Limited efficacy of adipose stromal cell secretome-loaded skin-derived hydrogels to augment skin flap regeneration in rats

The Hidden Power of the Secretome: Therapeutic Potential on Wound Healing and Cell-Free Regenerative Medicine-A Systematic Review

Various types of wounds represent a persistent healthcare burden that demands innovative and effective therapeutic solutions. Innovative approaches have emerged that focus on skin regeneration with minimal side effects. One such method is cell-free therapy that utilizes the secretome of human mesenchymal stem cells (hMSCs) as a promising alternative to traditional cell-based therapies, leveraging a complex mixture of bioactive molecules, including growth factors, cytokines, and extracellular vesicles, to accelerate tissue regeneration. This systematic review synthesizes the findings of 35 studies evaluating the impact of hMSC-derived secretomes on wound healing, with a focus on their regenerative, immunomodulatory, and angiogenic effects. The influence of MSC sources (adipose tissue, bone marrow, umbilical cord) and culture conditions on secretome composition and efficacy in the cutaneous wound healing process is examined, highlighting their therapeutic potential in regenerative medicine. This review also explores emerging preclinical and clinical applications, highlighting promising results, such as enhanced fibroblast proliferation, reduced inflammation, and improved extracellular matrix remodeling. In addition, advances in secretome-based biomaterials, including hydrogels and scaffolds, which optimize therapeutic delivery and efficacy are discussed. Despite the growing body of evidence supporting the safety and efficacy of secretomes, challenges remain regarding standardization, large-scale production, and clinical validation. This review highlights the potential of MSC-derived secretomes as a next-generation cell-free approach for wound healing and regenerative medicine.

The paradigm of stem cell secretome in tissue repair and regeneration: Present and future perspectives

As the number of patients requiring organ transplants continues to rise exponentially, there is a dire need for therapeutics, with repair and regenerative properties, to assist in alleviating this medical crisis. Over the past decade, there has been a shift from conventional stem cell treatments towards the use of the secretome, the protein and factor secretions from cells. These components may possess novel druggable targets and hold the key to profoundly altering the field of regenerative medicine. Despite the progress in this field, clinical translation of secretome-containing products is limited by several challenges including but not limited to ensuring batch-to-batch consistency, the prevention of further heterogeneity, production of sufficient secretome quantities, product registration, good manufacturing practice protocols and the pharmacokinetic/pharmacodynamic profiles of all the components. Despite this, the secretome may hold the key to unlocking the regenerative blockage scientists have encountered for years. This review critically analyses the secretome derived from different cell sources and used in several tissues for tissue regeneration. Furthermore, it provides an overview of the current delivery strategies and the future perspectives for the secretome as a potential therapeutic. The success and possible shortcomings of the secretome are evaluated.

A Versatile Skin-Derived Extracellular Matrix Hydrogel-Based Platform to Investigate the Function of a Mechanically Isolated Adipose Tissue Stromal Vascular Fraction

Introduction: To accelerate cutaneous wound healing and prevent scarring, regenerative approaches such as injecting a mechanically derived tissue stromal vascular fraction (tSVF) are currently under clinical and laboratory investigations. The aim of our study was to investigate a platform to assess the interaction between skin-derived extracellular matrix (ECM) hydrogels and tSVF and their effects on their microenvironment in the first ten days of culture. Material and Methods: A tSVF mixed with ECM hydrogel was cultured for ten days. After 0, 3, 5, and 10 days of culture viability, histology, immunohistochemistry, gene expression, and collagen alignment and organization were assessed. Results: The viability analysis showed that tSVF remained viable during 10 days of culture and seemed to remain within their constitutive ECM. The fiber analysis demonstrated that collagen alignment and organization were not altered. No outgrowth of capillaries was observed in (immuno)histochemical staining. The gene expression analysis revealed that paracrine factors TGFB1 and VEGFA did not change and yet were constitutively expressed. Pro-inflammatory factors IL1B and IL6 were downregulated. Matrix remodeling gene MMP1 was upregulated from day three on, while MMP14 was upregulated at day three and ten. Interestingly, MMP14 was downregulated at day five compared to day three while MMP2 was downregulated after day zero. Conclusions: Skin-derived ECM hydrogels appear to be a versatile platform for investigating the function of a mechanically isolated adipose tissue stromal vascular fraction. In vitro tSVF remained viable for 10 days and sustained the expression of pro-regenerative factors, but is in need of additional triggers to induce vascularization or show signs of remodeling of the surrounding ECM. In the future, ECM-encapsulated tSVF may show promise for clinical administration to improve wound healing.

The role of extracellular matrix hydrogels and adipose-derived stromal cells in soft tissue vascularization - A systematic review

Decellularized extracellular matrix (dECM) hydrogels loaded with adipose-derived stromal cells (ASC) or their conditioned medium (ASC CM) present a promising and versatile treatment approach for tissue vascularization and regeneration. These hydrogels are easy to produce, store, personalize, manipulate, and deliver to the target tissue. This literature review aimed to investigate the applications of dECM hydrogels with ASC or ASC CM for in vivo tissue vascularization. Fourteen experimental studies have been reviewed using vessel density as the primary outcome parameter for in vivo vascularization. The studies consistently reported an increased efficacy in augmenting angiogenesis by the ASC or ASC CM-loaded hydrogels compared to untreated controls. However, this systematic review shows the need to standardize procedures and characterization, particularly of the final administered product(s). The findings from these experimental studies highlight the potential of dECM hydrogel with ASC or ASC CM in novel tissue regeneration and regenerative medicine applications.

Advancing wound healing by hydrogel-based dressings loaded with cell-conditioned medium: a systematic review

BACKGROUND

Wound healing represents a complex biological process, critically important in clinical practice due to its direct implication in a patient's recovery and quality of life. Conservative wound management frequently falls short in providing an ideal environment for the optimal tissue regeneration, often resulting in extended healing periods and elevated risk of infection and other complications. The emerging biomaterials, particularly hydrogels, have shown substantial promise in addressing these challenges by offering properties such as biocompatibility, biodegradability, and the ability to cure wound environment. Recent advancements have highlighted the therapeutic potential of integrating cell-derived conditioned medium (CM) into hydrogel matrices. Cell-derived CM represents a rich array of bioactive molecules, demonstrating significant efficacy in modulating cellular activities crucial for wound healing, including cellular proliferation, migration, and angiogenesis.

METHODS

The methodology of this review adheres to the standards set by the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) guidelines. The review includes a selection of studies published within the last five years, focusing on in vivo experiments involving various types of skin injuries treated with topically applied hydrogels loaded with CM (H-CM). The search strategy refers to the PICO framework and includes the assessment of study quality by CAMARADES tool.

RESULTS

The systematic review represents a detailed evaluation of H-CM dressings wound healing efficiency based on the experimental results of cell-based assays and animal wound models. The study targets to reveal wound healing capacity of H-CM dressings, and provides a comparative data analysis, limitations of methods and discussions of H-CM role in advancing the wound healing therapy.

CONCLUSIONS

The data presented demonstrate that H-CM is a promising material for advanced wound healing and regenerative medicine. These dressings possess proved in vitro/in vivo efficacy that highlights their strong clinical potential and paves the way to further investigations of H-CM formulations within clinical trials.

Collagen-rich liver-derived extracellular matrix hydrogels augment survival and function of primary rat liver sinusoidal endothelial cells and hepatocytes

Liver sinusoidal endothelial cells (LSECs) are key targets for addressing metabolic dysfunction-associated steatotic liver disease (MASLD). However, isolating and culturing primary LSECs is challenging due to rapid dedifferentiation, resulting in loss of function. The extracellular matrix (ECM) likely plays a crucial role in maintaining the fate and function of LSECs. In this study, we explored the influence of liver-ECM (L-ECM) on liver cells and developed culture conditions that maintain the differentiated function of liver cells in vitro for prolonged periods. Porcine liver-derived L-ECM, containing 34.9 % protein, 0.045 % glycosaminoglycans, and negligible residual DNA (41.2 ng/mg), was utilized to culture primary rat liver cells in generated hydrogels. Proteomic analyses and molecular weight distribution of proteins of solubilized L-ECM revealed the typical diverse ECM core matrisome, with abundant collagens. L-ECM hydrogels showed suitable stiffness and stress relaxation properties. Furthermore, we demonstrated that collagen-rich L-ECM hydrogels enhanced LSECs' and hepatocytes' viability, and reduced the dedifferentiation rate of LSECs. In addition, hepatocyte function was maintained longer by culture on L-ECM hydrogels compared to traditional culturing. These beneficial effects are likely attributed to the bioactive macromolecules including collagens, and mechanical and microarchitectural properties of the L-ECM hydrogels.

Physical Properties and Biochemical Composition of Extracellular Matrix-Derived Hydrogels Dictate Vascularization Potential in an Organ-Dependent Fashion

The inherent extracellular matrix (ECM) originating from a specific tissue impacts the process of vascularization, specifically vascular network formation (VNF) orchestrated by endothelial cells (ECs). The specific contribution toward these processes of ECM from highly disparate organs such as the skin and lungs remains a relatively unexplored area. In this study, we compared VNF and ECM remodeling mediated by microvascular ECs within gel, lung, and combinations thereof (hybrid) ECM hydrogels. Irrespective of the EC source, the skin-derived ECM hydrogel exhibited a higher propensity to drive and support VNF compared to both lung and hybrid ECM hydrogels. There were distinct disparities in the physical properties of the three types of hydrogels, including viscoelastic properties and complex architectural configurations, including fiber diameter, pore area, and numbers among the fibers. The hybrid ECM hydrogel properties were unique and not the sum of the component ECM parts. Furthermore, cellular ECM remodeling responses varied with skin ECM hydrogels promoting matrix metalloproteinase 1 (MMP1) secretion, while hybrid ECM hydrogels exhibited increased MMP9, fibronectin, and collagen IV deposition. Principal component analysis (PCA) indicated that the influence of a gel's mechanical properties on VNF was stronger than the biochemical composition. These data indicate that the organ-specific properties of an ECM dictate its capacity to support VNF, while intriguingly showing that ECs respond to more than just the biochemical constituents of an ECM. The study suggests potential applications in regenerative medicine by strategically selecting ECM origin or combinations to manipulate vascularization, offering promising prospects for enhancing wound healing through pro-regenerative interventions.

Human mesenchymal stem cell secretomes: Factors affecting profiling and challenges in clinical application

The promising field of regenerative medicine is thrilling as it can repair and restore organs for various debilitating diseases. Mesenchymal stem cells are one of the main components in regenerative medicine that work through the release of secretomes. By adopting the use of the secretome in cell-free-based therapy, we may be able to address the challenges faced in cell-based therapy. As one of the components of cell-free-based therapy, secretome has the advantage of a better safety and efficacy profile than mesenchymal stem cells. However, secretome has its challenges that need to be addressed, such as its bioprocessing methods that may impact the secretome content and its mechanisms of action in clinical settings. Effective and standardization of bioprocessing protocols are important to ensure the supply and sustainability of secretomes for clinical applications. This may eventually impact its commercialization and marketability. In this review, the bioprocessing methods and their impacts on the secretome profile and treatment are discussed. This improves understanding of its fundamental aspects leading to potential clinical applications.

Decellularized extracellular matrix biomaterials for regenerative therapies: Advances, challenges and clinical prospects

Tissue engineering and regenerative medicine have shown potential in the repair and regeneration of tissues and organs via the use of engineered biomaterials and scaffolds. However, current constructs face limitations in replicating the intricate native microenvironment and achieving optimal regenerative capacity and functional recovery. To address these challenges, the utilization of decellularized tissues and cell-derived extracellular matrix (ECM) has emerged as a promising approach. These biocompatible and bioactive biomaterials can be engineered into porous scaffolds and grafts that mimic the structural and compositional aspects of the native tissue or organ microenvironment, both in vitro and in vivo. Bioactive dECM materials provide a unique tissue-specific microenvironment that can regulate and guide cellular processes, thereby enhancing regenerative therapies. In this review, we explore the emerging frontiers of decellularized tissue-derived and cell-derived biomaterials and bio-inks in the field of tissue engineering and regenerative medicine. We discuss the need for further improvements in decellularization methods and techniques to retain structural, biological, and physicochemical characteristics of the dECM products in a way to mimic native tissues and organs. This article underscores the potential of dECM biomaterials to stimulate in situ tissue repair through chemotactic effects for the development of growth factor and cell-free tissue engineering strategies. The article also identifies the challenges and opportunities in developing sterilization and preservation methods applicable for decellularized biomaterials and grafts and their translation into clinical products.

Adipose stem cells in tissue regeneration and repair: From bench to bedside

ADSCs are a large number of mesenchymal stem cells in Adipose tissue, which can be applied to tissue engineering. ADSCs have the potential of multi-directional differentiation, and can differentiate into bone tissue, cardiac tissue, urothelial cells, skin tissue, etc. Compared with other mesenchymal stem cells, ADSCs have a multitude of promising advantages, such as abundant number, accessibility in cell culture, stable function, and less immune rejection. There are two main methods to use ADSCs for tissue repair and regeneration. One is to implant the "ADSCs-scaffold composite" into the injured site to promote tissue regeneration. The other is cell-free therapy: using ADSC-exos or ADSC-CM alone to release a large number of miRNAs, cytokines and other bioactive substances to promote tissue regeneration. The tissue regeneration potential of ADSCs is regulated by a variety of cytokines, signaling molecules, and external environment. The differentiation of ADSCs into different tissues is also induced by growth factors, ions, hormones, scaffold materials, physical stimulation, and other factors. The specific mechanisms are complex, and most of the signaling pathways need to be further explored. This article reviews and summarizes the mechanism and clinical application of ADSCs in tissue injury repair so far, and puts forward further problems that need to be solved in this field, hoping to provide directions for further research in this field.

Adipose Tissue-Derived Components: From Cells to Tissue Glue to Treat Dermal Damage

In recent decades, adipose tissue transplantation has become an essential treatment modality for tissue (volume) restoration and regeneration. The regenerative application of adipose tissue has only recently proven its usefulness; for example, the method is useful in reducing dermal scarring and accelerating skin-wound healing. The therapeutic effect is ascribed to the tissue stromal vascular fraction (tSVF) in adipose tissue. This consists of stromal cells, the trophic factors they secrete and the extracellular matrix (ECM), which have immune-modulating, pro-angiogenic and anti-fibrotic properties. This concise review focused on dermal regeneration using the following adipose-tissue components: adipose-tissue-derived stromal cells (ASCs), their secreted trophic factors (ASCs secretome), and the ECM. The opportunities of using a therapeutically functional scaffold, composed of a decellularized ECM hydrogel loaded with trophic factors of ASCs, to enhance wound healing are explored as well. An ECM-based hydrogel loaded with trophic factors combines all regenerative components of adipose tissue, while averting the possible disadvantages of the therapeutic use of adipose tissue, e.g., the necessity of liposuction procedures with a (small) risk of complications, the impossibility of interpatient use, and the limited storage options.