Tailoring of apoptotic bodies for diagnostic and therapeutic applications:advances, challenges, and prospects

Abstract

Apoptotic bodies (ABs) are extracellular vesicles released during apoptosis and possess diverse biological activities. Initially, ABs were regarded as garbage bags with the main function of apoptotic cell clearance. Recent research has found that ABs carry and deliver various biological agents and are taken by surrounding and distant cells, affecting cell functions and behavior. ABs-mediated intercellular communications are involved in various physiological processes including anti-inflammation and tissue regeneration as well as the pathogenesis of a variety of diseases including cancer, cardiovascular diseases, neurodegeneration, and inflammatory diseases. ABs in biological fluids can be used as a window of altered cellular and tissue states which can be applied in the diagnosis and prognosis of various diseases. The structural and constituent versatility of ABs provides flexibility for tailoring ABs according to disease diagnostic and therapeutic needs. An in-depth understanding of ABs' constituents and biological functions is mandatory for the effective tailoring of ABs including modification of bio membrane and cargo constituents. ABs' tailoring approaches including physical, chemical, biological, and genetic have been proposed for bench-to-bed translation in disease diagnosis, prognosis, and therapy. This review summarizes the updates on ABs tailoring approaches, discusses the existing challenges, and speculates the prospects for effective diagnostic and therapeutic applications.

Keywords: Apoptotic bodies; Biology function; Engineering method.

Fig. 1

Illustration of the mechanism of ABs biogenesis. (I) Cell membrane blebbing is activated by active cysteine protease 3 to activate ROCK1, PAK2, MLCK, and LIMK1, leading to actomyosin contraction. (II) Apoptotic membrane protrusion formation through the PANX1 channels and vesicle transport, resulting in the formation of microtubule spikes, bead-like protrusions, and apoptopodia. (III) Fragmentation to form ABs. LIMK1 lim domain kinase 1, MLCK myosin light chain kinase, PAK2 p21-activated kinase, PANX1 pan-catenin 1, PlexB2 plexus B2, ROCK1 Rho-associated protein kinase 1. Created with BioRender.com

Fig. 2

The surface markers and bioactive cargos of ABs. CRT calreticulin, PS phosphatidylserine, PTPRC protein tyrosine phosphatase receptor C, TSP thrombospondin, LFA-1 lymphocyte function-associated antigen 1

Fig. 3

The sources and induction methods of ABs. ABs can be derived from cells, body fluids, and tissues. The in vitro induction methods of ABs to improve the yield. Created with BioRender.com

Fig. 4

Illustration of ABs involved in intercellular communication. ABs can harbor “find-me” signals to attract phagocytic cells, as well as “eat-me” signals to promote uptake by phagocytes. ABs transport biomolecules (e.g., DNA, RNA, protein, and metabolite) to neighboring cells via endocytosis and membrane fusion. BAI1 brain-specific angiogenesis inhibitor 1, MerTK tyrosine-protein kinase Mer, TIM T cell immunoglobulin mucin proteins. Created with BioRender.com

Fig. 5

Reported mechanisms of ABs regulating cell proliferation. A ABs promoted receptor cell proliferation through COX2/IPGE2/EP signaling pathway[17]. B ABs activated the Wnt/β-catenin pathway through the signal protein Wnt8a to promote cell proliferation [18]. C ABs induce proliferation of the recipient cells via miR-221/222 [67]. D ABs promoted cell proliferation by releasing IGF2BP3 and activating PI3K/AKT and P42/44 MAPK pathways in receptor cells [20]. IGF2BP3 insulin growth factor 2 mRNA-binding protein 3. Created with BioRender.com

Fig. 6

Reported mechanisms of ABs regulating cell differentiation. A ABs promote receptor cell differentiation through the PI3K/AKT/mTOR signaling pathway [7, 9, 19]. B ABs carrying PDGF-BB may activate PI3K/AKT pathways to promote cell differentiation [7]. C ABs inhibit the SMAD2 signaling pathway via miR-155 for promoting cell differentiation [68]. D RNF146 and miR-328-3p in ABs inhibit the expression of gene Axin1 to activate the Wnt/β-catenin pathway, thereby promoting cell differentiation [14]. PDGF-BB platelet-derived growth factor-BB, SMAD2 drosophila mothers against decapentaplegic protein 2, RNF146 ring finger protein 146. Created with BioRender.com

Fig. 7

ABs mediated immune response. Anti-inflammatory effect: ABs reduce the expression of pro-inflammatory factors (TNF-α, IL-6, and IL-12) in receptor macrophages, and increase the expression of anti-inflammatory factors (TGF-β and IL-10), inducing M2 macrophage polarization. Pro-inflammatory effect: ABs carry IL-1α, which can induce high expression of neutrophil chemokines and promote neutrophil infiltration to drive sterile inflammation after injection into the peritoneal cavity of mice. Created with BioRender.com

Fig. 8

ABs promote wound healing. A Representative image of scanning electron microscopy analysis analysis of MSC-ABs. B Size distribution of MSC-ABs. C Representative images of C1q and Annexin V staining of MSC-ABs. D Representative images of the H&E staining of the skin samples. E Representative images of the Masson staining of the skin samples. F The immunofluorescence images and quantification of the CD206 expression level of macrophages treated with different concentrations of ABs. G Schema of transplanted MSCs undergo apoptosis after transplantation in a mouse skin wound model and releasing ABs, converting macrophages towards the M2 phenotype and further enhancing the functions of fibroblasts, together contributing to the cutaneous wound healing process. Adapted with permission from ref. [39], image licensed under http://creativecommons.org/licenses/by/4.0/

Fig. 9

Engineering ABs for therapeutic application. A Schematic of engineered neutrophil ABs (eNABs) for MI treatment. B Representative fluorescence images of the macrophage phenotypes and the percentage of the iNOS/CD206-positive population. C Representative echocardiographic images for various groups after 4 weeks. Distance between yellow arrows indicates left ventricular internal end-diastolic dimension (LVIDd) and left ventricular internal end-systolic dimension (LVIDs), respectively. Adapted with permission from ref [38]

Fig. 10

Drug loading strategies for ABs. A transfection, B co-incubation, and C membrane coating. Created with BioRender.com

Fig. 11

Potential feasible methods for surface modification of ABs. Created with BioRender.com

Fig. 12

Engineering modification of ABs. Created with BioRender.com