1 levels, inhibits the endogenous expression of leptin by OA osteoblasts and can promote the Wnt/β-catenin and Erk1/2 signaling pathways, which are altered in these cells.

Childhood cancer chemotherapy-induced bone damage: pathobiology and protective effects of resveratrol and other nutraceuticals

Intensive cancer chemotherapy causes significant bone loss, for which the mechanisms remain unclear and effective treatments are lacking. This is a significant issue particularly for childhood cancers, as the most common ones have a >75% cure rate following chemotherapy; there is an increasing population of survivors who live with chronic bone defects. Studies suggest that these defects are the result of reduced bone from increased marrow fat formation and increased bone resorption following chemotherapy. These changes probably result from altered expression/activation of regulatory molecules or pathways regulating skeletal cell formation and activity. Treatment with methotrexate, an antimetabolite commonly used in childhood oncology, has been shown to increase levels of proinflammatory/pro-osteoclastogenic cytokines (e.g., enhanced NF-κB activation), leading to increased osteoclast formation and bone resorption, as well as to attenuate Wnt signaling, leading to both decreased bone and increased marrow fat formation. In recent years, understanding the mechanisms of action and potential health benefits of selected nutraceuticals, including resveratrol, genistein, icariin, and inflammatory fatty acids, has led to preclinical studies that, in some cases, indicate efficacy in reducing chemotherapy-induced bone defects. We summarize the supporting evidence.

Resveratrol Enhances Self-Renewal of Mouse Embryonic Stem Cells

Resveratrol (RSV) has been shown to affect the differentiation of several types of stem cells, while the detailed mechanism is elusive. Here, we aim to investigate the function of RSV in self-renewal of mouse embryonic stem cells (ESCs) and the related mechanisms. In contrast with its reported roles, we found unexpectedly that differentiated ESCs or iPSCs treated by RSV would not show further differentiation, but regained a naïve pluripotency state with higher expressions of core transcriptional factors and with the ability to differentiate into all three germ layers when transplanted in vivo. In accordance with these findings, RSV also enhanced cell cycle progression of ESCs via regulating cell cycle-related proteins. Finally, enhanced activation of JAK/STAT3 signaling pathway and suppressed activation of mTOR were found essential in enhancing the self-renewal of ESCs by RSV. Our finding discovered a novel function of RSV in enhancing the self-renewal of ESCs, and suggested that the timing of treatment and concentration of RSV determined the final effect of it. Our work may contribute to understanding of RSV in the self-renewal maintenance of pluripotent stem cells, and may also provide help to the generation and maintenance of iPSCs in vitro. J. Cell. Biochem. 118: 1928-1935, 2017. © 2017 Wiley Periodicals, Inc.