Oxygenated Scaffolds for Pancreatic Endocrine Differentiation from Induced Pluripotent Stem Cells.

A 3D microenvironment is known to endorse pancreatic islet development from human induced pluripotent stem cells (iPSCs). However, oxygen supply becomes a limiting factor in a scaffold culture. In this study, oxygen-releasing biomaterials are fabricated and an oxygenated scaffold culture platform is developed to offer a better oxygen supply during 3D iPSC pancreatic differentiation. It is found that the oxygenation does not alter the scaffold's mechanical properties. The in situ oxygenation improves oxygen tension within the scaffolds. The unique 3D differentiation system enables the generation of islet organoids with enhanced expression of islet signature genes and proteins. Additionally, it is discovered that the oxygenation at the early stage of differentiation has more profound impacts on islet development from iPSCs. More C-peptide+ /MAFA+ ß and glucagon+ /MAFB+ α cells formed in the iPSC-derived islet organoids generated under oxygenated conditions, suggesting enhanced maturation of the organoids. Furthermore, the oxygenated 3D cultures improve islet organoids' sensitivity to glucose for insulin secretion. It is herein demonstrated that the oxygenated scaffold culture empowers iPSC islet differentiation to generate clinically relevant tissues for diabetes research and treatment.

Co-Delivery of Bioengineered Exosomes and Oxygen for Treating Critical Limb Ischemia in Diabetic Mice.

Diabetic patients with critical limb ischemia face a high rate of limb amputation. Regeneration of the vasculature and skeletal muscles can salvage diseased limbs. Therapy using stem cell-derived exosomes that contain multiple proangiogenic and promyogenic factors represents a promising strategy. Yet the therapeutic efficacy is not optimal because exosomes alone cannot efficiently rescue and recruit endothelial and skeletal muscle cells and restore their functions under hyperglycemic and ischemic conditions. To address these limitations, we fabricated ischemic-limb-targeting stem cell-derived exosomes and oxygen-releasing nanoparticles and codelivered them in order to recruit endothelial and skeletal muscle cells, improve cell survival under ischemia before vasculature is established, and restore cell morphogenic function under high glucose and ischemic conditions. The exosomes and oxygen-releasing nanoparticles, delivered by intravenous injection, specifically accumulated in the ischemic limbs. Following 4 weeks of delivery, the exosomes and released oxygen synergistically stimulated angiogenesis and muscle regeneration without inducing substantial inflammation and reactive oxygen species overproduction. Our work demonstrates that codelivery of exosomes and oxygen is a promising treatment solution for saving diabetic ischemic limbs.

DNA methylation-mediated Rbpjk suppression protects against fracture nonunion caused by systemic inflammation.

Challenging skeletal repairs are frequently seen in patients experiencing systemic inflammation. To tackle the complexity and heterogeneity of the skeletal repair process, we performed single-cell RNA sequencing and revealed that progenitor cells were one of the major lineages responsive to elevated inflammation and this response adversely affected progenitor differentiation by upregulation of Rbpjk in fracture nonunion. We then validated the interplay between inflammation (via constitutive activation of Ikk2, Ikk2ca) and Rbpjk specifically in progenitors by using genetic animal models. Focusing on epigenetic regulation, we identified Rbpjk as a direct target of Dnmt3b. Mechanistically, inflammation decreased Dnmt3b expression in progenitor cells, consequently leading to Rbpjk upregulation via hypomethylation within its promoter region. We also showed that Dnmt3b loss-of-function mice phenotypically recapitulated the fracture repair defects observed in Ikk2ca-transgenic mice, whereas Dnmt3b-transgenic mice alleviated fracture repair defects induced by Ikk2ca. Moreover, Rbpjk ablation restored fracture repair in both Ikk2ca mice and Dnmt3b loss-of-function mice. Altogether, this work elucidates a common mechanism involving a NF-κB/Dnmt3b/Rbpjk axis within the context of inflamed bone regeneration. Building on this mechanistic insight, we applied local treatment with epigenetically modified progenitor cells in a previously established mouse model of inflammation-mediated fracture nonunion and showed a functional restoration of bone regeneration under inflammatory conditions through an increase in progenitor differentiation potential.

Thermosensitive and antioxidant wound dressings capable of adaptively regulating TGFß pathways promote diabetic wound healing.

Various therapies have been utilized for treating diabetic wounds, yet current regiments do not simultaneously address the key intrinsic causes of slow wound healing, i.e., abnormal skin cell functions (particularly migration), delayed angiogenesis, and chronic inflammation. To address this clinical gap, we develop a wound dressing that contains a peptide-based TGFß receptor II inhibitor (PTßR2I), and a thermosensitive and reactive oxygen species (ROS)-scavenging hydrogel. The wound dressing can quickly solidify on the diabetic wounds following administration. The released PTßR2I inhibits the TGFß1/p38 pathway, leading to improved cell migration and angiogenesis, and decreased inflammation. Meanwhile, the PTßR2I does not interfere with the TGFß1/Smad2/3 pathway that is required to regulate myofibroblasts, a critical cell type for wound healing. The hydrogel's ability to scavenge ROS in diabetic wounds further decreases inflammation. Single-dose application of the wound dressing significantly accelerates wound healing with complete wound closure after 14 days. Overall, using wound dressings capable of adaptively modulating TGFß pathways provides a new strategy for diabetic wound treatment.

Increased 10-year cardiovascular disease risk in depressed patients with coexisting subclinical hypothyroidism.

Purpose: The prevalence of depressive disorder (DD) and subclinical hypothyroidism (SH) was almost twofold higher in women compared with men, both of which are confirmed to be related to cardiovascular disease (CVD) risk. The current study aimed to identify the prevalence of CVD risk factors and evaluate the 10-year CVD risk in female depressed patients with and without comorbid SH. Methods: We recruited 1744 female inpatients with a diagnosis of DD. Venous blood samples were taken from all patients for lipid and thyroid hormones. Framingham Risk Score (FRS) was used to estimate the 10-year CVD risk. Results: Female depressed patients with SH had increased BMI, higher Hamilton Anxiety Scale (HAMA) scores, higher LDL-C, TC, UA, and a higher 10-year CVD risk than euthyroid DD groups. Serum TSH levels and HAMA scores were critical predictive variables for 10-year CVD risk in female depressed patients with comorbid SH. Conclusion: Our study suggests that female depressed patients with SH have a high 10-year CVD risk. Serum TSH levels and HAMA scores may be helpful to predict cardiovascular risk in female patients with SH. The increased CVD risk in female depressed patients with comorbid SH requires more attention from researchers and clinicians.

Rescuing Cardiac Cells and Improving Cardiac Function by Targeted Delivery of Oxygen-Releasing Nanoparticles after or Even before Acute Myocardial Infarction.

Myocardial infarction (MI) causes massive cell death due to restricted blood flow and oxygen deficiency. Rapid and sustained oxygen delivery following MI rescues cardiac cells and restores cardiac function. However, current oxygen-generating materials cannot be administered during acute MI stage without direct injection or suturing methods, both of which risk rupturing weakened heart tissue. Here, we present infarcted heart-targeting, oxygen-releasing nanoparticles capable of being delivered by intravenous injection at acute MI stage, and specifically accumulating in the infarcted heart. The nanoparticles can also be delivered before MI, then gather at the injured area after MI. We demonstrate that the nanoparticles, delivered either pre-MI or post-MI, enhance cardiac cell survival, stimulate angiogenesis, and suppress fibrosis without inducing substantial inflammation and reactive oxygen species overproduction. Our findings demonstrate that oxygen-delivering nanoparticles can provide a nonpharmacological solution to rescue the infarcted heart during acute MI and preserve heart function.

Sustained delivery of rhMG53 promotes diabetic wound healing and hair follicle development.

MG53 is an essential component of the cell membrane repair machinery, participating in the healing of dermal wounds. Here we develop a novel delivery system using recombinant human MG53 (rhMG53) protein and a reactive oxygen species (ROS)-scavenging gel to treat diabetic wounds. Mice with ablation of MG53 display defective hair follicle structure, and topical application of rhMG53 can promote hair growth in the mg53 -/- mice. Cell lineage tracing studies reveal a physiological function of MG53 in modulating the proliferation of hair follicle stem cells (HFSCs). We find that rhMG53 protects HFSCs from oxidative stress-induced apoptosis and stimulates differentiation of HSFCs into keratinocytes. The cytoprotective function of MG53 is mediated by STATs and MAPK signaling in HFSCs. The thermosensitive ROS-scavenging gel encapsulated with rhMG53 allows for sustained release of rhMG53 and promotes healing of chronic cutaneous wounds and hair follicle development in the db/db mice. These findings support the potential therapeutic value of using rhMG53 in combination with ROS-scavenging gel to treat diabetic wounds.

Delivery of VEGF and delta-like 4 to synergistically regenerate capillaries and arterioles in ischemic limbs.

Vascularization of the poorly vascularized limbs affected by critical limb ischemia (CLI) is necessary to salvage the limbs and avoid amputation. Effective vascularization requires forming not only capillaries, but also arterioles and vessel branching. These processes rely on the survival, migration and morphogenesis of endothelial cells in the ischemic limbs. Yet endothelial cell functions are impaired by the upregulated TGFß. Herein, we developed an injectable hydrogel-based drug release system capable of delivering both VEGF and Dll4 to synergistically restore endothelial cellular functions, leading to accelerated formation of capillaries, arterioles and vessel branching. In vitro, the Dll4 and VEGF synergistically promoted the human arterial endothelial cell (HAEC) survival, migration, and formation of filopodial structure, lumens, and branches under the elevated TGFß1 condition mimicking that of the ischemic limbs. The synergistic effect was resulted from activating VEGFR2, Notch-1 and Erk1/2 signaling pathways. After delivering the Dll4 and VEGF via an injectable and thermosensitive hydrogel to the ischemic mouse hindlimbs, 95% of blood perfusion was restored at day 14, significantly higher than delivery of Dll4 or VEGF only. The released Dll4 and VEGF significantly increased density of capillaries and arterioles, vessel branching point density, and proliferating cell density. Besides, the delivery of Dll4 and VEGF stimulated skeletal muscle regeneration and improved muscle function. Overall, the developed hydrogel-based Dll4 and VEGF delivery system promoted ischemic limb vascularization and muscle regeneration. STATEMENT OF SIGNIFICANCE: Effective vascularization of the poorly vascularized limbs affected by critical limb ischemia (CLI) requires forming not only capillaries, but also arterioles and vessel branching. These processes rely on the survival, migration and morphogenesis of endothelial cells. Yet endothelial cell functions are impaired by the upregulated TGFß in the ischemic limbs. Herein, we developed an injectable hydrogel-based drug release system capable of delivering both VEGF and Dll4 to synergistically restore endothelial cell functions, leading to accelerated formation of capillaries, arterioles and vessel branching.

Effect of R Angle of the Outer Extension Tube against the in-Core Flux Thimble in Nuclear Power Plant on Its Wear Behavior.

Wear failure of the in-core flux thimble is an important problem in the neutron flux measurement system, which threatens the safety of the nuclear power plant. To figure out the wear mechanism of the thimble, a wear tester was designed and manufactured to simulate the wear process of the in-core flux thimble. Outer guide tubes with different R angles were used to abrade the thimbles. The designed tester can well simulate the wear process in the real power plant. R angle of the outer guide tube played important role in the wear behavior of the in-core flux thimbles.

Sustained oxygenation accelerates diabetic wound healing by promoting epithelialization and angiogenesis and decreasing inflammation.

Nonhealing diabetic wounds are common complications for diabetic patients. Because chronic hypoxia prominently delays wound healing, sustained oxygenation to alleviate hypoxia is hypothesized to promote diabetic wound healing. However, sustained oxygenation cannot be achieved by current clinical approaches, including hyperbaric oxygen therapy. Here, we present a sustained oxygenation system consisting of oxygen-release microspheres and a reactive oxygen species (ROS)-scavenging hydrogel. The hydrogel captures the naturally elevated ROS in diabetic wounds, which may be further elevated by the oxygen released from the administered microspheres. The sustained release of oxygen augmented the survival and migration of keratinocytes and dermal fibroblasts, promoted angiogenic growth factor expression and angiogenesis in diabetic wounds, and decreased the proinflammatory cytokine expression. These effects significantly increased the wound closure rate. Our findings demonstrate that sustained oxygenation alone, without using drugs, can heal diabetic wounds.

VR/AR Technology in Human Anatomy Teaching and Operation Training.

AR/VR technology can fuse the clinical imaging data and information to build an anatomical environment combining virtual and real, which is helpful to improve the interest of teaching and the learning initiative of medical students, and then improve the effect of clinical teaching. This paper studies the application and learning effect of the VR/AR system in human anatomy surgery teaching. This paper first shows the learning environment and platform of the VR/AR system, then explains the interface and operation of the system, and evaluates the teaching situation. This paper takes the VR/AR operation simulation system of an Irish company as an example and evaluates the learning effect of 41 students in our hospital. Research shows that the introduction of the feature reweighting module in the VR/AR surgery simulation system improves the accuracy of bone structure segmentation (IOU value increases from 79.62% to 83.56%). For real human ultrasound image data, the IOU value increases from 80.21% to 82.23% after the feature reweighting module is introduced. Therefore, the dense convolution module and feature reweighting module improve the learning ability of the network for bone structure features in ultrasound images from two aspects of feature connection and importance understanding and effectively improve the performance of bone structure segmentation.

Targeting angiogenesis for fracture nonunion treatment in inflammatory disease.

Atrophic fracture nonunion poses a significant clinical problem with limited therapeutic interventions. In this study, we developed a unique nonunion model with high clinical relevance using serum transfer-induced rheumatoid arthritis (RA). Arthritic mice displayed fracture nonunion with the absence of fracture callus, diminished angiogenesis and fibrotic scar tissue formation leading to the failure of biomechanical properties, representing the major manifestations of atrophic nonunion in the clinic. Mechanistically, we demonstrated that the angiogenesis defect observed in RA mice was due to the downregulation of SPP1 and CXCL12 in chondrocytes, as evidenced by the restoration of angiogenesis upon SPP1 and CXCL12 treatment in vitro. In this regard, we developed a biodegradable scaffold loaded with SPP1 and CXCL12, which displayed a beneficial effect on angiogenesis and fracture repair in mice despite the presence of inflammation. Hence, these findings strongly suggest that the sustained release of SPP1 and CXCL12 represents an effective therapeutic approach to treat impaired angiogenesis and fracture nonunion under inflammatory conditions.

Targeted Delivery of a Matrix Metalloproteinases-2 Specific Inhibitor Using Multifunctional Nanogels to Attenuate Ischemic Skeletal Muscle Degeneration and Promote Revascularization.

Critical limb ischemia (CLI) is a severe form of peripheral artery disease (PAD). It is featured by degenerated skeletal muscle and poor vascularization. During the development of CLI, the upregulated matrix metalloproteinase-2 (MMP-2) degrades muscle extracellular matrix to initiate the degeneration. Meanwhile, MMP-2 is necessary for blood vessel formation. It is thus hypothesized that appropriate MMP-2 bioactivity in ischemic limbs will not only attenuate muscle degeneration but also promote blood vessel formation. Herein, we developed ischemia-targeting poly(N-isopropylacrylamide)-based nanogels to specifically deliver an MMP-2 inhibitor CTTHWGFTLC (CTT) into ischemic limbs to tailor MMP-2 bioactivity. Besides acting as an MMP-2 inhibitor, CTT promoted endothelial cell migration under conditions mimicking the ischemic limbs. The nanogels were sensitive to the pH of ischemic tissues, allowing them to largely aggregate in the injured area. To help reduce nanogel uptake by macrophages and increase circulation time, the nanogels were cloaked with a platelet membrane. An ischemia-targeting peptide CSTSMLKA (CST) was further conjugated on the platelet membrane for targeted delivery of nanogels into the ischemic area. CTT gradually released from the nanogels for 4 weeks. The nanogels mostly accumulated in the ischemic area for 28 days. The released CTT preserved collagen in the muscle and promoted its regeneration. In addition, CTT stimulated angiogenesis. Four weeks after CLI, the blood flow and vessel density of the ischemic limbs treated with the nanogels were remarkably higher than the control groups without CTT release. These results demonstrate that the developed nanogel-based CTT release system has the potential to stimulate ischemic limb regeneration.

Oxygen-release microspheres capable of releasing oxygen in response to environmental oxygen level to improve stem cell survival and tissue regeneration in ischemic hindlimbs.

Stem cell transplantation has been extensively explored to promote ischemic limb vascularization and skeletal muscle regeneration. Yet the therapeutic efficacy is low due to limited cell survival under low oxygen environment of the ischemic limbs. Therefore, continuously oxygenating the transplanted cells has potential to increase their survival. During tissue regeneration, the number of blood vessels are gradually increased, leading to the elevation of tissue oxygen content. Accordingly, less exogenous oxygen is needed for the transplanted cells. Excessive oxygen may induce reactive oxygen species (ROS) formation, causing cell apoptosis. Thus, it is attractive to develop oxygen-release biomaterials that are responsive to the environmental oxygen level. Herein, we developed oxygen-release microspheres whose oxygen release was controlled by oxygen-responsive shell. The shell hydrophilicity and degradation rate decreased as the environmental oxygen level increased, leading to slower oxygen release. The microspheres were capable of directly releasing molecular oxygen, which are safer than those oxygen-release biomaterials that release hydrogen peroxide and rely on its decomposition to form oxygen. The released oxygen significantly enhanced mesenchymal stem cell (MSC) survival without inducing ROS production under hypoxic condition. Co-delivery of MSCs and microspheres to the mouse ischemic limbs ameliorated MSC survival, proliferation and paracrine effects under ischemic conditions. It also significantly accelerated angiogenesis, blood flow restoration, and skeletal muscle regeneration without provoking tissue inflammation. The above results demonstrate that the developed microspheres have potential to augment cell survival in ischemic tissues, and promote ischemic tissue regeneration in a safer and more efficient manner.

Abnormal connectivity of anterior-insular subdivisions and relationship with somatic symptom in depressive patients.

Depressive patients frequently present with somatic complaints such as pain and fatigue. The anterior insula (AI) is a crucial region for somatic processing, but reported contributions of AI dysfunction to somatic symptoms have varied across studies. We speculated that functional heterogeneity among AI subdivisions may contribute to this inconsistency. To reveal the correlation between each subdivision and somatic symptoms, we investigated resting-state functional connectivity (RSFC) based on seeds within distinct AI subdivisions in 45 depressive patients and 35 matched healthy controls (HCs). Depressive and somatic symptoms were assessed using the Hamilton Depression Rating Scale (HDRS) and the 15-item somatic symptom severity scale of the Patient Health Questionnaire (PHQ-15), respectively. The contributions of AI subregion-specific pathways to depression were further validated by examining changes in symptom severity and RSFC following electroconvulsive therapy (ECT). At baseline, depressive patients exhibited weaker RSFC between ventral AI (vAI) and right orbitofrontal cortex (rOFC) than HCs. Moreover, vAI-rOFC RSFC strength was negatively correlated with PHQ-15 and HDRS scores, indicating that weaker RSFC predicted greater symptom severity. ECT reduced depressive and somatic symptoms, and symptom mitigation was correlated with enhanced vAI-rOFC RSFC. The findings suggest that reduced vAI-rOFC RSFC underlies the somatic symptoms of depression and that enhancing vAI-rOFC RSFC can contribute to amelioration of somatic symptoms.

LncRNA BACE1-AS Promotes Autophagy-Mediated Neuronal Damage Through The miR-214-3p/ATG5 Signalling Axis In Alzheimer's Disease.

Alzheimer's disease (AD) is the most common neurodegenerative disease and is characterized by progressive memory loss and cognitive dysfunction. Long non-coding RNAs (lncRNAs) have been shown to be among the most promising biomarkers and therapeutic targets of AD. Here, we aimed to investigate whether lncRNA BACE1-AS plays a role in the potential mechanisms of AD. The expression of BACE1-AS, miR-214-3p and ATG5 mRNA was detected using qRT-PCR. The expression of the LC3, P62, ATG5, Bcl-2, p-Tau and cleaved-caspase 3 proteins was examined using western blot analysis. Cell apoptosis, cytotoxicity and ROS levels were estimated using flow cytometry, an LDH kit and a DCFH-DA assay, respectively. The interaction between BACE1-AS or ATG5 and miR-214-3p was validated using a dual-luciferase reporter assay. HE staining and a TUNEL assay were employed to evaluate hippocampal neuronal injury. The BACE1-AS level was found to be upregulated in serum samples of AD patients, brain tissues of AD transgenic (Tg) mice and Aß1-42-treated SH-SY5Y cells. Autophagy activity was increased in both Tg mice and Aß1-42-treated cells. BACE1-AS knockdown alleviated Aß1-42-induced cell injury. Rapamycin abolished the protective effects of sh BACE1-AS against Aß1-42 induced cell injury. BACE1-AS indirectly regulated ATG5 expression by binding miR-214-3p. The miR-214-3p inhibitor reversed the protective effects of sh BACE1-AS and sh ATG5 against Aß1-42-induced cell injury. Knockdown of BACE1-AS alleviated neuronal injury by repressing autophagy in vivo. Our findings demonstrate that silencing of BACE1-AS alleviated neuronal injury by regulating autophagy through the miR-214-3p/ATG5 signalling axis in AD.

Photoluminescent oxygen-release microspheres to image the oxygen release process in vivo.

Cell therapy is a promising strategy to treat ischemic diseases, but the efficacy is limited due to high rate of cell death under low oxygen environment of the ischemic tissues. Sustained release of oxygen to continuously oxygenate the transplanted cells may augment cell survival and improve therapeutic efficacy. We have shown previously that oxygen released from oxygen-release microspheres stimulated cell survival in ischemic tissue [1]. To understand how oxygen is released in vivo and duration of release, it is attractive to image the process of oxygen release. Herein, we have developed photoluminenscent oxygen-release microspheres where the in vivo oxygen release can be non-invasively and real-time monitored by an In Vivo Imaging System (IVIS). In the oxygen-release microspheres, a complex of polyvinylpyrrolidone, H2O2 and a fluorescent drug hypericin (HYP) was used as core, and poly(N-isopropylacrylamide-co-acrylate-oligolactide-co-hydroxyethyl methacrylate-co-N-acryloxysuccinimide) conjugated with catalase was used as shell. To distinguish fluorescent signal change for different oxygen release kinetics, the microspheres with various release profiles were developed by using the shell with different degradation rates. In vitro, the fluorescent intensity gradually decreased during the 21-day oxygen release period, consistent with oxygen release kinetics. The released oxygen significantly augmented mesenchymal stem cell (MSC) survival under hypoxic condition. In vivo, the oxygen release rate was faster. The fluorescent signal can be detected for 17 days for the microspheres with the slowest oxygen release kinetics. The implanted microspheres did not induce substantial inflammation. The above results demonstrate that the developed microspheres have potential to monitor the in vivo oxygen release.

Selective colorimetric and fluorescence detection of nitroreductase enzymes in living cells.

Rhodamine dyes bearing aromatic nitro group has been synthesized for nitroreductase enzyme chemosensing applications. The probe is showing very selective turn-on fluorescent response towards nitroreductase enzymes and in hypoxic conditions. The sensor displays a remarkable fluorescent enhancement at 557 nm (λex = 500 nm) without the interference of other biologically relevant species under hypoxic conditions in a physiological medium. The nitro group in the sensor is reduced by the nitroreductase enzyme to the amino group, resulting in the hydrolysis of the probe and subsequent release of highly fluorescent rhodamine 6G dye is observed. This rhodamine based fluorescent probe has been utilized for the imaging of nitroreductase enzymes as well as hypoxia in live cells.

Dnmt3b ablation impairs fracture repair through upregulation of Notch pathway.

We previously established that DNA methyltransferase 3b (Dnmt3b) is the sole Dnmt responsive to fracture repair and that Dnmt3b expression is induced in progenitor cells during fracture repair. In the current study, we confirmed that Dnmt3b ablation in mesenchymal progenitor cells (MPCs) resulted in impaired endochondral ossification, delayed fracture repair, and reduced mechanical strength of the newly formed bone in Prx1-Cre;Dnmt3bf/f (Dnmt3bPrx1) mice. Mechanistically, deletion of Dnmt3b in MPCs led to reduced chondrogenic and osteogenic differentiation in vitro. We further identified Rbpjκ as a downstream target of Dnmt3b in MPCs. In fact, we located 2 Dnmt3b binding sites in the murine proximal Rbpjκ promoter and gene body and confirmed Dnmt3b interaction with the 2 binding sites by ChIP assays. Luciferase assays showed functional utilization of the Dnmt3b binding sites in murine C3H10T1/2 cells. Importantly, we showed that the MPC differentiation defect observed in Dnmt3b deficiency cells was due to the upregulation of Rbpjκ, evident by restored MPC differentiation upon Rbpjκ inhibition. Consistent with in vitro findings, Rbpjκ blockage via dual antiplatelet therapy reversed the differentiation defect and accelerated fracture repair in Dnmt3bPrx1 mice. Collectively, our data suggest that Dnmt3b suppresses Notch signaling during MPC differentiation and is necessary for normal fracture repair.

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.