The delivery of therapeutics to the central nervous system (CNS) remains a major challenge in part due to the presence of the blood-brain barrier (BBB). Recently, cell-derived vesicles, particularly exosomes, have emerged as an attractive vehicle for targeting drugs to the brain, but whether or how they cross the BBB remains unclear. Here, we investigated the interactions between exosomes and brain microvascular endothelial cells (BMECs) in vitro under conditions that mimic the healthy and inflamed BBB in vivo. Transwell assays revealed that luciferase-carrying exosomes can cross a BMEC monolayer under stroke-like, inflamed conditions (TNF-α activated) but not under normal conditions. Confocal microscopy showed that exosomes are internalized by BMECs through endocytosis, co-localize with endosomes, in effect primarily utilizing the transcellular route of crossing. Together, these results indicate that cell-derived exosomes can cross the BBB model under stroke-like conditions in vitro. This study encourages further development of engineered exosomes as drug delivery vehicles or tracking tools for treating or monitoring neurological diseases.

Figures S1-S16 and Table S1 and S2, which depict additional results (PDF) The authors declare the following competing financial interest(s): W.Z. is a co-founder of Velox Biosystems Inc., Baylx Inc., and Amberstone Biosciences Inc. J.L. has equity in Codiak BioSciences and holds the rights to multiple extracellular vesicle diagnostics and therapeutics patents.

Interleukin-34 (IL-34) was recently characterized as the M-CSF "twin" cytokine, regulating the proliferation/differentiation/survival of myeloid cells. The implication of M-CSF in oncology was initially suspected by the reduced metastatic dissemination in knock-out mice, due to angiogenesis impairment. Based on this observation, our work studied the involvement of IL-34 in the pathogenesis of osteosarcoma. The in vivo effects of IL-34 were assessed on tissue vasculature and macrophage infiltration in a murine preclinical model based on a paratibial inoculation of human osteosarcoma cells overexpressing or not IL-34 or M-CSF. In vitro investigations using endothelial cell precursors and mature HUVEC cells were performed to analyse the involvement of IL-34 in angiogenesis and myeloid cell adhesion. The data revealed that IL-34 overexpression was associated with the progression of osteosarcoma (tumor growth, lung metastases) and an increase of neo-angiogenesis. In vitro analyses demonstrated that IL-34 stimulated endothelial cell proliferation and vascular cord formation. Pre-treatment of endothelial cells by chondroitinases/heparinases reduced the formation of vascular tubes and abolished the associated cell signalling. In addition, IL-34 increased the in vivo recruitment of M2 tumor-associated macrophages into the tumor tissue. IL-34 increased in vitro monocyte/CD34 1 cell adhesion to activated HUVEC monolayers under physiological shear stress conditions. This work also demonstrates that IL-34 is expressed by osteosarcoma cells, is regulated by TNF-a, IL-1b, and contributes to osteosarcoma growth by increasing the neo-angiogenesis and the recruitment of M2 macrophages. By promoting new vessel formation and extravasation of immune cells, IL-34 may play a key role in tumor development and inflammatory diseases.Angiogenesis and vasculogenesis are central events during embryogenesis and growth.

Adoptive T cell transfer, in particular TCR T cell therapy, holds great promise for cancer immunotherapy with encouraging clinical results. However, finding the right TCR T cell clone is a tedious, time-consuming, and costly process. Thus, there is a critical need for single cell technologies to conduct fast and multiplexed functional analyses followed by recovery of the clone of interest. Here, we use droplet microfluidics for functional screening and real-time monitoring of single TCR T cell activation upon recognition of target tumor cells. Notably, our platform includes a tracking system for each clone as well as a sorting procedure with 100% specificity validated by downstream single cell reverse-transcription PCR and sequencing of TCR chains. Our TCR screening prototype will facilitate immunotherapeutic screening and development of T cell therapies.

Objectives— The apolipoprotein (apo)A-I mimetic peptide 5A is highly specific for ATP-binding cassette transporter (ABC)A1-mediated cholesterol efflux. We investigated whether the 5A peptide shares other beneficial features of apoA-I, such as protection against inflammation and oxidation. Methods— New Zealand white rabbits received an infusion of apoA-I, reconstituted high-density lipoprotein (HDL) containing apoA-I ([A-I]rHDL), or the 5A peptide complexed with phospholipids (1-palmitoyl-2-linoleoyl phosphatidylcholine [PLPC]), before inserting a collar around the carotid artery. Human coronary artery endothelial cells (HCAECs) were incubated with (A-I)rHDL or 5A/PLPC before stimulation with tumor necrosis factor α. Results— ApoA-I, (A-I)rHDL, and 5A/PLPC reduced the collar-mediated increase in (1) endothelial expression of cell adhesion molecules vascular cell adhesion molecule-1 and intercellular adhesion molecule-1; (2) production, as well as the expression of the Nox4 catalytic subunits of the NADPH oxidase; and (3) infiltration of circulating neutrophils into the carotid intima–media. In HCAECs, both 5A/PLPC and (A-I)rHDL inhibited tumor necrosis factor-α–induced intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 expression, as well as the nuclear factor κB signaling cascade and production. The effects of the 5A/PLPC complex were no longer apparent in HCAECs knocked down for ABCA1. Conclusion— Like apoA-I, the 5A peptide inhibits acute inflammation and oxidative stress in rabbit carotids and HCAECs. In vitro, the 5A peptide exerts these beneficial effects through interaction with ABCA1.

Bone cancers are characterised by the development of tumour cells in bone sites, associated with a dysregulation of their environment. In the last two decades, numerous therapeutic strategies have been developed to target the cancer cells or tumour niche. As the crosstalk between these two entities is tightly controlled by the release of polypeptide mediators activating signalling pathways through several receptor tyrosine kinases (RTKs), RTK inhibitors have been designed. These inhibitors have shown exciting clinical impacts, such as imatinib mesylate, which has become a reference treatment for chronic myeloid leukaemia and gastrointestinal tumours. The present review gives an overview of the main molecular and functional characteristics of RTKs, and focuses on the clinical applications that are envisaged and already assessed for the treatment of bone sarcomas and bone metastases.

IL-34 is a challenging cytokine sharing functional similarities with M-CSF through M-CSFR activation. It also plays a singular role that has recently been explained in the brain, through a binding to the receptor protein tyrosine phosphatase RPTPβ/ζ. The aim of this paper was to look for alternative binding of IL-34 on other cell types. Myeloid cells (HL-60, U-937, THP-1) were used as cells intrinsically expressing M-CSFR, and M-CSFR was expressed in TF-1 and HEK293 cells. IL-34 binding was studied by Scatchard and binding inhibition assays, using 125I-radiolabelled cytokines, and surface plasmon resonance. M-CSFR activation was analysed by Western blot after glycosaminoglycans abrasion, syndecan-1 overexpression or repression and addition of a blocking anti-syndecan antibody. M-CSF and IL-34 induced different patterns of M-CSFR phosphorylations, suggesting the existence of alternative binding for IL-34. Binding experiments and chondroitinase treatment confirmed low affinity binding to chondroitin sulphate chains on cells lacking both M-CSFR and RPTPβ/ζ. Amongst the proteoglycans with chondroitin sulphate chains, syndecan-1 was able to modulate the IL-34-induced M-CSFR signalling pathways. Interestingly, IL-34 induced the migration of syndecan-1 expressing cells. Indeed, IL-34 significantly increased the migration of THP-1 and M2a macrophages that was inhibited by addition of a blocking anti-syndecan-1 antibody. This paper provides evidence of alternative binding of IL-34 to chondroitin sulphates and syndecan-1 at the cell surface that modulates M-CSFR activation. In addition, IL-34-induced myeloid cell migration is a syndecan-1 dependent mechanism.

Despite decades of effort, little progress has been made to improve the treatment of cancer metastases. To leverage the central role of the mechanoenvironment in cancer metastasis, we present a mechanoresponsive cell system (MRCS) to selectively identify and treat cancer metastases by targeting the specific biophysical cues in the tumor niche in vivo. Our MRCS uses mechanosensitive promoter-driven mesenchymal stem cell (MSC)-based vectors, which selectively home to and target cancer metastases in response to specific mechanical cues to deliver therapeutics to effectively kill cancer cells, as demonstrated in a metastatic breast cancer mouse model. Our data suggest a strong correlation between collagen cross-linking and increased tissue stiffness at the metastatic sites, where our MRCS is specifically activated by the specific cancer-associated mechano-cues. MRCS has markedly reduced deleterious effects compared to MSCs constitutively expressing therapeutics. MRCS indicates that biophysical cues, specifically matrix stiffness, are appealing targets for cancer treatment due to their long persistence in the body (measured in years), making them refractory to the development of resistance to treatment. Our MRCS can serve as a platform for future diagnostics and therapies targeting aberrant tissue stiffness in conditions such as cancer and fibrotic diseases, and it should help to elucidate mechanobiology and reveal what cells “feel” in the microenvironment in vivo.