Diabetes diminishes muscle precursor cell-mediated microvascular angiogenesis.

The skeletal muscles of Type II diabetic (T2D) patients can be characterized by a reduced vessel density, corresponding to deficiencies in microvascular angiogenesis. Interestingly, T2D also inhibits the function of many myogenic cells resident within skeletal muscle, including satellite cells, which are well-known for the role they play in maintaining homeostasis. The current study was undertaken to gain a better understanding of the mechanisms whereby satellite cell progeny, muscle precursor cells (MPCs), influence microvascular angiogenesis. Network growth and the expression of genes associated with angiogenesis were reduced when microvessels were treated with conditioned media generated by proliferating MPCs isolated from diabetic, as compared to control rat skeletal muscle, a phenomenon that was also observed when myoblasts from control or diabetic human skeletal muscle were used. When only exosomes derived from diabetic or control MPCs were used to treat microvessels, no differences in microvascular growth were observed. An evaluation of the angiogenesis factors in control and diabetic MPCs revealed differences in Leptin, vascular endothelial growth factor (VEGF), IL1-ß, interleukin 10, and IP-10, and an evaluation of the MPC secretome revealed differences in interleukin 6, MCP-1, VEGF, and interleukin 4 exist. Angiogenesis was also reduced in tissue-engineered skeletal muscles (TE-SkM) containing microvessels when they were generated from MPCs isolated from diabetic as compared to control skeletal muscle. Lastly, the secretome of injured control, but not diabetic, TE-SkM was able to increase VEGF and increase microvascular angiogenesis. This comprehensive analysis of the interaction between MPCs and microvessels in the context of diabetes points to an area for alleviating the deleterious effects of diabetes on skeletal muscle.

Three-Dimensional Culture of Vascularized Thermogenic Adipose Tissue from Microvascular Fragments.

Engineering thermogenic adipose tissue (e.g., beige or brown adipose tissues) has been investigated as a potential therapy for metabolic diseases or for the design of personalized microtissues for health screening and drug testing. Current strategies are often quite complex and fail to accurately fully depict the multicellular and functional properties of thermogenic adipose tissue. Microvascular fragments, small intact microvessels comprised of arteriole, venules, and capillaries isolated from adipose tissue, serve as a single autologous source of cells that enable vascularization and adipose tissue formation. This article describes methods for optimizing culture conditions to enable the generation of three-dimensional, vascularized, and functional thermogenic adipose tissues from microvascular fragments, including protocols for isolating microvascular fragments from adipose tissue and culture conditions. Additionally, best practices are discussed, as are techniques for characterizing the engineered tissues, and sample results from both rodent and human microvascular fragments are provided. This approach has the potential to be utilized for the understanding and development of treatments for obesity and metabolic disease.

Nanoparticle-Reinforced Tough Hydrogel as a Versatile Platform for Pharmaceutical Drug Delivery: Preparation and in Vitro Characterization.

Natural polymer-based hydrogels are excellent for encapsulating hydrophilic drugs, but they are mechanically weak and degrade easily. In this communication, we exploit the electrostatic interaction between nanosilicates (nSi) and gelatin methacrylate (GelMA) to form a mechanically tough nanocomposite hydrogel for pharmaceutical drug delivery. These hydrogels, prepared at subzero temperatures to form cryogels, displayed macroporous structures, which favors cell infiltration. The designed tough cryogel also showed a slower rate of degradation. Furthermore, we encapsulated the small molecule metformin and sustained the drug release under physiological conditions. Cryogel-loaded metformin reduced the effect of endothelial cell injury caused by nutrient deprivation in vitro. Finally, we hypothesize that this versatile nanocomposite material will find use in diverse biomedical applications.

Investigation of human adipose-derived stem-cell behavior using a cell-instructive polydopamine-coated gelatin-alginate hydrogel.

Hydrogels can be fabricated and designed to exert direct control over stem cells' adhesion and differentiation. In this study, we have investigated the use of polydopamine (pDA)-treatment as a binding platform for bioactive compounds to create a versatile gelatin-alginate (Gel-Alg) hydrogel for tissue engineering applications. Precisely, pDA was used to modify the surface properties of the hydrogel and better control the adhesion and osteogenic differentiation of human adipose-derived stem cells (hASCs). pDA enabled the adsorption of different types of bioactive molecules, including a model osteoinductive drug (dexamethasone) as well as a model pro-angiogenic peptide (QK). The pDA treatment efficiently retained the drug and the peptide compared to the untreated hydrogel and proved to be effective in controlling the morphology, cell area, and osteogenic differentiation of hASCs. Overall, the findings of this study confirm the efficacy of pDA treatment as a valuable strategy to modulate the biological properties of biocompatible Gel-Alg hydrogels and further extend their value in regenerative medicine.

Diabetic Conditions Confer Metabolic and Structural Modifications to Tissue-Engineered Skeletal Muscle.

Skeletal muscle is a tissue that is directly involved in the progression and persistence of type 2 diabetes (T2D), a disease that is becoming increasingly common. Gaining better insight into the mechanisms that are affecting skeletal muscle dysfunction in the context of T2D has the potential to lead to novel treatments for a large number of patients. Through its ability to emulate skeletal muscle architecture while also incorporating aspects of disease, tissue-engineered skeletal muscle (TE-SkM) has the potential to provide a means for rapid high-throughput discovery of therapies to treat skeletal muscle dysfunction, to include that which occurs with T2D. Muscle precursor cells isolated from lean or obese male Zucker diabetic fatty rats were used to generate TE-SkM constructs. Some constructs were treated with adipogenic induction media to accentuate the presence of adipocytes that is a characteristic feature of T2D skeletal muscle. The maturity (compaction and creatine kinase activity), mechanical integrity (Young's modulus), organization (myotube orientation), and metabolic capacity (insulin-stimulated glucose uptake) were all reduced by diabetes. Treating constructs with adipogenic induction media increased the quantity of lipid within the diabetic TE-SkM constructs, and caused changes in construct compaction, cell orientation, and insulin-stimulated glucose uptake in both lean and diabetic samples. Collectively, the findings herein suggest that the recapitulation of structural and metabolic aspects of T2D can be accomplished by engineering skeletal muscle in vitro.

Dextran-polyethylene glycol cryogels as spongy scaffolds for drug delivery.

Cryogels are a particular type of hydrogels that possess great potential in both fields of drug delivery and tissue engineering. Based on these premises, the goal of this work was to develop a cytocompatible polymeric cryogel, which could be used as a spongy scaffold to promote the delivery of biomolecules. Precisely, the novel formulation was fabricated by combining dextran methacrylate (DEX-MA) and polyethylene glycol dimethacrylate (PEG-DMA) through radical polymerization at a temperature of -15 °C. The swelling, porosity, mechanical properties, and the drug release profile of vitamin B12 from the optimized cryogel were evaluated and compared to hydrogels fabricated at room temperature. The use of the cryo-gelation technique enabled the formation of scaffolds with improved swelling, increased interconnected porosity, and higher mechanical resistance than conventional hydrogels. The cryogels proved to be non-toxic and suitable carriers for the delivery of water-soluble biomolecules. Overall, the novel cytocompatible cryogel formulation could be used for biomedical applications that require the need of a macroporous scaffold for localized delivery of bioactive molecules.

Investigation of human adipose stem cell-derived nanoparticles as a biomimetic carrier for intracellular drug delivery.

Prevailing drug delivery strategies rely on the use of synthetic nanocarriers like metal nanoparticles and polymeric liposomes to control the release of therapeutics in a safe and efficacious manner. Despite their high efficiency in encapsulating drugs, these systems exhibit low to moderate biocompatibility, low cellular uptake, and sub-optimal targeting capabilities. Conversely, cell-derived nanoparticles (CDNs) have emerged as a promising alternative to these artificial drug delivery carriers for achieving safer clinical outcomes. In this study, we have generated CDNs from human adipose-derived stem cells (hASCs) using a high-yield fabrication strategy. Briefly, hASCs were subjected to a cell-shearing approach that entails passing the cells through an array of filters, along with serial centrifugations to eliminate intracellular contents. Ultimately, the fragmented parent cell membrane self-assembles to form the CDNs. This strategy successfully converted 80% of the plasma membrane into the novel nanocarriers with an average hydrodynamic diameter of 100 nm. Stability analysis confirmed that the formulated nanocarriers are stable for over 3 weeks, making them a potent candidate for long-term therapies. To demonstrate their potential in drug delivery, we encapsulated trehalose, a cell-impermeable sugar molecule, into the CDNs via an extrusion loading technique. Drug-loaded CDNs were effectively internalized into human umbilical vein endothelial cells (HUVECs) and hASCs, without inducing any significant cytotoxicity. Overall, the findings of this study establish the potential of hASC-derived CDNs as customizable biomimetic nanocarriers for drug delivery and other translational medicine applications.

Divergent effects of myogenic differentiation and diabetes on the capacity for muscle precursor cell adipogenic differentiation in a fibrin matrix.

The development of ectopic adipose tissue in skeletal muscle is associated with several skeletal muscle and metabolic pathologies, including Type II Diabetes Mellitus. The adipogenic differentiation of muscle precursor cells (MPCs) has been postulated to occur in skeletal muscle in vivo in a three-dimensional (3-D) configuration; therefore, it is appropriate to investigate this phenomenon using 3-D matrices in vitro. The capacity for MPC adipogenic differentiation in a 3-D environment was investigated in fibrin hydrogels by treating MPCs derived from healthy or diabetic animals with adipogenic induction medias that differed in their ability to increase lipid accumulation and activate the expression of genes associated with adipogenic differentiation (peroxisome proliferator-activated receptor gamma (PPARG), adiponectin (ADIPOQ), and fatty acid synthase (FAS)). The capacity for adipogenic differentiation was diminished, but not prevented, if myogenic differentiation preceded MPC exposure to adipogenic induction conditions. Conversely, adipogenic differentiation was greater in hydrogels containing MPCs from diabetic rats as compared to those derived from lean rats, as evidenced by an increase in lipid accumulation and adipogenic gene expression. Collectively, the data herein support a role for the MPCs in adipogenesis in a 3-D environment and that they may contribute to the ectopic accumulation of adipose tissue. The observation that the potential for adipogenic differentiation is maintained even after a period of myogenic differentiation alludes to the possibility that adipogenesis may occur during different phases of muscle development. Finally, the increase in adipogenic differentiation in hydrogels containing MPCs derived from diabetic animals provides strong evidence that a pathological environment in vivo increases their capacity for adipogenesis.

Self-healing DNA-based injectable hydrogels with reversible covalent linkages for controlled drug delivery.

Injectable hydrogels represent a valuable tool for the delivery of therapeutic molecules aimed to restore the functionality of damaged tissues. In this study, we report the design of a nanocomposite DNA-based hydrogel crosslinked with oxidized alginate (OA) via the formation of reversible imine linkages. The formulated hydrogel functioned as an injectable carrier for the sustained delivery of a small molecule drug, simvastatin. The degree of oxidation of alginate and the concentration of silicate-based nanoparticles (nSi) were varied to modulate the rheological properties of the hydrogels. Specifically, the formulations consisting of OA with higher degree of oxidation displayed the highest value of storage moduli, yield stress, yield strain, and rapid recovery after removal of cyclic stress. The hydrogel formulations exhibited self-healing and shear-thinning properties due to the reversible nature of the covalent imine bonds formed between the aldehyde groups of OA and the amine groups present in the DNA nucleotides. Moreover, the incorporation of charged nSi further enhanced the shear strength of the formulated hydrogels by establishing electrostatic interactions with the phosphate groups of the DNA network. The optimized hydrogel was able to promote the sustained release of simvastatin for more than a week. The bioactivity of the released drug was confirmed by testing its ability to induce osteogenic differentiation and migration of human adipose-derived stem cells in vitro. Overall, the results obtained from this study demonstrate that DNA could be used as a natural biopolymer to fabricate self-healing injectable hydrogels with sustained release properties for minimally invasive therapeutic approaches. STATEMENT OF SIGNIFICANCE: Dynamic covalent chemistry, especially Schiff base reactions have emerged as a promising route for the formation of injectable hydrogels. Our study demonstrated the development of a DNA-based self-healing hydrogel formed via Schiff base reaction occurring at physiological conditions. The hydrogels functioned as sustained delivery vehicles for the hydrophobic drug simvastatin, which requires a polymeric carrier for controlled delivery of therapeutic concentrations of the drug without exhibiting cytotoxic effects. Presently available hydrogel-based drug delivery systems encounter major challenges for the delivery of hydrophobic drugs due to the hydrophilic nature of the base matrix. Our strategy presents a platform technology for the design of minimally invasive approaches for the sustained delivery of hydrophobic drugs similar to simvastatin.

Fabricating Tough Interpenetrating Network Cryogels with DNA as the Primary Network for Biomedical Applications.

This work investigates a sequential strategy to develop DNA-based hydrogel scaffolds with interpenetrating polymeric network. The scaffolds were formed via a two-step procedure. First, a covalently cross-linked DNA-based cryogel was formed by the chemical reaction between DNA strands and a bifunctional cross-linker, polyethylene glycol diepoxide at subzero temperatures. In the second step, alginate chains were absorbed into the preformed macroporous DNA cryogel network, followed by ionic cross-linking with divalent calcium ions. The individual and synergistic effects of covalent and ionic cross-linkings on mechanical and physical properties of the IPN cryogel were tested. The IPN cryogels were able to sustain large deformations higher than 95% of strain under compressive forces without exhibiting any failure. Addition of a physically cross-linked alginate network to the covalently linked DNA cryogel significantly enhanced its toughness and energy dissipation compared to the covalent network alone. The formulated hydrogels also exhibited excellent biocompatibility with human stem cells. Overall, this DNA-based IPN cryogel has the potential to be used as a biomaterial scaffold for a diverse range of tissue engineering applications.

Investigating the Role of Polydopamine to Modulate Stem Cell Adhesion and Proliferation on Gellan Gum-Based Hydrogels.

Gellan gum-based hydrogels display limited cell adhesion ability due to the absence of cell-anchorage points usually present in proteins found in the extracellular matrix (ECM). This issue limits their use in the biomedical field as scaffolds to promote tissue repair. Our work addresses this challenge by investigating the use of polydopamine (pDA) as a bioactive layer to improve the surface and biological properties of gellan gum-based hydrogels cross-linked using carbodiimide chemistry. Upon treatment with a pDA layer, the hydrogel displayed an increase in wettability and swelling properties. This change in physical properties had a direct impact on the biological properties of the scaffolds. Precisely, human adipose-derived stem cells (hASCs) seeded on the pDA coated gellan gum hydrogels displayed larger cell area, increased proliferation rate, and enhanced gene expression of focal adhesion and cytoskeletal proteins. Overall, the findings of this research support the use of pDA coating as a possible approach to improve the biological features of gellan gum-based scaffolds and modulate stem cell morphology and proliferation.

Nucleic Acid-Based Dual Cross-Linked Hydrogels for in Situ Tissue Repair via Directional Stem Cell Migration.

In situ tissue repair holds great potential as a cell-free regenerative strategy. A critical aspect of this approach is the selection of cell instructive materials that can efficiently regulate the defect microenvironment via the release of chemoattractant factors to mobilize and recruit endogenous stem cells toward the site of implantation. Here we report the design of a DNA-based hydrogel as a drug delivery platform for the sustained release of a promising chemoattractant, SDF-1α. The hydrogel is composed of chemically cross-linked DNA strands, which are bridged via silicate nanodisks (nSi). Silicate nanodisks electrostatically interact with the negatively charged DNA backbone resulting in the formation of a dual cross-linked nanocomposite hydrogel with a combination of chemical and physical cross-link points. The formulated nanocomposites display enhanced elasticity and mechanical toughness as compared to their nonsilicate containing counterparts. Moreover, the electrostatic interaction between nSi and SDF-1α leads to sustained release of the chemokine from the hydrogels. The in vitro bioactivity assays confirm the retention of chemotactic properties of the protein after its release. Overall, the dual cross-linked DNA-based hydrogel platform could be potentially used as a cell-instructive material for the recruitment of host stem cells to guide the process of in situ tissue repair.

Development of MicroRNA-146a-Enriched Stem Cell Secretome for Wound-Healing Applications.

Secretome-based therapies have the potential to become the next generation of viable therapeutic wound repair treatments. However, precise strategies aimed to refine and control the secretome composition are necessary to enhance its therapeutic efficacy and facilitate clinical translation. In this study, we aim to accomplish this by transfecting human adipose-derived stem cells (hASCs) with microRNA-146a, which is a potent regulator of angiogenesis and inflammation. The secretome composition obtained from the transfected hASCs (secretome146a) was characterized and compared to nontransfected hASCs secretome to evaluate changes in angiogenic and anti-inflammatory growth factor, cytokine, and miRNA content. In vitro proliferation, migration, and tubular morphogenesis assays using human umbilical vein endothelial cells (HUVECs) were completed to monitor the proangiogenic efficacy of the secretome146a. Finally, the anti-inflammatory efficacy of the secretome146a was assessed using HUVECs that were activated to an inflammatory state by IL-1ß. The resulting HUVEC gene expression and protein activity of key inflammatory mediators were evaluated before and after secretome treatment. Overall, the secretome146a contained a greater array and concentration of therapeutic paracrine molecules, which translated into a superior angiogenic and anti-inflammatory efficacy. Therefore, this represents a promising strategy to produce therapeutic secretome for the promotion of wound repair processes.

Design of a cytocompatible hydrogel coating to modulate properties of ceramic-based scaffolds for bone repair.

INTRODUCTION: Physical and mechanical properties of ceramic-based scaffolds can be modulated by introducing hydrogel coatings on their surface. For instance, hydrogels can be used as elastic layers to overcome the brittleness of synthetic ceramic materials or to control the delivery of essential osteogenic factors. In this work, we aimed to achieve both goals by fabricating a novel cytocompatible hydrogel made of gelatin-alginate as a coating for beta-tricalcium phosphate (ß-TCP) scaffolds. METHODS: The hydrogel synthesis was optimized by varying the concentration of the crosslinkers N-hydroxysuccinimide and N-Ethyl-N'-(3-dimethyl aminopropyl) carbodiimide (NHS/EDC). Swelling, degradability and mechanical studies were carried out to identify the suitable hydrogel coating formulation for the ß-TCP scaffolds. The cytocompatibility of the coated ceramic was assessed in vitro by testing the proliferation and the osteogenic differentiation of human adipose stem cell (hASCs) for two weeks. RESULTS: The designed hydrogel layer could withstand cyclic compression and protected the brittle internal core of the ceramic. The hydrogel coating modulated the diffusion of the model protein BSA according to the degree of crosslinking of the hydrogel layer. Additionally, the polymeric network was able to retain positively charged proteins such as lysozyme due to the strong electrostatic interactions with carboxylic groups of alginate. A higher expression of alkaline phosphates activity was found on hASCs seeded on the coated scaffolds compared to the hydrogels without any ß-TCP. CONCLUSION: Overall, the hydrogel coating characterized in this study represents a valid strategy to overcome limitations of brittle ceramic-based materials used as scaffolds for bone tissue engineering applications.

Harnessing the Noncovalent Interactions of DNA Backbone with 2D Silicate Nanodisks To Fabricate Injectable Therapeutic Hydrogels.

Injectable hydrogels present several advantages over prefabricated scaffolds including ease of delivery, shear-thinning property, and broad applicability in the fields of drug delivery and tissue engineering. Here, we report an approach to develop injectable hydrogels with sustained drug release properties, exploiting the chemical nature of the DNA backbone and silicate nanodisks. A two-step gelation method is implemented for generating a combination of noncovalent network points, leading to a physically cross-linked hydrogel. The first step initiates the development of an interconnected structure by utilizing DNA denaturation and rehybridization mechanism to form hydrogen bonds between complementary base pairs of neighboring DNA strands. The anisotropic charge distribution of two-dimensional silicate nanodisks (nSi) makes them an active center in the second step of the gelation process. Silicate nanodisks create additional network points via attractive electrostatic interactions with the DNA backbone, thereby enhancing the mechanical resilience of the formulated hydrogel. The thermally stable hydrogels displayed an increase in elasticity and yield stress as a function of nSi concentration. They were able to form self-supporting structures post injection due to their rapid recovery after removal of cyclic stress. Moreover, the presence of nanosilicate was shown to modulate the release of a model osteogenic drug dexamethasone (Dex). The bioactivity of released Dex was confirmed from in vitro osteogenic differentiation of human adipose stem cells and in vivo bone formation in a rat cranial bone defect model. Overall, our DNA-based nanocomposite hydrogel obtained from a combination of noncovalent network points can serve as an injectable material for bone regeneration and carrier for sustained release of therapeutics.

Fabrication of a Double-Cross-Linked Interpenetrating Polymeric Network (IPN) Hydrogel Surface Modified with Polydopamine to Modulate the Osteogenic Differentiation of Adipose-Derived Stem Cells.

Hydrogel surface properties can be modified to form bioactive interfaces to modulate the osteogenic differentiation of stem cells. In this work, a hydrogel made of gelatin methacrylamide (GelMA) and alginate was designed and tested as a scaffold to control stem-cell osteogenic differentiation. The hydrogel's surface was treated with polydopamine (pDA) to create an adhesive layer for the adsorption of the osteoinductive drug dexamethasone (Dex). The presence of the pDA coating enhanced Dex adsorption and retention over 21 days. This effect resulted in a delay in the osteogenic differentiation of hASCs cultured on the hydrogel treated with a pDA layer.

Effect of glycerol on the physical and mechanical properties of thin gellan gum films for oral drug delivery.

In this work, deacylated gellan gum and the plasticizer glycerol were used as primary components for the preparation of thin films intended for the oral delivery of therapeutic molecules. The samples were prepared by a solvent casting method and characterized for their thickness, tensile properties, swelling ability, mucoadhesion capacity and uniform drug distribution. The amount of glycerol was varied from 20% to 75% w/w in order to obtain films with tunable mechanical properties and high drug loading efficiency. The addition of glycerol was able to positively influence the mechanical characteristics of gellan gum thin film overcoming the brittleness caused by the rigid interconnection among the polymeric chains. Plasticized gellan gum films containing 50% w/w of glycerol showed optimal mechanical resistance and mucoadhesion capacity, which were adversely affected by the inclusion of higher concentrations of glycerol. On the contrary, only high amounts of the plasticizer (≥70% w/w) enabled a homogeneous distribution of the model drug fluconazole within the polymeric matrix. Overall, these results indicate that gellan gum-based thin films can be potentially used for buccal drug delivery upon precise selection of the appropriate concentration of glycerol used as a plasticizer.

Deciphering the role of substrate stiffness in enhancing the internalization efficiency of plasmid DNA in stem cells using lipid-based nanocarriers.

This study investigates the role of substrate stiffness in the non-viral transfection of human adipose-derived stem cells (hASCs) with the aim to maximize the hASC expression of vascular endothelial growth factor (VEGF). The results confirm the direct effect of substrate stiffness in regulating cytoskeletal remodeling and corresponding plasmid internalization.

Pre-Conditioning Stem Cells in a Biomimetic Environment for Enhanced Cardiac Tissue Repair: In Vitro and In Vivo Analysis.

INTRODUCTION: Stem cell-based therapies represent a valid approach to restore cardiac function due to their beneficial effect in reducing scar area formation and promoting angiogenesis. However, their translation into the clinic is limited by the poor differentiation and inability to secrete sufficient therapeutic factors. To address this issue, several strategies such as genetic modification and biophysical preconditioning have been used to enhance the efficacy of stem cells for cardiac tissue repair. METHODS: In this study, a biomimetic approach was used to mimic the natural mechanical stimulation of the myocardium tissue. Specifically, human adipose-derived stem cells (hASCs) were cultured on a thin gelatin methacrylamide (GelMA) hydrogel disc and placed on top of a beating cardiomyocyte layer. qPCR studies and metatranscriptomic analysis of hASCs gene expression were investigated to confirm the correlation between mechanical stimuli and cardiomyogenic differentiation. In vivo intramyocardial delivery of pre-conditioned hASCs was carried out to evaluate their efficacy to restore cardiac function in mice hearts post-myocardial infarction. RESULTS: The cyclic strain generated by cardiomyocytes significantly upregulated the expression of both mechanotransduction and cardiomyogenic genes in hASCs as compared to the static control group. The inherent angiogenic secretion profile of hASCs was not hindered by the mechanical stimulation provided by the designed biomimetic system. Finally, in vivo analysis confirmed the regenerative potential of the pre-conditioned hASCs by displaying a significant improvement in cardiac function and enhanced angiogenesis in the peri-infarct region. CONCLUSION: Overall, these findings indicate that cyclic strain provided by the designed biomimetic system is an essential stimulant for hASCs cardiomyogenic differentiation, and therefore can be a potential solution to improve stem-cell based efficacy for cardiovascular repair.

Stem cell-inspired secretome-rich injectable hydrogel to repair injured cardiac tissue.

The objective of this study was to develop an injectable and biocompatible hydrogel that can deliver a cocktail of therapeutic biomolecules (secretome) secreted by human adipose-derived stem cells (hASCs) to the peri-infarct myocardium. Gelatin and Laponite® were combined to formulate a shear-thinning, nanocomposite hydrogel (nSi Gel) as an injectable carrier of secretome (nSi Gel+). The growth factor composition and the pro-angiogenic activity of the secretome were tested in vitro by evaluating the proliferation, migration and tube formation of human umbilical endothelial cells. The therapeutic efficacy of the nSi Gel + system was then investigated in vivo in rats by intramyocardial injection into the peri-infarct region. Subsequently, the inflammatory response, angiogenesis, scar formation, and heart function were assessed. Biocompatibility of the developed nSi Gel was confirmed by quantitative PCR and immunohistochemical tests which showed no significant differences in the level of inflammatory genes, microRNAs, and cell marker expression compared to the untreated control group. In addition, the only group that showed a significant increase in capillary density, reduction in scar area and improved cardiac function was treated with the nSi Gel+. Our in vitro and in vivo findings demonstrate the potential of this new secretome-loaded hydrogel as an alternative strategy to treat myocardial infarction. STATEMENT OF SIGNIFICANCE: Stem cell based-therapies represent a possible solution to repair damaged myocardial tissue by promoting cardioprotection, angiogenesis, and reduced fibrosis. However, recent evidence indicates that most of the positive outcomes are likely due to the release of paracrine factors (cytokines, growth factors, and exosomes) from the cells and not because of the local engraftment of stem cells. This cocktail of essential growth factors and paracrine signals is known as secretome can be isolated in vitro, and the biomolecule composition can be controlled by varying stem-cell culture conditions. Here, we propose a straightforward strategy to deliver secretome produced from hASCs by using a nanocomposite injectable hydrogel made of gelatin and Laponite®. The designed secretome-loaded hydrogel represents a promising alternative to traditional stem cell therapy for the treatment of acute myocardial infarction.