Analysis of the Secretome of Apoptotic Peripheral Blood Mononuclear Cells: Impact of Released Proteins and Exosomes for Tissue Regeneration

Abstract

We previously showed that, when peripheral blood mononuclear cells (PBMCs) were stressed with ionizing radiation, they released paracrine factors that showed regenerative capacity in vitro and in vivo. This study aimed to characterize the secretome of PBMCs and to investigate its biologically active components in vitro and vivo. Bioinformatics analysis revealed that irradiated PBMCs differentially expressed genes that encoded secreted proteins. These genes were primarily involved in (a) pro-angiogenic and regenerative pathways and (b) the generation of oxidized phospholipids with known pro-angiogenic and inflammation-modulating properties. Subsequently, in vitro assays showed that the exosome and protein fractions of irradiated and non-irradiated PBMC secretome were the major biological components that enhanced cell mobility; conversely, secreted lipids and microparticles had no effects. We tested a viral-cleared PBMC secretome, prepared according to good manufacturing practice (GMP), in a porcine model of closed chest, acute myocardial infarction. We found that the potency for preventing ventricular remodeling was similar with the GMP-compliant and experimentally-prepared PBMC secretomes. Our results indicate that irradiation modulates the release of proteins, lipid-mediators and extracellular vesicles from human PBMCs. In addition our findings implicate the use of secretome fractions as valuable material for the development of cell-free therapies in regenerative medicine.

Peripheral Blood Mononuclear Cell Secretome for Tissue Repair

“…They drew attention to the fact that 5-25 % of all injected stem cells are apoptotic [34] and proposed that these dying cells attenuate inflammatory reactions via the induction of anti-inflammatory cytokines (e.g., TGF-β, IL-10) by macrophages. This hypothesis was supported by the observation that apoptotic neutrophils augment TGF-β, prostaglandin E2 (PGE2), and platelet activation factor expression in phagocytes, whereas inflammatory survival, such as nanovesicles [58], lipids [59], exosomes, and proteins [60].…”

Peripheral blood mononuclear cell secretome for tissue repair

“…Figuratively speaking, the apoptotic cells alert surrounding cells of danger and help protect and survive by entering the process of programmed cell death in a kamikaze-like mission. Apoptotic cells release growth signals that stimulate cell proliferation and survival, such as nanovesicles [58], lipids [59], exosomes, and proteins [60]. …”

Therapeutic Potential of Paracrine Factors and Secretome-based Treatment in Spinal Cord Injury

“…Aside from secreted proteins, we found oxidized lipids, microvesicles and exosomes. Within these vesicles, either actively secreted or a by-product of apoptotic breakdown, high contents of specific RNA, proteins and lipids were observed [29,30] .…”

“…Thirdly, ApoSec was shown to be capable of modulating the inflammatory response in-vitro and in-vivo [25] . And finally, many factors present in the secretome were successfully tested as single-factor treatment in various pre-clinical SCI studies [27,30] .…”