Oxygen cycling in conjunction with stem cell transplantation induces NOS3 expression leading to attenuation of fibrosis and improved cardiac function

The Role of Hyperbaric Oxygen Therapy in Neuroregeneration and Neuroprotection: A Review

Neurogenesis is a high energy-demanding process, which is why blood vessels are an active part of the neurogenic niche since they allow the much-needed oxygenation of progenitor cells. In this regard, although neglected for a long time, the "oxygen niche" should be considered an important intervenient in adult neurogenesis. One possible hypothesis for the failure of numerous neuroprotective trials is that they relied on compounds that target a highly specific neuroprotective pathway. This approach may be too limited, given the complexity of the processes that lead to cell death. Therefore, research should adopt a more multifactorial approach. Among the limited range of agents with multimodal neuromodulatory capabilities, hyperbaric oxygen therapy has demonstrated effectiveness in reducing secondary brain damage in various brain injury models. This therapy functions not only as a neuroprotective mechanism but also as a powerful neuroregenerative mechanism.

Ultrasound-controlled nano oxygen carriers enhancing cell viability in 3D GelMA hydrogel for the treatment of myocardial infarction

Heart failure is a critical and ultimate phase of cardiovascular ailment that leads to a considerable incidence of disability and mortality. Among various factors contributing to heart failure, myocardial infarction is one of the most frequent and significant causes, which is still difficult to manage effectively. An innovative therapeutic strategy, namely a 3D bio-printed cardiac patch, has recently emerged as a promising approach to substitute damaged cardiomyocytes in a localized infarct region. Nevertheless, the efficacy of this treatment primarily relies on the long-term viability of the transplanted cells. In this study, we aimed to construct acoustically sensitive nano oxygen carriers to improve cell survival inside the bio-3D printed patch. In this study, we initially created nanodroplets capable of phase transition triggered by ultrasound and integrated them into GelMA (Gelatin Methacryloyl) hydrogels, which were then employed for 3D bioprinting. After adding nanodroplets and ultrasonic irradiation, numerous pores appeared inside the hydrogel with improved permeability. We further encapsulated hemoglobin into nanodroplets (ND-Hb) to construct oxygen carriers. Results of in vitro experiments showed the highest cell survival within the patch of ND-Hb irradiated by the low-intensity pulsed ultrasound (LIPUS) group. The genomic analysis discovered that the increased survival of seeded cells within the patch might be related to the protection of mitochondrial function owing to the improved hypoxic state. Eventually, in vivo studies revealed that the LIPUS+ND-Hb group had improved cardiac function and increased revascularization after myocardial infarction. To summarize, our study successfully improved the permeability of the hydrogel in a non-invasive and efficient manner, facilitating the exchange of substances in the cardiac patch. Moreover, ultrasound-controlled oxygen release augmented the viability of the transplanted cells and expedited the repair of infarcted tissues.

Hyperbaric oxygen therapy for healthy aging: From mechanisms to therapeutics

Hyperbaric oxygen therapy (HBOT), a technique through which 100% oxygen is provided at a pressure higher than 1 atm absolute (ATA), has become a well-established treatment modality for multiple conditions. The noninvasive nature, favorable safety profile, and common clinical application of HBOT make it a competitive candidate for several new indications, one of them being aging and age-related diseases. In fact, despite the conventional wisdom that excessive oxygen accelerates aging, appropriate HBOT protocols without exceeding the toxicity threshold have shown great promise in therapies against aging. For one thing, an extensive body of basic research has expanded our mechanistic understanding of HBOT. Interestingly, the therapeutic targets of HBOT overlap considerably with those of aging and age-related diseases. For another, pre-clinical and small-scale clinical investigations have provided validated information on the efficacy of HBOT against aging from various aspects. However, a generally applicable protocol for HBOT to be utilized in therapies against aging needs to be defined as a subsequent step. It is high time to look back and summarize the recent advances concerning biological mechanisms and therapeutic implications of HBOT in promoting healthy aging and shed light on prospective directions. Here we provide the first comprehensive overview of HBOT in the field of aging and geriatric research, which allows the scientific community to be aware of the emerging tendency and move beyond conventional wisdom to scientific findings of translational value.

A critical review of fibrous polyurethane-based vascular tissue engineering scaffolds

Certain polymeric materials such as polyurethanes (PUs) are the most prevalent class of used biomaterials in regenerative medicine and have been widely explored as vascular substitutes in several animal models. It is thought that PU-based biomaterials possess suitable hemo-compatibility with comparable performance related to the normal blood vessels. Despite these advantages, the possibility of thrombus formation and restenosis limits their application as artificial functional vessels. In this regard, various surface modification approaches have been developed to enhance both hemo-compatibility and prolong patency. While critically reviewing the recent advances in vascular tissue engineering, mainly PU grafts, this paper summarizes the application of preferred cell sources to vascular regeneration, physicochemical properties, and some possible degradation mechanisms of PU to provide a more extensive perspective for future research.

Oxygen Delivery Approaches to Augment Cell Survival After Myocardial Infarction: Progress and Challenges

Myocardial infarction (MI), triggered by blockage of a coronary artery, remains the most common cause of death worldwide. After MI, the capability of providing sufficient blood and oxygen significantly decreases in the heart. This event leads to depletion of oxygen from cardiac tissue and consequently leads to massive cardiac cell death due to hypoxemia. Over the past few decades, many studies have been carried out to discover acceptable approaches to treat MI. However, very few have addressed the crucial role of efficient oxygen delivery to the injured heart. Thus, various strategies were developed to increase the delivery of oxygen to cardiac tissue and improve its function. Here, we have given an overall discussion of the oxygen delivery mechanisms and how the current technologies are employed to treat patients suffering from MI, including a comprehensive view on three major technical approaches such as oxygen therapy, hemoglobin-based oxygen carriers (HBOCs), and oxygen-releasing biomaterials (ORBs). Although oxygen therapy and HBOCs have shown promising results in several animal and clinical studies, they still have a few drawbacks which limit their effectiveness. More recent studies have investigated the efficacy of ORBs which may play a key role in the future of oxygenation of cardiac tissue. In addition, a summary of conducted studies under each approach and the remaining challenges of these methods are discussed.

PTEN as a Therapeutic Target in Pulmonary Hypertension Secondary to Left-heart Failure: Effect of HO-3867 and Supplemental Oxygenation

Pulmonary hypertension (PH) is a condition when the pressure in the lung blood vessels is elevated. This leads to increase in thickness of the blood vessels and increases the workload of the heart and lungs. The incidence and prevalence of PH has been on the increase in the last decade. It is estimated that PH affects about 1% of the global population and about 10% of individuals >65 years of age. Of the various types, Group 2 PH is the most common type seen in the elderly population. Fixed PH or PH refractive to therapies is considered a contraindication for heart transplantation; the 30-day mortality in heart transplant recipients is significantly increased in the subset of this population. In general, the pathobiology of PH involves multiple factors including hypoxia, oxidative stress, growth factor receptors, vascular stress, etc. Hence, it is challenging and important to identify specific mechanisms, diagnosis and develop effective therapeutic strategies. The focus of this manuscript is to review some of the important pathobiological processes and mechanisms in the development of PH. Results from our previously reported studies, including targeted treatments along with some new data on PH secondary to left-heart failure, are presented.

Functional role and molecular mechanisms underlying prohibitin 2 in platelet mitophagy and activation

Platelet mitophagy is a major pathway involved in the clearance of injured mitochondria during hemostasis and thrombosis. Prohibitin 2 (PHB2) has recently emerged as an inner mitochondrial membrane receptor involved in mitophagy. However, the mechanisms underlying PHB2-mediated platelet mitophagy and activation are not completely understood. PHB2 is a highly conserved inner mitochondrial membrane protein that regulates mitochondrial assembly and function due to its unique localization on the mitochondrial membrane. The present study aimed to investigate the role and mechanism underlying PHB2 in platelet mitophagy and activation. Phorbol-12-myristate-13-acetate (PMA) was used to induce MEG-01 cells maturation and differentiate into platelets following PHB2 knockdown. Cell Counting Kit-8 assays were performed to examine platelet viability. Flow cytometry was performed to assess platelet mitochondrial membrane potential. RT-qPCR and western blotting were conducted to measure mRNA and protein expression levels, respectively. Subsequently, platelets were exposed to CCCP and the role of PHB2 was assessed. The results of the present study identified a crucial role for PHB2 in platelet mitophagy and activation, suggesting that PHB2-mediated regulation of mitophagy may serve as a novel strategy for downregulating the expression of platelet activation genes. Although further research into mitophagy is required, the present study suggested that PHB2 may serve as a novel therapeutic target for thrombosis-related diseases due to its unique localization on the mitochondrial membrane.

High oxygen preservation hydrogels to augment cell survival under hypoxic condition

Cell therapy is a promising approach for ischemic tissue regeneration. However, high death rate of delivered cells under low oxygen condition, and poor cell retention in tissues largely limit the therapeutic efficacy. Using cell carriers with high oxygen preservation has potential to improve cell survival. To increase cell retention, cell carriers that can quickly solidify at 37 °C so as to efficiently immobilize the carriers and cells in the tissues are necessary. Yet there lacks cell carriers with these combined properties. In this work, we have developed a family of high oxygen preservation and fast gelation hydrogels based on N-isopropylacrylamide (NIPAAm) copolymers. The hydrogels were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization of NIPAAm, acrylate-oligolactide (AOLA), 2-hydroxyethyl methacrylate (HEMA), and methacrylate-poly(ethylene glycol)-perfluorooctane (MAPEGPFC). The hydrogel solutions exhibited sol-gel temperatures around room temperature and were flowable and injectable at 4°C. They can quickly solidify (≤6 s) at 37°C to form flexible gels. These hydrogels lost 9.4~29.4% of their mass after incubation in Dulbecco's Phosphate-Buffered Saline (DPBS) for 4 weeks. The hydrogels exhibited a greater oxygen partial pressure than DPBS after being transferred from a 21% O2 condition to a 1% O2 condition. When bone marrow mesenchymal stem cells (MSCs) were encapsulated in the hydrogels and cultured under 1% O2, the cells survived and proliferated during the 14-day culture period. In contrast, the cells experienced extensive death in the control hydrogel that had low oxygen preservation capability. The hydrogels possessed excellent biocompatibility. The final degradation products did not provoke cell death even when the concentration was as high as 15 mg/ml, and the hydrogel implantation did not induce substantial inflammation. These hydrogels are promising as cell carriers for cell transplantation into ischemic tissues. STATEMENT OF SIGNIFICANCE: Stem cell therapy for ischemic tissues experiences low therapeutic efficacy largely due to poor cell survival under low oxygen condition. Using cell carriers with high oxygen preservation capability has potential to improve cell survival. In this work, we have developed a family of hydrogels with this property. These hydrogels promoted the encapsulated stem cell survival and growth under low oxygen condition.

Supplemental Oxygen Protects Heart Against Acute Myocardial Infarction

Myocardial infarction (MI), which occurs often due to acute ischemia followed by reflow, is associated with irreversible loss (death) of cardiomyocytes. If left untreated, MI will lead to progressive loss of viable cardiomyocytes, deterioration of cardiac function, and congestive heart failure. While supplemental oxygen therapy has long been in practice to treat acute MI, there has not been a clear scientific basis for the observed beneficial effects. Further, there is no rationale for the amount or duration of administration of supplemental oxygenation for effective therapy. The goal of the present study was to determine an optimum oxygenation protocol that can be clinically applicable for treating acute MI. Using EPR oximetry, we studied the effect of exposure to supplemental oxygen cycling (OxCy) administered by inhalation of 21–100% oxygen for brief periods (15–90 min), daily for 5 days, using a rat model of acute MI. Myocardial oxygen tension (pO₂), cardiac function and pro-survival/apoptotic signaling molecules were used as markers of treatment outcome. OxCy resulted in a significant reduction of infarct size and improvement of cardiac function. An optimal condition of 30-min OxCy with 95% oxygen + 5% CO₂ under normobaric conditions was found to be effective for cardioprotection.

PEDF protects cardiomyocytes by promoting FUNDC1‑mediated mitophagy via PEDF-R under hypoxic condition

Pigment epithelial-derived factor (PEDF) is known to exert diverse physiological activities. Previous studies suggest that hypoxia could induce mitophagy. Astoundingly, under hypoxic condition, we found that PEDF decreased the mitochondrial density of cardiomyocytes. In this study, we evaluated whether PEDF could decrease the mitochondrial density and play a protective role in hypoxic cardiomyocytes via promoting mitophagy. Immunostaining and western blotting were used to analyze mitochondrial density and mitophagy of hypoxic cardiomyocytes. Gas chromatography-mass spectrometry and ELISA were used to analyze levels of palmitic acid and diacylglycerol. Transmission Electron Microscopy was used to detect mitophagy and the mitochondrial density in adult male Sprague-Dawley rat model of acute myocardial infarction. Compared to the control group, we observed that PEDF decreased mitochondrial density through promoting hypoxic cardiomyocyte mitophagy. PEDF increased the levels of palmitic acid and diacylglycerol, and then upregulated the levels of protein kinase Cα (PKC-α) and its activation. Furthermore, inhibition of PKC-α by Go6976 could effectively suppress PEDF-induced mitophagy. Besides, we found that PEDF promoted FUNDC1-mediated cardiomyocyte mitophagy via ULK1, which depended on the activation of PKC-α. Finally, we discovered that mitophagy was increased and mitochondrial density was reduced in adult male Sprague-Dawley rat model of acute myocardial infarction. We concluded that PEDF promotes mitophagy to protect hypoxic cardiomyocytes, through PEDF/PEDF-R/PA/DAG/PKC-α/ULK1/FUNDC1 pathway.

An Injectable Oxygen Release System to Augment Cell Survival and Promote Cardiac Repair Following Myocardial Infarction

Oxygen deficiency after myocardial infarction (MI) leads to massive cardiac cell death. Protection of cardiac cells and promotion of cardiac repair are key therapeutic goals. These goals may be achieved by re-introducing oxygen into the infarcted area. Yet current systemic oxygen delivery approaches cannot efficiently diffuse oxygen into the infarcted area that has extremely low blood flow. In this work, we developed a new oxygen delivery system that can be delivered specifically to the infarcted tissue, and continuously release oxygen to protect the cardiac cells. The system was based on a thermosensitive, injectable and fast gelation hydrogel, and oxygen releasing microspheres. The fast gelation hydrogel was used to increase microsphere retention in the heart tissue. The system was able to continuously release oxygen for 4 weeks. The released oxygen significantly increased survival of cardiac cells under the hypoxic condition (1% O₂) mimicking that of the infarcted hearts. It also reduced myofibroblast formation under hypoxic condition (1% O₂). After implanting into infarcted hearts for 4 weeks, the released oxygen significantly augmented cell survival, decreased macrophage density, reduced collagen deposition and myofibroblast density, and stimulated tissue angiogenesis, leading to a significant increase in cardiac function.

Hyperbaric oxygen therapy stimulates colonic stem cells and induces mucosal healing in patients with refractory ulcerative colitis: a prospective case series

BACKGROUND

Hyperbaric oxygen (HBO) is used as part of treatment in a variety of clinical conditions. Its use in the treatment of ulcerative colitis has been reported in few clinical reports.

OBJECTIVE

We report the effect of HBO on refractory ulcerative colitis exploring one potential mechanism of action.

DESIGN

A review of records of patients with refractory ulcerative colitis who received HBO was conducted. Clinical and histopathological scoring was utilised to evaluate the response to HBO therapy (HBOT).

RESULTS

All patients manifested clinical improvement by the 40th cycle of HBOT. The median number of stool frequency dropped from seven motions/day (range=3-20) to 1/day (range=0.5-3), which was significant (z=-4.6, p<0.001). None of the patients manifested persistent blood passage after HBOT (z=-3.2, p=0.002). The severity index significantly improved after HBOT (z=-4.97, p<0.001). Histologically, a significant reduction of the scores of activity was recorded accompanied by a significant increase in the proliferating cell nuclear antigen labelling index of the CD44 cells of the colonic mucosa (p=0.001).

CONCLUSIONS

HBOT is effective in the setting of refractory ulcerative colitis. The described protocol is necessary for successful treatment. HBOT stimulates colonic stem cells to promote healing.

MicroRNA-133a engineered mesenchymal stem cells augment cardiac function and cell survival in the infarct heart

: Cardiovascular disease is the number 1 cause of morbidity and mortality in the United States. The most common manifestation of cardiovascular disease is myocardial infarction (MI), which can ultimately lead to congestive heart failure. Cell therapy (cardiomyoplasty) is a new potential therapeutic treatment alternative for the damaged heart. Recent preclinical and clinical studies have shown that mesenchymal stem cells (MSCs) are a promising cell type for cardiomyoplasty applications. However, a major limitation is the poor survival rate of transplanted stem cells in the infarcted heart. miR-133a is an abundantly expressed microRNA (miRNA) in the cardiac muscle and is downregulated in patients with MI. We hypothesized that reprogramming MSCs using miRNA mimics (double-stranded oligonucleotides) will improve survival of stem cells in the damaged heart. MSCs were transfected with miR-133a mimic and antagomirs, and the levels of miR-133a were measured by quantitative real-time polymerase chain reaction. Rat hearts were subjected to MI and MSCs transfected with miR-133a mimic or antagomir were implanted in the ischemic hearts. Four weeks after MI, cardiac function, cardiac fibrosis, miR-133a levels, and apoptosis-related genes (Apaf-1, Caspase-9, and Caspase-3) were measured in the heart. We found that transfecting MSCs with miR-133a mimic improves survival of MSCs as determined by the MTT assay. Similarly, transplantation of miR-133a mimic transfected MSCs in rat hearts subjected to MI led to a significant increase in cell engraftment, cardiac function, and decreased fibrosis when compared with MSCs only or MI groups. At the molecular level, quantitative real-time polymerase chain reaction data demonstrated a significant decrease in expression of the proapoptotic genes; Apaf-1, caspase-9, and caspase-3 in the miR-133a mimic transplanted group. Furthermore, luciferase reporter assay confirmed that miR-133a is a direct target for Apaf-1. Overall, bioengineering of stem cells through miRNAs manipulation could potentially improve the therapeutic outcome of patients undergoing stem cell transplantation for MI.

Translational applications of molecular imaging in cardiovascular disease and stem cell therapy

Cardiovascular disease (CVD) is the leading cause of mortality and morbidity worldwide. Molecular imaging techniques provide valuable information at cellular and molecular level, as opposed to anatomical and structural layers acquired from traditional imaging modalities. More specifically, molecular imaging employs imaging probes which interact with specific molecular targets and therefore makes it possible to visualize biological processes in vivo. Molecular imaging technology is now progressing towards preclinical and clinical application that gives an integral and comprehensive guidance for the investigation of cardiovascular disease. In addition, cardiac stem cell therapy holds great promise for clinical translation. Undoubtedly, combining stem cell therapy with molecular imaging technology will bring a broad prospect for the study and treatment of cardiac disease. This review will focus on the progresses of molecular imaging strategies in cardiovascular disease and cardiac stem cell therapy. Furthermore, the perspective on the future role of molecular imaging in clinical translation and potential strategies in defining safety and efficacy of cardiac stem cell therapies will be discussed.

Comparison of human induced pluripotent stem-cell derived cardiomyocytes with human mesenchymal stem cells following acute myocardial infarction

INTRODUCTION

Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) have recently been shown to express key cardiac proteins and improve in vivo cardiac function when administered following myocardial infarction. However, the efficacy of hiPSC-derived cell therapies, in direct comparison to current, well-established stem cell-based therapies, is yet to be elucidated. The goal of the current study was to compare the therapeutic efficacy of human mesenchymal stem cells (hMSCs) with hiPSC-CMs in mitigating myocardial infarction (MI).

METHODS

Male athymic nude hyrats were subjected to permanent ligation of the left-anterior-descending (LAD) coronary artery to induce acute MI. Four experimental groups were studied: 1) control (non-MI), 2) MI, 3) hMSCs (MI+MSC), and 4) hiPSC-CMs (MI+hiPSC-derived cardiomyocytes). The hiPSC-CMs and hMSCs were labeled with superparamagnetic iron oxide (SPIO) in vitro to track the transplanted cells in the ischemic heart by high-field cardiac MRI. These cells were injected into the ischemic heart 30-min after LAD ligation. Four-weeks after MI, cardiac MRI was performed to track the transplanted cells in the infarct heart. Additionally, echocardiography (M-mode) was performed to evaluate the cardiac function. Immunohistological and western blot studies were performed to assess the cell tracking, engraftment and cardiac fibrosis in the infarct heart tissues.

RESULTS

Echocardiography data showed a significantly improved cardiac function in the hiPSC-CMs and hMSCs groups, when compared to MI. Immunohistological studies showed expression of connexin-43, α-actinin and myosin heavy chain in engrafted hiPSC-CMs. Cardiac fibrosis was significantly decreased in hiPSC-CMs group when compared to hMSCs or MI groups. Overall, this study demonstrated improved cardiac function with decreased fibrosis with both hiPSC-CMs and hMSCs groups when compared with MI group.

Hyperbaric oxygen, vasculogenic stem cells, and wound healing

SIGNIFICANCE

Oxidative stress is recognized as playing a role in stem cell mobilization from peripheral sites and also cell function.

RECENT ADVANCES

This review focuses on the impact of hyperoxia on vasculogenic stem cells and elements of wound healing.

CRITICAL ISSUES

Components of the wound-healing process in which oxidative stress has a positive impact on the various cells involved in wound healing are highlighted. A slightly different view of wound-healing physiology is adopted by departing from the often used notion of sequential stages: hemostatic, inflammatory, proliferative, and remodeling and instead organizes the cascade of wound healing as overlapping events or waves pertaining to reactive oxygen species, lactate, and nitric oxide. This was done because hyperoxia has effects of a number of cell signaling events that converge to influence cell recruitment/chemotaxis and gene regulation/protein synthesis responses which mediate wound healing.

FUTURE DIRECTIONS

Our alternative perspective of the stages of wound healing eases recognition of the multiple sites where oxidative stress has an impact on wound healing. This aids the focus on mechanistic events and the interplay among various cell types and biochemical processes. It also highlights the areas where additional research is needed.

Gene expression analysis reveals inhibition of radiation-induced TGFβ-signaling by hyperbaric oxygen therapy in mouse salivary glands

A side effect of radiation therapy in the head and neck region is injury to surrounding healthy tissues such as irreversible impaired function of the salivary glands. Hyperbaric oxygen therapy (HBOT) is clinically used to treat radiation-induced damage but its mechanism of action is largely unknown. In this study, we investigated the molecular pathways that are affected by HBOT in mouse salivary glands two weeks after radiation therapy by microarray analysis. Interestingly, HBOT led to significant attenuation of the radiation-induced expression of a set of genes and upstream regulators that are involved in processes such as fibrosis and tissue regeneration. Our data suggest that the TGFβ-pathway, which is involved in radiation-induced fibrosis and chronic loss of function after radiation therapy, is affected by HBOT. On the longer term, HBOT reduced the expression of the fibrosis-associated factor α-smooth muscle actin in irradiated salivary glands. This study highlights the potential of HBOT to inhibit the TGFβ-pathway in irradiated salivary glands and to restrain consequential radiation induced tissue injury.

CD34+/CD45-dim stem cell mobilization by hyperbaric oxygen - changes with oxygen dosage

Because hyperbaric oxygen treatment mobilizes bone marrow derived-stem/progenitor cells by a free radical mediated mechanism, we hypothesized that there may be differences in mobilization efficiency based on exposure to different oxygen partial pressures. Blood from twenty consecutive patients was obtained before and after the 1st, 10th and 20th treatment at two clinical centers using protocols involving exposures to oxygen at either 2.0 or 2.5 atmospheres absolute (ATA). Post-treatment values of CD34+, CD45-dim leukocytes were always 2-fold greater than the pre-treatment values for both protocols. Values for those treated at 2.5 ATA were significantly greater than those treated at 2.0 ATA by factors of 1.9 to 3-fold after the 10th and before and after the 20th treatments. Intracellular content of hypoxia inducible factors -1, -2, and -3, thioredoxin-1 and poly-ADP-ribose polymerase assessed in permeabilized CD34+ cells with fluorophore-conjugated antibodies were twice as high in all post- versus pre-treatment samples with no significant differences between 2.0 and 2.5 ATA protocols. We conclude that putative progenitor cell mobilization is higher with 2.5 versus 2.0 ATA treatments, and all newly mobilized cells exhibit higher concentrations of an array of regulatory proteins.

The stem cell adjuvant with Exendin-4 repairs the heart after myocardial infarction via STAT3 activation

The poor survival of cells in ischaemic myocardium is a major obstacle for stem cell therapy. Exendin-4 holds the potential of cardioprotective effect based on its pleiotropic activity. This study investigated whether Exendin-4 in conjunction with adipose-derived stem cells (ADSCs) could improve the stem cell survival and contribute to myocardial repairs after infarction. Myocardial infarction (MI) was induced by the left anterior descending artery ligation in adult male Sprague-Dawley rats. ADSCs carrying double-fusion reporter gene [firefly luciferase and monomeric red fluorescent protein (fluc-mRFP)] were quickly injected into border zone of MI in rats treated with or without Exendin-4. Exendin-4 enhanced the survival of transplanted ADSCs, as demonstrated by the longitudinal in vivo bioluminescence imaging. Moreover, ADSCs adjuvant with Exendin-4 decreased oxidative stress, apoptosis and fibrosis. They also improved myocardial viability and cardiac function and increased the differentiation rates of ADSCs into cardiomyocytes and vascular smooth muscle cells in vivo. Then, ADSCs were exposed to hydrogen peroxide/serum deprivation (H₂O₂/SD) to mimic the ischaemic environment in vitro. Results showed that Exendin-4 decreased the apoptosis and enhanced the paracrine effect of ADSCs. In addition, Exendin-4 activated signal transducers and activators of transcription 3 (STAT3) through the phosphorylation of Akt and ERK1/2. Furthermore, Exendin-4 increased the anti-apoptotic protein Bcl-2, but decreased the pro-apoptotic protein Bax of ADSCs. In conclusion, Exendin-4 could improve the survival and therapeutic efficacy of transplanted ADSCs through STAT3 activation via the phosphorylation of Akt and ERK1/2. This study suggests the potential application of Exendin-4 for stem cell–based heart regeneration.

p53's choice of myocardial death or survival: Oxygen protects infarct myocardium by recruiting p53 on NOS3 promoter through regulation of p53-Lys(118) acetylation

Myocardial infarction, an irreversible cardiac tissue damage, involves progressive loss of cardiomyocytes due to p53-mediated apoptosis. Oxygenation is known to promote cardiac survival through activation of NOS3 gene. We hypothesized a dual role for p53, which, depending on oxygenation, can elicit apoptotic death signals or NOS3-mediated survival signals in the infarct heart. p53 exhibited a differential DNA-binding, namely, BAX-p53RE in the infarct heart or NOS3-p53RE in the oxygenated heart, which was regulated by oxygen-induced, post-translational modification of p53. In the infarct heart, p53 was heavily acetylated at Lys¹¹⁸ residue, which was exclusively reversed in the oxygenated heart, apparently regulated by oxygen-dependent expression of TIP60. The inhibition of Lys¹¹⁸ acetylation promoted the generation of NOS3-promoting prosurvival form of p53. Thus, oxygenation switches p53-DNA interaction by regulating p53 core-domain acetylation, promoting a prosurvival transcription activity of p53. Understanding this novel oxygen-p53 survival pathway will open new avenues in cardioprotection molecular therapy.

Nanofiber for cardiovascular tissue engineering

INTRODUCTION

Organ/tissue replacement therapy is inherently difficult for application in the tissue engineering field due to immune rejection that limits the long-term efficacy of implanted devices. As the application of tissue engineering in the biomedical field has steadily expanded, stem cells have emerged as a viable option to promote the immune acceptance of implantable devices and to expedite alleviation of the pathological conditions. With various novel scaffolds being introduced, nanofibers which have a three-dimensional architecture can be considered as an efficient carrier for stem cells.

AREAS COVERED

This article reviews the novel tissue engineering processes involved with nanofiber and stem cells. Topics such as the fabrication of nanofiber via electrospinning techniques, the interaction between nanofiber scaffold and specific cell and advanced techniques to enhance the stability of stem cells are delineated in detail. In addition, cardiovascular applications of nanofiber scaffolds loaded with stem cells are examined from a clinical perspective.

EXPERT OPINION

Electrospun nanofibers have been intensively explored as a tool for the architecture control of cardiovascular tissue engineering due to their tunable physicochemical properties. The modification of nanofiber with biological cues, which provide rapid differentiation of stem cells into a specific lineage and protect stem cells under the harsh conditions (i.e., hypoxia), will significantly enhance therapeutic efficacies of transplanted cells. A combination of nanofiber carriers and stem cell therapy for tissue regeneration seems to pose enormous potential for the treatment of cardiac diseases including atherosclerosis and myocardial infarction.

Long course hyperbaric oxygen stimulates neurogenesis and attenuates inflammation after ischemic stroke

Several studies have provided evidence with regard to the neuroprotection benefits of hyperbaric oxygen (HBO) therapy in cases of stroke, and HBO also promotes bone marrow stem cells (BMSCs) proliferation and mobilization. This study investigates the influence of HBO therapy on the migration of BMSCs, neurogenesis, gliosis, and inflammation after stroke. Rats that sustained transient middle cerebral artery occlusion (MCAO) were treated with HBO three weeks or two days. The results were examined using a behavior test (modified neurological severity score, mNSS) and immunostaining to evaluate the effects of HBO therapy on migration of BMSCs, neurogenesis, and gliosis, and expression of neurotrophic factors was also evaluated. There was a lower mNSS score in the three-week HBO group when compared with the two-day HBO group. Mobilization of BMSCs to an ischemic area was more improved in long course HBO treatments, suggesting the duration of therapy is crucial for promoting the homing of BMSCs to ischemic brain by HBO therapies. HBO also can stimulate expression of trophic factors and improve neurogenesis and gliosis. These effects may help in neuronal repair after ischemic stroke, and increasing the course of HBO therapy might enhance therapeutic effects on ischemic stroke.

Stem cell transplantation as a therapy for cardiac fibrosis

Cardiac fibrosis is a fundamental constituent of most cardiac pathologies and represents the upshot of nearly all types of cardiac injury. Generally, fibrosis is a scarring process, characterized by accumulation of fibroblasts and deposition of increasing amounts of extracellular matrix (ECM) proteins in the myocardium. Therapeutic approaches that control fibroblast activity and evade maladaptive processes could represent a potential strategy to attenuate progression towards heart failure. Currently, cell therapy is actively perceived as an alternative to traditional pharmacological management of myocardial infarction (MI). The majority of the studies applying stem cell therapy following MI have demonstrated a decline in fibrosis. However, it was not clearly recognized whether the decline in cardiac fibrosis was due to replacement of dead cardiomyocytes or because of the direct effects of paracrine factors released from the transplanted stem cells on the ECM. Therefore, the main focus of this review is to discuss the impact of different types of stem cells on cardiac fibrosis and associated cardiac remodelling in a variety of experimental models of heart failure, particularly MI.

Carvedilol enhances mesenchymal stem cell therapy for myocardial infarction via inhibition of caspase-3 expression

Adult stem cells have shown great promise toward repairing infarcted heart and restoring cardiac function. Mesenchymal stem cells (MSCs), because of their inherent multipotent nature and their ability to secrete a multitude of growth factors and cytokines, have been used for cardiac repair with encouraging results. Preclinical studies showed that MSCs injected into infarcted hearts improve cardiac function and attenuate fibrosis. Although stem cell transplantation is a promising therapeutic option to repair the infarcted heart, it is faced with a number of challenges, including the survival of the transplanted cells in the ischemic region, due to excessive oxidative stress present in the ischemic region. The objective of this study was to determine the effect of Carvedilol (Carv), a nonselective β-blocker with antioxidant properties, on the survival and engraftment of MSCs in the infarcted heart. MSCs were subjected to a simulated host-tissue environment, similar to the one present in the infarcted myocardium, by culturing them in the presence of hydrogen peroxide (H(2)O(2)) to induce oxidative stress. MSCs were treated with 2.5 μM Carv for 1 h in serum-free medium, followed by treatment with H(2)O(2) for 2 h. The treated cells exhibited significant protection against H(2)O(2)-induced cell death versus untreated controls as determined by 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assays. Likewise, transplantation of MSCs after permanent left coronary artery ligation and treatment of animals after myocardial infarction (MI) with Carv (5 mg/kg b.wt.) led to significant improvement in cardiac function, decreased fibrosis, and caspase-3 expression compared with the MI or MSC-alone groups.

Mesenchymal stem cells for cardiac regeneration: translation to bedside reality

Cardiovascular disease (CVD) is the leading cause of death worldwide. According to the World Health Organization (WHO), an estimate of 17.3 million people died from CVDs in 2008 and by 2030, the number of deaths is estimated to reach almost 23.6 million. Despite the development of a variety of treatment options, heart failure management has failed to inhibit myocardial scar formation and replace the lost cardiomyocyte mass with new functional contractile cells. This shortage is complicated by the limited ability of the heart for self-regeneration. Accordingly, novel management approaches have been introduced into the field of cardiovascular research, leading to the evolution of gene- and cell-based therapies. Stem cell-based therapy (aka, cardiomyoplasty) is a rapidly growing alternative for regenerating the damaged myocardium and attenuating ischemic heart disease. However, the optimal cell type to achieve this goal has not been established yet, even after a decade of cardiovascular stem cell research. Mesenchymal stem cells (MSCs) in particular have been extensively investigated as a potential therapeutic approach for cardiac regeneration, due to their distinctive characteristics. In this paper, we focus on the therapeutic applications of MSCs and their transition from the experimental benchside to the clinical bedside.

Bone tissue engineering: current strategies and techniques--part II: Cell types

Bone repair and regeneration is a dynamic process that involves a complex interplay between the (1) ground substance; (2) cells; and (3) milieu. Each constituent is integral to the final product, but it is often helpful to consider each component individually. While bone tissue engineering has capitalized on a number of breakthrough technologies, one of the most valued advancements is the incorporation of mesenchymal stem cells (SCs) into bone tissue engineering applications. With this new idea, however, came new found problems of guiding SC differentiation. Moreover, investigators are still working to understand which SCs source produces optimal bone formation in vitro and in vivo. Bone marrow-derived mesenchymal SCs and adipose-derived SCs have been researched most extensively, but other SC sources, including dental pulp, blood, umbilical cord blood, epithelial cells reprogrammed to become induced pluripotent SCs, among others, are being investigated. In Part II of this review series, we discuss the variety of cell types (e.g., osteocytes, osteoblasts, osteoclasts, chondrocytes, mesenchymal SCs, and vasculogenic cells) important in bone tissue engineering.

Hyperbaric oxygen treatment for inflammatory bowel disease: a systematic review and analysis

Background

Traditionally, hyperbaric oxygen treatment (HBOT) has been used to treat a limited repertoire of disease, including decompression sickness and healing of problem wounds. However, some investigators have used HBOT to treat inflammatory bowel disease (IBD), including Crohn's disease and ulcerative colitis.

Methods

Comprehensive searches were conducted in 8 scientific databases through 2011 to identify publications using HBOT in IBD. Human studies and animal models were collated separately.

Results

Thirteen studies of HBOT in Crohn's disease and 6 studies in ulcerative colitis were identified. In all studies, participants had severe disease refractory to standard medical treatments, including corticosteroids, immunomodulators and anti-inflammatory medications. In patients with Crohn's disease, 31/40 (78%) had clinical improvements with HBOT, while all 39 patients with ulcerative colitis improved. One study in Crohn's disease reported a significant decrease in proinflammatory cytokines (IL-1, IL-6 and TNF-alpha) and one study in ulcerative colitis reported a decrease in IL-6 with HBOT. Adverse events were minimal. Twelve publications reported using HBOT in animal models of experimentally-induced IBD, including several studies reporting decreased markers of inflammation or immune dysregulation, including TNF-alpha (3 studies), IL-1beta (2 studies), neopterin (1 study) and myeloperoxidase activity (5 studies). HBOT also decreased oxidative stress markers including malondialdehyde (3 studies) and plasma carbonyl content (2 studies), except for one study that reported increased plasma carbonyl content. Several studies reported HBOT lowered nitric oxide (3 studies) and nitric oxide synthase (3 studies) and one study reported a decrease in prostaglandin E₂ levels. Four animal studies reported decreased edema or colonic tissue weight with HBOT, and 8 studies reported microscopic improvements on histopathological examination. Although most publications reported improvements with HBOT, some studies suffered from limitations, including possible publication and referral biases, the lack of a control group, the retrospective nature and a small number of participants.

Conclusions

HBOT lowered markers of inflammation and oxidative stress and ameliorated IBD in both human and animal studies. Most treated patients were refractory to standard medical treatments. Additional studies are warranted to investigate the effects of HBOT on biomarkers of oxidative stress and inflammation as well as clinical outcomes in individuals with IBD.