Safety and clinical efficacy of the secretome of stressed peripheral blood mononuclear cells in patients with diabetic foot ulcer-study protocol of the randomized, placebo-controlled, double-blind, multicenter, international phase II clinical trial MARSYAS II

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.

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.

Therapeutic Application of Cell Secretomes in Cutaneous Wound Healing

Although the application of stem cells to chronic wounds emerged as a candidate therapy in the previous century, the mechanism of action remains unclear. Recent evidence has implicated secreted paracrine factors in the regenerative properties of cell-based therapies. In the last two decades, considerable research advances involving the therapeutic potential of stem cell secretomes have expanded the scope of secretome-based therapies beyond stem cell populations. In this study, we review the modes of action of cell secretomes in wound healing, important preconditioning strategies for enhancing their therapeutic efficacy, and clinical trials on secretome-based wound healing.

The Secretome of Irradiated Peripheral Mononuclear Cells Attenuates Hypertrophic Skin Scarring

Hypertrophic scars can cause pain, movement restrictions, and reduction in the quality of life. Despite numerous options to treat hypertrophic scarring, efficient therapies are still scarce, and cellular mechanisms are not well understood. Factors secreted by peripheral blood mononuclear cells (PBMCsec) have been previously described for their beneficial effects on tissue regeneration. In this study, we investigated the effects of PBMCsec on skin scarring in mouse models and human scar explant cultures at single-cell resolution (scRNAseq). Mouse wounds and scars, and human mature scars were treated with PBMCsec intradermally and topically. The topical and intradermal application of PBMCsec regulated the expression of various genes involved in pro-fibrotic processes and tissue remodeling. We identified elastin as a common linchpin of anti-fibrotic action in both mouse and human scars. In vitro, we found that PBMCsec prevents TGFβ-mediated myofibroblast differentiation and attenuates abundant elastin expression with non-canonical signaling inhibition. Furthermore, the TGFβ-induced breakdown of elastic fibers was strongly inhibited by the addition of PBMCsec. In conclusion, we conducted an extensive study with multiple experimental approaches and ample scRNAseq data demonstrating the anti-fibrotic effect of PBMCsec on cutaneous scars in mouse and human experimental settings. These findings point at PBMCsec as a novel therapeutic option to treat skin scarring.

Future Directions in Research in Transcriptomics in the Healing of Diabetic Foot Ulcers

Diabetic foot ulcers are a health crisis that affect millions of individuals worldwide. Current standard of care involves diligent wound care with adjunctive antibiotics and surgical debridement. However, despite this, the majority will still become infected and fail to heal. Recent efforts using bioengineered skin initially appeared promising, but randomized clinical trials have disappointed. Scientists have now begun to understand that the normal wound healing physiology does not apply to diabetic foot ulcers as they maintain a chronic state of inflammation and fail to progress in a linear pathway. Using transcriptomics, research over the past decade has started identifying master genes and protein pathways that are dysregulated in patients with diabetes. This review paper discusses those genes involved and how novel advancements are using this information to create new biologically based compounds to accelerate wound healing in patients with diabetic foot ulcers.

Paracrine Factors of Stressed Peripheral Blood Mononuclear Cells Activate Proangiogenic and Anti-Proteolytic Processes in Whole Blood Cells and Protect the Endothelial Barrier

Tissue-regenerative properties have been attributed to secreted paracrine factors derived from stem cells and other cell types. In particular, the secretome of γ-irradiated peripheral blood mononuclear cells (PBMCsec) has been shown to possess high tissue-regenerative and proangiogenic capacities in a variety of preclinical studies. In light of future therapeutic intravenous applications of PBMCsec, we investigated the possible effects of PBMCsec on white blood cells and endothelial cells lining the vasculature. To identify changes in the transcriptional profile, whole blood was drawn from healthy individuals and stimulated with PBMCsec for 8 h ex vivo before further processing for single-cell RNA sequencing. PBMCsec significantly altered the gene signature of granulocytes (17 genes), T-cells (45 genes), B-cells (72 genes), and, most prominently, monocytes (322 genes). We detected a strong upregulation of several tissue-regenerative and proangiogenic cyto- and chemokines in monocytes, including VEGFA, CXCL1, and CXCL5. Intriguingly, inhibitors of endopeptidase activity, such as SERPINB2, were also strongly induced. Measurement of the trans-endothelial electrical resistance of primary human microvascular endothelial cells revealed a strong barrier-protective effect of PBMCsec after barrier disruption. Together, we show that PBMCsec induces angiogenic and proteolytic processes in the blood and is able to attenuate endothelial barrier damage. These regenerative properties suggest that systemic application of PBMCsec might be a promising novel strategy to restore damaged organs.

The secretome of irradiated peripheral blood mononuclear cells attenuates activation of mast cells and basophils

BACKGROUND

IgE-mediated hypersensitivity is becoming increasingly prevalent and activation of mast cells and basophils represent key events in the pathophysiology of allergy. We have previously reported that the secretome of γ-irradiated peripheral blood mononuclear cells (PBMCsec) exerts beneficial anti-inflammatory effects. Yet, its ability to alleviate allergic symptoms has not been investigated so far.

METHODS

Several experimental in vitro and in vivo models have been used in this basic research study. A murine ear swelling model was used to study the effects of PBMCsec on 48/80-induced mast cell degranulation in vivo. The transcriptional profile of murine mast cells was analysed by single cell RNA sequencing (scRNAseq). Mast cell activation was studied in vitro using primary skin mast cells. Basophils from individuals allergic to birch pollens were used to investigate basophile activation by allergens. Transcriptomic and lipidomic analyses were used to identify mRNA expression and lipid species present in PBMCsec, respectively.

FINDINGS

Topical application of PBMCsec on mouse ears (C57BL/6) significantly reduced tissue swelling following intradermal injection of compound 48/80, an inducer of mast cell degranulation. Single cell RNA sequencing of PBMCsec-treated murine dermal mast cells (Balb/c) revealed a downregulation of genes involved in immune cell degranulation and Fc-receptor signalling. In addition, treatment of primary human dermal mast cells with PBMCsec strongly inhibited compound 48/80- and α-IgE-induced mediator release in vitro. Furthermore, PBMCsec remarkably attenuated allergen driven activation of basophils from allergic individuals. Transcriptomic analysis of these basophils showed that PBMCsec downregulated a distinct gene battery involved in immune cell degranulation and Fc-receptor signalling, corroborating results obtained from dermal mast cells. Finally, we identified the lipid fraction of PBMCsec as the major active ingredient involved in effector cell inhibition.

INTERPRETATION

Collectively, our data demonstrate that PBMCsec is able to reduce activation of mast cells and basophils, encouraging further studies on the potential use of PBMCsec for treating allergy.

FUNDING

Austrian Research Promotion Agency (852748 and 862068, 2015-2019), Vienna Business Agency (2343727, 2018-2020), Aposcience AG, Austrian Federal Ministry of Education, Science and Research (SPA06/055), Danube Allergy Research Cluster, Austrian Science Fund (I4437 and P32953).

Role of mesenchymal stromal cells derivatives in diabetic foot ulcers: a controlled randomized phase 1/2 clinical trial

BACKGROUND

Diabetes-related foot complications have been identified as the most common isolated cause of morbidity among patients with diabetes and the leading cause of amputation. Therefore, new strategies to stimulate skin regeneration may provide a novel therapeutic approach to reduce non-healing ulcer disease. Recently, we demonstrated in proof-of-concept in humans that administration of allogeneic bone marrow mesenchymal stromal cellss derivatives (allo-hBM-MSCDs) is effective in a similar way to the use of allogeneic bone marrow mesenchymal stromal cellss (allo-hBM-MSCs) in grade 2 diabetic foot ulcers (DFUs).

AIM

To assess the safety and efficacy profile of the allo-hBM-MSCDs relative to the conventional approach (PolyMen® dressing) in 1/2 clinical trial phases in patients with grade 1 and 2 DFUs.

METHODS

In the present study, we used 2 doses of allo-hBM-MSCDs (1 mL) or 1 dose of allo-hBM-MSCs (1 × 106 cells) intradermally injected around wounds and assessed their safety and effectiveness, relative to the conventional approach (PolyMem dressing). Allo-hBM-MSCDs and allo-hBM-MSCs were produced in a certified Good Manufacturing Practice-type Laboratory. Patients with grade 1 and 2 DFUs were randomized to receive allo-hBM-MSCDs (n=12), allo-hBM-MSCs (n=6) or conventional treatment (PolyMem dressing) (n=10). The wound-healing process was macroscopically evaluated until the complete closure of the ulcers.

RESULTS

No adverse events were reported. Patients with grade 1 and 2 DFUs treated with either allo-hBM-MSCDs or allo-hBM-MSCs, achieved greater percentages of wound closure, enhanced skin regeneration in shorter times and a greater ulcer-free survival relative to the patients who received conventional treatment. Finally, through proteomic analysis, we elucidated the proteins and growth factors that are secreted by allo-hBM-MSCs and relevant to the wound-healing process. In addition, by combining proteomics with Gene Ontology analysis, we comprehensively classified secreted proteins on both biological process and molecular function.

CONCLUSIONS

In this phase 1/2 trial, our cumulative results suggest that 2 doses of allo-hBM-MSCDs combined with a wound dressing are a safe and effective treatment for grade 1 and 2 DFUs.

Secretomes as an emerging class of bioactive ingredients for enhanced cosmeceutical applications

Skin aging is predominantly caused by either intrinsic or extrinsic factors, leading to undesirable skin features. Advancements in both molecular and cellular fields have created possibilities in developing novel stem cell-derived active ingredients for cosmeceutical applications and the beauty industry. Mesenchymal stromal cell (MSC)-derived secretomes or conditioned media hold great promise for advancing skin repair and regeneration due to the presence of varying cytokines. These cytokines signal our cells and trigger biological mechanisms associated with anti-inflammatory, antioxidant, anti-aging, proliferative, and immunomodulatory effects. In this review, we discuss the potential of MSC secretomes as novel biomaterials for skincare and rejuvenation by illustrating their mechanism of action related to wound healing, anti-aging, and whitening properties. The advantages and disadvantages of secretomes are compared to both plant-based and animal-derived extracts. In addition, this paper reviews the current safety standards, regulations, market products and research work related to the cosmeceutical applications of secretomes along with strategies to maintain and improve the therapeutic efficacy and production of secretomes. The future outlook of beauty industry is also presented. Lastly, we highlight significant challenges to be addressed for the clinical realization of MSC secretomes-based skin therapies as well as providing perspectives for the future direction of secretomes.

Polymeric Hydrogels as Mesenchymal Stem Cell Secretome Delivery System in Biomedical Applications

Secretomes of mesenchymal stem cells (MSCs) have been successfully studied in preclinical models for several biomedical applications, including tissue engineering, drug delivery, and cancer therapy. Hydrogels are known to imitate a three-dimensional extracellular matrix to offer a friendly environment for stem cells; therefore, hydrogels can be used as scaffolds for tissue construction, to control the distribution of bioactive compounds in tissues, and as a secretome-producing MSC culture media. The administration of a polymeric hydrogel-based MSC secretome has been shown to overcome the fast clearance of the target tissue. In vitro studies confirm the bioactivity of the secretome encapsulated in the gel, allowing for a controlled and sustained release process. The findings reveal that the feasibility of polymeric hydrogels as MSC -secretome delivery systems had a positive influence on the pace of tissue and organ regeneration, as well as an enhanced secretome production. In this review, we discuss the widely used polymeric hydrogels and their advantages as MSC secretome delivery systems in biomedical applications.

Secretome of Stressed Peripheral Blood Mononuclear Cells Alters Transcriptome Signature in Heart, Liver, and Spleen after an Experimental Acute Myocardial Infarction: An In Silico Analysis

Simple Summary

Acute myocardial infarction is characterized by impaired coronary blood flow, which leads to cardiac ischemia and, ultimately, compromised heart function. Damage and cellular responses are not limited to the non-perfused area, but rather affect the entire heart, as well as distal organs, such as the liver and spleen. We found that the therapeutic secretome of stressed white blood cells improved short-term and long-term cardiac performance in a porcine infarction model. In order to unravel the molecular events governing secretome-mediated tissue regeneration, we performed transcriptional analyses of the non-perfused, transition, and perfused heart, as well as the liver and spleen 24 h after myocardial infarction. We observed a highly tissue-specific effect of the secretome and, except for the transition zone, a uniform downregulation of pro-inflammatory factors and pathways. Simultaneously, the secretome strongly promoted the expression of genes that are essential for heart function in the non-perfused area. In the liver and spleen, different metabolic processes were induced. Together, our data suggest several plausible mechanisms by which the secretome improves heart function after cardiac ischemia. Deepening our understanding of the molecular processes identified here might uncover further pharmacologic strategies aiming at delimiting adverse cardiac remodeling and sequelae after myocardial infarction.

Abstract

Acute myocardial infarction (AMI) is a result of cardiac non-perfusion and leads to cardiomyocyte necrosis, inflammation, and compromised cardiac performance. Here, we showed that the secretome of γ-irradiated peripheral blood mononuclear cells (PBMCsec) improved heart function in a porcine AMI model and displayed beneficial long- and short-term effects. As an AMI is known to strongly affect gene regulation of the ischemia non-affected heart muscle and distal organs, we employed a transcriptomics approach to further study the immediate molecular events orchestrated using the PBMCsec in myocardium, liver, and spleen 24 h post ischemia. In the infarcted area, the PBMCsec mainly induced genes that were essential for cardiomyocyte function and simultaneously downregulated pro-inflammatory genes. Interestingly, genes associated with pro-inflammatory processes were activated in the transition zone, while being downregulated in the remote zone. In the liver, we observed a pronounced inhibition of immune responses using the PBMCsec, while genes involved in urea and tricarboxylic cycles were induced. The spleen displayed elevated lipid metabolism and reduced immunological processes. Together, our study suggested several types of pharmacodynamics by which the PBMCsec conferred immediate cardioprotection. Furthermore, our data supported the assumption that an AMI significantly affects distal organs, suggesting that a holistic treatment of an AMI, as achieved by PBMCsec, might be highly beneficial.

Iron-Quercetin Complex Preconditioning of Human Peripheral Blood Mononuclear Cells Accelerates Angiogenic and Fibroblast Migration: Implications for Wound Healing

Cell-based therapy is a highly promising treatment paradigm in ischemic disease due to its ability to repair tissue when implanted into a damaged site. These therapeutic effects involve a strong paracrine component resulting from the high levels of bioactive molecules secreted in response to the local microenvironment. Therefore, the secreted therapeutic can be modulated by preconditioning the cells during in vitro culturing. Herein, we investigated the potential use of magnetic resonance imaging (MRI) probes, the "iron-quercetin complex" or IronQ, for preconditioning peripheral blood mononuclear cells (PBMCs) to expand proangiogenic cells and enhance their secreted therapeutic factors. PBMCs obtained from healthy donor blood were cultured in the presence of the iron-quercetin complex. Differentiated preconditioning PBMCs were characterized by immunostaining. An enzyme-linked immunosorbent assay was carried out to describe the secreted cytokines. In vitro migration and tubular formation using human umbilical vein endothelial cells (HUVECs) were completed to investigate the proangiogenic efficacy. IronQ significantly increased mononuclear progenitor cell proliferation and differentiation into spindle-shape-like cells, expressing both hematopoietic and stromal cell markers. The expansion increased the number of colony-forming units (CFU-Hill). The conditioned medium obtained from IronQ-treated PBMCs contained high levels of interleukin 8 (IL-8), IL-10, urokinase-type-plasminogen-activator (uPA), matrix metalloproteinases-9 (MMP-9), and tumor necrosis factor-alpha (TNF-α), as well as augmented migration and capillary network formation of HUVECs and fibroblast cells, in vitro. Our study demonstrated that the IronQ-preconditioning PBMC protocol could enhance the angiogenic and reparative potential of non-mobilized PBMCs. This protocol might be used as an adjunctive strategy to improve the efficacy of cell therapy when using PBMCs for ischemic diseases and chronic wounds. However, in vivo assessment is required for further validation.

Nanomaterials in Skin Regeneration and Rejuvenation

Skin is the external part of the human body; thus, it is exposed to outer stimuli leading to injuries and damage, due to being the tissue mostly affected by wounds and aging that compromise its protective function. The recent extension of the average lifespan raises the interest in products capable of counteracting skin related health conditions. However, the skin barrier is not easy to permeate and could be influenced by different factors. In the last decades an innovative pharmacotherapeutic approach has been possible thanks to the advent of nanomedicine. Nanodevices can represent an appropriate formulation to enhance the passive penetration, modulate drug solubility and increase the thermodynamic activity of drugs. Here, we summarize the recent nanotechnological approaches to maintain and replace skin homeostasis, with particular attention to nanomaterials applications on wound healing, regeneration and rejuvenation of skin tissue. The different nanomaterials as nanofibers, hydrogels, nanosuspensions, and nanoparticles are described and in particular we highlight their main chemical features that are useful in drug delivery and tissue regeneration.

Comparing the efficacy of γ- and electron-irradiation of PBMCs to promote secretion of paracrine, regenerative factors

Cell-free secretomes represent a promising new therapeutic avenue in regenerative medicine, and γ-irradiation of human peripheral blood mononuclear cells (PBMCs) has been shown to promote the release of paracrine factors with high regenerative potential. Recently, the use of alternative irradiation sources, such as artificially generated β- or electron-irradiation, is encouraged by authorities. Since the effect of the less hazardous electron-radiation on the production and functions of paracrine factors has not been tested so far, we compared the effects of γ- and electron-irradiation on PBMCs and determined the efficacy of both radiation sources for producing regenerative secretomes. Exposure to 60 Gy γ-rays from a radioactive nuclide and 60 Gy electron-irradiation provided by a linear accelerator comparably induced cell death and DNA damage. The transcriptional landscapes of PBMCs exposed to either radiation source shared a high degree of similarity. Secretion patterns of proteins, lipids, and extracellular vesicles displayed similar profiles after γ- and electron-irradiation. Lastly, we detected comparable biological activities in functional assays reflecting the regenerative potential of the secretomes. Taken together, we were able to demonstrate that electron-irradiation is an effective, alternative radiation source for producing therapeutic, cell-free secretomes. Our study paves the way for future clinical trials employing secretomes generated with electron-irradiation in tissue-regenerative medicine.