Synthesis and secretome release by human bone marrow mesenchymal stem cell spheroids within three-dimensional collagen hydrogels: Integrating experiments and modelling

Synthesis and characterization of a bovine collagen: GAG scaffold with Uruguayan raw material for tissue engineering

Tissue engineering (TE) and regenerative medicine offer strategies to improve damaged tissues by using scaffolds and cells. The use of collagen-based biomaterials in the field of TE has been intensively growing over the past decades. Mesenchymal stromal cells (MSCs) and dental pulp stem cells (DPSCs) are promising cell candidates for development of clinical composites. In this study, we proposed the development of a bovine collagen type I: chondroitin-6-sulphate (CG) scaffold, obtained from Uruguayan raw material (certified as free bovine spongiform encephalopathy), with CG crosslinking enhancement using different gamma radiation doses. Structural, biomechanical and chemical characteristics of the scaffolds were assessed by Scanning Electron Microscopy, axial tensile tests, FT-IR and Raman Spectroscopy, respectively. Once we selected the most appropriate scaffold for future use as a TE product, we studied the behavior of MSCs and DPSCs cultured on the scaffold by cytotoxicity, proliferation and differentiation assays. Among the diverse porous scaffolds obtained, the one with the most adequate properties was the one exposed to 15 kGy of gamma radiation. This radiation dose contributed to the crosslinking of molecules, to the formation of new bonds and/or to the reorganization of the collagen fibers. The selected scaffold was non-cytotoxic for the tested cells and a suitable substrate for cell proliferation. Furthermore, the scaffold allowed MSCs differentiation to osteogenic, chondrogenic, and adipogenic lineages. Thus, this work shows a promising approach to the synthesis of a collagen-scaffold suitable for TE.

Recent advances in mesenchymal stem cell therapy for myocardial infarction

Myocardial infarction refers to the ischemic necrosis of myocardium, characterized by a sharp reduction or interruption of blood flow in the coronary arteries due to the coronary artery occlusion, resulting in severe and prolonged ischemia in the corresponding myocardium and ultimately leading to ischemic necrosis of the myocardium. Given its high risk, it is considered as one of the most serious health threats today. In current clinical practice, multiple approaches have been explored to diminish myocardial oxygen consumption and alleviate symptoms, but notable success remains elusive. Accumulated clinical evidence has showed that the implantation of mesenchymal stem cell for treating myocardial infarction is both effective and safe. Nevertheless, there persists controversy and variability regarding the standardizing MSC transplantation protocols, optimizing dosage, and determining the most effective routes of administration. Addressing these remaining issues will pave the way of integration of MSCs as a feasible mainstream cardiac treatment.

Advances in the design, generation, and application of tissue-engineered myocardial equivalents

Due to the limited regenerative ability of cardiomyocytes, the disabling irreversible condition of myocardial failure can only be treated with conservative and temporary therapeutic approaches, not able to repair the damage directly, or with organ transplantation. Among the regenerative strategies, intramyocardial cell injection or intravascular cell infusion should attenuate damage to the myocardium and reduce the risk of heart failure. However, these cell delivery-based therapies suffer from significant drawbacks and have a low success rate. Indeed, cardiac tissue engineering efforts are directed to repair, replace, and regenerate native myocardial tissue function. In a regenerative strategy, biomaterials and biomimetic stimuli play a key role in promoting cell adhesion, proliferation, differentiation, and neo-tissue formation. Thus, appropriate biochemical and biophysical cues should be combined with scaffolds emulating extracellular matrix in order to support cell growth and prompt favorable cardiac microenvironment and tissue regeneration. In this review, we provide an overview of recent developments that occurred in the biomimetic design and fabrication of cardiac scaffolds and patches. Furthermore, we sift in vitro and in situ strategies in several preclinical and clinical applications. Finally, we evaluate the possible use of bioengineered cardiac tissue equivalents as in vitro models for disease studies and drug tests.

Stem Cell's Secretome Delivery Systems

Stem cells' secretome contains biomolecules that are ready to give therapeutic activities. However, the biomolecules should not be administered directly because of their in vivo instability. They can be degraded by enzymes or seep into other tissues. There have been some advancements in localized and stabilized secretome delivery systems, which have increased their effectiveness. Fibrous, in situ, or viscoelastic hydrogel, sponge-scaffold, bead powder/ suspension, and bio-mimetic coating can maintain secretome retention in the target tissue and prolong the therapy by sustained release. Porosity, young's modulus, surface charge, interfacial interaction, particle size, adhesiveness, water absorption ability, in situ gel/film, and viscoelasticity of the preparation significantly affect the quality, quantity, and efficacy of the secretome. Therefore, the dosage forms, base materials, and characteristics of each system need to be examined to develop a more optimal secretome delivery system. This article discusses the clinical obstacles and potential solutions for secretome delivery, characterization of delivery systems, and devices used or potentially used in secretome delivery for therapeutic applications. This article concludes that secretome delivery for various organ therapies necessitates the use of different delivery systems and bases. Coating, muco-, and cell-adhesive systems are required for systemic delivery and to prevent metabolism. The lyophilized form is required for inhalational delivery, and the lipophilic system can deliver secretomes across the blood-brain barrier. Nano-sized encapsulation and surface-modified systems can deliver secretome to the liver and kidney. These dosage forms can be administered using devices such as a sprayer, eye drop, inhaler, syringe, and implant to improve their efficacy through dosing, direct delivery to target tissues, preserving stability and sterility, and reducing the immune response.

Mesenchymal stromal/stem cells spheroid culture effect on the therapeutic efficacy of these cells and their exosomes: A new strategy to overcome cell therapy limitations

Cell therapy is one of the new treatment methods in which mesenchymal stem/stromal cell (MSCs) transplantation is one of the cells widely used in this field. The results of MSCs application in the clinic prove their therapeutic efficacy. For this reason, many clinical trials have been designed based on the application of MSCs for various diseases, especially inflammatory disease and regenerative medicine. These cells perform their therapeutic functions through multiple mechanisms, including the differentiative potential, immunomodulatory properties, production of therapeutic exosomes, production of growth factors and cytokines, and anti-apoptotic effects. Exosomes are nanosized extracellular vesicles (EVs) that change target cell functions by transferring different cargos. The therapeutic ability of MSCs-derived exosomes has been demonstrated in many studies. However, some limitations, such as the low production of exosomes by cells and the need for large amounts of them and also their limited therapeutic ability, have encouraged researchers to find methods that increase exosomes' therapeutic potential. One of these methods is the spheroid culture of MSCs. Studies show that the three-dimensional culture (3DCC) of MSCs in the form of multicellular spheroids increases the therapeutic efficacy of these cells in laboratory and animal applications. In addition, the spheroid culture of MSCs leads to enhanced therapeutic properties of their exosomes and production rate. Due to the novelty of the field of using 3DCC MSCs-derived exosomes, examination of their properties and the results of their therapeutic application can increase our view of this field. This review discussed MSCs and their exosomes enhanced properties in spheroid culture.

Complexed Polymer Film-Forming Spray: An Optimal Delivery System for Secretome of Mesenchymal Stem Cell as Diabetic Wound Dressing?

Diabetes-related wounds have physiological factors that make healing more complicated. High sugar levels can increase microbial infection risk while limiting nutrition and oxygen transfer to the wound area. The secretome of mesenchymal stem cells has been widely known for its efficacy in regenerative therapy. However, applying the secretome directly to the wound can reduce its effectiveness. In this review, we examined the literature on synthesizing the combinations of carboxymethyl chitosan, hyaluronic acid, and collagen tripeptides, as well as the possibility of physicochemical properties enhancement of the hydrogel matrix, which could potentially be used as an optimal delivery system of stem cell's secretome for diabetic wound healing.

Delivery of Stem Cell Secretome for Therapeutic Applications

Intensive studies on stem cell therapy reveal that benefits of stem cells attribute to the paracrine effects. Hence, direct delivery of stem cell secretome to the injured site shows the comparative therapeutic efficacy of living cells while avoiding the potential limitations. However, conventional systemic administration of stem cell secretome often leads to rapid clearance in vivo. Therefore, a variety of different biomaterials are developed for sustained and controllable delivery of stem cell secretome to improve therapeutic efficiency. In this review, we first introduce current approaches for the preparation and characterization of stem cell secretome as well as strategies to improve their therapeutic efficacy and production. The up-to-date delivery platforms are also summarized, including nanoparticles, injectable hydrogels, microneedles, and scaffold patches. Meanwhile, we discuss the underlying therapeutic mechanism of stem cell secretome for the treatment of various diseases. In the end, future opportunities and challenges are proposed.

Dissolvable microgel-templated macroporous hydrogels for controlled cell assembly

Mesenchymal stem cells (MSCs)-based therapies have been widely used to promote tissue regeneration and to modulate immune/inflammatory response. The therapeutic potential of MSCs can be further improved by forming multi-cellular spheroids. Meanwhile, hydrogels with macroporous structures are advantageous for improving mass transport properties for the cell-laden matrices. Herein, we report the fabrication of MSC-laden macroporous hydrogel scaffolds through incorporating rapidly dissolvable spherical cell-laden microgels. Dissolvable microgels were fabricated by tandem droplet-microfluidics and thiol-norbornene photopolymerization using a novel fast-degrading macromer poly(ethylene glycol)-norbornene-dopamine (PEGNB-Dopa). The cell-laden PEGNB-Dopa microgels were subsequently encapsulated within another bulk hydrogel matrix, whose porous structure was generated efficiently by the rapid degradation of the PEGNB-Dopa microgels. The cytocompatibility of this in situ pore-forming approach was demonstrated with multiple cell types. Furthermore, adjusting the stiffness and cell adhesiveness of the bulk hydrogels afforded the formation of solid cell spheroids or hollow spheres. The assembly of solid or hollow MSC spheroids led to differential activation of AKT pathway. Finally, MSCs solid spheroids formed in situ within the macroporous hydrogels exhibited robust secretion of HGF, VEGF-A, IL-6, IL-8, and TIMP-2. In summary, this platform provides an innovative method for forming cell-laden macroporous hydrogels for a variety of future biomedical applications.

Adipose-derived stem cell spheroids are superior to single-cell suspensions to improve fat autograft long-term survival

Autologous fat transplantation is a widely used procedure for surgical reconstruction of tissues. The resorption rate of this transplantation remains high and unpredictable, reinforcing the need of adjuvant treatments that increase the long‐term stability of grafts. Adipose‐derived stem cells (ASC) introduced as single cells in fat has been shown clinically to reduce the resorption of fat grafts. On the other hand, the formulation of ASC into cell spheroids results in the enhancement of their regenerative potential. In this study, we developed a novel method to produce highly homogeneous ASC spheroids and characterized their features and efficacy on fat transplantation. Spheroids conserved ASC markers and multipotency. A regenerative gene expression profile was maintained, and genes linked to autophagy were upregulated whereas proliferation was decreased. Their secreted proteome was enriched in comparison with single‐cell ASC suspension. Addition of spheroids to fat graft in an animal model of transplantation resulted in a better graft long‐term stability when compared to single ASC suspension. In conclusion, we provide a novel method to manufacture homogenous ASC spheroids. These ASC spheroids are superior to ASC in single‐cell suspension to improve the stability of fat transplants, reinforcing their potential in reconstructive surgery.

Mesenchymal Stromal Cells Adapt to Chronic Tendon Disease Environment with an Initial Reduction in Matrix Remodeling

Tendon lesions are common sporting injuries in humans and horses alike. The healing process of acute tendon lesions frequently results in fibrosis and chronic disease. In horses, local mesenchymal stromal cell (MSC) injection is an accepted therapeutic strategy with positive influence on acute lesions. Concerning the use of MSCs in chronic tendon disease, data are scarce but suggest less therapeutic benefit. However, it has been shown that MSCs can have a positive effect on fibrotic tissue. Therefore, we aimed to elucidate the interplay of MSCs and healthy or chronically diseased tendon matrix. Equine MSCs were cultured either as cell aggregates or on scaffolds from healthy or diseased equine tendons. Higher expression of tendon-related matrix genes and tissue inhibitors of metalloproteinases (TIMPs) was found in aggregate cultures. However, the tenogenic transcription factor scleraxis was upregulated on healthy and diseased tendon scaffolds. Matrix metalloproteinase (MMPs) expression and activity were highest in healthy scaffold cultures but showed a strong transient decrease in diseased scaffold cultures. The release of glycosaminoglycan and collagen was also higher in scaffold cultures, even more so in those with tendon disease. This study points to an early suppression of MSC matrix remodeling activity by diseased tendon matrix, while tenogenic differentiation remained unaffected.

Regeneration of irradiation-damaged esophagus by local delivery of mesenchymal stem-cell spheroids encapsulated in a hyaluronic-acid-based hydrogel

Radiation therapy (RT) is a typical treatment for head and neck cancers. Generally, prolonged irradiation of the esophagus causes esophageal fibrosis due to increased reactive oxygen species and proinflammatory cytokines. This study was designed to determine whether catechol-functionalized hyaluronic acid (HA-CA) hydrogel-encapsulated human mesenchymal stem-cell spheroids (MSC-SPs) could ameliorate damage to the esophagus in a mouse model of radiation-induced esophageal fibrosis. MSC-SPs were cultured in concave microwells 600 μm in diameter at a cell density of 1 × 10⁶ cells per mL. Most cells formed spheroids with a 100-300 μm size distribution in concave microwells. MSC-SPs were well maintained in the HA gel, and live-dead staining confirmed that most cells survived. The HA gel containing the MSC-SPs was then injected into the damaged esophageal layer. Inflammatory signs or adverse tissue reactions were not observed after esophageal injection of HA-gel-encapsulated MSC-SPs. Based on Masson's trichrome staining at 4 and 12 weeks postinjection, the inner esophageal layer (IEL) was significantly thinner in the MSC-SP + HA gel group compared to those in the other experimental groups. While the saline and HA gel treatments made the esophageal muscles loose and thick, the MSC-SP + HA gel group showed bundles of tightly packed esophageal muscles, as assayed by desmin immunostaining. qPCR analysis showed that epithelial genes tended to increase over time in the MSC-SP + HA gel group, and the expression of most fibrosis-related genes decreased. This study proposes the potential of using HA-CA-hydrogel-encapsulated MSC-SPs as a promising therapy against radiation-induced esophageal fibrosis.

Mechanisms underlying the protective effects of mesenchymal stem cell-based therapy

Mesenchymal stem cells (MSCs) have been extensively investigated for the treatment of various diseases. The therapeutic potential of MSCs is attributed to complex cellular and molecular mechanisms of action including differentiation into multiple cell lineages and regulation of immune responses via immunomodulation. The plasticity of MSCs in immunomodulation allow these cells to exert different immune effects depending on different diseases. Understanding the biology of MSCs and their role in treatment is critical to determine their potential for various therapeutic applications and for the development of MSC-based regenerative medicine. This review summarizes the recent progress of particular mechanisms underlying the tissue regenerative properties and immunomodulatory effects of MSCs. We focused on discussing the functional roles of paracrine activities, direct cell-cell contact, mitochondrial transfer, and extracellular vesicles related to MSC-mediated effects on immune cell responses, cell survival, and regeneration. This will provide an overview of the current research on the rapid development of MSC-based therapies.

Simplified low-cost methodology to establish, histologically process and analyze three-dimensional cancer cell spheroid arrays

Differently of two-dimensional cell culture, three-dimensional (3D) multicellular spheroid model allows cells to establish cell-cell/cell-matrix interactions over the entire cell surface, more closely mimicking tumor microenvironments and cellular subpopulations with specific standards of morphology, differentiation and gene expression. Thenceforth several methodologies involving or the 3D cell aggregates generation or its histological processing and analysis have emerged, but in general they are laborious, expensive and complex to set up as a routine technique. Thus, we developed a complete methodology, detailing a simple, accessible and low-cost step by step, including 1) the 3D cell aggregate generation using hanging drop technique; 2) providing a simple way to assess morphological parameters of generated spheroids; followed by 3) a multiple and organized histological processing, keeping several individual spheroids inside an agarose apparatus, maintaining a known order and position of each ones, similar to tissue microarray principle; 4) until the last step, where it is allowed a simultaneous histological composition analysis of several spheroid slices, organized side by side, in a same block section, through conventional stainings or 5) immunostaining against different molecular markers. Therefore, the present methodology aims to popularize 3D cell culture, allowing to make this a regular technique in basic cell biology research, once all steps are performed without using onerous reagents, materials or equipment. In addition to bring the agarose apparatus as a simple low cost novelty, allowing high-throughput analysis of several spheroids simultaneously in an organized manner.