Noninvasive application of mesenchymal stem cell spheres derived from hESC accelerates wound healing in a CXCL12-CXCR4 axis-dependent manner

Developmental potency of human ES cell-derived mesenchymal stem cells revealed in mouse embryos following blastocyst injection

Mesenchymal stem cells (MSCs) are present in almost all the tissues in the body, critical for their homeostasis and regeneration. However, the stemness of MSCs is mainly an in vitro observation, and lacking exclusive markers for endogenous MSCs makes it difficult to study the multipotency of MSCs in vivo, especially for human MSCs. To address this hurdle, we injected GFP-tagged human embryonic stem cell (hESC)-derived MSCs (EMSCs) into mouse blastocysts. EMSCs survived well and penetrated both the inner cell mass and trophectoderm, correlating to the higher anti-apoptotic capability of EMSCs than hESCs. Injected EMSCs contributed to skeletal, dermal, and extraembryonic tissues in the resultant chimera and partially rescued skeletal defects in Sox9+/- mouse fetuses. Thus, this study provides evidence for the stemness and developmental capability of human MSCs through chimerization with the mouse blastocyst, serving as a model for studying human mesenchymal and skeletal development.

Improving vasculoprotective effects of MSCs in coronary microvessels - benefits of 3D culture, sub-populations and heparin

Introduction

Opening occluded coronary arteries in patients with myocardial infarction (MI) damages the delicate coronary microvessels through a process called myocardial ischaemia-reperfusion injury. Although mesenchymal stromal cells (MSCs) have the potential to limit this injury, clinical success remains limited. This may be due to (i) poor MSC homing to the heart (ii) infused MSCs, even if derived from the same site, being a heterogeneous population with varying therapeutic efficacy and (iii) conventional 2D culture of MSCs decreasing their homing and beneficial properties. This study investigated whether 3D culture of two distinctly different bone marrow (BM)-derived MSC sub-populations could improve their homing and coronary vasculoprotective efficacy.

Methods

Intravital imaging of the anaesthetised mouse beating heart was used to investigate the trafficking and microvascular protective effects of two clonally-derived BM-derived MSC lines, namely CD317neg MSCs-Y201 and CD317pos MSCs-Y202, cultured using conventional monolayer and 3D hanging drop methods.

Results

3D culture consistently improved the adhesive behaviour of MSCs-Y201 to various substrates in vitro. However, it was their differential ability to reduce neutrophil events within the coronary capillaries and improve ventricular perfusion in vivo that was most remarkable. Moreover, dual therapy combined with heparin further improved the vasculoprotection afforded by 3D cultured MSCs-Y201 by also modifying platelet as well as neutrophil recruitment, which subsequently led to the greatest salvage of viable myocardium. Therapeutic benefit could mechanistically be explained by reductions in coronary endothelial oxidative stress and intercellular adhesion molecule-1 (ICAM-1)/vascular cell adhesion molecule-1 (VCAM-1) expression. However, since this was noted by both 2D and 3D cultured MSCs-Y201, therapeutic benefit is likely explained by the fact that 3D cultured MSCs-Y201 were the most potent sub-population at reducing serum levels of several pro-inflammatory cytokines.

Conclusion

This novel study highlights the importance of not only 3D culture, but also of a specific CD317neg MSC sub-population, as being critical to realising their full coronary vasculoprotective potential in the injured heart. Since the smallest coronary blood vessels are increasingly recognised as a primary target of reperfusion injury, therapeutic interventions must be able to protect these delicate structures from inflammatory cells and maintain perfusion in the heart. We propose that relatively feasible technical modifications in a specific BM-derived MSC sub-population could achieve this.

An Engineered Dermal Substitute with Mesenchymal Stem Cells Enhances Cutaneous Wound Healing

The treatment of refractory cutaneous wounds remains to be a clinical challenge. There is growing evidence to show that mesenchymal stem cells (MSCs) have great potential in promoting wound healing. However, the therapeutic effects of MSCs are greatly dampened by their poor survival and engraftment in the wounds. To address this limitation, in this study, MSCs were grown into a collagen-glycosaminoglycan (C-GAG) matrix to form a dermis-like tissue sheet, named engineered dermal substitute (EDS). When seeded on C-GAG matrix, MSCs adhered rapidly, migrated into the pores, and proliferated readily. When applied onto excisional wounds in healthy and diabetic mice, the EDS survived well, and accelerated wound closure, compared with C-GAG matrix alone or MSCs in collagen hydrogel. Histological analysis revealed that EDS prolonged the retention of MSCs in the wounds, associated with increased macrophage infiltration and enhanced angiogenesis. RNA-Seq analysis of EDS-treated wounds uncovered the expression of abundant human chemokines and proangiogenic factors and their corresponding murine receptors, suggesting a mechanism of ligand/receptor-mediated signals in wound healing. Thus, our results indicate that EDS prolongs the survival and retention of MSCs in the wounds and enhances wound healing.

Exosomal microRNAs from Mesenchymal Stem Cells: Novel Therapeutic Effect in Wound Healing

BACKGROUND

Wound healing is a complicated biological process that leads to the regeneration of damaged skin tissue. Determining the methods to promote wound healing has become a hot topic in medical cosmetology and tissue repair research. Mesenchymal stem cells (MSCs) are a group of stem cells with the potential of self-renewal and multi-differentiation. MSCs transplantation has a broad application prospect in wound healing therapy. Many studies have demonstrated that the therapeutic capacity of MSCs is mainly mediated by paracrine actions. Exosomes (EXOs), which are nanosized vesicles carrying a variety of nucleic acids, proteins and lipids, are an important component of paracrine secretion. It has been demonstrated that exosomal microRNAs (EXO-miRNAs) play a key role in the function of exosomes.

METHODS

In this review, we focus on current research on miRNAs from MSC-derived exosomes (MSC-EXO miRNAs) in terms of sorting, releasing and function and their effects on inflammation regulation, epidermal cell function, fibroblast function, and extracellular matrix formation. At last, we discuss the current attempts to improve the treatment of MSC-EXO-miRNAs.

RESULTS

Many studies have demonstrated that MSC-EXO miRNAs play a key role in promoting wound healing. They have been shown to regulate inflammation response, enhance epidermal cell proliferation and migration, stimulate fibroblast proliferation and collagen synthesis, and regulate extracellular matrix formation. Besides, there have been a number of strategies developed to promote MSC-EXO and MSC-EXO miRNAs for wound healing treatment.

CONCLUSION

Utilizing the association of exosomes from MSCs with miRNAs may be a promising strategy to promote trauma healing. MSC-EXO miRNAs may provide a new approach to promote wound healing and improve the quality of life for patients with skin injuries.

Three-Dimensional Spheroid Culture of Human Mesenchymal Stem Cells: Offering Therapeutic Advantages and In Vitro Glimpses of the In Vivo State

As invaluable as the standard 2-dimensional (2D) monolayer in vitro cell culture system has been, there is increasing evidence that 3-dimensional (3D) non-adherent conditions are more relevant to the in vivo condition. While one of the criteria for human mesenchymal stem cells (MSCs) has been in vitro plastic adherence, such 2D culture conditions are not representative of in vivo cell-cell and cell-extracellular matrix (ECM) interactions, which may be especially important for this progenitor/stem cell of skeletal and connective tissues. The 3D spheroid, a multicellular aggregate formed under non-adherent 3D in vitro conditions, may be particularly suited as an in vitro method to better understand MSC physiological processes, since expression of ECM and other adhesion proteins are upregulated in such a cell culture system. First used in embryonic stem cell in vitro culture to recapitulate in vivo developmental processes, 3D spheroid culture has grown in popularity as an in vitro method to mimic the 3-dimensionality of the native niche for MSCs within tissues/organs. In this review, we discuss the relevance of the 3D spheroid culture for understanding MSC biology, summarize the biological outcomes reported in the literature based on such this culture condition, as well as contemplate limitations and future considerations in this rapidly evolving and exciting area.

A multifunctional hydrogel loaded with two nanoagents improves the pathological microenvironment associated with radiation combined with skin wounds

Persistent oxidative stress and recurring waves of inflammation with excessive reactive oxygen species (ROS) and free radical accumulation could be generated by radiation. Exposure to radiation in combination with physical injuries such as wound trauma would produce a more harmful set of medical complications, which was known as radiation combined with skin wounds (RCSWs). However, little attention has been given to RCSW research despite the unsatisfactory therapeutic outcomes. In this study, a dual-nanoagent-loaded multifunctional hydrogel was fabricated to ameliorate the pathological microenvironment associated with RCSWs. The injectable, adhesive, and self-healing hydrogel was prepared by crosslinking carbohydrazide-modified gelatin (Gel-CDH) and oxidized hyaluronic acid (OHA) through the Schiff-base reaction under mild condition. Polydopamine nanoparticles (PDA-NPs) and mesenchymal stem cell-secreted small extracellular vesicles (MSC-sEV) were loaded to relieve radiation-produced tissue inflammation and oxidation impairment and enhance cell vitality and angiogenesis individually or jointly. The proposed PDA-NPs@MSC-sEV hydrogel enhanced cell vitality, as shown by cell proliferation, migration, colony formation, and cell cycle and apoptosis assays in vitro, and promoted reepithelization by attenuating microenvironment pathology in vivo. Notably, a gene set enrichment analysis of proteomic data revealed significant enrichment with adipogenic and hypoxic pathways, which play prominent roles in wound repair. Specifically, target genes were predicted based on differential transcription factor expression. The results suggested that MSC-sEV- and PDA-NP-loaded multifunctional hydrogels may be promising nanotherapies for RCSWs. STATEMENT OF SIGNIFICANCE: The small extracellular vesicle (sEV) has distinct advantages compared with MSCs, and polydopamine nanoparticles (PDA-NPs), known as the biological materials with good cell affinity and histocompatibility which have been reported to scavenge ROS free radicals. In this study, an adhesive, injectable, self-healing, antibacterial, ROS scavenging and amelioration of the radiation related microenvironment hydrogel encapsulating nanoscale particles of MSC-sEV and PDA-NPs (PDA-NPs@MSC-sEV hydrogel) was synthesized for promoting radiation combined with skin wounds (RCSWs). GSEA analysis profiled by proteomics data revealed significant enrichments in the regulations of adipogenic and hypoxic pathways with this multi-functional hydrogel. This is the first report of combining this two promising nanoscale agents for the special skin wounds associated with radiation.

Metformin coordinates with mesenchymal cells to promote VEGF-mediated angiogenesis in diabetic wound healing through Akt/mTOR activation

INTRODUCTION

Cell therapy with mesenchymal stem cells (MSCs) and biomaterials holds great potential for the treatment of diabetic ulceration; however, the underlying mechanism as well as its compatibility with the first-line anti-diabetic drug, metformin (MTF), has not been well elucidated.

METHODS

MSCs derived from the umbilical cord were labeled with fluorescent proteins, followed by transplantation in a fibrin scaffold (MSCs/FG) onto the STZ-induced diabetic wound in a C57BL6/J mouse model. MTF was administered by oral gavage at a dose of 250 mg/kg/day. The wound healing rate, epithelization, angiogenesis, and underlying mechanism were evaluated in MSCs/FG- and MTF-treated diabetic wounds. Moreover, the dose-dependent effects of MTF and involvement of the Akt/mTOR pathway were analyzed in keratinocyte and fibroblast cultures.

RESULTS

MSCs/FG significantly promoted angiogenesis in diabetic wound healing without signs of differentiation or integration. The recruitment of fibroblasts and keratinocytes by MSCs/FG promotes migration and vascular endothelial growth factor (VEGF) expression in an Akt/mTOR-dependent manner. MTF, which is generally considered a mTOR inhibitor, displayed dose-dependent effects on MSC-unregulated Akt/mTOR and VEGF expression. Oral administration of MTF at an anti-diabetic dosage synergistically acted with MSCs/FG to promote Akt/mTOR activation, VEGF expression, and subsequent angiogenesis in diabetic wounds; however, it reduced the survival of MSCs.

CONCLUSIONS

Our study identifies that MTF coordinates with mesenchymal cells to promote Akt/mTOR activation and VEGF-mediated angiogenesis during diabetic wound healing. These findings offer new insights into MSCs engraftment in FG scaffolds for diabetic wound healing and provide support for the promotion of MSCs therapy in patients prescribed with MTF.

Hydrogel-Encapsulated Engineered Microbial Consortium as a Photoautotrophic "Living Material" for Promoting Skin Wound Healing

Genetically modified engineered microorganisms have been encapsulated in hydrogels and used as "living materials" for the treatment of skin diseases. However, their applications are often limited by the epidermal dry, nutrient-poor environment and cannot maintain functions stably for an expected sufficient time. To solve this problem, a photoautotrophic "living material" containing an engineered microbial consortium was designed and fabricated. The engineered microbial consortium comprised Synechococcus elongatus PCC7942 for producing sucrose by photosynthesis and another heterotrophic engineered bacterium (Escherichia coli or Lactococcus lactis) that can utilize sucrose for the growth and secretion of functional biomolecules. These engineered microorganisms in the "living material" were proved to function stably for a longer time than only individual microbes. Subsequently, CXCL12-secreting engineered L. lactis was used to construct the "living material", and its effect on promoting wound healing was verified in a full-thickness rat-skin defect model. The wounds treated by our hydrogel-encapsulated engineered microbial consortium (HeEMC) healed faster, with a wound area ratio of only 13.2% at day 14, compared to the remaining 62.6, 51.4, and 40.8% of the control, PEGDA, and PEGDA/CS groups, respectively. In conclusion, we established an efficient living material HeEMC to offer promising applications in the treatment of skin diseases.

Combination therapy of hydrogel and stem cells for diabetic wound healing

Diabetic wounds (DWs) are a common complication of diabetes mellitus; DWs have a low cure rate and likely recurrence, thus affecting the quality of patients’ lives. As traditional therapy cannot effectively improve DW closure, DW has become a severe clinical medical problem worldwide. Unlike routine wound healing, DW is difficult to heal because of its chronically arrested inflammatory phase. Although mesenchymal stem cells and their secreted cytokines can alleviate oxidative stress and stimulate angiogenesis in wounds, thereby promoting wound healing, the biological activity of mesenchymal stem cells is compromised by direct injection, which hinders their therapeutic effect. Hydro-gels form a three-dimensional network that mimics the extracellular matrix, which can provide shelter for stem cells in the inflammatory microenvironment with reactive oxygen species in DW, and maintains the survival and viability of stem cells. This review summarizes the mechanisms and applications of stem cells and hydrogels in treating DW; additionally, it focuses on the different applications of therapy combining hydrogel and stem cells for DW treatment.

Revealing the mystery of persistent smell loss in Long COVID patients

COVID-19 is hopefully approaching its end in many countries as herd immunity develops and weaker strains of SARS-CoV-2 dominate. However, a new concern occurs over the long-term effects of COVID-19, collectively called "Long COVID", as some symptoms of the nervous system last even after patients recover from COVID-19. This review focuses on studies of anosmia, i.e., impairment of smell, which is the most common sensory defect during the disease course and is caused by olfactory dysfunctions. It remains mysterious how the olfactory functions are affected since the virus can't invade olfactory receptor neurons. We describe several leading hypotheses about the mystery in hope to provide insights into the pathophysiology and treatment strategies for anosmia.

TET1 dioxygenase is required for FOXA2-associated chromatin remodeling in pancreatic beta-cell differentiation

Existing knowledge of the role of epigenetic modifiers in pancreas development has exponentially increased. However, the function of TET dioxygenases in pancreatic endocrine specification remains obscure. We set out to tackle this issue using a human embryonic stem cell (hESC) differentiation system, in which TET1/TET2/TET3 triple knockout cells display severe defects in pancreatic β-cell specification. The integrative whole-genome analysis identifies unique cell-type-specific hypermethylated regions (hyper-DMRs) displaying reduced chromatin activity and remarkable enrichment of FOXA2, a pioneer transcription factor essential for pancreatic endoderm specification. Intriguingly, TET depletion leads to significant changes in FOXA2 binding at the pancreatic progenitor stage, in which gene loci with decreased FOXA2 binding feature low levels of active chromatin modifications and enriches for bHLH motifs. Transduction of full-length TET1 but not the TET1-catalytic-domain in TET-deficient cells effectively rescues β-cell differentiation accompanied by restoring PAX4 hypomethylation. Taking these findings together with the defective generation of functional β-cells upon TET1-inactivation, our study unveils an essential role of TET1-dependent demethylation in establishing β-cell identity. Moreover, we discover a physical interaction between TET1 and FOXA2 in endodermal lineage intermediates, which provides a mechanistic clue regarding the complex crosstalk between TET dioxygenases and pioneer transcription factors in epigenetic regulation during pancreas specification.

Here the authors show that TET1 is required for the generation of functional insulin-producing cells, FOXA2 physically interacts with TET1 and contributes to specific recruitment of TET1 to mediate chromatin opening at the regulatory elements of pancreatic lineage determinants.

Therapeutic Effect of Astragali Radix Extract Injection Combined with Bone Marrow Mesenchymal Stem Cells in Bleomycin-Induced Pulmonary Fibrotic Rats

Pulmonary fibrosis is a serious disease for which effective drugs are unavailable. Here, we treated rat models of bleomycin (BLM)-induced pulmonary fibrosis with Astragali Radix extract injection (AI) combined with or without bone marrow mesenchymal stem cells (BMSCs). We injected rats intratracheally with BLM and transplanted BMSCs via tail vein injection 15 days later. We also intraperitoneally injected AI daily from days 15 to 28. Changes in lung pathology and function, as well as the levels of matrix metalloproteinases, collagen, C-X-C motif chemokine ligand 12 (CXCL12), and cluster of differentiation 90 (CD90) were assessed. The results revealed that compared with the BLM group, groups treated with ARE and BMSCs (alone or combined) reduced the expression levels of TGF-β1 and collagens I and III, ameliorated pathological lung fibrotic damage, and improved lung function. The expression levels of MMP-1, MMP-3, and MMP-9 were reduced by either AI or BMSCs alone, whereas those of MMP-3, MMP-9, TIMP-1, CXCL12, and CD90 were elevated by combined AI and BMSCs compared with the BLM group. Overall, these findings demonstrated that AI and BMSCs both can reduce damage caused by PF in rats and that AI altered the expression of chemokines and surface markers in BMSCs.

Mesenchymal stem cells inhibited the apoptosis of alveolar epithelial cells caused by ARDS through CXCL12/CXCR4 axis

Mesenchymal stem cells (MSCs) have a wide range of anti-inflammatory and immunomodulatory effects and have been observed to have potential therapeutic potential in the clinical treatment of various diseases. We pretreated lung cancer cells A549 with tumor necrosis factor (TNF-α), knocked down the key chemokine receptor CXCR4 on MSCs using lentivirus, and induced acute respiratory distress syndrome (ARDS) mouse model using lipopolysaccharide (LPS) and CXCL12 expression in vivo by adeno-associated virus (AAV-rh10) infection in mice. By co-culturing the MSCs with A549 and in vivo experiments, we observed the effects of MSCs on cell biological functions after inflammatory stimulation, oxidative stress, and the amelioration of lung injury in ARDS mice. TNF-α inhibited A549 proliferation and promoted apoptosis, scorch death-related factor activity, and oxidative stress factor were increased and CXCL12 levels in the cell supernatant were decreased. The co-culture of MSCs was able to increase cell activity and decrease oxidative stress factor levels, and this effect was not present after the knockdown of CXCR4 in MSCs. In vivo transplantation of MSCs significantly attenuated lung injury in ARDS, inhibited serum pro-inflammatory factors in mice, and down-regulated expression of apoptotic and focal factors in lung tissues while blocking CXCR4 or CXCL12 lost the repairing effect of MSCs on ARDS lung tissues. After the co-culture of MSC and lung cancer cells, the expression of CXCR4 on the surface of lung cancer cells was significantly increased, and more CXCR4 and CXCL12 acted together to activate more pro-survival pathways and inhibit apoptosis induced by TNF-α.

Therapeutic effect of adipose stromal vascular fraction spheroids for partial bladder outlet obstruction induced underactive bladder

BACKGROUND

Underactive bladder (UAB) is a common clinical problem but related research is rarely explored. As there are currently no effective therapies, the administration of adipose stromal vascular fraction (ad-SVF) provides a new potential method to treat underactive bladder.

METHODS

Male Sprague-Dawley rats were induced by partial bladder outlet obstruction (PBOO) for four weeks and randomly divided into three groups: rats treated with PBS (Sham group); rats administrated with ad-SVF (ad-SVF group) and rats performed with ad-SVF spheroids (ad-SVFsp group). After four weeks, urodynamic studies were performed to evaluate bladder functions and all rats were sacrificed for further studies.

RESULTS

We observed that the bladder functions and symptoms of UAB were significantly improved in the ad-SVFsp group than that in the Sham group and ad-SVF group. Meanwhile, our data showed that ad-SVF spheroids could remarkably promote angiogenesis, suppress cell apoptosis and stimulate cell proliferation in bladder tissue than that in the other two groups. Moreover, ad-SVF spheroids increased the expression levels of bFGF, HGF and VEGF-A than ad-SVF. IVIS Spectrum small-animal in vivo imaging system revealed that ad-SVF spheroids could increase the retention rate of transplanted cells in bladder tissue.

CONCLUSIONS

Ad-SVF spheroids improved functions and symptoms of bladder induced by PBOO, which contributes to promote angiogenesis, suppress cell apoptosis and stimulate cell proliferation. Ad-SVF spheroids provide a potential treatment for the future patients with UAB.

Engineering of human mesenchymal stem cells resistant to multiple natural killer subtypes

Mesenchymal stem cells (MSCs) as a therapeutic promise are often quickly cleared by innate immune cells of the host including natural killer (NK) cells. Efforts have been made to generate immune-escaping human embryonic stem cells (hESCs) where T cell immunity is evaded by defecting β-2-microglobulin (B2M), a common unit for human leukocyte antigen (HLA) class I, and NK cells are inhibited via ectopic expression of HLA-E or -G. However, NK subtypes vary among recipients and even at different pathologic statuses. It is necessary to dissect and optimize the efficacy of the immune-escaping cells against NK subtypes. Here, we first generated B2M knockout hESCs and differentiated them to MSCs (EMSCs) and found that NK resistance occurred with B2M^-/- EMSCs expressing HLA-E and -G only when they were transduced via an inducible lentiviral system in a dose-dependent manner but not when they were inserted into a safe harbor. HLA-E and -G expressed at high levels together in transduced EMSCs inhibited three major NK subtypes, including NKG2A⁺/LILRB1⁺, NKG2A⁺/LILRB1^-, and NKG2A^-/LILRB1⁺, which was further potentiated by IFN-γ priming. Thus, this study engineers MSCs with resistance to multiple NK subtypes and underscores that dosage matters when a transgene is used to confer a novel effect to host cells, especially for therapeutic cells to evade immune rejection.

Smart and Biomimetic 3D and 4D Printed Composite Hydrogels: Opportunities for Different Biomedical Applications

In recent years, smart/stimuli-responsive hydrogels have drawn tremendous attention for their varied applications, mainly in the biomedical field. These hydrogels are derived from different natural and synthetic polymers but are also composite with various organic and nano-organic fillers. The basic functions of smart hydrogels rely on their ability to change behavior; functions include mechanical, swelling, shaping, hydrophilicity, and bioactivity in response to external stimuli such as temperature, pH, magnetic field, electromagnetic radiation, and biological molecules. Depending on the final applications, smart hydrogels can be processed in different geometries and modalities to meet the complicated situations in biological media, namely, injectable hydrogels (following the sol-gel transition), colloidal nano and microgels, and three dimensional (3D) printed gel constructs. In recent decades smart hydrogels have opened a new horizon for scientists to fabricate biomimetic customized biomaterials for tissue engineering, cancer therapy, wound dressing, soft robotic actuators, and controlled release of bioactive substances/drugs. Remarkably, 4D bioprinting, a newly emerged technology/concept, aims to rationally design 3D patterned biological matrices from synthesized hydrogel-based inks with the ability to change structure under stimuli. This technology has enlarged the applicability of engineered smart hydrogels and hydrogel composites in biomedical fields. This paper aims to review stimuli-responsive hydrogels according to the kinds of external changes and t recent applications in biomedical and 4D bioprinting.

Zwitterionic Hydrogel Activates Autophagy to Promote Extracellular Matrix Remodeling for Improved Pressure Ulcer Healing

Pressure ulcer (PU) is a worldwide problem that is hard to heal because of its prolonged inflammatory response and impaired ECM deposition caused by local hypoxia and repeated ischemia/reperfusion. Our previous study discovered that the non-fouling zwitterionic sulfated poly (sulfobetaine methacrylate) (SBMA) hydrogel can improve PU healing with rapid ECM rebuilding. However, the mechanism of the SBMA hydrogel in promoting ECM rebuilding is unclear. Therefore, in this work, the impact of the SBMA hydrogel on ECM reconstruction is comprehensively studied, and the underlying mechanism is intensively investigated in a rat PU model. The in vivo data demonstrate that compared to the PEG hydrogel, the SBMA hydrogel enhances the ECM remolding by the upregulation of fibronectin and laminin expression as well as the inhibition of MMP-2. Further investigation reveals that the decreased MMP-2 expression of zwitterionic SBMA hydrogel treatment is due to the activation of autophagy through the inhibited PI3K/Akt/mTOR signaling pathway and reduced inflammation. The association of autophagy with ECM remodeling may provide a way in guiding the design of biomaterial-based wound dressing for chronic wound repair.

CCR2-engineered mesenchymal stromal cells accelerate diabetic wound healing by restoring immunological homeostasis

Impaired wound healing presents great health risks to patients. While encouraging, the current clinical successes of mesenchymal stromal cell (MSC)-based therapies for tissue repair have been limited. Genetic engineering could endow MSCs with more robust regenerative capacities. Here, we identified that C-C motif chemokine receptor 2 (CCR2) overexpression enhanced the targeted migration and immunoregulatory potential of MSCs in response to C-C motif chemokine ligand 2 (CCL2) in vitro. Intravenously infusion of CCR2-engineered MSCs (MSCs^CCR2) exhibited improved homing efficiencies to injured sites and lungs of diabetic mice. Accordingly, MSC^CCR2 infusion inhibited monocyte infiltration, reshaped macrophage inflammatory properties, prompted the accumulation of regulatory T cells (Treg cells) in injured sites, and reshaped systemic immune responses via the lung and spleen in mouse diabetic wound models. In summary, CCR2-engineered MSCs restore immunological homeostasis to accelerate diabetic wound healing via their improved homing and immunoregulatory potentials in response to CCL2. Therefore, these findings provide a novel strategy to explore genetically engineered MSCs as tools to facilitate tissue repair in diabetic wounds.

3D Printing of Thermoresponsive Hydrogel Laden with an Antimicrobial Agent towards Wound Healing Applications

Thermoresponsive hydrogel-based wound dressings with an incorporated antimicrobial agent can be fabricated employing 3D printing technology. A novel printable ink containing poly(N-isopropylacrylamide) (PNIPAAm) precursors, sodium alginate (ALG), methylcellulose (MC) that is laden with a mixture of octenidine dihydrochloride and 2-phenoxyethanol (Octenisept®, OCT) possess accurate printability and shape fidelity. This study also provides the protocol of ink's use for the 3D printing of hydrogel scaffolds. The hydrogel's physicochemical properties and drug release profiles from the hydrogel specimens to the external solution have been determined at two temperatures (20 and 37 °C). The release test showed a sustained OCT delivery into ultrapure water and the PBS solution. The temperature-responsive hydrogel exhibited antimicrobial activity against Staphylococcus aureus, Candida albicans, and Pseudomonas aeruginosa and demonstrated non-cytotoxicity towards fibroblasts. The thermoresponsive behavior along with biocompatibility, antimicrobial activity, and controlled drug release make this hydrogel a promising class of materials for wound dressing applications.

Chemokines and their receptors: predictors of the therapeutic potential of mesenchymal stromal cells

Multipotent mesenchymal stromal cells (MSCs) are promising cellular therapeutics for the treatment of inflammatory and degenerative disorders due to their anti-inflammatory, immunomodulatory and regenerative potentials. MSCs can be sourced from a variety of tissues within the body, but bone marrow is the most frequently used starting material for clinical use. The chemokine family contains many regulators of inflammation, cellular function and cellular migration-all critical factors in understanding the potential potency of a novel cellular therapeutic. In this review, we focus on expression of chemokine receptors and chemokine ligands by MSCs isolated from different tissues. We discuss the differential migratory, angiogenetic and immunomodulatory potential to understand the role that tissue source of MSC may play within a clinical context. Furthermore, this is strongly associated with leukocyte recruitment, immunomodulatory potential and T cell inhibition potential and we hypothesize that chemokine profiling can be used to predict the in vivo therapeutic potential of MSCs isolated from new sources and compare them to BM MSCs.

Human ESC-derived MSCs enhance fat engraftment by promoting adipocyte reaggregation, secreting CCL2 and mobilizing macrophages

Mesenchymal stem cells (MSCs) derived from somatic tissues have been used to promote lipotransfer, a common practice in cosmetic surgery. However, the effect of lipotransfer varies, and the mechanism of action remains vague. To address these questions, we differentiated human embryonic stem cells, a stable and unlimited source, into MSCs (EMSCs). Then we subcutaneously transplanted human fat aspirates together with EMSCs or PBS as a control into the back of nude mice. Within 24 h of transplantation, EMSCs promoted aggregation and encapsulation of injected fat tissues. Afterward, all grafts gradually shrank. However, EMSC-containing grafts were larger, heavier and had fewer dark areas on the surface than the control grafts. Histologically, more live adipocytes, vascular cells, and macrophages and less fibrosis were observed in EMSC-containing grafts than in the controls. Some EMSCs differentiated into vascular cells and adipocytes in the EMSC-containing grafts. RNA sequencing revealed that human RNA was shown to decline rapidly, while mouse RNA increased in the grafts; further, human genes related to extracellular matrix remodeling, adipogenesis, and chemokine (including CCL2) signaling were expressed at higher levels in the EMSC-containing grafts than they were in the controls. CCL2 knockout reduced macrophage migration towards EMSCs in vitro and early macrophage recruitment to the grafts and the pro-engraftment effect of EMSCs in vivo. Treating mice with a macrophage inhibitor abolished the EMSC effects and converted the grafts to heavy masses of cell debris. Together, these data demonstrate that EMSCs promote fat engraftment via enhanced tissue reconstitution and encapsulation of implanted tissues, which was followed by increased angiogenesis and adipocyte survival and reduced fibrosis, in which stimulated CCL2 signaling and mobilized macrophages play pivotal roles.

Thermosensitive Injectable Chitosan/Collagen/β-Glycerophosphate Composite Hydrogels for Enhancing Wound Healing by Encapsulating Mesenchymal Stem Cell Spheroids

Chronic wounds caused by diabetic or venous diseases remain a social and healthcare burden. In this work, a new strategy is proposed in which injectable thermosensitive chitosan/collagen/β-glycerophosphate (β-GP) hydrogels were combined with three-dimensional mesenchymal stem cell (3D MSC) spheroids to accelerate chronic wound healing by enhanced vascularization and paracrine effects. Chitosan/collagen/β-GP solution mixed with 3D MSC spheroids was rapidly transformed to a gel at body temperature by physical cross-linking, then overlapped the wounds fully and fitted to any shape of the wound. The results showed that the combination therapy exhibited a markedly therapeutic effect than the hydrogel-loaded two-dimensional (2D) MSCs or 2D MSCs alone. The hydrogel could provide an environment conductive to the attachment and proliferation of encapsulated MSCs, especially accelerating the proliferation and paracrine factor secretion of 3D MSC spheroids. These results supplied a novel alternative approach to treat chronic wounds caused by diabetic or venous diseases.

Increased intracellular Cl- concentration improves airway epithelial migration by activating the RhoA/ROCK Pathway

In the airway, Cl- is the most abundant anion and is critically involved in transepithelial transport. The correlation of the abnormal expression and activation of chloride channels (CLCs), such as cystic fibrosis transmembrane conductance regulators (CFTRs), anoctamin-1, and CLC-2, with cell migration capability suggests a relationship between defective Cl- transport and epithelial wound repair. However, whether a correlation exists between intracellular Cl- and airway wound repair capability has not been explored thus far, and the underlying mechanisms involved in this relationship are not fully defined. Methods: In this work, the alteration of intracellular chloride concentration ([Cl-]i) was measured by using a chloride-sensitive fluorescent probe (N-[ethoxycarbonylmethyl]-6-methoxyquinolium bromide). Results: We found that clamping with high [Cl-]i and 1 h of treatment with the CLC inhibitor CFTR blocker CFTRinh-172 and chloride intracellular channel inhibitor IAA94 increased intracellular Cl- concentration ([Cl-]i) in airway epithelial cells. This effect improved epithelial cell migration. In addition, increased [Cl-]i in cells promoted F-actin reorganization, decreased cell stiffness, and improved RhoA activation and LIMK1/2 phosphorylation. Treatment with the ROCK inhibitor of Y-27632 and ROCK1 siRNA significantly attenuated the effects of increased [Cl-]i on LIMK1/2 activation and cell migration. In addition, intracellular Ca2+ concentration was unaffected by [Cl-]i clamping buffers and CFTRinh-172 and IAA94. Conclusion: Taken together, these results suggested that Cl- accumulation in airway epithelial cells could activate the RhoA/ROCK/LIMK cascade to induce F-actin reorganization, down-regulate cell stiffness, and improve epithelial migration.

Stem cell therapy of myocardial infarction: a promising opportunity in bioengineering

Myocardial infarction (MI) is a life-threatening disease resulting from irreversible death of cardiomyocytes (CMs) and weakening of the heart blood-pumping function. Stem cell-based therapies have been studied for MI treatment over the last two decades with promising outcome. In this review, we critically summarize the past work in this field to elucidate the advantages and disadvantages of treating MI using pluripotent stem cells (PSCs) including both embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs), adult stem cells, and cardiac progenitor cells. The main advantage of the latter is their cytokine production capability to modulate immune responses and control the progression of healing. However, human adult stem cells have very limited (if not 'no') capacity to differentiate into functional CMs in vitro or in vivo. In contrast, PSCs can be differentiated into functional CMs although the protocols for the cardiac differentiation of PSCs are mainly for adherent cells under 2D culture. Derivation of PSC-CMs in 3D, allowing for large-scale production of CMs via modulation of the Wnt/β-catenin signal pathway with defined chemicals and medium, may be desired for clinical translation. Furthermore, the technology of purification and maturation of the PSC-CMs may need further improvements to eliminate teratoma formation after in vivo implantation of the PSC-CMs for treating MI. In addition, in vitro derived PSC-CMs may have mechanical and electrical mismatch with the patient's cardiac tissue, which causes arrhythmia. This supports the use of PSC-derived cells committed to cardiac lineage without beating for implantation to treat MI. In this case, the PSC derived cells may utilize the mechanical, electrical, and chemical cues in the heart to further differentiate into mature/functional CMs in situ. Another major challenge facing stem cell therapy of MI is the low retention/survival of stem cells or their derivatives (e.g., PSC-CMs) in the heart for MI treatment after injection in vivo. This may be resolved by using biomaterials to engineer stem cells for reduced immunogenicity, immobilization of the cells in the heart, and increased integration with the host cardiac tissue. Biomaterials have also been applied in the derivation of CMs in vitro to increase the efficiency and maturation of differentiation. Collectively, a lot has been learned from the past failure of simply injecting intact stem cells or their derivatives in vivo for treating MI, and bioengineering stem cells with biomaterials is expected to be a valuable strategy for advancing stem cell therapy towards its widespread application for treating MI in the clinic.

Mesenchymal stem cell transplantation alleviates experimental Sjögren's syndrome through IFN-β/IL-27 signaling axis

Rationale: Although mesenchymal stem cell (MSC) transplantation has been proved to be an effective therapeutic approach to treat experimental Sjögren's syndrome (SS), the detailed underlying mechanisms remains unknown. IL-27 has diverse influences on the regulation of T cell differentiation and was involved in SS through modulating immune response. Here we aimed to explore whether IL-27-mediated regulation of immune cells was responsible for the beneficial effects of MSC transplantation on SS.

Methods: The SS-like symptoms were evaluated in IL-27 deficient and recombinant IL-27-treated NOD mice. The MSCs were infused into NOD mice via the tail vein. The histological features of submandibular glands, saliva flow rate and serum IL-27 were examined. The effects of MSCs on the IL-27 production and Th17/Treg cell in SS patients and mice in vitro and in vivo were determined for the mechanistic study.

Results: This study showed that SS patients had decreased IL-27 level and increased ratio of Th17/Treg cells. Consistently, exacerbated SS-like symptoms were observed in IL-27 deficient NOD mice, along with increased ratio of Th17/Treg cells. Importantly, MSC transplantation alleviated SS-like symptoms by elevating the level of IL-27 to restore Th17/Treg balance in NOD mice. Mechanistically, MSC-secreted interferon-β (IFN-β) promote dendritic cells to produce IL-27.

Conclusions: Thus, we have revealed a previously unrecognized function of MSC-mediated IL-27 production by DCs in suppressing SS-like syndrome, which provided evidences for clinical application of MSC in patients with SS.