Enhanced tumor growth inhibition by mesenchymal stem cells derived from iPSCs with targeted integration of interleukin24 into rDNA loci

The application potential of iMSCs and iMSC-EVs in diseases

The immune system, functioning as the body's "defense army", plays a role in surveillance, defense. Any disruptions in immune system can lead to the development of immune-related diseases. Extensive researches have demonstrated the crucial immunoregulatory role of mesenchymal stem cells (MSCs) in these diseases. Of particular interest is the ability to induce somatic cells under specific conditions, generating a new cell type with stem cell characteristics known as induced pluripotent stem cell (iPSC). The differentiation of iPSCs into MSCs, specifically induced pluripotent stem cell-derived mesenchymal stem cells (iMSCs), hold promise as a potential solution to the challenges of MSCs, potentially serving as an alternative to traditional drug therapies. Moreover, the products of iMSCs, termed induced pluripotent stem cell-derived mesenchymal stem cell-derived extracellular vesicles (iMSC-EVs), may exhibit functions similar to iMSCs. With the biological advantages of EVs, they have become the focus of "cell-free therapy". Here, we provided a comprehensive summary of the biological impact of iMSCs on immune cells, explored the applications of iMSCs and iMSC-EVs in diseases, and briefly discussed the fundamental characteristics of EVs. Finally, we overviewed the current advantages and challenges associated with iMSCs and iMSC-EVs. It is our hope that this review related to iMSCs and iMSC-EVs will contribute to the development of new approaches for the treatment of diseases.

Fusion with ARRDC1 or CD63: A Strategy to Enhance p53 Loading into Extracellular Vesicles for Tumor Suppression

Small extracellular vesicles (sEVs) have emerged as promising therapeutic agents and drug delivery vehicles. Targeted modification of sEVs and their contents using genetic modification strategies is one of the most popular methods. This study investigated the effects of p53 fusion with arrestin domain-containing protein 1 (ARRDC1) and CD63 on the generation of sEVs, p53 loading efficiency, and therapeutic efficacy. Overexpression of either ARRDC1-p53 (ARP) or CD63-p53 (CDP) significantly elevated p53 mRNA and protein levels. The incorporation of ARRDC1 and CD63 significantly enhanced HEK293T-sEV biogenesis, evidenced by significant increases in sEV-associated proteins TSG101 and LAMP1, resulting in a boost in sEV production. Importantly, fusion with ARRDC1 or CD63 substantially increased the efficiency of loading both p53 fusion proteins and its mRNA into sEVs. sEVs equipped with ARP or CDP significantly enhanced the enrichment of p53 fusion proteins and mRNA in p53-null H1299 cells, resulting in a marked increase in apoptosis and a reduction in cell proliferation, with ARP-sEVs demonstrating greater effectiveness than CDP-sEVs. These findings underscore the enhanced functionality of ARRDC1- and CD63-modified sEVs, emphasizing the potential of genetic modifications in sEV-based therapies for targeted cancer treatment.

iPSC-derived NK cells with site-specific integration of CAR19 and IL24 at the multi-copy rDNA locus enhanced antitumor activity and proliferation

The generation of chimeric antigen receptor-modified natural killer (CAR-NK) cells using induced pluripotent stem cells (iPSCs) has emerged as one of the paradigms for manufacturing off-the-shelf universal immunotherapy. However, there are still some challenges in enhancing the potency, safety, and multiple actions of CAR-NK cells. Here, iPSCs were site-specifically integrated at the ribosomal DNA (rDNA) locus with interleukin 24 (IL24) and CD19-specific chimeric antigen receptor (CAR19), and successfully differentiated into iPSC-derived NK (iNK) cells, followed by expansion using magnetic beads in vitro. Compared with the CAR19-iNK cells, IL24 armored CAR19-iNK (CAR19-IL24-iNK) cells showed higher cytotoxic capacity and amplification ability in vitro and inhibited tumor progression more effectively with better survival in a B-cell acute lymphoblastic leukaemia (B-ALL) (Nalm-6 (Luc1))-bearing mouse model. Interestingly, RNA-sequencing analysis showed that IL24 may enhance iNK cell function through nuclear factor kappa B (NFκB) pathway-related genes while exerting a direct effect on tumor cells. This study proved the feasibility and potential of combining IL24 with CAR-iNK cell therapy, suggesting a novel and promising off-the-shelf immunotherapy strategy.

Identification of the Efficient Enhancer Elements in FVIII-Padua for Gene Therapy Study of Hemophilia A

Hemophilia A (HA) is a common X-linked recessive hereditary bleeding disorder. Coagulation factor VIII (FVIII) is insufficient in patients with HA due to the mutations in the F8 gene. The restoration of plasma levels of FVIII via both recombinant B-domain-deleted FVIII (BDD-FVIII) and B-domain-deleted F8 (BDDF8) transgenes was proven to be helpful. FVIII-Padua is a 23.4 kb tandem repeat mutation in the F8 associated with a high F8 gene expression and thrombogenesis. Here we screened a core enhancer element in FVIII-Padua for improving the F8 expression. In detail, we identified a 400 bp efficient enhancer element, C400, in FVIII-Padua for the first time. The core enhancer C400 extensively improved the transcription of BDDF8 driven by human elongation factor-1 alpha in HepG2, HeLa, HEK-293T and induced pluripotent stem cells (iPSCs) with different genetic backgrounds, as well as iPSCs-derived endothelial progenitor cells (iEPCs) and iPSCs-derived mesenchymal stem cells (iMSCs). The expression of FVIII protein was increased by C400, especially in iEPCs. Our research provides a novel molecular target to enhance expression of FVIII protein, which has scientific value and application prospects in both viral and nonviral HA gene therapy strategies.

Current trends and promising clinical utility of IPSC-derived MSC (iMSC)

Mesenchymal stem cells (MSCs) differentiated from human induced pluripotent stem cells (iPSC) or induced MSC (iMSCs) are expected to address issues of scalability and safety as well as the difficulty in producing homogenous clinical grade MSCs as demonstrated by the promising outcomes from preclinical and clinical trials, currently ongoing. The assessment of iMSCs based in vitro and in vivo studies have thus far showed more superior performance as compared to that of the primary or native human MSCs, in terms of cell proliferation, expansion capacity, immunomodulation properties as well as the influence of paracrine signaling and exosomal influence in cell-cell interaction. In this chapter, an overview of current well-established methods in generating a sustainable source of iMSCs involving well defined culture media is discussed followed by the properties of iMSC as compared to that of MSC and its promising prospects for continuous development into potential clinical grade applications.

Current developments and therapeutic potentials of exosomes from induced pluripotent stem cells-derived mesenchymal stem cells

Mesenchymal stem cells (MSCs) are multipotent cells derived from adult human tissues that have the ability to proliferate in vitro and maintain their multipotency, making them attractive cell sources for regenerative medicine. However, MSCs reportedly show limited proliferative capacity with inconsistent therapeutic outcomes due to their heterogeneous nature. On the other hand, induced pluripotent stem cells (iPSC) have emerged as an alternative source for the production of various specialized cell types via their ability to differentiate from all three primary germ layers, leading to applications in regenerative medicine, disease modeling, and drug therapy. Notably, iPSCs can differentiate into MSCs in monolayer, commonly referred to as induced mesenchymal stem cells (iMSCs). These cells show superior therapeutic qualities compared with adult MSCs as the applications of the latter are restricted by passage number and autoimmune rejection when applied in tissue regeneration trials. Furthermore, increasing evidence shows that the therapeutic properties of stem cells are a consequence of the paracrine effects mediated by their secretome such as from exosomes, a type of extracellular vesicle secreted by most cell types. Several studies that investigated the potential of exosomes in regenerative medicine and therapy have revealed promising results. Therefore, this review focuses on the recent findings of exosomes secreted from iMSCs as a potential noncell-based therapy.

Stem Cells for Cancer Therapy: Translating the Uncertainties and Possibilities of Stem Cell Properties into Opportunities for Effective Cancer Therapy

Cancer recurrence and drug resistance following treatment, as well as metastatic forms of cancer, are trends that are commonly encountered in cancer management. Amidst the growing popularity of personalized medicine and targeted therapy as effective cancer treatment, studies involving the use of stem cells in cancer therapy are gaining ground as promising translational treatment options that are actively pursued by researchers due to their unique tumor-homing activities and anti-cancer properties. Therefore, this review will highlight cancer interactions with commonly studied stem cell types, namely, mesenchymal stroma/stem cells (MSC), induced pluripotent stem cells (iPSC), iPSC-derived MSC (iMSC), and cancer stem cells (CSC). A particular focus will be on the effects of paracrine signaling activities and exosomal miRNA interaction released by MSC and iMSCs within the tumor microenvironment (TME) along with their therapeutic potential as anti-cancer delivery agents. Similarly, the role of exosomal miRNA released by CSCs will be further discussed in the context of its role in cancer recurrence and metastatic spread, which leads to a better understanding of how such exosomal miRNA could be used as potential forms of non-cell-based cancer therapy.

Application of mesenchymal stem cells in tumor therapy

Mesenchymal stem cells (MSCs) are multipotent stem cells that exist widely in the human body, which can self-renewal and differentiate into different types of cell. Due to its advantages of tumor tissue tropism and easy to be engineered, it has been widely used in cancer treatment research recently. However, the tumor-promoting or anti-tumor effect of MSCs is controversial, especially for unmodified MSCs. Therefore, researchers are more inclined to use MSCs as carriers to engineer them. With the deepening in understanding of vesicles, it is found that the vesicles derived from MSCs seem to have greater advantages as carriers. Although the current research of MSCs in the treatment of tumors has been initiated in the clinic, there are still many problems to be solved in the pre-clinical application.

The study of cancer cell in stromal environment through induced pluripotent stem cell-derived mesenchymal stem cells

BACKGROUND

The development of mesenchymal stem cells (MSCs) has gained reputation from its therapeutic potential in stem cell regeneration, anti-inflammation, tumor suppression, and drug delivery treatment. Previous studies have shown MSCs have both promoting and suppressing effects against cancer cells. While the limitation of obtaining a large quantity of homologous MSCs for studies and treatment remains a challenge, an alternative approach involving the production of MSCs derived from induced pluripotent stem cells (iPSCs; induced MSCs [iMSCs]) may be a promising prospect given its ability to undergo prolonged passage and with similar therapeutic profiles as that of their MSC counterparts. However, the influence of iMSC in the interaction of cancer cells remains to be explored as such studies are not well established. In this study, we aim to differentiate iPSCs into MSC-like cells as a potential substitute for adult MSCs and evaluate its effect on non-small-cell lung cancer (NSCLC).

METHODS

iMSCs were derived from iPSCs and validated with reference to the International Society of Cellular Therapy guidelines on MSC criteria. To create a stromal environment, the conditioned medium (CM) of iMSCs was harvested and applied for coculturing of NSCLC of H1975 at different concentrations. The H1975 was then harvested for RNA extraction and subjected to next-generation sequencing (NGS) for analysis.

RESULTS

The morphology of iMSCs-CM-treated H1975 was different from an untreated H1975. Our NGS data suggest the occurrence of apoptotic events and the presence of cytokines from H1975's RNA that are treated with iMSCs-CM.

CONCLUSION

Our results have shown that iMSCs may suppress the growth of H1975 by releasing proapoptotic cytokines into coculture media. Using iPSC-derived MSC models allows a deeper study of tumor cross talk between MSC and cancer cells that can be applied for potential future cancer therapy.

Ectopic Expression of FVIII in HPCs and MSCs Derived from hiPSCs with Site-Specific Integration of ITGA2B Promoter-Driven BDDF8 Gene in Hemophilia A

Hemophilia A (HA) is caused by mutations in the coagulation factor VIII (FVIII) gene (F8). Gene therapy is a hopeful cure for HA; however, FVIII inhibitors formation hinders its clinical application. Given that platelets promote coagulation via locally releasing α-granule, FVIII ectopically expressed in platelets has been attempted, with promising results for HA treatment. The B-domain-deleted F8 (BDDF8), driven by a truncated ITGA2B promoter, was targeted at the ribosomal DNA (rDNA) locus of HA patient-specific induced pluripotent stem cells (HA-iPSCs). The F8-modified, human induced pluripotent stem cells (2bF8-iPSCs) were differentiated into induced hematopoietic progenitor cells (iHPCs), induced megakaryocytes (iMKs), and mesenchymal stem cells (iMSCs), and the FVIII expression was detected. The ITGA2B promoter-driven BDDF8 was site-specifically integrated into the rDNA locus of HA-iPSCs. The 2bF8-iPSCs were efficiently differentiated into 2bF8-iHPCs, 2bF8-iMKs, and 2bF8-iMSCs. FVIII was 10.31 ng/10⁶ cells in lysates of 2bF8-iHPCs, compared to 1.56 ng/10⁶ cells in HA-iHPCs, and FVIII was 3.64 ng/10⁶ cells in 2bF8-iMSCs lysates, while 1.31 ng/10⁶ cells in iMSCs with CMV-driven BDDF8. Our results demonstrated a high expression of FVIII in iHPCs and iMSCs derived from hiPSCs with site-specific integration of ITGA2B promoter-driven BDDF8, indicating potential clinical prospects of this platelet-targeted strategy for HA gene therapy.

OUP accepted manuscript

Mesenchymal stem cells (MSCs) are a promising cellular vehicle for transferring anti-cancer factors to malignant tumors. Currently, a variety of anti-cancer agents, including the tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL), have been loaded into MSCs derived from a range of sources through different engineering methods. These engineered MSCs exhibit enormous therapeutic potential for various cancers. To avoid the intrinsic defects of MSCs derived from tissues and the potential risk of viral vectors, TRAIL was site-specifically integrated into the ribosomal DNA (rDNA) locus of human-induced pluripotent stem cells (iPSCs) using a non-viral rDNA-targeting vector and transcription activator-like effector nickases (TALENickases). These genetically modified human iPSCs were differentiated into an unlimited number of homogeneous induced MSCs (TRAIL-iMSCs) that overexpressed TRAIL in both culture supernatants and cell lysates while maintaining MSC-like characteristics over continuous passages. We found that TRAIL-iMSCs significantly induced apoptosis in A375, A549, HepG2, and MCF-7 cells in vitro. After intravenous infusion, TRAIL-iMSCs had a prominent tissue tropism for A549 or MCF-7 xenografts and significantly inhibited tumor growth through the activation of apoptotic signaling pathways without obvious side effects in tumor-bearing mice models. Altogether, our results showed that TRAIL-iMSCs have strong anti-tumor effects in vitro and in vivo on a range of cancers. This study allows for the development of an unlimited number of therapeutic gene-targeted MSCs with stable quality and high homogeneity for cancer therapy, thus highlighting a universal and safe strategy for stem cell-based gene therapy with high potential for clinical applications.

Genetically-Modified Stem Cell in Regenerative Medicine and Cancer Therapy; A New Era

Recently, genetic engineering by various strategies to stimulate gene expression in a specific and controllable mode is a speedily growing therapeutic approach. Genetic modification of human stem or progenitor cells, such as embryonic stem cells (ESCs), neural progenitor cells (NPCs), mesenchymal stem/stromal cells (MSCs), and hematopoietic stem cells (HSCs) for direct delivery of specific therapeutic molecules or genes has been evidenced as an opportune plan in the context of regenerative medicine due to their supported viability, proliferative features, and metabolic qualities. On the other hand, a large number of studies have investigated the efficacy of modified stem cells in cancer therapy using cells from various sources, disparate transfection means for gene delivery, different transfected yields, and wide variability of tumor models. Accordingly, cell-based gene therapy holds substantial aptitude for the treatment of human malignancy as it could relieve signs or even cure cancer succeeding expression of therapeutic or suicide transgene products; however, there exist inconsistent results in this regard. Herein, we deliver a brief overview of stem cell potential to use in cancer therapy and regenerative medicine and importantly discuss stem cells based gene delivery competencies to stimulate tissue repair and replacement in concomitant with their potential to use as an anti-cancer therapeutic strategy, focusing on the last two decades in vivo studies.

A regulative epigenetic circuit supervised by HDAC7 represses IGFBP6 and IGFBP7 expression to sustain mammary stemness

Background: In the breast, the pleiotropic epigenetic regulator HDAC7 can influence stemness. Materials & Methods: The authors used MCF10 cells knocked-out for HDAC7 to explore the contribution of HDAC7 to IGF1 signaling. Results: HDAC7 buffers H3K27ac levels at the IGFBP6 and IGFBP7 genomic loci and influences their expression. In this manner, HDAC7 can tune IGF1 signaling to sustain stemness. In HDAC7 knocked-out cells, RXRA promotes the upregulation of IGFBP6/7 mRNAs. By contrast, HDAC7 increases FABP5 expression, possibly through repression of miR-218. High levels of FABP5 can reduce the delivery of all-trans-retinoic acid to RXRA. Accordingly, the silencing of FABP5 increases IGFBP6 and IGFBP7 expression and reduces mammosphere generation. Conclusion: The authors propose that HDAC7 controls the uptake of all-trans-retinoic acid, thus influencing RXRA activity and IGF1 signaling.

Efficient Nuclease-Directed Integration of Lentivirus Vectors into the Human Ribosomal DNA Locus

Lentivirus vectors (LVs) are efficient tools for gene transfer, but the non-specific nature of transgene integration by the viral integration machinery carries an inherent risk for genotoxicity. We modified the integration machinery of LVs and harnessed the cellular DNA double-strand break repair machinery to integrate transgenes into ribosomal DNA, a promising genomic safe-harbor site for transgenes. LVs carrying modified I-PpoI-derived homing endonuclease proteins were characterized in detail, and we found that at least 21% of all integration sites localized to ribosomal DNA when LV transduction was coupled to target DNA cleavage. In addition to the primary sequence recognized by the endonuclease, integration was also enriched in chromatin domains topologically associated with nucleoli, which contain the targeted ribosome RNA genes. Targeting of this highly repetitive region for integration was not associated with detectable DNA deletions or negative impacts on cell health in transduced primary human T cells. The modified LVs characterized here have an overall lower risk for insertional mutagenesis than regular LVs and can thus improve the safety of gene and cellular therapy.

Mesenchymal stem cells derived from iPSCs expressing interleukin-24 inhibit the growth of melanoma in the tumor-bearing mouse model

Background

Interleukin-24 (IL-24) is a therapeutic gene for melanoma, which can induce melanoma cell apoptosis. Mesenchymal stem cells (MSCs) show promise as a carrier to delivery anti-cancer factors to tumor tissues. Induced pluripotent stem cells (iPSCs) are an alternative source of mesenchymal stem cells (MSCs). We previously developed a novel non-viral gene targeting vector to target IL-24 to human iPSCs. This study aims to investigate whether MSCs derived from the iPSCs with the site-specific integration of IL-24 can inhibit the growth of melanoma in a tumor-bearing mouse model via retro-orbital injection.

Methods

IL-24-iPSCs were differentiated into IL-24-iMSCs in vitro, of which cellular properties and potential of differentiation were characterized. The expression of IL-24 in the IL-24-iMSCs was measured by qRT-PCR, Western Blotting, and ELISA analysis. IL-24-iMSCs were transplanted into the melanoma-bearing mice by retro-orbital intravenous injection. The inhibitory effect of IL-24-iMSCs on the melanoma cells was investigated in a co-culture system and tumor-bearing mice. The molecular mechanisms underlying IL-24-iMSCs in exerting anti-tumor effect were also explored.

Results

iPSCs-derived iMSCs have the typical profile of cell surface markers of MSCs and have the ability to differentiate into osteoblasts, adipocytes, and chondroblasts. The expression level of IL-24 in IL-24-iMSCs reached 95.39 ng/10⁶ cells/24 h, which is significantly higher than that in iMSCs, inducing melanoma cells apoptosis more effectively in vitro compared with iMSCs. IL-24-iMSCs exerted a significant inhibitory effect on the growth of melanoma in subcutaneous mouse models, in which the migration of IL-24-iMSCs to tumor tissue was confirmed. Additionally, increased expression of Bax and Cleaved caspase-3 and down-regulation of Bcl-2 were observed in the mice treated with IL-24-iMSCs.

Conclusion

MSCs derived from iPSCs with the integration of IL-24 at rDNA locus can inhibit the growth of melanoma in tumor-bearing mouse models when administrated via retro-orbital injection.

Human Wharton's Jelly Stem Cell (hWJSC) Extracts Inhibit Ovarian Cancer Cell Lines OVCAR3 and SKOV3 in vitro by Inducing Cell Cycle Arrest and Apoptosis

Ovarian cancer is a highly lethal and the second highest in mortality among gynecological cancers. Stem cells either naïve or engineered are reported to inhibit various human cancers in both in-vitro and in-vivo. Herein we report the cancer inhibitory properties of human Wharton's jelly stem cell (hWJSC) extracts, namely its conditioned medium (hWJSC-CM) and cell lysate (hWJSC-CL) against two ovarian cancer cell lines (OVCAR3 and SKOV3) in-vitro. Cell metabolic activity assay of OVCAR3 and SKOV3 cells treated with hWJSC-CM (12.5, 25, 50, 75, 100%) and hWJSC-CL (5, 10, 15, 30, and 50 μg/ml) demonstrated concentration dependent inhibition at 24-72 h. Morphological analysis of OVCAR3 and SKOV3 cells treated with hWJSC-CM (50, 75, 100%) and hWJSC-CL (15, 30, and 50 μg/ml) for 24-72 h showed cell shrinkage, membrane damage/blebbings and cell death. Cell cycle assay demonstrated an increase in the sub-G1 and G2M phases of cell cycle following treatment with hWJSC-CM (50, 75, 100%) and hWJSC-CL (10, 15, and 30 μg/ml) at 48 h. Both OVCAR3 and SKOV3 cells demonstrated mild positive expression of activated caspase 3 following treatment with hWJSC-CM (50%) and hWJSC-CL (15 μg/ml) for 24 h. Cell migration of OVCAR3 and SKOV3 cells were inhibited following treatment with hWJSC-CM (50%) and hWJSC-CL (15 μg/ml) for 48 h. Tumor spheres (TS) of OVCAR3 and SKOV3 treated with hWJSC-CM (50, 75, 100%) and hWJSC-CL (10, 15, 30 μg/ml) for 48 h showed altered surface changes including vacuolations and reduction in size of TS. TS of OVCAR3 and SKOV3 also showed the presence of few ovarian cancer stem cells (CSCs) in minimal numbers following treatment with hWJSC-CM (50%) or hWJSC-CL (15 μg/ml) for 48 h. Real-time gene expression analysis of OVCAR3 and SKOV3 treated with hWJSC-CM (50%) or hWJSC-CL (15 μg/ml) for 48 h demonstrated decreased expression of cell cycle regulatory genes (cyclin A2, Cyclin E1), prostaglandin receptor signaling genes (EP2, EP4) and the pro-inflmmatory genes (IL-6, TNF-α) compared to untreated controls. The results indicate that hWJSC-CM and hWJSC-CL inhibit ovarian cancer cells at mild to moderate levels by inducing cellular changes, cell cycle arrest, apoptosis, decreasing the expression of CSC markers and related genes regulation. Therefore, the stem cell factors in hWJSCs extracts can be useful in cancer management.

Paired CRISPR/Cas9 Nickases Mediate Efficient Site-Specific Integration of F9 into rDNA Locus of Mouse ESCs

Hemophilia B (HB) is an X-linked recessive bleeding disorder, caused by F9 gene deficiency. Gene therapy combined with the CRISPR/Cas9 technology offers a potential cure for hemophilia B. Now the Cas9 nickase (Cas9n) shows a great advantage in reducing off-target effect compared with wild-type Cas9. In this study, we found that in the multicopy ribosomal DNA (rDNA) locus, the homology directed recombination (HDR) efficiency induced by sgRNA-Cas9n was much higher than sgRNA-Cas9, meanwhile without off-target in six predicted sites. After co-transfection into mESCs with sgRNA-Cas9n and a non-viral rDNA targeting vector pMrnF9, harboring the homology donor template and the human F9 expression cassette, a recombination efficiency of 66.7% was achieved and all targeted clones were confirmed to be site-specific integration of F9 in the rDNA locus by PCR and southern blotting. Targeted mESCs retained the main pluripotent properties and were then differentiated into hepatic progenitor like cells (HPLCs) and mature hepatocytes, which were characterized by hepatic markers and functional assays. Importantly, the differentiated cells could transcribe exogenous F9 and secrete coagulation factor IX (FIX) proteins, suggesting active transcription and stable inheritance of transgenes in the rDNA locus. After intrasplenical transplantation in severe combined immune deficiency (SCID) mice, targeted HPLCs could survive and migrate from spleen to liver, resulting in secretion of exogenous FIX into blood. In summary, we demonstrate an efficient and site-specific gene targeting strategy in rDNA locus for stem cell-based gene therapy for hemophilia B.

Bioengineered cellular and cell membrane-derived vehicles for actively targeted drug delivery: So near and yet so far

Cellular carriers for drug delivery are attractive alternatives to synthetic nanoparticles owing to their innate homing/targeting abilities. Here, we review molecular interactions involved in the homing of Mesenchymal stem cells (MSCs) and other cell types to understand the process of designing and engineering highly efficient, actively targeting cellular vehicles. In addition, we comprehensively discuss various genetic and non-genetic strategies and propose futuristic approaches of engineering MSC homing using micro/nanotechnology and high throughput small molecule screening. Most of the targeting abilities of a cell come from its plasma membrane, thus, efforts to harness cell membranes as drug delivery vehicles are gaining importance and are highlighted here. We also recognize and report the lack of detailed characterization of cell membranes in terms of safety, structural integrity, targeting functionality, and drug transport. Finally, we provide insights on future development of bioengineered cellular and cell membrane-derived vesicles for successful clinical translation.