Self-assembled GFFYK peptide hydrogel enhances the therapeutic efficacy of mesenchymal stem cells in a mouse hindlimb ischemia model

Injectable thermosensitive selenium-containing hydrogel as mesenchymal stem cell carrier to improve treatment efficiency in limb ischemia

Limb ischemia is a refractory disease characterized by persistent inflammation, insufficient angiogenesis, and tissue necrosis. Although mesenchymal stem cells (MSCs) have shown potential for treating limb ischemia, their therapeutic effects are limited by low engraftment rates. Therefore, developing an optimal MSC delivery system that enhances cell viability is imperative. Selenium, known for its cytoprotective properties in various cell types, offers a potential strategy to enhance therapeutic effect of MSCs. In this study, we evaluated the cytoprotective effects of selenium on MSCs, and developed an injectable thermosensitive selenium-containing hydrogel based on PLGA-PEG-PLGA triblock copolymer, as a cell carrier to improve MSC viability after engraftment. The biocompatibility, biodegradability, and cytoprotective capabilities of selenium-containing hydrogels were assessed. Furthermore, the therapeutic potential of MSCs encapsulated within a thermosensitive selenium-containing hydrogel in limb ischemia was evaluated using cellular and animal experiments. Selenium protects MSCs from oxidative damage by upregulating GPX4 through a transcriptional mechanism. The injectable thermosensitive selenium-containing hydrogel exhibited favorable biocompatibility, biodegradability, and antioxidant properties. It can be easily injected into the target area in liquid form at room temperature and undergoes gelation at body temperature, thereby preventing the diffusion of selenium and promoting the cytoprotection of MSCs. Furthermore, MSCs encapsulated within the selenium-containing hydrogel effectively inhibited macrophage M1 polarization while promoting macrophage M2 polarization, thus accelerating angiogenesis and restoring blood perfusion in ischemic limbs. This study demonstrated the potential of an injectable thermosensitive selenium-containing hydrogel as a promising method for MSC delivery. By addressing the challenge of low retention rate, which is a major obstacle in MSC application, this strategy effectively improves limb ischemia.

Enhancing Immunomodulatory Function of Mesenchymal Stromal Cells by Hydrogel Encapsulation

Mesenchymal stromal cells (MSCs) showcase remarkable immunoregulatory capabilities in vitro, positioning them as promising candidates for cellular therapeutics. However, the process of administering MSCs and the dynamic in vivo environment may impact the cell-cell and cell-matrix interactions of MSCs, consequently influencing their survival, engraftment, and their immunomodulatory efficacy. Addressing these concerns, hydrogel encapsulation emerges as a promising solution to enhance the therapeutic effectiveness of MSCs in vivo. Hydrogel, a highly flexible crosslinked hydrophilic polymer with a substantial water content, serves as a versatile platform for MSC encapsulation. Demonstrating improved engraftment and heightened immunomodulatory functions in vivo, MSCs encapsulated by hydrogel are at the forefront of advancing therapeutic outcomes. This review delves into current advancements in the field, with a focus on tuning various hydrogel parameters to elucidate mechanistic insights and elevate functional outcomes. Explored parameters encompass hydrogel composition, involving monomer type, functional modification, and co-encapsulation, along with biomechanical and physical properties like stiffness, viscoelasticity, topology, and porosity. The impact of these parameters on MSC behaviors and immunomodulatory functions is examined. Additionally, we discuss potential future research directions, aiming to kindle sustained interest in the exploration of hydrogel-encapsulated MSCs in the realm of immunomodulation.

Mesenchymal stem cells aligned and stretched in self-assembling peptide hydrogels

The presented research highlights a novel approach using fmoc-protected peptide hydrogels for the encapsulation and stretching of mesenchymal stem cells (MSCs). This study utilized a custom mechanical stretching device with a PDMS chamber to stretch human MSCs encapsulated in Fmoc hydrogels. The study assessed the influence of various solvents on the self-assembly and mechanical properties of the hydrogels, and MSC viability and alignment. Particularly we focused on fluorenylmethoxycarbonyl-diphenylalanine (Fmoc-FF) prepared in dimethyl sulfoxide (DMSO), hexafluoro-2-propanol (HFP), and deionized water (DiH2O). Through molecular self-assembly of the peptide sequence into β-sheets connected by π-π aromatic stacking of F-F groups, the peptide hydrogel was found to form a stiff, hydrated gel with nanofiber morphology and a compressive modulus ranging from 174 to 277 Pa. Therefore, this hydrogel can mimic certain critical features of the extracellular matrix and collagen. Evaluations of MSCs cultured on the peptide hydrogels, including viability, morphology, and alignment assessments using various staining techniques, demonstrated that 3D-cultured MSCs in Fmoc-FF/HFP and Fmoc-FF/DMSO, followed by mechanical stretching, exhibited elongated morphology with distinct microfilament fibers compared to the control cells, which maintained a round and spherical F-actin shape. Notably, peptide gels with a concentration of 5 mM maintained 100 % MSC viability. The findings indicate the potential and specific conditions for successful cell encapsulation and alignment within peptide hydrogels, highlighting a promising tissue engineering platform through the encapsulation of MSCs in peptide nanofibers followed by a stretching process. By enhancing our understanding of MSC-peptide hydrogel interactions, this research contributes to the development of biomaterials tailored for regenerative medicine.

Hybrid spheroids containing mesenchymal stem cells promote therapeutic angiogenesis by increasing engraftment of co-transplanted endothelial colony-forming cells in vivo

BACKGROUND

Peripheral artery disease is an ischemic vascular disease caused by the blockage of blood vessels supplying blood to the lower extremities. Mesenchymal stem cells (MSCs) and endothelial colony-forming cells (ECFCs) have been reported to alleviate peripheral artery disease by forming new blood vessels. However, the clinical application of MSCs and ECFCs has been impeded by their poor in vivo engraftment after cell transplantation. To augment in vivo engraftment of transplanted MSCs and ECFCs, we investigated the effects of hybrid cell spheroids, which mimic a tissue-like environment, on the therapeutic efficacy and survival of transplanted cells.

METHODS

The in vivo survival and angiogenic activities of the spheroids or cell suspension composed of MSCs and ECFCs were measured in a murine hindlimb ischemia model and Matrigel plug assay. In the hindlimb ischemia model, the hybrid spheroids showed enhanced therapeutic effects compared with the control groups, such as adherent cultured cells or spheroids containing either MSCs or ECFCs.

RESULTS

Spheroids from MSCs, but not from ECFCs, exhibited prolonged in vivo survival compared with adherent cultured cells, whereas hybrid spheroids composed of MSCs and ECFCs substantially increased the survival of ECFCs. Moreover, single spheroids of either MSCs or ECFCs secreted greater levels of pro-angiogenic factors than adherent cultured cells, and the hybrid spheroids of MSCs and ECFCs promoted the secretion of several pro-angiogenic factors, such as angiopoietin-2 and platelet-derived growth factor.

CONCLUSION

These results suggest that hybrid spheroids containing MSCs can serve as carriers for cell transplantation of ECFCs which have poor in vivo engraftment efficiency.

Mesenchymal stem cell-based therapy for non-healing wounds due to chronic limb-threatening ischemia: A review of preclinical and clinical studies

Progressive peripheral arterial disease (PAD) can result in chronic limb-threatening ischemia (CLTI) characterized by clinical complications including rest pain, gangrene and tissue loss. These complications can propagate even more precipitously in the setting of common concomitant diseases in patients with CLTI such as diabetes mellitus (DM). CLTI ulcers are cutaneous, non-healing wounds that persist due to the reduced perfusion and dysfunctional neovascularization associated with severe PAD. Existing therapies for CLTI are primarily limited to anatomic revascularization and medical management of contributing factors such as atherosclerosis and glycemic control. However, many patients fail these treatment strategies and are considered "no-option," thereby requiring extremity amputation, particularly if non-healing wounds become infected or fulminant gangrene develops. Given the high economic burden imposed on patients, decreased quality of life, and poor survival of no-option CLTI patients, regenerative therapies aimed at neovascularization to improve wound healing and limb salvage hold significant promise. Cell-based therapy, specifically utilizing mesenchymal stem/stromal cells (MSCs), is one such regenerative strategy to stimulate therapeutic angiogenesis and tissue regeneration. Although previous reviews have focused primarily on revascularization outcomes after MSC treatments of CLTI with less attention given to their effects on wound healing, here we review advances in pre-clinical and clinical studies related to specific effects of MSC-based therapeutics upon ischemic non-healing wounds associated with CLTI.

Gelatin Microspheres Loaded with Wharton's Jelly Mesenchymal Stem Cells Promote Acute Full-Thickness Skin Wound Healing and Regeneration in Mice

Objective: At present, there is an urgent need to develop a novel and practical therapeutic approach to accelerate the healing of acute wounds. Mesenchymal stem cell (MSC)-based therapy is emerging as a promising therapeutic approach for acute skin wounds. However, there are still challenges in clinical application of this strategy, such as low survivability, low retention time, and less engraftment in skin wounds. Approach: Wharton's jelly mesenchymal stem cells (WJMSCs) were seeded into three-dimensional (3D) gelatin microspheres (GMs) to identify the biocompatibility of GMs. WJMSCs were embedded in GMs and then encapsulated with Pluronic F-127 (PF-127) and sodium ascorbyl phosphate (SAP) combination to transplant onto acute full-thickness skin wound in mice. Histology, immunohistochemistry, and immunofluorescence assay were used to investigate the skin wound healing, dermis regeneration, collagen deposition, cell proliferation, and neovascularization. Results: Three-dimensional GM had strong biocompatibility, compared with two-dimensional adherent culturing, GM loading increased the cell viability and proliferation ability of WJMSCs. WJMSCs+GM+PF-127+SAP transplantation increased skin wound healing rate, dermis regeneration, and type III collagen deposition through improving macrophage polarization, cell proliferation, neovascularization, cell retention, and engraftment at skin wound site. Innovation: The effective 3D encapsulation technology for WJMSCs solved the main problems of cell activity and residence time during MSC transplantation. WJMSCs+GM+PF-127+SAP transplantation will be a new and effective MSC biomaterials-based therapeutic strategy for acute skin traumatic wounds. Conclusion: WJMSCs+GM+PF-127+SAP transplantation facilitated acute full-thickness skin wound healing and regeneration and might be a new and effective therapy for acute skin traumatic wounds.

pH/Thermosensitive dual-responsive hydrogel based sequential delivery for site-specific acute limb ischemia treatment

Acute limb ischemia (ALI) is the most severe manifestation of peripheral artery disease, accompanied by pH/temperature-microenvironment changes in two different phases. In the acute phase, temperature and pH are significantly decreased, and reactive oxygen species (ROS) are excessively generated owing to the sharp reduction of blood perfusion. Afterwards, in the chronic phase, although the temperature gradually recovers, angiogenesis is delayed due to chronic vascular injury, skeletal muscle cell apoptosis and endothelial cell dysfunction. Current therapeutic strategies mainly focus on recanalization; however, their effects on scavenging ROS in the acute phase and promoting angiogenesis in the chronic phase are quite limited. Herein, an injectable pH and temperature dual-responsive poloxamer 407 (PF127)/hydroxymethyl cellulose (HPMC)/sodium alginate (SA)-derived hydrogel (FHSgel), encapsulating melatonin and diallyl trisulfide-loaded biodegradable hollow mesoporous silica nanoparticles (DATS@dHMSNs), is developed, which can intelligently respond to the different phases of ALI. In the acute phase of ischemia, the decreased pH results in the rapid release of melatonin to scavenge excessive ischemia-induced ROS. On the other hand, in the chronic repair phase, the recovered temperature triggers the sustained release of DATS@dHMSNs from the FHSgel, thus generating hydrogen sulfide (H₂S) to enhance the angiogenesis and microcirculation reconstruction of ischemic limbs.

Therapeutic potential and molecular mechanisms of salidroside in ischemic diseases

Rhodiola is an ancient wild plant that grows in rock areas in high-altitude mountains with a widespread habitat in Asia, Europe, and America. From empirical belief to research studies, Rhodiola has undergone a long history of discovery, and has been used as traditional medicine in many countries and regions for treating high-altitude sickness, anoxia, resisting stress or fatigue, and for promoting longevity. Salidroside, a phenylpropanoid glycoside, is the main active component found in all species of Rhodiola. Salidroside could enhance cell survival and angiogenesis while suppressing oxidative stress and inflammation, and thereby has been considered a potential compound for treating ischemia and ischemic injury. In this article, we highlight the recent advances in salidroside in treating ischemic diseases, such as cerebral ischemia, ischemic heart disease, liver ischemia, ischemic acute kidney injury and lower limb ischemia. Furthermore, we also discuss the pharmacological functions and underlying molecular mechanisms. To our knowledge, this review is the first one that covers the protective effects of salidroside on different ischemia-related disease.

Advances for the treatment of lower extremity arterial disease associated with diabetes mellitus

Lower extremity arterial disease (LEAD) is a major vascular complication of diabetes. Vascular endothelial cells dysfunction can exacerbate local ischemia, leading to a significant increase in amputation, disability, and even mortality in patients with diabetes combined with LEAD. Therefore, it is of great clinical importance to explore proper and effective treatments. Conventional treatments of diabetic LEAD include lifestyle management, medication, open surgery, endovascular treatment, and amputation. As interdisciplinary research emerges, regenerative medicine strategies have provided new insights to treat chronic limb threatening ischemia (CLTI). Therapeutic angiogenesis strategies, such as delivering growth factors, stem cells, drugs to ischemic tissues, have also been proposed to treat LEAD by fundamentally stimulating multidimensional vascular regeneration. Recent years have seen the rapid growth of tissue engineering technology; tissue-engineered biomaterials have been used to study the treatment of LEAD, such as encapsulation of growth factors and drugs in hydrogel to facilitate the restoration of blood perfusion in ischemic tissues of animals. The primary purpose of this review is to introduce treatments and novel biomaterials development in LEAD. Firstly, the pathogenesis of LEAD is briefly described. Secondly, conventional therapies and therapeutic angiogenesis strategies of LEAD are discussed. Finally, recent research advances and future perspectives on biomaterials in LEAD are proposed.

Integrin receptor-binding nanofibrous peptide hydrogel for combined mesenchymal stem cell therapy and nitric oxide delivery in renal ischemia/reperfusion injury

Background

Mesenchymal-based therapy has been utilized as a practical approach in the treatment of renal ischemia/reperfusion (I/R) injury. However, low cell retention and survival in the ischemic site have remained challenging issues. To bridge this gap, the integrin receptor-binding RGD peptide-functionalized, s-nitroso-n-acetyl penicillamine (SNAP)-loaded hydrogel was used to transplant Wharton's jelly-mesenchymal stem cells (WJ-MSCs).

Methods

Apart from physicochemical and rheological characterizations that confirmed entangled interlocking β-sheets with nanofibrous morphology, real-time RT-PCR, ROS production, serum biomarker concentrations, and histopathological alterations were explored in a mouse model to assess the therapeutic efficacy of formulations in the treatment of renal I/R injury.

Results

The RGD-functionalized Fmoc-diphenylalanine (Fmoc-FF + Fmoc-RGD) hydrogel supported the spread and proliferation of WJ-MSCs in vivo. Notably, intralesional injection of nitric oxide donor combined with the embedded WJ-MSCs caused superior recovery of renal I/R injury compared to free WJ-MSCs alone in terms of histopathological scores and renal function indices. Compared to the I/R control group, oxidative stress and inducible nitric oxide synthase (iNOS) expression biomarkers showed a significant decline, whereas endothelial nitric oxide synthase (eNOS) and vascular endothelial growth factor (VEGF) expression exhibited a significant increment, indicating regeneration of the injured endothelial tissue.

Conclusion

The findings confirmed that the hydrogels containing WJ-MSCs and nitric oxide donors can promote the regeneration of renal I/R injuries by increasing angiogenic factors and cell engraftment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-03045-1.

Therapeutic angiogenesis-based strategy for peripheral artery disease

Peripheral artery disease (PAD) poses a great challenge to society, with a growing prevalence in the upcoming years. Patients in the severe stages of PAD are prone to amputation and death, leading to poor quality of life and a great socioeconomic burden. Furthermore, PAD is one of the major complications of diabetic patients, who have higher risk to develop critical limb ischemia, the most severe manifestation of PAD, and thus have a poor prognosis. Hence, there is an urgent need to develop an effective therapeutic strategy to treat this disease. Therapeutic angiogenesis has raised concerns for more than two decades as a potential strategy for treating PAD, especially in patients without option for surgery-based therapies. Since the discovery of gene-based therapy for therapeutic angiogenesis, several approaches have been developed, including cell-, protein-, and small molecule drug-based therapeutic strategies, some of which have progressed into the clinical trial phase. Despite its promising potential, efforts are still needed to improve the efficacy of this strategy, reduce its cost, and promote its worldwide application. In this review, we highlight the current progress of therapeutic angiogenesis and the issues that need to be overcome prior to its clinical application.

Mesenchymal Stromal Cells Combined With Elastin-Like Recombinamers Increase Angiogenesis In Vivo After Hindlimb Ischemia

Hindlimb ischemia is an unmet medical need, especially for those patients unable to undergo vascular surgery. Cellular therapy, mainly through mesenchymal stromal cell (MSC) administration, may be a potentially attractive approach in this setting. In the current work, we aimed to assess the potential of the combination of MSCs with a proangiogenic elastin-like recombinamer (ELR)–based hydrogel in a hindlimb ischemia murine model. Human bone marrow MSCs were isolated from four healthy donors, while ELR biomaterials were genetically engineered. Hindlimb ischemia was induced through ligation of the right femoral artery, and mice were intramuscularly injected with ELR biomaterial, 0.5 × 10⁶ MSCs or the combination, and also compared to untreated animals. Tissue perfusion was monitored using laser Doppler perfusion imaging. Histological analysis of hindlimbs was performed after hematoxylin and eosin staining. Immunofluorescence with anti–human mitochondria antibody was used for human MSC detection, and the biomaterial was detected by elastin staining. To analyze the capillary density, immunostaining with an anti–CD31 antibody was performed. Our results show that the injection of MSCs significantly improves tissue reperfusion from day 7 (p = 0.0044) to day 21 (p = 0.0216), similar to the infusion of MSC + ELR (p = 0.0038, p = 0.0014), without significant differences between both groups. After histological evaluation, ELR hydrogels induced minimal inflammation in the injection sites, showing biocompatibility. MSCs persisted with the biomaterial after 21 days, both in vitro and in vivo. Finally, we observed a higher blood vessel density when mice were treated with MSCs compared to control (p<0.0001), but this effect was maximized and significantly different to the remaining experimental conditions when mice were treated with the combination of MSCs and the ELR biomaterial (p < 0.0001). In summary, the combination of an ELR-based hydrogel with MSCs may improve the angiogenic effects of both strategies on revascularization of ischemic tissues.

Intravenously transplanted mesenchymal stromal cells: a new endocrine reservoir for cardioprotection

Background

Intravenous administration of mesenchymal stromal cells (MSCs) has an acknowledged competence of cardiac repair, despite a lack of systematic description of the underlying biological mechanisms. The lung, but not the heart, is the main trapped site for intravenously transplanted MSCs, which leaves a spatial gap between intravenously transplanted MSCs and the injured myocardium. How lung-trapped MSCs after intravenous transplantation rejuvenate the injured myocardium remains unknown.

Methods

MSCs were isolated from human placenta tissue, and DF-MSCs or Gluc-MSCs were generated by transduced with firefly luciferase (Fluc)/enhanced green fluorescence protein (eGFP) or Gaussia luciferase (Gluc) lactadherin fusion protein. The therapeutic efficiency of intravenously transplanted MSCs was investigated in a murine model of doxorubicin (Dox)-induced cardiotoxicity. Trans-organ communication from the lung to the heart with the delivery of blood was investigated by testing the release of MSC-derived extracellular vesicles (MSC-EVs), and the potential miRNA inner MSC-EVs were screened out and verified. The potential therapeutic miRNA inner MSC-EVs were then upregulated or downregulated to assess the further therapeutic efficiency

Results

Dox-induced cardiotoxicity, characterized by cardiac atrophy, left ventricular dysfunction, and injured myocardium, was alleviated by consecutive doses of MSCs. These cardioprotective effects might be attributed to suppressing GRP78 triggering endoplasmic reticulum (ER) stress-induced apoptosis in cardiomyocytes. Our results confirmed that miR-181a-5p from MSCs-derived EVs (MSC-EVs) inhibited GRP78. Intravenous DF-MSCs were trapped in lung vasculature, secreted a certain number of EVs into serum, which could be confirmed by the detection of eGFP⁺ EVs. GLuc activity was increased in serum EVs from mice administrated with GLuc-MSCs. MiR-181a-5p, inhibiting GRP78 with high efficacy, was highly expressed in serum EVs and myocardium after injecting consecutive doses of MSCs into mice treated with Dox. Finally, upregulation or downregulation of miR-181a-5p levels in MSC-EVs enhanced or weakened therapeutic effects on Dox-induced cardiotoxicity through modulating ER stress-induced apoptosis.

Conclusions

This study identifies intravenously transplanted MSCs, as an endocrine reservoir, to secrete cardioprotective EVs into blood continuously and gradually to confer the trans-organ communication that relieves Dox-induced cardiotoxicity.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-02922-z.

An amelogenin-based peptide hydrogel promoted the odontogenic differentiation of human dental pulp cells

Amelogenin can induce odontogenic differentiation of human dental pulp cells (HDPCs), which has great potential and advantages in dentine-pulp complex regeneration. However, the unstability of amelogenin limits its further application. This study constructed amelogenin self-assembling peptide hydrogels (L-gel or D-gel) by heating-cooling technique, investigated the effects of these hydrogels on the odontogenic differentiation of HDPCs and explored the underneath mechanism. The critical aggregation concentration, conformation, morphology, mechanical property and biological stability of the hydrogels were characterized, respectively. The effects of the hydrogels on the odontogenic differentiation of HDPCs were evaluated via alkaline phosphatase activity measurement, quantitative reverse transcription polymerase chain reaction, western blot, Alizarin red staining and scanning electron microscope. The mechanism was explored via signaling pathway experiments. Results showed that both the L-gel and D-gel stimulated the odontogenic differentiation of HDPCs on both Day 7 and Day 14, while the D-gel showed the highest enhancement effects. Meanwhile, the D-gel promoted calcium accumulation and mineralized matrix deposition on Day 21. The D-gel activated MAPK-ERK1/2 pathways in HDPCs and induced the odontogenic differentiation via ERK1/2 and transforming growth factor/smad pathways. Overall, our study demonstrated that the amelogenin peptide hydrogel stimulated the odontogenic differentiation and enhanced mineralization, which held big potential in the dentine-pulp complex regeneration.

FEK self-assembled peptide hydrogels facilitate primary hepatocytes culture and pharmacokinetics screening

A FEFEFKFK (FEK, F, phenylalaninyl; E, glutamyl; K, lysinyl)-based self-assembling peptide hydrogel (FEK-SAPH) was developed to replace sandwich culture (SC) for improved culture of primary hepatocytes in vitro. Under neutral conditions, FEK self-assembles to form β-sheet nanofibers, which in turn form FEK-SAPH. For the culture of rat primary hepatocytes (RPH), the use of FEK-SAPH simplified operation steps and promoted excellent cell-cell interactions while maintaining the SC-related RPH polarity trend. Compared with SC, FEK-SAPH cultured RPH for 14 days, the bile duct network was formed, the secretion of albumin and urea was improved, and the metabolic clearance rate based on cytochrome P450 (CYPs) was comparable. In FEK-SAPH culture, the expression level of the biliary efflux transporter bile salt export pump increased by 230.7%, while the biliary excretion index value of deuterium-labeled sodium taurocholate (d8-TCA) differed slightly from the SC value (72% and 77%, respectively, p = .0195). The inhibitory effect of cholestasis drugs on FEK-SAPH was significantly higher than that of SC. In FEK-SAPH, hepatoprotective drugs were more effective in antagonizing hepatotoxicity induced by lithocholic acid (LCA). FEK-SAPH cultured RPH with hepatoprotective drugs can better recover from LCA-induced damage. In summary, FEK-SAPH can be used as a substitute for SC for pharmacokinetic screening to evaluate the drug absorption, disposition, metabolism, excretion, and toxicity (ADMET) in hepatocytes.

The sustained PGE2 release matrix improves neovascularization and skeletal muscle regeneration in a hindlimb ischemia model

BACKGROUND

The promising therapeutic strategy for the treatment of peripheral artery disease (PAD) is to restore blood supply and promote regeneration of skeletal muscle regeneration. Increasing evidence revealed that prostaglandin E₂ (PGE₂), a lipid signaling molecule, has significant therapeutic potential for tissue repair and regeneration. Though PGE₂ has been well reported in tissue regeneration, the application of PGE₂ is hampered by its short half-life in vivo and the lack of a viable system for sustained release of PGE₂.

RESULTS

In this study, we designed and synthesized a new PGE₂ release matrix by chemically bonding PGE₂ to collagen. Our results revealed that the PGE₂ matrix effectively extends the half-life of PGE₂ in vitro and in vivo. Moreover, the PGE₂ matrix markedly improved neovascularization by increasing angiogenesis, as confirmed by bioluminescence imaging (BLI). Furthermore, the PGE₂ matrix exhibits superior therapeutic efficacy in the hindlimb ischemia model through the activation of MyoD1-mediated muscle stem cells, which is consistent with accelerated structural recovery of skeletal muscle, as evidenced by histological analysis.

CONCLUSIONS

Our findings highlight the chemical bonding strategy of chemical bonding PGE₂ to collagen for sustained release and may facilitate the development of PGE₂-based therapies to significantly improve tissue regeneration.

Effect of extracellular matrix proteins on the differentiation of human pluripotent stem cells into mesenchymal stem cells

The transplantation of human mesenchymal stem cells (hMSCs), such as bone marrow stem cells (BMSCs) and adipose-derived stem cells (ADSCs), has shown beneficial effects in protecting transplanted tissues and cells...

The role of mesenchymal stem cells in liver injury

Recently, mesenchymal stem cell (MSC) therapy has been suggested as an effective alternate approach for the treatment of hepatic diseases. MSCs have potential therapeutic value, because these have high self-renewal ability, are capable of multipotent differentiation, and have low immunogenicity. Furthermore, MSCs have the potential to differentiate into hepatocytes, and the therapeutic value exists in their immune-modulatory properties and secretion of trophic factors, such as growth factors and cytokines. Moreover, MSCs can suppress inflammatory responses, reduce hepatocyte apoptosis, increase hepatocyte regeneration, regress liver fibrosis, and enhance liver functionality. This article is protected by copyright. All rights reserved.

Placenta: A gold mine for translational research and regenerative medicine

Stem cell therapy has gained much impetus in regenerative medicine due to some of the encouraging results obtained in the laboratory as well as in translational/clinical studies. Although stem cells are of various types and their therapeutic potential has been documented in several studies, mesenchymal stromal/stem cells (MSCs) have an edge, as in addition to being multipotent, these cells are easy to obtain and expand, pose fewer ethical issues, and possess immense regenerative potential when used in a scientifically correct manner. Currently, MSCs are being sourced from various tissues such as bone marrow, cord, cord blood, adipose tissue, dental tissue, etc., and, quite often, the choice depends on the availability of the source. One such rich source of tissue suitable for obtaining good quality MSCs in large numbers is the placenta obtained in a full-term delivery leading to a healthy child's birth. Several studies have demonstrated the regenerative potential of human placenta-derived MSCs (hPMSC), and most show that these MSCs possess comparable, in some instances, even better, therapeutic potential as that shown by human bone marrow-derived (hBMSC) or human umbilical cord-derived (hUC-MSC) MSCs. The placenta can be easily sourced from the OB/GYN department of any hospital, and if its derivatives such as hPMSC or their EVs are produced under GMP conditions, it could serve as a gold mine for translational/clinical research. Here, we have reviewed recent studies revealing the therapeutic potential of hPMSC and their extracellular vesicles (EVs) published over the past three years.

Hydrogel-based therapeutic angiogenesis: An alternative treatment strategy for critical limb ischemia

Critical limb ischemia (CLI) is the most severe clinical manifestation of peripheral arterial disease (PAD), resulting in the total or partial loss of limb function. Although the conventional treatment strategy of CLI (e.g., medical treatment and surgery) can improve blood perfusion and restore limb function, many patients are unsuitable for these strategies and they still face the threats of amputation or death. Therapeutic angiogenesis, as a potential solution for these problems, attempts to manipulate blood vessel growth in vivo for augment perfusion without the help of extra pharmaceutics and surgery. With the rise of interdisciplinary research, regenerative medicine strategies provide new possibilities for treating many clinical diseases. Hydrogel, as an excellent biocompatibility material, is an ideal candidate for delivering bioactive molecules and cells for therapeutic angiogenesis. Besides, hydrogel could precisely deliver, control release, and keep the bioactivity of cargos, making hydrogel-based therapeutic angiogenesis a new strategy for CLI therapy. In this review, we comprehensively discuss the approaches of hydrogel-based strategy for CLI treatment as well as their challenges, and future directions.

Therapeutic Biomaterial Approaches to Alleviate Chronic Limb Threatening Ischemia

Chronic limb threatening ischemia (CLTI) is a severe condition defined by the blockage of arteries in the lower extremities that leads to the degeneration of blood vessels and is characterized by the formation of non-healing ulcers and necrosis. The gold standard therapies such as bypass and endovascular surgery aim at the removal of the blockage. These therapies are not suitable for the so-called "no option patients" which present multiple artery occlusions with a likelihood of significant limb amputation. Therefore, CLTI represents a significant clinical challenge, and the efforts of developing new treatments have been focused on stimulating angiogenesis in the ischemic muscle. The delivery of pro-angiogenic nucleic acid, protein, and stem cell-based interventions have limited efficacy due to their short survival. Engineered biomaterials have emerged as a promising method to improve the effectiveness of these latter strategies. Several synthetic and natural biomaterials are tested in different formulations aiming to incorporate nucleic acid, proteins, stem cells, macrophages, or endothelial cells in supportive matrices. In this review, an overview of the biomaterials used alone and in combination with growth factors, nucleic acid, and cells in preclinical models is provided and their potential to induce revascularization and regeneration for CLTI applications is discussed.

Bioengineering strategies for the treatment of peripheral arterial disease

Peripheral arterial disease (PAD) is a progressive atherosclerotic disorder characterized by narrowing and occlusion of arteries supplying the lower extremities. Approximately 200 million people worldwide are affected by PAD. The current standard of operative care is open or endovascular revascularization in which blood flow restoration is the goal. However, many patients are not appropriate candidates for these treatments and are subject to continuous ischemia of their lower limbs. Current research in the therapy of PAD involves developing modalities that induce angiogenesis, but the results of simple cell transplantation or growth factor delivery have been found to be relatively poor mainly due to difficulties in stem cell retention and survival and rapid diffusion and enzymolysis of growth factors following injection of these agents in the affected tissues. Biomaterials, including hydrogels, have the capability to protect stem cells during injection and to support cell survival. Hydrogels can also provide a sustained release of growth factors at the injection site. This review will focus on biomaterial systems currently being investigated as carriers for cell and growth factor delivery, and will also discuss biomaterials as a potential stand-alone method for the treatment of PAD. Finally, the challenges of development and use of biomaterials systems for PAD treatment will be reviewed.

A nitric oxide-releasing hydrogel for enhancing the therapeutic effects of mesenchymal stem cell therapy for hindlimb ischemia

Therapeutic angiogenesis with mesenchymal stem cells (MSCs) is promising for the clinical treatment of peripheral artery disease (PAD). However, the heterogeneous proangiogenic nature of MSCs is a key challenge in developing more effective treatments with MSCs for therapeutic angiogenesis purposes. Here, we propose to enhance the therapeutic function of human placenta-derived MSCs (hP-MSCs) in hindlimb ischemia therapy by using nitric oxide (NO)-releasing chitosan hydrogel (CS-NO). Our data showed that the co-transplantation of CS-NO hydrogel with hP-MSCs remarkably improved the grafting of hP-MSCs and ameliorated the functional recovery of ischemic hindlimbs. Moreover, we found that the neovascularization of damaged hindlimbs was significantly increased after co-transplanting CS-NO hydrogel and hP-MSCs, as confirmed by bioluminescence imaging (BLI). Further analysis revealed an endothelial-like status transformation of hP-MSCs in the presence of NO, which was identified as a potential mechanism contributing to the enhanced endothelium-protective and proangiogenic capacities of hP-MSCs that promote angiogenesis in mouse models of hindlimb ischemia. In conclusion, this study provides a promising approach for using NO hydrogel to improve the proangiogenic potency of MSCs in ischemic diseases, and the strategy used here facilitates the development of controlled-release scaffolds for enhancing the therapeutic efficiency of MSCs in angiogenic therapy. STATEMENT OF SIGNIFICANCE: The heterogeneous proangiogenic nature of mesenchymal stem cells (MSCs) is a key challenge in developing more effective treatments with MSCs for therapeutic angiogenesis purposes. In this study, we investigated whether nitric oxide (NO)-releasing chitosan hydrogel (CS-NO) could improve the proangiogenic potency of MSCs in ischemic diseases. Our results revealed an endothelial-like status transformation of human placenta-derived MSCs (hP-MSCs) in the presence of NO, which was identified as a potential mechanism contributing to the enhanced endothelium-protective and proangiogenic capacities of hP-MSCs that promote angiogenesis in mouse models of hindlimb ischemia. The strategy for enhancing the pro-angiogenic activity of MSCs with biomaterials provides a practical idea for overcoming the challenges associated with the clinical application of MSCs in therapeutic angiogenesis.

Micropatterning Decellularized ECM as a Bioactive Surface to Guide Cell Alignment, Proliferation, and Migration

Bioactive surfaces and materials have displayed great potential in a variety of tissue engineering applications but often struggle to completely emulate complex bodily systems. The extracellular matrix (ECM) is a crucial, bioactive component in all tissues and has recently been identified as a potential solution to be utilized in combination with biomaterials. In tissue engineering, the ECM can be utilized in a variety of applications by employing the biochemical and biomechanical cues that are crucial to regenerative processes. However, viable solutions for maintaining the dimensionality, spatial orientation, and protein composition of a naturally cell-secreted ECM remain challenging in tissue engineering. Therefore, this work used soft lithography to create micropatterned polydimethylsiloxane (PDMS) substrates of a three-dimensional nature to control cell adhesion and alignment. Cells aligned on the micropatterned PDMS, secreted and assembled an ECM, and were decellularized to produce an aligned matrix biomaterial. The cells seeded onto the decellularized, patterned ECM showed a high degree of alignment and migration along the patterns compared to controls. This work begins to lay the groundwork for elucidating the immense potential of a natural, cell-secreted ECM for directing cell function and offers further guidance for the incorporation of natural, bioactive components for emerging tissue engineering technologies.

Enhanced therapeutic effects of MSC-derived extracellular vesicles with an injectable collagen matrix for experimental acute kidney injury treatment

BACKGROUND

Mesenchymal stem cell (MSC)-derived extracellular vesicles (EVs) have been shown to have therapeutic potential for ischemic diseases and are considered an alternative to cell therapy. However, the low retention and poor stability of EVs post-transplantation in vivo remain obstacle prior to the clinical application of EVs.

METHODS

This study was designed to investigate whether collagen matrix could increase the retention and stability of EVs and further improve the therapeutic effects in murine acute kidney injury (AKI) model. EVs were isolated from human placental MSCs (hP-MSC-EVs) and encapsulated in a collagen matrix. Then, we investigated whether collagen matrix can prolong the retention of EVs in vivo, further enhancing the therapeutic efficiency of EVs in AKI.

RESULTS

Our results indicated that collagen matrix could effectively encapsulate EVs, significantly increase the stability of EVs, and promote the sustained release of EVs. Collagen matrix has improved the retention of EVs in the AKI model, which was proved by Gaussia luciferase (Gluc) imaging. The application of collagen matrix remarkably facilitated the proliferation of renal tubular epithelial cells in AKI compared with EVs alone. Moreover, collagen matrix could further augment the therapeutic effects of hP-MSC-EVs as revealed by angiogenesis, fibrosis and apoptosis, and functional analysis. Finally, we found that EVs play a therapeutic role by inhibiting endoplasmic reticulum (ER) stress.

CONCLUSIONS

Collagen matrix markedly enhanced the retention of EVs and further augmented the therapeutic effects of EVs for AKI. This strategy for improving the efficacy of EVs therapy provides a new direction for cell-free therapy.

Molecular mechanism underlying the difference in proliferation between placenta-derived and umbilical cord-derived mesenchymal stem cells

The placenta and umbilical cord are pre-eminent candidate sources of mesenchymal stem cells (MSCs). However, placenta-derived MSCs (P-MSCs) showed greater proliferation capacity than umbilical cord-derived MSCs (UC-MSCs) in our study. We investigated the drivers of this proliferation difference and elucidated the mechanisms of proliferation regulation. Proteomic profiling and Gene Ontology (GO) functional enrichment were conducted to identify candidate proteins that may influence proliferation. Using lentiviral or small interfering RNA infection, we established overexpression and knockdown models and observed changes in cell proliferation to examine whether a relationship exists between the candidate proteins and proliferation capacity. Real-time quantitative polymerase chain reaction, western blot analysis, and immunofluorescence assays were conducted to elucidate the mechanisms underlying proliferation. Six candidate proteins were selected based on the results of proteomic profiling and GO functional enrichment. Through further validation, yes-associated protein 1 (YAP1) and β-catenin were confirmed to affect MSCs proliferation rates. YAP1 and β-catenin showed increased nuclear colocalization during cell expansion. YAP1 overexpression significantly enhanced proliferation capacity and upregulated the expression of both β-catenin and the transcriptional targets of Wnt signaling, CCND1, and c-MYC, whereas silencing β-catenin attenuated this influence. We found that YAP1 directly interacts with β-catenin in the nucleus to form a transcriptional YAP/β-catenin/TCF4 complex. Our study revealed that YAP1 and β-catenin caused the different proliferation capacities of P-MSCs and UC-MSCs. Mechanism analysis showed that YAP1 stabilized the nuclear β-catenin protein, and also triggered the Wnt/β-catenin pathway, promoting proliferation.

Human umbilical cord mesenchymal stem cell derived exosomes encapsulated in functional peptide hydrogels promote cardiac repair

Stem cell-derived exosomes have been recognized as a potential therapy for cardiovascular disease. However, the low retention rate of exosomes after transplantation in vivo remains a major challenge in clinical applications. The aim of this study is to investigate whether human umbilical cord mesenchymal stem cell derived exosomes (UMSC-Exo) encapsulated in functional peptide hydrogels could increase the retention and stability of exosomes and improve heart function in a rat myocardial infarction model. Our results demonstrated that the PA-GHRPS peptide protected H9C2 cells from H2O2-induced oxidative stress. The gelatinization ability of PA-GHRPS can be enhanced by peptide NapFF. Therefore, these two peptides were mixed to form the PGN hydrogel, which was used to encapsulate exosomes. Our data showed that the PGN hydrogel was able to encapsulate exosomes effectively and ensured a stable and sustained release of exosomes. The exosome/PGN hydrogel mixture was injected into the infarcted border zone of rat hearts. Compared to the exosome treatment alone, the mixture improved the myocardial function by reducing inflammation, fibrosis and apoptosis, and by promoting angiogenesis. The strategy used in this study provided a practical and effective method to harness exosomes for myocardial regeneration.