Current challenges and future directions for engineering extracellular vesicles for heart, lung, blood and sleep diseases

Extracellular vesicles (EVs) carry diverse bioactive components including nucleic acids, proteins, lipids and metabolites that play versatile roles in intercellular and interorgan communication. The capability to modulate their stability, tissue-specific targeting and cargo render EVs as promising nanotherapeutics for treating heart, lung, blood and sleep (HLBS) diseases. However, current limitations in large-scale manufacturing of therapeutic-grade EVs, and knowledge gaps in EV biogenesis and heterogeneity pose significant challenges in their clinical application as diagnostics or therapeutics for HLBS diseases. To address these challenges, a strategic workshop with multidisciplinary experts in EV biology and U.S. Food and Drug Administration (USFDA) officials was convened by the National Heart, Lung and Blood Institute. The presentations and discussions were focused on summarizing the current state of science and technology for engineering therapeutic EVs for HLBS diseases, identifying critical knowledge gaps and regulatory challenges and suggesting potential solutions to promulgate translation of therapeutic EVs to the clinic. Benchmarks to meet the critical quality attributes set by the USFDA for other cell-based therapeutics were discussed. Development of novel strategies and approaches for scaling-up EV production and the quality control/quality analysis (QC/QA) of EV-based therapeutics were recognized as the necessary milestones for future investigations.

Understanding ER homeostasis and the UPR to enhance treatment efficacy of acute myeloid leukemia

Protein biogenesis, maturation and degradation are tightly regulated processes that are governed by a complex network of signaling pathways. The endoplasmic reticulum (ER) is responsible for biosynthesis and maturation of secretory proteins. Circumstances that alter cellular protein homeostasis, determine accumulation of misfolded and unfolded proteins in the ER, a condition defined as ER stress. In case of stress, the ER activates an adaptive response called unfolded protein response (UPR), a series of pathways of major relevance for cancer biology. The UPR plays a preeminent role in adaptation of tumor cells to the harsh conditions that they experience, due to high rates of proliferation, metabolic abnormalities and hostile environment scarce in oxygen and nutrients. Furthermore, the UPR is among the main adaptive cell stress responses contributing to the development of resistance to drugs and chemotherapy. Clinical management of Acute Myeloid Leukemia (AML) has improved significantly in the last decade, thanks to development of molecular targeted therapies. However, the emergence of treatment-resistant clones renders the rate of AML cure dismal. Moreover, different cell populations that constitute the bone marrow niche recently emerged as a main determinant leading to drug resistance. Herein we summarize the most relevant literature regarding the role played by the UPR in expansion of AML and ability to develop drug resistance and we discuss different possible modalities to overturn this adaptive response against leukemia. To this aim, we also describe the interconnection of the UPR with other cellular stress responses regulating protein homeostasis. Finally, we review the newest findings about the crosstalk between AML cells and cells of the bone marrow niche, under physiological conditions and in response to therapies, discussing in particular the importance of the niche in supporting survival of AML cells by favoring protein homeostasis.

Leukemia-Induced Cellular Senescence and Stemness Alterations in Mesenchymal Stem Cells Are Reversible upon Withdrawal of B-Cell Acute Lymphoblastic Leukemia Cells

Leukemic cell growth in the bone marrow (BM) induces a very stressful condition. Mesenchymal stem cells (MSC), a key component of this BM niche, are affected in several ways with unfavorable consequences on hematopoietic stem cells favoring leukemic cells. These alterations in MSC during B-cell acute lymphoblastic leukemia (B-ALL) have not been fully studied. In this work, we have compared the modifications that occur in an in vitro leukemic niche (LN) with those observed in MSC isolated from B-ALL patients. MSC in this LN niche showed features of a senescence process, i.e., altered morphology, increased senescence-associated β-Galactosidase (SA-βGAL) activity, and upregulation of p53 and p21 (without p16 expression), cell-cycle arrest, reduced clonogenicity, and some moderated changes in stemness properties. Importantly, almost all of these features were found in MSC isolated from B-ALL patients. These alterations rendered B-ALL cells susceptible to the chemotherapeutic agent dexamethasone. The senescent process seems to be transient since when leukemic cells are removed, normal MSC morphology is re-established, SA-βGAL expression is diminished, and MSC are capable of re-entering cell cycle. In addition, few cells showed low γH2AX phosphorylation that was reduced to basal levels upon cultivation. The reversibility of the senescent process in MSC must impinge important biological and clinical significance depending on cell interactions in the bone marrow at different stages of disease progression in B-ALL.

Bone Marrow Niches for Skeletal Progenitor Cells and their Inhabitants in Health and Disease

The bone marrow hosts skeletal progenitor cells which have most widely been referred to as Mesenchymal Stem or Stromal Cells (MSCs), a heterogeneous population of adult stem cells possessing the potential for self-renewal and multilineage differentiation. A consensus agreement on minimal criteria has been suggested to define MSCs in vitro, including adhesion to plastic, expression of typical surface markers and the ability to differentiate towards the adipogenic, osteogenic and chondrogenic lineages but they are critically discussed since the differentiation capability of cells could not always be confirmed by stringent assays in vivo. However, these in vitro characteristics have led to the notion that progenitor cell populations, similar to MSCs in bone marrow, reside in various tissues. MSCs are in the focus of numerous (pre)clinical studies on tissue regeneration and repair. Recent advances in terms of genetic animal models enabled a couple of studies targeting skeletal progenitor cells in vivo. Accordingly, different skeletal progenitor cell populations could be identified by the expression of surface markers including nestin and leptin receptor. While there are still issues with the identity of, and the overlap between different cell populations, these studies suggested that specific microenvironments, referred to as niches, host and maintain skeletal progenitor cells in the bone marrow. Dynamic mutual interactions through biological and physical cues between niche constituting cells and niche inhabitants control dormancy, symmetric and asymmetric cell division and lineage commitment. Niche constituting cells, inhabitant cells and their extracellular matrix are subject to influences of aging and disease e.g. via cellular modulators. Protective niches can be hijacked and abused by metastasizing tumor cells, and may even be adapted via mutual education. Here, we summarize the current knowledge on bone marrow skeletal progenitor cell niches in physiology and pathophysiology. We discuss the plasticity and dynamics of bone marrow niches as well as future perspectives of targeting niches for therapeutic strategies.

Is related the hematopoietic stem cells differentiation in the Nile tilapia with GABA exposure?

The signaling mediated by small non-proteinogenic molecules, which probably have the capacity to serve as a bridge amongst complex systems is one of the most exiting challenges for the study. In the current report, stem cells differentiation of the immune system in Nile tilapia treated with sub-basal doses of GABA evaluated as c-kit⁺ and Sca-1⁺ cells disappearance on pronephros, thymus, spleen and peripheral blood mononuclear cells by flow cytometry was assessed. Explanation of biological response was performed by molecular docking approach and multiparametric analysis. Stem cell differentiation depends on a delicate balance of negative and positive interactions of this neurotransmitter with receptors and transcription factors involved in this process. This in turn depends on the type of interaction with hematopoietic niche to differentiate into primordial, early or late hematopoiesis as well as from the dose delivery. In fish treated with the low doses of GABA (0.1% over basal value) primordial hematopoiesis is regulated by interaction of glutamate (Glu) with the Ly-6 antigen. Early hematopoiesis was influenced by the bond of GABA near or adjacent to turns of FLTR3-Ig-IV domain. During late hematopoiesis, negative regulation by structural modifications on PU.1/IRF-4 complex, IL-7Rα and GM-CSFR mainly prevails. Results of molecular docking were in agreement with the percentages of the main blood cells lineages estimated in pronephros by flow cytometry. Current study provides the first evidences about the role of inhibitory and excitatory neurotransmitters such as GABA and Glu, respectively with the most transcriptional factors and receptors involved on hematopoiesis in adult Nile tilapia.

Developmental programming of adult haematopoiesis system

The Barker hypothesis of 'foetal origin of adult diseases' has led to emphasize the concept of 'developmental programming', based on the crucial role of epigenetic factors. Accordingly, it has been demonstrated that parental adversity (before conception and during pregnancy) and foetal factors (i.e., hypoxia, malnutrition and placental insufficiency) permanently modify the physiological systems of the progeny, predisposing them to premature ageing and chronic disease during adulthood. Thus, an altered functionality of the endocrine, immune, nervous and cardiovascular systems is observed in the progeny. However, it remains to be understood whether the haematopoietic system itself also represents a portrait of foetal programming. Here, we provide evidence, reporting and discussing related theories, and results of studies described in the literature. In addition, we have outlined our opinions and suggest how it is possible to intervene to correct foetal mal-programming. Some pro-health interventions and recommendations are proposed, with the hope of guarantee the health of future generations and trying to combat the continuous increase in age-related diseases in human populations.

Stress and catecholamines modulate the bone marrow microenvironment to promote tumorigenesis

High vascularization and locally secreted factors make the bone marrow (BM) microenvironment particularly hospitable for tumor cells and bones to a preferred metastatic site for disseminated cancer cells of different origins. Cancer cell homing and proliferation in the BM are amongst other regulated by complex interactions with BM niche cells (e.g. osteoblasts, endothelial cells and mesenchymal stromal cells (MSCs)), resident hematopoietic stem and progenitor cells (HSPCs) and pro-angiogenic cytokines leading to enhanced BM microvessel densities during malignant progression. Stress and catecholamine neurotransmitters released in response to activation of the sympathetic nervous system (SNS) reportedly modulate various BM cells and may thereby influence cancer progression. Here we review the role of catecholamines during tumorigenesis with particular focus on pro-tumorigenic effects mediated by the BM niche.

Expression of the Immune Checkpoint Modulator OX40 in Acute Lymphoblastic Leukemia Is Associated with BCR-ABL Positivity

OX40 and its ligand are members of the TNF/TNF receptor superfamily, which includes various molecules influencing cellular signaling and function of both tumor and immune cells. The ability of OX40 to promote proliferation and differentiation of activated T cells fueled present attempts to modulate this immune checkpoint to reinforce antitumor immunity. While we recently found evidence for the involvement of OX40 in pathophysiology of acute myeloid leukemia including natural killer (NK) cell immunosurveillance, less is known on its role in acute lymphoblastic leukemia (ALL). In the present study, OX40 expression on ALL cells was significantly associated with positivity for the adverse risk factor BCR-ABL. In line, signaling via OX40 increased metabolic activity of primary ALL cells and resulted in release of cytokines involved in disease pathophysiology. Furthermore, interaction of ALL-expressed OX40 with its cognate ligand on NK cells stimulated ALL cell lysis. The data presented thus not only identify the yet unknown involvement of OX40/OX40L in ALL pathophysiology and NK cell immunosurveillance but also point to the necessity to thoroughly consider the consequences of modulating the OX40/OX40L molecule system beyond its effects on T cells when developing OX40-targeting approaches for cancer immunotherapy.

Transmissible ER stress reconfigures the AML bone marrow compartment

Successive adaptation of the bone marrow (BM) from homeostatic hematopoietic microenvironment to a self-reinforcing niche is an integral aspect of leukemogenesis. Yet, the cellular mechanisms underlying these functional alterations remain to be defined. Here, we found that AML incursion precipitates compartmental endoplasmic reticulum (ER) stress and an unfolded protein response (UPR) in both leukemia and stromal cells. We observed that extracellular vesicles (EV) transmit ER stress in vivo from the AML xenograft to BM stroma, whereby the upregulation of core UPR components drives subsequent osteolineage differentiation of mesenchymal stem cells (MSC). Finally, we show that the underlying mechanism involves quantitative incorporation and cell-cell transfer of Bone Morphogenic Protein 2 (BMP2), a potent osteogenic signal, by AML-EVs. Corroborative studies in AML patient samples support the translational relevance of AML-EVs as a platform for BMP trafficking and source of compartmental crosstalk. Transmissible ER stress was previously identified as a source of chemoresistance in solid tumor models, and this work reveals a role in remodeling the BM niche in AML.