An infusible biologically active adhesive for chemotherapy-related heart failure in elderly rats.

Chemotherapy-induced cardiotoxicity with subsequent heart failure (HF) is a major cause of morbidity and mortality in cancer survivors worldwide. Chemotherapy-induced HF is exceptionally challenging as it generally manifests in patients who are typically not eligible for left ventricular device implantation or heart transplantation. To explore alternative treatment strategies for cancer survivors suffering from chemotherapy-induced HF, we developed a minimally invasive infusible cardiac stromal cell secretomes adhesive (MISA) that could be delivered locally through an endoscope-guided intrapericardial injection. To mimic the typical clinical presentation of chemotherapy-induced HF in elder patients, we established an aged rat model in which restrictive cardiomyopathy with sequential HF was induced via consecutive doxorubicin injections. In vitro, we prove that MISA not only enhanced cardiomyocytes proliferation potency and viability, but also inhibited their apoptosis. In vivo, we prove that MISA improved the ventricular contractility indexes and led to beneficial effects on histological and structural features of restrictive cardiomyopathy via promoting cardiomyocyte proliferation, angiogenesis, and mitochondrial respiration. Additionally, we also evaluated the safety and feasibility of MISA intrapericardial delivery in a healthy porcine model with an intact immune system. In general, our data indicates that MISA has a strong potential for translation into large animal models and ultimately clinical applications for chemotherapy-induced HF prior to the final option of heart transplantation.

Optimizing cell therapy by sorting cells with high extracellular vesicle secretion.

Critical challenges remain in clinical translation of extracellular vesicle (EV)-based therapeutics due to the absence of methods to enrich cells with high EV secretion. Current cell sorting methods are limited to surface markers that are uncorrelated to EV secretion or therapeutic potential. Here, we utilize a nanovial technology for enrichment of millions of single cells based on EV secretion. This approach is applied to select mesenchymal stem cells (MSCs) with high EV secretion as therapeutic cells for improving treatment. The selected MSCs exhibit distinct transcriptional profiles associated with EV biogenesis and vascular regeneration and maintain high levels of EV secretion after sorting and regrowth. In a mouse model of myocardial infarction, treatment with high-secreting MSCs improves heart functions compared to treatment with low-secreting MSCs. These findings highlight the therapeutic importance of EV secretion in regenerative cell therapies and suggest that selecting cells based on EV secretion could enhance therapeutic efficacy.

Intrapericardial Exosome Therapy Dampens Cardiac Injury via Activating Foxo3.

BACKGROUND: Mesenchymal stem cell (MSC)-derived exosomes are well recognized immunomodulating agents for cardiac repair, while the detailed mechanisms remain elusive. The Pericardial drainage pathway provides the heart with immunosurveillance and establishes a simplified model for studying the mechanisms underlying the immunomodulating effects of therapeutic exosomes. METHODS: Myocardial infarction (MI) models with and without pericardiectomy (corresponding to Tomy MI and NonTomy MI) were established to study the functions of pericardial drainage pathway in immune activation of cardiac-draining mediastinal lymph node (MLN). Using the NonTomy MI model, MSC exosomes or vehicle PBS was intrapericardially injected for MI treatment. Via cell sorting and RNA-seq (RNA-sequencing) analysis, the differentially expressed genes were acquired for integrated pathway analysis to identify responsible mechanisms. Further, through functional knockdown/inhibition studies, application of cytokines and neutralizing antibodies, western blot, flow cytometry, and cytokine array, the molecular mechanisms were studied. In addition, the therapeutic efficacy of intrapericardially injected exosomes for MI treatment was evaluated through functional and histological analyses. RESULTS: We show that the pericardial draining pathway promoted immune activation in the MLN following MI. Intrapericardially injected exosomes accumulated in the MLN and induced regulatory T cell differentiation to promote cardiac repair. Mechanistically, uptake of exosomes by major histocompatibility complex (MHC)-II+ antigen-presenting cells (APCs) induced Foxo3 activation via the protein phosphatase (PP)-2A/p-Akt/forkhead box O3 (Foxo3) pathway. Foxo3 dominated APC cytokines (IL-10, IL-33, and IL-34) expression and built up a regulatory T cell (Treg)-inducing niche in the MLN. The differentiation of Tregs as well as their cardiac deployment were elevated, which contributed to cardiac inflammation resolution and cardiac repair. CONCLUSIONS: This study reveals a novel mechanism underlying the immunomodulation effects of MSC exosomes and provides a promising candidate (PP2A/p-Akt/Foxo3 signaling pathway) with a favorable delivery route (intrapericardial injection) for cardiac repair.

Decoy Exosomes Offer Protection Against Chemotherapy-Induced Toxicity.

Cancer patients often face severe organ toxicity caused by chemotherapy. Among these, chemotherapy-induced hepatotoxicity and cardiotoxicity are the main causes of death of cancer patients. Chemotherapy-induced cardiotoxicity even creates a new discipline termed "cardio-oncology". Therefore, relieving toxicities induced by chemotherapy has become a key issue for improving the survival and quality of life in cancer patients. In this work, mesenchymal stem cell exosomes with the "G-C" abundant tetrahedral DNA nanostructure (TDN) are modified to form a decoy exosome (Exo-TDN). Exo-TDN reduces DOX-induced hepatotoxicity as the "G-C" base pairs scavenge DOX. Furthermore, Exo-TDN with cardiomyopathic peptide (Exo-TDN-PCM) is engineered for specific targeting to cardiomyocytes. Injection of Exo-TDN-PCM significantly reduces DOX-induced cardiotoxicity. Interestingly, Exo-TDN-PCM can also promote macrophage polarization into the M2 type for tissue repair. In addition, those decoy exosomes do not affect the anticancer effects of DOX. This decoy exosome strategy serves as a promising therapy to reduce chemo-induced toxicity.

Detachable Microneedle Patches Deliver Mesenchymal Stromal Cell Factor-Loaded Nanoparticles for Cardiac Repair.

Intramyocardial injection is a direct and efficient approach to deliver therapeutics to the heart. However, the injected volume must be very limited, and there is injury to the injection site and leakage issues during heart beating. Herein, we developed a detachable therapeutic microneedle (MN) patch, which is comprised of mesenchymal stromal cell-secreted factors (MSCF)-loaded poly(lactic-co-glycolic acid) nanoparticles (NP) in MN tips made of elastin-like polypeptide gel, with a resolvable non-cross-linked hyaluronic acid (HA) gel as the MN base. The tips can be firmly inserted into the infarcted myocardium after base removal, and no suture is needed. In isolated neonatal rat cardiac cells, we found that the cellular uptake of MSCF-NP in the cardiomyocytes was higher than in cardiac fibroblasts. MSCF-NP promoted the proliferation of injured cardiomyocytes. In a rat model of myocardial infarction, MN-MSCF-NP treatment reduced cardiomyocyte apoptosis, restored myocardium volume, and reduced fibrosis during the cardiac remodeling process. Our work demonstrated the therapeutic potential of MN to deliver MSCF directly into the myocardium and provides a promising treatment approach for cardiac diseases.

Nanoparticles functionalized with stem cell secretome and CXCR4-overexpressing endothelial membrane for targeted osteoporosis therapy.

BACKGROUND: Osteoporosis is a chronic condition affecting patients' morbidity and mortality and represents a big socioeconomic burden. Because stem cells can proliferate and differentiate into bone-forming cells, stem cell therapy for osteoporosis has been widely studied. However, cells as a live drug face multiple challenges because of their instability during preservation and transportation. In addition, cell therapy has potential adverse effects such as embolism, tumorigenicity, and immunogenicity. RESULTS: Herein, we sought to use cell-mimicking and targeted therapeutic nanoparticles to replace stem cells. We fabricated nanoparticles (NPs) using polylactic-co-glycolic acid (PLGA) loaded with the secretome (Sec) from mesenchymal stem cells (MSCs) to form MSC-Sec NPs. Furthermore, we cloaked the nanoparticles with the membranes from C-X-C chemokine receptor type 4 (CXCR4)-expressing human microvascular endothelial cells (HMECs) to generate MSC-Sec/CXCR4 NP. CXCR4 can target the nanoparticles to the bone microenvironment under osteoporosis based on the CXCR4/SDF-1 axis. CONCLUSIONS: In a rat model of osteoporosis, MSC-Sec/CXCR4 NP were found to accumulate in bone, and such treatment inhibited osteoclast differentiation while promoting osteogenic proliferation. In addition, our results showed that MSC-Sec/CXCR4 NPs reduce OVX-induced bone mass attenuation in OVX rats.

A fluid-powered refillable origami heart pouch for minimally invasive delivery of cell therapies in rats and pigs.

BACKGROUND: Cardiac repair after heart injury remains a big challenge and current drug delivery to the heart is suboptimal. Repeated dosing of therapeutics is difficult due to the invasive nature of such procedures. METHODS: We developed a fluid-driven heart pouch with a memory-shaped microfabricated lattice structure inspired by origami. The origami structure allowed minimally invasive delivery of the pouch to the heart with two small incisions and can be refilled multiple times with the therapeutic of choice. FINDINGS: We tested the pouch's ability to deliver mesenchymal stem cells (MSCs) in a rodent model of acute myocardial infarction and demonstrated the feasibility of minimally invasive delivery in a swine model. The pouch's semi-permeable membrane successfully protected delivered cells from their surroundings, maintaining their viability while releasing paracrine factors to the infarcted site for cardiac repair. CONCLUSIONS: In summary, we developed a fluid-driven heart pouch with a memory-shaped microfabricated lattice structure inspired by origami. The origami structure allowed minimally invasive delivery of the pouch to the heart with two small incisions and can be refilled with the therapeutic of choice.

Extruded Mesenchymal Stem Cell Nanovesicles Are Equally Potent to Natural Extracellular Vesicles in Cardiac Repair.

Mesenchymal stem cells (MSCs) repair injured tissues mainly through their paracrine actions. One of the important paracrine components of MSC secretomes is the extracellular vesicle (EV). The therapeutic potential of MSC-EVs has been established in various cardiac injury preclinical models. However, the large-scale production of EVs remains a challenge. We sought to develop a scale-up friendly method to generate a large number of therapeutic nanovesicles from MSCs by extrusion. Those extruded nanovesicles (NVs) are miniature versions of MSCs in terms of surface marker expression. The yield of NVs is 20-fold more than that of EVs. In vitro, cell-based assays demonstrated the myocardial protective effects and therapeutic potential of NVs. Intramyocardial delivery of NVs in the injured heart after ischemia-reperfusion led to a reduction in scar sizes and preservation of cardiac functions. Such therapeutic benefits are similar to those injected with natural EVs from the same MSC parental cells. In addition, NV therapy promoted angiogenesis and proliferation of cardiomyocytes in the post-injury heart. In summary, extrusion is a highly efficient method to generate a large quantity of therapeutic NVs that can potentially replace extracellular vesicles in regenerative medicine applications.

A stem cell-derived ovarian regenerative patch restores ovarian function and rescues fertility in rats with primary ovarian insufficiency.

Rationale: Primary ovarian insufficiency (POI) normally occurs before age 40 and is associated with infertility. Hormone replacement therapy is often prescribed to treat vasomotor symptom, but it cannot restore ovarian function or fertility. Stem cell therapy has been studied for the treatment of POI. However, the application of live stem cells has suffered from drawbacks, such as low cell retention/engraftment rate, risks for tumorigenicity and immunogenicity, and lack of off-the-shelf feasibility. Methods: We developed a therapeutic ovarian regenerative patch (ORP) that composed of clinically relevant hydrolysable scaffolds and synthetic mesenchymal stem cells (synMSCs), which are microparticles encapsulating the secretome from MSCs. The therapeutic potency of ORP was tested in rats with cisplatin induced POI injury. Results:In vitro studies revealed that ORP stimulated proliferation of ovarian somatic cells (OSCs) and inhibited apoptosis under injury stress. In a rat model of POI, implantation of ORP rescued fertility by restoring sexual hormone secretion, estrus cycle duration, and follicle development. Conclusion: ORP represents a cell-free, off-the-shelf, and clinically feasible treatment for POI.

A Minimally Invasive Exosome Spray Repairs Heart after Myocardial Infarction.

Myocardial infarction (MI) remains the most common cause of death worldwide. Many MI survivors will suffer from recurrent heart failure (HF), which has been recognized as a determinant of adverse prognosis. Despite the success of improved early survival after MI by primary percutaneous coronary intervention, HF after MI is becoming the major driver of late morbidity, mortality, and healthcare costs. The development of regenerative medicine has brought hope to MI treatment in the past decade. Mesenchymal stem cell (MSC)-derived exosomes have been established as an essential part of stem cell paracrine factors for heart regeneration. However, its regenerative power is hampered by low delivery efficiency to the heart. We designed, fabricated, and tested a minimally invasive exosome spray (EXOS) based on MSC exosomes and biomaterials. In a mouse model of acute myocardial infarction, EXOS improved cardiac function and reduced fibrosis, and promoted endogenous angiomyogenesis in the post-injury heart. We further tested the feasibility and safety of EXOS in a pig model. Our results indicate that EXOS is a promising strategy to deliver therapeutic exosomes for heart repair.

Cell-mimicking nanodecoys neutralize SARS-CoV-2 and mitigate lung injury in a non-human primate model of COVID-19.

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has grown into a global pandemic, and only a few antiviral treatments have been approved to date. Angiotensin-converting enzyme 2 (ACE2) plays a fundamental role in SARS-CoV-2 pathogenesis because it allows viral entry into host cells. Here we show that ACE2 nanodecoys derived from human lung spheroid cells (LSCs) can bind and neutralize SARS-CoV-2 and protect the host lung cells from infection. In mice, these LSC-nanodecoys were delivered via inhalation therapy and resided in the lungs for over 72 h post-delivery. Furthermore, inhalation of the LSC-nanodecoys accelerated clearance of SARS-CoV-2 mimics from the lungs, with no observed toxicity. In cynomolgus macaques challenged with live SARS-CoV-2, four doses of these nanodecoys delivered by inhalation promoted viral clearance and reduced lung injury. Our results suggest that LSC-nanodecoys can serve as a potential therapeutic agent for treating COVID-19.

Cardiac Cell Therapy for Heart Repair: Should the Cells Be Left Out?

Cardiovascular disease (CVD) is still the leading cause of death worldwide. Coronary artery occlusion, or myocardial infarction (MI) causes massive loss of cardiomyocytes. The ischemia area is eventually replaced by a fibrotic scar. From the mechanical dysfunctions of the scar in electronic transduction, contraction and compliance, pathological cardiac dilation and heart failure develops. Once end-stage heart failure occurs, the only option is to perform heart transplantation. The sequential changes are termed cardiac remodeling, and are due to the lack of endogenous regenerative actions in the adult human heart. Regenerative medicine and biomedical engineering strategies have been pursued to repair the damaged heart and to restore normal cardiac function. Such strategies include both cellular and acellular products, in combination with biomaterials. In addition, substantial progress has been made to elucidate the molecular and cellular mechanisms underlying heart repair and regeneration. In this review, we summarize and discuss current therapeutic approaches for cardiac repair and provide a perspective on novel strategies that holding potential opportunities for future research and clinical translation.

Minimally invasive delivery of therapeutic agents by hydrogel injection into the pericardial cavity for cardiac repair.

Cardiac patches are an effective way to deliver therapeutics to the heart. However, such procedures are normally invasive and difficult to perform. Here, we develop and test a method to utilize the pericardial cavity as a natural "mold" for in situ cardiac patch formation after intrapericardial injection of therapeutics in biocompatible hydrogels. In rodent models of myocardial infarction, we demonstrate that intrapericardial injection is an effective and safe method to deliver hydrogels containing induced pluripotent stem cells-derived cardiac progenitor cells or mesenchymal stem cells-derived exosomes. After injection, the hydrogels form a cardiac patch-like structure in the pericardial cavity, mitigating immune response and increasing the cardiac retention of the therapeutics. With robust cardiovascular repair and stimulation of epicardium-derived cells, the delivered therapeutics mitigate cardiac remodeling and improve cardiac functions post myocardial infarction. Furthermore, we demonstrate the feasibility of minimally-invasive intrapericardial injection in a clinically-relevant porcine model. Collectively, our study establishes intrapericardial injection as a safe and effective method to deliver therapeutic-bearing hydrogels to the heart for cardiac repair.

Delivery of MSCs with a Hybrid ß-Sheet Peptide Hydrogel Consisting IGF-1C Domain and D-Form Peptide for Acute Kidney Injury Therapy.

PURPOSE: By providing a stem cell microenvironment with particular bioactive constituents in vivo, synthetic biomaterials have been progressively successful in stem cell-based tissue regeneration by enhancing the engraftment and survival of transplanted cells. Designs with bioactive motifs to influence cell behavior and with D-form amino acids to modulate scaffold stability may be critical for the development and optimization of self-assembling biomimetic hydrogel scaffolds for stem cell therapy. MATERIALS AND METHODS: In this study, we linked naphthalene (Nap) covalently to a short D-form peptide (Nap-DFDFG) and the C domain of insulin-like growth factor-1 (IGF-1C) as a functional hydrogel-based scaffolds, and we hypothesized that this hydrogel could enhance the therapeutic efficiency of human placenta-derived mesenchymal stem cells (hP-MSCs) in a murine acute kidney injury (AKI) model. RESULTS: The self-assembling peptide was constrained into a classical ß-sheet structure and showed hydrogel properties. Our results revealed that this hydrogel exhibited increased affinity for IGF-1 receptor. Furthermore, cotransplantation of the ß-IGF-1C hydrogel and hP-MSCs contributed to endogenous regeneration post-injury and boosted angiogenesis in a murine AKI model, leading to recovery of renal function. CONCLUSION: This hydrogel could provide a favorable niche for hP-MSCs and thereby rescue renal function in an AKI model by promoting cell survival and angiogenesis. In conclusion, by covalently linking the desired functional groups to D-form peptides to create functional hydrogels, self-assembling ß-sheet peptide hydrogels may serve as a promising platform for tissue-engineering and stem cell therapy.

Bispecific Antibody Inhalation Therapy for Redirecting Stem Cells from the Lungs to Repair Heart Injury.

Stem cell therapy is a promising strategy for cardiac repair. However, clinical efficacy is hampered by poor cell engraftment and the elusive repair mechanisms of the transplanted stem cells. The lung is a reservoir of hematopoietic stem cells (HSCs) and a major biogenesis site for platelets. A strategy is sought to redirect lung resident stem cells to the injured heart for therapeutic repair after myocardial infarction (MI). To achieve this goal, CD34-CD42b platelet-targeting bispecific antibodies (PT-BsAbs) are designed to simultaneously recognize HSCs (via CD34) and platelets (via CD42b). After inhalation delivery, PT-BsAbs reach the lungs and conjoined HSCs and platelets. Due to the innate injury-finding ability of platelets, PT-BsAbs guide lung HSCs to the injured heart after MI. The redirected HSCs promote endogenous repair, leading to increased cardiac function. The repair mechanism involves angiomyogenesis and inflammation modulation. In addition, the inhalation route is superior to the intravenous route to deliver PT-BsAbs in terms of the HSCs' homing ability and therapeutic benefits. This work demonstrates that this novel inhalable antibody therapy, which harnesses platelets derived from the lungs, contributes to potent stem cell redirection and heart repair. This strategy is safe and effective in a mouse model of MI.

Lactobacillus maintains healthy gut mucosa by producing L-Ornithine.

Gut mucosal layers are crucial in maintaining the gut barrier function. Gut microbiota regulate homeostasis of gut mucosal layer via gut immune cells such as RORγt (+) IL-22(+) ILC3 cells, which can influence the proliferation of mucosal cells and the production of mucin. However, it is unclear how gut microbiota execute this regulation. Here we show that lactobacilli promote gut mucosal formation by producing L-Ornithine from arginine. L-Ornithine increases the level of aryl hydrocarbon receptor ligand L-kynurenine produced from tryptophan metabolism in gut epithelial cells, which in turn increases RORγt (+)IL-22(+) ILC3 cells. Human REG3A transgenic mice show an increased proportion of L-Ornithine producing lactobacilli in the gut contents, suggesting that gut epithelial REG3A favors the expansion of L-Ornithine producing lactobacilli. Our study implicates the importance of a crosstalk between arginine metabolism in Lactobacilli and tryptophan metabolism in gut epithelial cells in maintaining gut barrier.

Resveratrol synergizes with low doses of L-DOPA to improve MPTP-induced Parkinson disease in mice.

L-DOPA (L-3,4-dihydroxyphenylalanine) relieves symptoms of Parkinson disease (PD), but long-term use can cause serious side effects. Resveratrol (3,5,4'-trihydroxy-trans-stilbene, RV), a polyphenolic compound derived from grapes and red wine that has antioxidant activity, has been shown to have neuroprotective effects. RV was investigated to enhance the therapeutic effect of L-DOPA in a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated mouse model of Parkinson disease. Mice received a saline or RV injection (10 mg/kg/day), then 2 h later, saline or MPTP (15 mg/kg/day) was administered for 7 consecutive days. Saline or L-DOPA (5 or 8 mg/kg/day) was injected post-administration of MPTP for the last 2 consecutive days. Our results indicated that RV alleviated MPTP-induced loss of dopaminergic neurons and attenuated astroglial activation in the nigrostriatal pathway. In parallel, RV reduced the expression of α-synuclein in the striatum. In addition, RV also increased levels of the anti-apoptotic signalling molecule Bcl-2, reduced levels of the pro-apoptotic signalling molecule Bax, and reduced activation of caspase-3 in the striatum. Specifically, RV significantly reduced motor dysfunction in MPTP-treated mice. Furthermore, the RV-treated group showed less IL-1ß and an enhanced pAkt/Akt ratio, which promoted dopamine neuron survival in the striatum. We found that the effects of co-administration of RV with L-DOPA (5 mg/kg) were equivalent to those of administration of 8 mg/kg L-DOPA in MPTP-induced PD mice. Therefore, with fewer side effects, L-DOPA can be effectively used in the treatment of PD over a long period of time.

A collagen hydrogel loaded with HDAC7-derived peptide promotes the regeneration of infarcted myocardium with functional improvement in a rodent model.

Myocardial infarction (MI) leads to the loss of cardiomyocytes, left ventricle (LV) dilation, and cardiac dysfunction, eventually developing into heart failure. Most of the strategies for MI therapy require biomaterials that can support tissue regeneration. In this study, we hypothesized that the extracellular matrix (ECM)-derived collagen I hydrogel loaded with histone deacetylase 7 (HDAC7)-derived-phosphorylated 7-amino-acid peptide (7Ap) could restrain LV remodeling and improve cardiac function after MI. An MI model was established by ligation of the left anterior descending coronary artery (LAD) of C57/B6 mice. The 7Ap-loaded collagen I hydrogel was intramyocardially injected to the infarcted region of the LV wall of the heart. After local delivery, the 7Ap-collagen increased neo-microvessel formation, enhanced stem cell antigen-1 positive (Sca-1+) stem cell recruitment and differentiation, decreased cellular apoptosis, and promoted cardiomyocyte cycle progression. Furthermore, the 7Ap-collagen restricted the fibrosis of the LV wall, reduced the infarct wall thinning, and improved cardiac performance significantly at 2 weeks post-MI. These results highlight the promising implication of 7Ap-collagen as a novel candidate for MI therapy. STATEMENT OF SIGNIFICANCE: The mammalian myocardium has a limited regenerative capability following myocardial infarction (MI). MI leads to extensive loss of cardiomyocytes, thus culminating in adverse cardiac remodeling and congestive heart failure. In situ tissue regeneration through endogenous cell mobilization has great potential for tissue regeneration. A 7-amino-acid-peptide (7A) domain encoded by a short open-reading frame (sORF) of the HDAC7 gene. The phosphorylated from of 7A (7Ap) has been reported to promote in situ tissue repair via the mobilization and recruitment of endogenous stem cell antigen-1 positive (Sca-l+) stem cells. In this study, 7Ap was shown to improve H9C2 cell survival, in vitro. In vivo investigations in a mouse MI model demonstrated that intra-myocardial delivery of 7Ap-loaded collagen hydrogel promoted neovascularization, stimulated Sca-l+ stem cell recruitment and differentiation, reduced cardiomyocyte apoptosis and promoted cell cycle progression. As a result, treated infarcted hearts had increased wall thickness, had improved heart function and exhibited attenuation of adverse cardiac remodeling, observed for up to 2 weeks. Overall, these results highlighted the positive impact of implanting 7Ap-collagen as a novel constituent for MI repair.

Prostaglandin E2 hydrogel improves cutaneous wound healing via M2 macrophages polarization.

Wound healing is regulated by a complex series of events and overlapping phases. A delicate balance of cytokines and mediators in tissue repair is required for optimal therapy in clinical applications. Molecular imaging technologies, with their versatility in monitoring cellular and molecular events in living organisms, offer tangible options to better guide tissue repair by regulating the balance of cytokines and mediators at injured sites. Methods: A murine cutaneous wound healing model was developed to investigate if incorporation of prostaglandin E2 (PGE2) into chitosan (CS) hydrogel (CS+PGE2 hydrogel) could enhance its therapeutic effects. Bioluminescence imaging (BLI) was used to noninvasively monitor the inflammation and angiogenesis processes at injured sites during wound healing. We also investigated the M1 and M2 paradigm of macrophage activation during wound healing. Results: CS hydrogel could prolong the release of PGE2, thereby improving its tissue repair and regeneration capabilities. Molecular imaging results showed that the prolonged release of PGE2 could ameliorate inflammation by promoting the M2 phenotypic transformation of macrophages. Also, CS+PGE2 hydrogel could augment angiogenesis at the injured sites during the early phase of tissue repair, as revealed by BLI. Furthermore, our results demonstrated that CS+PGE2 hydrogel could regulate the balance among the three overlapping phases-inflammation, regeneration (angiogenesis), and remodeling (fibrosis)-during cutaneous wound healing. Conclusion: Our findings highlight the potential of the CS+PGE2 hydrogel as a novel therapeutic strategy for promoting tissue regeneration via M2 macrophage polarization. Moreover, molecular imaging provides a platform for monitoring cellular and molecular events in real-time during tissue repair and facilitates the discovery of optimal therapeutics for injury repair by regulating the balance of cytokines and mediators at injured sites.

Rhein and polydimethylsiloxane functionalized carbon/carbon composites as prosthetic implants for bone repair applications.

A major issue in bone tissue engineering is the selection of biocompatible materials for implants, to reduce unwanted inflammatory reactions and promote cell adhesion. Bone tissue growth on suitable biomedical implants can shorten recovery and hospitalization after surgery. Therefore, a method to improve tissue-implant integration and healing would be of scientific and clinical interest. In this work, we permeated polydimethylsiloxane (PDMS) into carbon/carbon (C/C) composites (PDMS-C/C) and then coated it with 4,5-dihydroxyanthraquinone-2-carboxylic acid (rhein) to create rhein-PDMS-C/C to increase its biocompatibility and reduce the occurrence of inflammatory reactions. We measured in vitro adhesion and proliferation of MC3T3-E1 cells and bacteria to evaluate the biocompatibility and antimicrobial properties of C/C, PDMS-C/C, and rhein-PDMS-C/C. In vivo, x-ray and micro-CT evaluation three, six and nine weeks after surgery revealed that rhein-PDMS-C/C was more effective than PDMS-C/C and C/C composite in terms of antibacterial activity, cell adhesion and tissue growth. Compared with C/C and PDMS-C/C, rhein-PDMS-C/C could be suitable for clinical applications for bone tissue engineering.