Toxicological testing of allogeneic secretome derived from peripheral mononuclear cells (APOSEC): a novel cell-free therapeutic agent in skin disease

Hydrogel Breakthroughs in Biomedicine: Recent Advances and Implications

OBJECTIVE

The objective of this review is to present a succinct summary of the latest advancements in the utilization of hydrogels for diverse biomedical applications, with a particular focus on their revolutionary impact in augmenting the delivery of drugs, tissue engineering, along with diagnostic methodologies.

METHODS

Using a meticulous examination of current literary works, this review systematically scrutinizes the nascent patterns in applying hydrogels for biomedical progress, condensing crucial discoveries to offer a comprehensive outlook on their ever-changing importance.

RESULTS

The analysis presents compelling evidence regarding the growing importance of hydrogels in biomedicine. It highlights their potential to significantly enhance drug delivery accuracy, redefine tissue engineering strategies, and advance diagnostic techniques. This substantiates their position as a fundamental element in the progress of modern medicine.

CONCLUSION

In summary, the constantly evolving advancement of hydrogel applications in biomedicine calls for ongoing investigation and resources, given their diverse contributions that can revolutionize therapeutic approaches and diagnostic methods, thereby paving the way for improved patient well-being.

Ultrasound Responsive Smart Implantable Hydrogels for Targeted Delivery of Drugs: Reviewing Current Practices

Over the last two decades, the process of delivering therapeutic drugs to a patient with a controlled release profile has been a significant focus of drug delivery research. Scientists have given tremendous attention to ultrasound-responsive hydrogels for several decades. These smart nanosystems are more applicable than other stimuli-responsive drug delivery vehicles (ie UV-, pH- and thermal-, responsive materials) because they enable more efficient targeted treatment via relatively non-invasive means. Ultrasound (US) is capable of safely transporting energy through opaque and complex media with minimal loss of energy. It is capable of being localized to smaller regions and coupled to systems operating at various time scales. However, the properties enabling the US to propagate effectively in materials also make it very difficult to transform acoustic energy into other forms that may be used. Recent research from a variety of domains has attempted to deal with this issue, proving that ultrasonic effects can be used to control chemical and physical systems with remarkable specificity. By obviating the need for multiple intravenous injections, implantable US responsive hydrogel systems can enhance the quality of life for patients who undergo treatment with a varied dosage regimen. Ideally, the ease of self-dosing in these systems would lead to increased patient compliance with a particular therapy as well. However, excessive literature has been reported based on implanted US responsive hydrogel in various fields, but there is no comprehensive review article showing the strategies to control drug delivery profile. So, this review was aimed at discussing the current strategies for controlling and targeting drug delivery profiles using implantable hydrogel systems.

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).

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.

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.

Current hydrogel advances in physicochemical and biological response-driven biomedical application diversity

Hydrogel is a type of versatile platform with various biomedical applications after rational structure and functional design that leverages on material engineering to modulate its physicochemical properties (e.g., stiffness, pore size, viscoelasticity, microarchitecture, degradability, ligand presentation, stimulus-responsive properties, etc.) and influence cell signaling cascades and fate. In the past few decades, a plethora of pioneering studies have been implemented to explore the cell-hydrogel matrix interactions and figure out the underlying mechanisms, paving the way to the lab-to-clinic translation of hydrogel-based therapies. In this review, we first introduced the physicochemical properties of hydrogels and their fabrication approaches concisely. Subsequently, the comprehensive description and deep discussion were elucidated, wherein the influences of different hydrogels properties on cell behaviors and cellular signaling events were highlighted. These behaviors or events included integrin clustering, focal adhesion (FA) complex accumulation and activation, cytoskeleton rearrangement, protein cyto-nuclei shuttling and activation (e.g., Yes-associated protein (YAP), catenin, etc.), cellular compartment reorganization, gene expression, and further cell biology modulation (e.g., spreading, migration, proliferation, lineage commitment, etc.). Based on them, current in vitro and in vivo hydrogel applications that mainly covered diseases models, various cell delivery protocols for tissue regeneration and disease therapy, smart drug carrier, bioimaging, biosensor, and conductive wearable/implantable biodevices, etc. were further summarized and discussed. More significantly, the clinical translation potential and trials of hydrogels were presented, accompanied with which the remaining challenges and future perspectives in this field were emphasized. Collectively, the comprehensive and deep insights in this review will shed light on the design principles of new biomedical hydrogels to understand and modulate cellular processes, which are available for providing significant indications for future hydrogel design and serving for a broad range of biomedical applications.

Mesenchymal Stem Cell Secretome for Dermatology Application: A Review

Secretome, also known as conditioned medium, is a secreted molecule from mesenchymal stem cells (MSCs) that has a variety of biological activities that can be used in various therapies, especially on the skin applications. A lack of conventional therapies makes secretome as a promising alternative therapy. The presence of growth factors, cytokines, and extracellular vesicles including microvesicles and exosomes in secretome has been widely reported, which serves in improving the proliferation and migration of cells to help in skin regeneration. Therefore, we were able to optimize the use of this secretome in a well-needed special review related to its work in addressing various skin problems. So, in this article, we discussed the benefits and biological activity of secretome on the skin application. This review was compiled based on the approval of several sites, such as Scopus, PubMed, Science Direct, and Google Scholar with the terms "MSC secretome for skin," "secretome for skin," "secretome dermatology," "secretome conditioned medium for skin," "secretome conditioned medium for skin wound," "secretome conditioned medium for aging," "secretome conditioned medium for hair growth," and "secretome conditioned medium for psoriasis." A total of 215 articles were collected for selection, of which 90 articles were used. Based on the results, it was concluded that secretome has a variety of useful activities to regenerate and repair tissue damage that have not been used on the skin, such as for wound healing, photoprotection, promotion of hair growth, psoriasis treatment, and other application as antimicrobial.

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.

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

Background

Diabetes and its sequelae such as diabetic foot ulcer are rising health hazards not only in western countries but all over the world. Effective, yet safe treatments are desperately sought for by physicians, healthcare providers, and of course patients.

Methods/design

APOSEC, a novel, innovative drug, is tested in the phase I/II study MARSYAS II, where its efficacy to promote healing of diabetic foot ulcers will be determined. To this end, the cell-free secretome of peripheral blood mononuclear cells (APOSEC) blended with a hydrogel will be applied topically three times weekly for 4 weeks. APOSEC is predominantly effective in hypoxia-induced tissue damages by modulating the immune system and enhancing angiogenesis, whereby its anti-microbial ability and neuro-regenerative capacity will exert further positive effects. In total, 132 patients will be enrolled in the multicenter, randomized, double-blind, placebo-controlled, parallel group, dose-ranging phase I/II study and treated with APOSEC at three dose levels or placebo for 4 weeks, followed by an 8-week follow-up period to evaluate safety and efficacy of the drug. Wound area reduction after 4 weeks of treatment will serve as the primary endpoint.

Conclusion

We consider our study protocol to be suitable to test topically administered APOSEC in patients suffering from diabetic foot ulcers in a clinical phase I/II trial.

Trial registration

EudraCT 2018-001653-27. Registered on 30 July 2019. ClinicalTrials.gov NCT04277598. Registered on 20 February 2020. Title: “A randomized, placebo-controlled, double-blind study to evaluate safety and dose-dependent clinical efficacy of APO-2 at three different doses in patients with diabetic foot ulcer (MARSYAS II)”

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-020-04948-1.

The secretome of stressed peripheral blood mononuclear cells increases tissue survival in a rodent epigastric flap model

Reconstructive surgery transfers viable tissue to cover defects and to restore aesthetic and functional properties. Failure rates after free flap surgery range from 3 to 7%. Co-morbidities such as diabetes mellitus or peripheral vascular disease increase the risk of flap failure up to 4.5-fold. Experimental therapeutic concepts commonly use a monocausal approach by applying single growth factors. The secretome of γ-irradiated, stressed peripheral blood mononuclear cells (PBMCsec) resembles the physiological environment necessary for tissue regeneration. Its application led to improved wound healing rates and a two-fold increase in blood vessel counts in previous animal models. We hypothesized that PBMCsec has beneficial effects on the survival of compromised flap tissue by reducing the necrosis rate and increasing angiogenesis. Surgery was performed on 39 male Sprague-Dawley rats (control, N = 13; fibrin sealant, N = 14; PBMCsec, N = 12). PBMCsec was produced according to good manufacturing practices (GMP) guidelines and 2 ml were administered intraoperatively at a concentration of 2.5 × 107 cells/ml using fibrin sealant as carrier substance. Flap perfusion and necrosis (as percentage of the total flap area) were analyzed using Laser Doppler Imaging and digital image planimetry on postoperative days 3 and 7. Immunohistochemical stainings for von Willebrand factor (vWF) and Vascular Endothelial Growth Factor-receptor-3 (Flt-4) were performed on postoperative day 7 to evaluate formation of blood vessels and lymphatic vessels. Seroma formation was quantified using a syringe and flap adhesion and tissue edema were evaluated clinically through a cranial incision by a blinded observer according to previously described criteria on postoperative day 7. We found a significantly reduced tissue necrosis rate (control: 27.8% ± 8.6; fibrin: 22.0% ± 6.2; 20.9% reduction, p = .053 vs. control; PBMCsec: 19.1% ± 7.2; 31.1% reduction, p = .012 vs. control; 12.9% reduction, 0.293 vs. fibrin) together with increased vWF+ vessel counts (control: 70.3 ± 16.3 vessels/4 fields at 200× magnification; fibrin: 67.8 ± 12.1; 3.6% reduction, p = .651, vs. control; PBMCsec: 85.9 ± 20.4; 22.2% increase, p = .045 vs. control; 26.7% increase, p = .010 vs. fibrin) on postoperative day 7 after treatment with PBMCsec. Seroma formation was decreased after treatment with fibrin sealant with or without the addition of PBMCsec. (control: 11.9 ± 9.7 ml; fibrin: 1.7 ± 5.3, 86.0% reduction, 0.004 vs. control; PBMCsec: 0.6 ± 2.0; 94.8% reduction, p = .001 vs. control; 62.8% reduction, p = .523 vs. fibrin). We describe the beneficial effects of a secretome derived from γ-irradiated PBMCs on tissue survival, angiogenesis, and clinical parameters after flap surgery in a rodent epigastric flap model.

TGF-β in the Secretome of Irradiated Peripheral Blood Mononuclear Cells Supports In Vitro Osteoclastogenesis

Osteoclastogenesis required for bone remodeling is also a key pathologic mechanism of inflammatory osteolysis being controlled by paracrine factors released from dying cells. The secretome of irradiated, dying peripheral blood mononuclear cells (PBMCs) has a major impact on the differentiation of myeloid cells into dendritic cells, and macrophage polarization. The impact on osteoclastogenesis, however, has not been reported. For this aim, we used murine bone marrow macrophages exposed to RANKL and M-CSF to initiate osteoclastogenesis, with and without the secretome obtained from γ-irradiated PBMCs. We reported that the secretome significantly enhanced in vitro osteoclastogenesis as determined by means of histochemical staining of the tartrate-resistant acid phosphatase (TRAP), as well as the expression of the respective target genes, including TRAP and cathepsin K. Considering that TGF-β enhanced osteoclastogenesis, we confirmed the TGF-β activity in the secretome with a bioassay that was based on the increased expression of IL11 in fibroblasts. Neutralizing TGF-β by an antibody decreased the ability of the secretome to support osteoclastogenesis. These findings suggested that TGF-β released by irradiated PBMCs could enhance the process of osteoclastogenesis in vitro.

Role for Lipids Secreted by Irradiated Peripheral Blood Mononuclear Cells in Inflammatory Resolution in Vitro

Periodontal inflammation is associated with dying cells that potentially release metabolites helping to promote inflammatory resolution. We had shown earlier that the secretome of irradiated, dying peripheral blood mononuclear cells support in vitro angiogenesis. However, the ability of the secretome to promote inflammatory resolution remains unknown. Here, we determined the expression changes of inflammatory cytokines in murine bone marrow macrophages, RAW264.7 cells, and gingival fibroblasts exposed to the secretome obtained from γ-irradiated peripheral blood mononuclear cells in vitro by RT-PCR and immunoassays. Nuclear translocation of p65 was detected by immunofluorescence staining. Phosphorylation of p65 and degradation of IκB was determined by Western blot. The secretome of irradiated peripheral blood mononuclear cells significantly decreased the expression of IL1 and IL6 in primary macrophages and RAW264.7 cells when exposed to LPS or saliva, and of IL1, IL6, and IL8 in gingival fibroblasts when exposed to IL-1β and TNFα. These changes were associated with decreased phosphorylation and nuclear translocation of p65 but not degradation of IκB in macrophages. We also show that the lipid fraction of the secretome lowered the inflammatory response of macrophages exposed to the inflammatory cues. These results demonstrate that the secretome of irradiated peripheral blood mononuclear cells can lower an in vitro simulated inflammatory response, supporting the overall concept that the secretome of dying cells promotes inflammatory resolution.

Therapeutic potential of lipids obtained from γ-irradiated PBMCs in dendritic cell-mediated skin inflammation

BACKGROUND

Since numerous pathological conditions are evoked by unwanted dendritic cell (DC) activity, therapeutic agents modulating DC functions are of great medical interest. In regenerative medicine, cellular secretomes have gained increasing attention and valuable immunomodulatory properties have been attributed to the secretome of γ-irradiated peripheral blood mononuclear cells (PBMCs). Potential effects of the PBMC secretome (PBMCsec) on key DC functions have not been elucidated so far.

METHODS

We used a hapten-mediated murine model of contact hypersensitivity (CH) to study the effects of PBMCsec on DCs in vivo. Effects of PBMCsec on human DCs were investigated in monocyte-derived DCs (MoDC) and ex vivo skin cultures. DCs were phenotypically characterised by transcriptomics analyses and flow cytometry. DC function was evaluated by cytokine secretion, antigen uptake, PBMC proliferation and T-cell priming.

FINDINGS

PBMCsec significantly alleviated tissue inflammation and cellular infiltration in hapten-sensitized mice. We found that PBMCsec abrogated differentiation of MoDCs, indicated by lower expression of classical DC markers CD1a, CD11c and MHC class II molecules. Furthermore, PBMCsec reduced DC maturation, antigen uptake, lipopolysaccharides-induced cytokine secretion, and DC-mediated immune cell proliferation. Moreover, MoDCs differentiated with PBMCsec displayed diminished ability to prime naïve CD4+T-cells into TH1 and TH2 cells. Furthermore, PBMCsec modulated the phenotype of DCs present in the skin in situ. Mechanistically, we identified lipids as the main biomolecule accountable for the observed immunomodulatory effects.

INTERPRETATION

Together, our data describe DC-modulatory actions of lipids secreted by stressed PBMCs and suggest PBMCsec as a therapeutic option for treatment of DC-mediated inflammatory skin conditions.

FUNDING

This research project was supported by the Austrian Research Promotion Agency (Vienna, Austria; grant "APOSEC" 862068; 2015-2019) and the Vienna Business Agency (Vienna, Austria; grant "APOSEC to clinic" 2343727).

Reproducibility of GMP-compliant production of therapeutic stressed peripheral blood mononuclear cell-derived secretomes, a novel class of biological medicinal products

BACKGROUND

The recent concept of secretome-based tissue regeneration has profoundly altered the field of regenerative medicine and offers promising novel therapeutic options. In contrast to medicinal products with a single active substance, cell-derived secretomes comprise pleiotropic bioactive ingredients, representing a major obstacle for reproducible drug product efficacy and warranting patient safety. Good manufacturing practice (GMP)-compliant production guarantees high batch-to-batch consistency and reproducible efficacy of biological medicinal products, but different batches of cellular secretomes produced under GMP have not been compared yet, and suitable quality control parameters have not been established. To this end, we analyzed diverse biological and functional parameters of different batches produced under GMP of the secretome obtained from γ-irradiated peripheral blood mononuclear cells with proven tissue regenerative properties in infarcted myocardium, stroke, spinal cord injury, and skin wounds.

METHODS

We quantified key secretome ingredients, including cytokines, lipids, and extracellular vesicles, and functionally assessed potency in tube formation assay, ex vivo aortic ring sprouting assay, and cell-based protein and reporter gene assays. Furthermore, we determined secretome stability in different batches after 6 months of storage at various ambient temperatures.

RESULTS

We observed that inter-batch differences in the bioactive components and secretome properties were small despite considerable differences in protein concentrations and potencies between individual donor secretomes. Stability tests showed that the analytical and functional properties of the secretomes remained stable when lyophilisates were stored at temperatures up to + 5 °C for 6 months.

CONCLUSIONS

We are the first to demonstrate the consistent production of cell-derived, yet cell-free secretome as a biological medicinal product. The results from this study provide the basis for selecting appropriate quality control parameters for GMP-compliant production of therapeutic cell secretomes and pave the way for future clinical trials employing secretomes in tissue regenerative medicine.

Tissue-regenerative potential of the secretome of γ-irradiated peripheral blood mononuclear cells is mediated via TNFRSF1B-induced necroptosis

Peripheral blood mononuclear cells (PBMCs) have been shown to produce and release a plethora of pro-angiogenetic factors in response to γ-irradiation, partially accounting for their tissue-regenerative capacity. Here, we investigated whether a certain cell subtype of PBMCs is responsible for this effect, and whether the type of cell death affects the pro-angiogenic potential of bioactive molecules released by γ-irradiated PBMCs. PBMCs and PBMC subpopulations, including CD4⁺ and CD8⁺ T cells, B cells, monocytes, and natural killer cells, were isolated and subjected to high-dose γ-irradiation. Transcriptome analysis revealed subpopulation-specific responses to γ-irradiation with distinct activation of pro-angiogenic pathways, cytokine production, and death receptor signalling. Analysis of the proteins released showed that interactions of the subsets are important for the generation of a pro-angiogenic secretome. This result was confirmed at the functional level by the finding that the secretome of γ-irradiated PBMCs displayed higher pro-angiogenic activity in an aortic ring assay. Scanning electron microscopy and image stream analysis of γ-irradiated PBMCs revealed distinct morphological changes, indicative for apoptotic and necroptotic cell death. While inhibition of apoptosis had no effect on the pro-angiogenic activity of the secretome, inhibiting necroptosis in stressed PBMCs abolished blood vessel sprouting. Mechanistically, we identified tumor necrosis factor (TNF) receptor superfamily member 1B as the main driver of necroptosis in response to γ-irradiation in PBMCs, which was most likely mediated via membrane-bound TNF-α. In conclusion, our study demonstrates that the pro-angiogenic activity of the secretome of γ-irradiated PBMCs requires interplay of different PBMC subpopulations. Furthermore, we show that TNF-dependent necroptosis is an indispensable molecular process for conferring tissue-regenerative activity and for the pro-angiogenic potential of the PBMC secretome. These findings contribute to a better understanding of secretome-based therapies in regenerative medicine.