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Sensory neurons have recently emerged as components of the tumor microenvironment. Nevertheless, whether sensory neuronal activity is important for tumor progression remains unknown. Here we used Designer Receptors Exclusively Activated by a Designer Drug (DREADD) technology to inhibit or activate sensory neurons’ firing within the melanoma tumor. Melanoma growth and angiogenesis were accelerated following inhibition of sensory neurons’ activity and were reduced following overstimulation of these neurons. Sensory neuron-specific overactivation also induced a boost in the immune surveillance by increasing tumor-infiltrating anti-tumor lymphocytes, while reducing immune-suppressor cells. In humans, a retrospective in silico analysis of melanoma biopsies revealed that increased expression of sensory neurons-related genes within melanoma was associated with improved survival. These findings suggest that sensory innervations regulate melanoma progression, indicating that manipulation of sensory neurons’ activity may provide a valuable tool to improve melanoma patients’ outcomes. Supplementary Information The online version contains supplementary material available at 10.1186/s40478-021-01273-9.

Multiple infectious diseases lead to impaired lung function. Revealing the cellular mechanisms involved in this impairment is crucial for the understanding of how the lungs shift from a physiologic to a pathologic state in each specific condition. In this context, we explored the pathogenesis of Paracoccidioidomycosis, which affects pulmonary functioning. The presence of cells expressing Nestin-GFP has been reported in different tissues, and their roles as tissue-specific progenitors have been stablished in particular organs. Here, we explored how Nestin-GFP+ cells are affected after lung infection by Paracoccidioides brasiliensis, a model of lung granulomatous inflammation with fibrotic outcome. We used Nestin-GFP transgenic mice, parabiosis surgery, confocal microscopy and flow cytometry to investigate the participation of Nestin-GFP+ cells in Paracoccidioides brasiliensis pathogenesis. We revealed that these cells increase in the lungs post-Paracoccidioides brasiliensis infection, accumulating around granulomas. This increase was due mainly to Nestin-GPF+ cells derived from the blood circulation, not associated to blood vessels, that co-express markers suggestive of hematopoietic cells (Sca-1, CD45 and CXCR4). Therefore, our findings suggest that circulating Nestin-GFP+ cells participate in the Paracoccidioides brasiliensis pathogenesis in the lungs.

Niches are specialized tissue microenvironments that control stem cells functioning. The bone marrow mesenchymal stem cell niche defines a location within the marrow in which mesenchymal stem cells are retained and produce new cells throughout life. Deciphering the signaling mechanisms by which the niche regulates stem cell fate will facilitate the use of these cells for therapy. Recent studies, by using state‐of‐the‐art methodologies, including sophisticated in vivo inducible genetic techniques, such as lineage‐tracing Cre/loxP mediated systems, in combination with pharmacological inhibition, provide evidence that sensory neuron is an important component of the bone marrow mesenchymal stem cell niche. Strikingly, knockout of a specific receptor in sensory neurons blocked stem cell function in the bone marrow. The knowledge arising from these discoveries will be crucial for stem cell manipulation in the future. Here, we review recent progress in our understanding of sensory nerves biology in the stem cell niche., Schematic illustration summarizing the findings from genetic deletion of EP4 specifically from sensory nerve fibers in the bone marrow mesenchymal stem cell niche.

Wound healing is a complex dynamic physiological process in response to cutaneous destructive stimuli that aims to restore the cutaneous’ barrier role. Deciphering the underlying mechanistic details that contribute to wound healing will create novel therapeutic strategies for skin repair. Recently, by using state‐of‐the‐art technologies, it was revealed that the cutaneous microbiota interact with skin immune cells. Strikingly, commensal Staphylococcus epidermidis‐induced CD8+ T cells induce re‐epithelization of the skin after injury, accelerating wound closure. From a drug development perspective, the microbiota may provide new therapeutic candidate molecules to accelerate skin healing. Here, we summarize and evaluate recent advances in the understanding of the microbiota in the skin microenvironment.

Sclareol (SC) is arousing great interest due to its cytostatic and cytotoxic activities in several cancer cell lines. However, its hydrophobicity is a limiting factor for its in vivo administration. One way to solve this problem is through nanoencapsulation. Therefore, solid lipid nanoparticles (SLN-SC) and nanostructured lipid carriers (NLC-SC) loaded with SC were produced and compared regarding their physicochemical properties. NLC-SC showed better SC encapsulation than SLN-SC and was chosen to be compared with free SC in human cancer cell lines (MDA-MB-231 and HCT-116). Free SC had slightly higher cytotoxicity than NLC-SC and produced subdiploid DNA content in both cell lines. On the other hand, NLC-SC led to subdiploid content in MDA-MB-231 cells and G2/M checkpoint arrest in HCT-116 cells. These findings suggest that SC encapsulation in NLC is a way to allow the in vivo administration of SC and might alter its biological properties

Photobiomodulation is being widely applied for improving dermal or mucosal wound healing. However, the underlying cellular and molecular processes that directly contribute to its effects remain poorly understood. Pericytes are relevant cells involved in the wound microenvironment and could be one of the main targets of photobiomodulation due to their plasticity and perivascular localization. Herein, we investigate tissue repair under the photobiomodulation stimulus using a pericyte labeled (or reporter) transgenic mice. Using a model of two contralateral back wounds, one the control and the other photoactivated daily (660 nm, 20 mW, 0.71 W/cm2, 5 J/cm2, 7 s, 0.14 J), we showed an overall influx of immune and undifferentiated cells and higher mobilization of a potent pericyte subpopulation (Type-2 pericytes) in the photoactivated wounds in comparison to the controls. Doppler analysis showed a significant increase in the blood flow in the photoactivated wounds, while marked vascular supply was observed histologically. Histochemical analysis has indicated more advanced stages of tissue repair after photoactivation. These data suggest that photobiomodulation significantly accelerates tissue repair through its vascular effects with direct recruitment of pericytes to the injury site.

Macrophages not only play a fundamental role in the pathogenesis of inflammatory bowel disease (IBD), but they also play a major role in preserving intestinal homeostasis. In this work, we evaluated the role of macrophages in IBD and investigated whether the functional reprogramming of macrophages to a very specific phenotype could decrease disease pathogenesis. Thus, macrophages were stimulated in the presence of high-density immune complexes which strongly upregulate their production of IL-10 and downregulate pro-inflammatory cytokines. The transfer of these high-density-immune-complex regulatory macrophages into mice with colitis was examined as a potential therapy proposal to control the disease. Animals subjected to colitis induction received these high-density-immune-complex regulatory macrophages, and then the Disease Activity Index (DAI), and macroscopic and microscopic lesions were measured. The treated group showed a dramatic improvement in all parameters analyzed, with no difference with the control group. The colon was macroscopically normal in appearance and size, and microscopically colon architecture was preserved. The immunofluorescence migration assay showed that these cells migrated to the inflamed intestine, being able to locally produce the cytokine IL-10, which could explain the dramatic improvement in the clinical and pathological condition of the animals. Thus, our results demonstrate that the polarization of macrophages to a high IL-10 producer profile after stimulation with high-density immune complexes was decisive in controlling experimental colitis, and that macrophages are a potential therapeutic target to be explored in the control of colitis.

The tumour mass is composed not only of heterogeneous neoplastic cells, but also a variety of other components that may affect cancer cells behaviour. The lack of detailed knowledge about all the constituents of the tumour microenvironment restricts the design of effective treatments. Nerves have been reported to contribute to the growth and maintenance of numerous tissues. The effects of sensory innervations on tumour growth remain unclear. Here, by using state‐of‐the‐art techniques, including Cre/loxP technologies, confocal microscopy, in vivo‐tracing and chemical denervation, we revealed the presence of sensory nerves infiltrating within the melanoma microenvironment, and affecting cancer progression. Strikingly, melanoma growth in vivo was accelerated following genetic ablation or chemical denervation of sensory nerves. In humans, a retrospective analysis of melanoma patients revealed that increased expression of genes related to sensory nerves in tumours was associated with better clinical outcomes. These findings suggest that sensory innervations counteract melanoma progression. The emerging knowledge from this research provides a novel target in the tumour microenvironment for therapeutic benefit in cancer patients.

Dermal wound healing is the process of repairing and remodeling skin following injury. Delayed or aberrant cutaneous healing pose a challenge for the health-care system. The lack of detailed understanding of cellular and molecular mechanisms involved in this process hamper the development of effective targeted treatments. In a recent study, Parfejevs and colleagues, by using state-of-the-art technologies, including in vivo sophisticated Cre/loxP techniques in combination with a mouse model of excisional cutaneous wounding, reveal that Schwann cells induce adult dermal wound healing. Strikingly, genetic ablation of Schwann cells delays wound contraction and closure, decreases myofibroblast formation, and impairs skin re-epithelization after injury. From a drug development perspective, Schwann cells are a new cellular candidate to be activated to accelerate skin healing. Here, we summarize and evaluate recent advances in the understanding of Schwann cells roles in the skin microenvironment.

Fibrosis following injury leads to aberrant regeneration and incomplete functional recovery of skeletal muscle, but the lack of detailed knowledge about the cellular and molecular mechanisms involved hampers the design of effective treatments. Using state-of-the-art technologies, Murray et al. (2017) found that perivascular PDGFRβ-expressing cells generate fibrotic cells in the skeletal muscle. Strikingly, genetic deletion of αv integrins from perivascular PDGFRβ-expressing cells significantly inhibited skeletal muscle fibrosis without affecting muscle vascularization or regeneration. In addition, the authors showed that a small molecule inhibitor of αv integrins, CWHM 12, attenuates skeletal muscle fibrosis. From a drug-development perspective, this study identifies a new cellular and molecular target to treat skeletal muscle fibrosis.

Glioblastoma multiforme is the most common and aggressive primary brain tumor, with an extremely poor prognosis. The lack of detailed knowledge about the cellular and molecular mechanisms involved in glioblastoma development restricts the design of efficient therapies. A recent study using state‐of‐art technologies explores the role of pericytes in the glioblastoma microenvironment. Glioblastoma‐activated pericytes develop an immunosuppressive phenotype, reducing T‐cell activation through the induction of an anti‐inflammatory response. Strikingly, pericytes support glioblastoma growth in vitro and in vivo. Here, we describe succinctly the results and implications of the findings reported in pericytes' and glioblastomas' biology. The emerging knowledge from this study will be essential for the treatment of brain tumors.

Bone marrow fibrosis is a critical component of primary myelofibrosis in which normal bone marrow tissue and blood-forming cells are gradually replaced with scar tissue. The specific cellular and molecular mechanisms that cause bone marrow fibrosis are not understood. A recent study using state-of-the-art techniques, including in vivo lineage tracing, provides evidence that Gli1+ cells are the cells responsible for fibrotic disease in the bone marrow. Strikingly, genetic depletion of Gli1+ cells rescues bone marrow failure and abolishes myelofibrosis. This work introduces a new central cellular target for bone marrow fibrosis. The knowledge that emerges from this research will be important for the treatment of several malignant and nonmalignant disorders.

Joint pain is a distressing symptom experienced by arthritic patients and it is frequently persistent even after treatments that reduce signs of local inflammation. Continuous production of algogenic factors activate/sensitize nociceptors in the joint structures and contribute to persistent pain, a challenging and difficult condition to treat. TNF is a crucial cytokine for pathogenesis of several rheumatic diseases and its inhibition is a mainstay of the treatment for controlling joint symptoms, including pain. Here, we sought to investigate the inflammatory changes and the role of TNF in dorsal root ganglia (DRG) during persistent hypernociception after the resolution of joint inflammation in mice. Using a model of antigen-induced arthritis, the peak of joint inflammation occurred at 12-24 h after local antigen injection and was characterized by intense influx of neutrophils, pro-inflammatory cytokine production and joint damage. Inflammatory parameters in the joint returned to basal levels between 6 and 8 days after antigen-challenge, characterizing the resolving phase of joint inflammation. Mechanical hyperalgesia was persistent up to 14 days after joint insult. The persistent nociception was associated with inflammatory status of DRG after resolution of joint inflammation. The late state of neuroinflammation in the ipsilateral side was evidenced by gene expression of TNF, TNFR2, IL-6, IL-1β, CXCL2, COX2 and iNOS in lumbar DRG (L3-L5) and leukocyte adhesion in the lumbar intumescent vessels between the days 6 and 8. Moreover, there were signs of resident macrophages activation in DRG, as evidenced by increase in Iba1-positive cells. Intrathecal or systemic injection of etanercept, an agent clinically utilized for TNF neutralization, at day 7 post arthritis induction reverted the persistent joint hyperalgesia by specific action in DRG. Our results suggest that neuroinflammation in DRG after the resolution of joint inflammation drives the continuous neural sensitization resulting in persistent joint nociception in a mechanism mainly dependent on TNF.

The extracellular matrix (ECM) regulates the development and maintains tissue homeostasis. The ECM is composed of a complex network of molecules presenting distinct biochemical properties to regulate cell growth, survival, motility, and differentiation. Among their components, proteoglycans (PGs) are considered one of the main components of ECM. Its composition, biomechanics, and anisotropy are exquisitely tuned to reflect the physiological state of the tissue. The loss of ECM's homeostasis is seen as one of the hallmarks of cancer and, typically, defines transitional events in tumor progression and metastasis. In this chapter, we discuss the types of proteoglycans and their roles in cancer. It has been observed that the amount of some ECM components is increased, while others are decreased, depending on the type of tumor. However, both conditions corroborate with tumor progression and malignancy. Therefore, ECM components have an increasingly important role in carcinogenesis and this leads us to believe that their understanding may be a key in the discovery of new anti-tumor therapies. In this book, the main ECM components will be discussed in more detail in each chapter.

Spinal cord injury results in locomotor impairment attributable to the formation of an inhibitory fibrous scar, which prevents axonal regeneration after trauma. The scarcity of knowledge about the molecular and cellular mechanisms involved in scar formation after spinal cord lesion impede the design of effective therapies. Recent studies, by using state-of-the-art technologies, including genetic tracking and blockage of pericytes in combination with optogenetics, reveal that pericyte blockage facilitates axonal regeneration and neuronal integration into the local neural circuitry. Strikingly, a pericyte subset is essential during scarring after spinal cord injury, and its arrest results in motor performance improvement. The arising knowledge from current research will contribute to novel approaches to develop therapies for spinal cord injury. We review novel advances in our understanding of pericyte biology in the spinal cord.

Complexes [Bi(2AcPh)Cl2]·0.5H2O (1), [Bi(2AcpClPh)Cl2] (2), [Bi(2AcpNO2Ph)Cl2] (3), [Bi(2AcpOHPh)Cl2]·2H2O (4), [Bi(H2BzPh)Cl3]·2H2O (5), [Bi(H2BzpClPh)Cl3] (6), [Bi(2BzpNO2Ph)Cl2]·2H2O (7) and [Bi(H2BzpOHPh)Cl3]·2H2O (8) were obtained with 2-acetylpyridine phenylhydrazone (H2AcPh), its -para-chloro-phenyl- (H2AcpClPh), -para-nitro-phenyl (H2AcpNO2Ph) and -para-hydroxy-phenyl (H2AcpOHPh) derivatives, as well as with the 2-benzoylpyridine phenylhydrazone analogues (H2BzPh, H2BzpClPh, H2BzpNO2Ph, H2BzpOHPh). Upon coordination to bismuth(III) antibacterial activity against Gram-positive and Gram-negative bacterial strains significantly improved except for complex (4). The cytotoxic effects of the compounds under study were evaluated on HL-60, Jurkat and THP-1 leukemia, and on MCF-7 and HCT-116 solid tumor cells, as well as on non-malignant Vero cells. In general, 2-acetylpyridine-derived hydrazones proved to be more potent and more selective as cytotoxic agents than the corresponding 2-benzoylpyridine-derived counterparts. Exposure of HCT-116 cells to H2AcpClPh, H2AcpNO2Ph and complex (3) led to 99% decrease of the clonogenic survival. The IC50 values of these compounds were three-fold smaller when cells were cultured in soft-agar (3D) than when cells were cultured in monolayer (2D), suggesting that they constitute interesting scaffolds, which should be considered in further studies aiming to develop new drug candidates for the treatment of colon cancer.

The respiratory system is essentially an external organ, constantly exposed to the external environment. As such, it is in contact with any number of antigens and chemical agents that can injure the upper (nasal cavity, pharynx, and larynx) or lower (trachea, bronchi, and lungs) respiratory tract [1]. Injuries to the lung parenchyma are particularly harmful, as the parenchyma is the site of gas (oxygen and carbon dioxide) exchange. Acute or chronic injuries to the lung result in acute or chronic hypoxemic or hypercapnic respiratory failure, respectively. While there are several structural and pathologic mechanisms that contribute to respiratory failure, some lung injuries result in a progressive fibroproliferative response that leads to respiratory failure and death.

Healing is a vital response important for the re-establishment of the skin integrity following injury. Delayed or aberrant dermal wound healing leads to morbidity in patients. The development of therapies to improve dermal healing would be useful. Currently, the design of efficient treatments is stalled by the lack of detailed knowledge about the cellular and molecular mechanisms involved in wound healing. Recently, using state-of-the-art technologies, it was revealed that macrophages signal via GPNMB to mesenchymal stem cells, accelerating skin healing. Strikingly, transplantation of macrophages expressing GPNMB improves skin healing in GPNMB-mutant mice. Additionally, topical treatment with recombinant GPNMB restored mesenchymal stem cells recruitment and accelerated wound closure in the diabetic skin. From a drug development perspective, this GPNMB is a new candidate for skin healing.

The cerebellum plays major role in motor coordination and learning. It contains half of the neurons in the brain. Thus, deciphering the mechanisms by which cerebellar neurons are generated is essential to understand the cerebellar functions and the pathologies associated with it. In a recent study, Wojcinski et al. (2017) by using in vivo Cre/loxP technologies reveal that Nestin-expressing progenitors repopulated the external granular cell layer after injury. Depletion of postnatal external granular cell layer is not sufficient to induce motor behavior defects in adults, as the cerebellum recovers these neurons. Strikingly, Nestin-expressing progenitors differentiate into granule cell precursors and mature granule neurons after ablation of perinatal external granular layer, either by irradiation or by genetic ablation. This work identified a novel role of Nestin-expressing progenitors in the cerebellar microenvironment during development, and revealed that extracellular signals can convert specified progenitors into multipotent stem cells. Here, we discuss the findings from this study, and evaluate recent advances in our understanding of the cerebellar neurogenesis.

The blood–retinal barrier (BRB) consists of tightly interconnected capillary endothelial cells covered with pericytes and glia, but the role of the pericytes in BRB regulation is not fully understood. Here, we show that platelet-derived growth factor (PDGF)-B/PDGF receptor beta (PDGFRβ) signalling is critical in formation and maturation of BRB through active recruitment of pericytes onto growing retinal vessels. Impaired pericyte recruitment to the vessels shows multiple vascular hallmarks of diabetic retinopathy (DR) due to BRB disruption. However, PDGF-B/PDGFRβ signalling is expendable for maintaining BRB integrity in adult mice. Although selective pericyte loss in stable adult retinal vessels surprisingly does not cause BRB disintegration, it sensitizes retinal vascular endothelial cells (ECs) to VEGF-A, leading to upregulation of angiopoietin-2 (Ang2) in ECs through FOXO1 activation and triggering a positive feedback that resembles the pathogenesis of DR. Accordingly, either blocking Ang2 or activating Tie2 greatly attenuates BRB breakdown, suggesting potential therapeutic approaches to reduce retinal damages upon DR progression., Blood-retinal barrier (BRB) is composed of tightly connected endothelium and supporting pericytes and glia. Here, the authors show that pericytes are crucial for BRB buildup during retinal development and its maintenance in adult retinas in response to VEGF-A-induced endothelial sensitization by regulating the Tie2/FOXO1/Ang2 axis.

Bone marrow fibrosis is a reactive process, and a central pathological feature of primary myelofibrosis. Revealing the origin of fibroblastic cells in the bone marrow is crucial, as these cells are considered an ideal, and essential target for anti-fibrotic therapy. In 2 recent studies, Decker et al. (2017) and Schneider et al. (2017), by using state-of-the-art techniques including in vivo lineage-tracing, provide evidence that leptin receptor (LepR)-expressing and Gli1-expressing cells are responsible for fibrotic tissue deposition in the bone marrow. However, what is the relationship between these 2 bone marrow cell populations, and what are their relative contributions to bone marrow fibrosis remain unclear. From a drug development perspective, these works bring new cellular targets for bone marrow fibrosis.

Platelets are released from megakaryocytes. The bone marrow has been proposed to be the major site where this process occurs. Lefrancais et al. (2017) using state-of-the-art techniques including two-photon microscopy, in vivo lineage-tracing technologies, and sophisticated lung transplants reveal that the lung is also a primary site for platelet biogenesis. Strikingly, lung megakaryocytes can completely reconstitute platelet counts in the blood in mice with thrombocytopenia. This study also shows that hematopoietic progenitors, with capacity to repopulate the bone marrow after irradiation, are present in the lungs. This work brings a novel unexpected role for the lung as a niche for hematopoiesis. The emerging knowledge from this research may be important for the treatment of several disorders.

Niches are specialized microenvironments that regulate stem cells' activity. The neural stem cell (NSC) niche defines a zone in which NSCs are retained and produce new cells of the nervous system throughout life. Understanding the signaling mechanisms by which the niche controls the NSC fate is crucial for the success of clinical applications. In a recent study, Sato and colleagues, by using state-of-the-art techniques, including sophisticated in vivo lineage-tracing technologies, provide evidence that endothelial amyloid precursor protein (APP) is an important component of the NSC niche. Strikingly, depletion of APP increased NSC proliferation in the subventricular zone, indicating that endothelial cells negatively regulate NSCs' growth. The emerging knowledge from this research will be important for the treatment of several neurological diseases.

N-(2-butanoyloxyethyl)-4-(chloromethyl)-3-nitrobenzamide (NBCN) is a nitroaromatic bioreducible compound with cytotoxic effects in cancer cell lines. The aim of this work was to investigate the molecular mechanisms involved in cell death promoted by NBCN in HL60 cells. We observed that NBCN treatment increased intracellular ROS and reduced mitochondria membrane potential (ΔΨm). NBCN treatment also induced morphological changes, phosphatidylserine exposure, cell cycle arrest in G2/M-phase, DNA condensation and fragmentation, but it did not show cytotoxic effects on normal human peripheral blood mononuclear cells (PBMCs). NBCN-induced caspase 3- and 9-dependent DNA fragmentation, which was blocked by pretreatment with the broad-spectrum caspase inhibitor, z-VAD-fmk. Flow cytometry analysis demonstrated that NBCN also increased of the number of autophagic vesicles in HL60 cells, which was not observed when cells were pre-treated with bafilomycin A1. Taken together, these results indicate that NBCN triggered the mitochondrial apoptotic pathway and led to the onset of autophagic cell death, which contributed to its cytotoxic effects.

Pericytes heterogeneity is based on their morphology, distribution, and markers. It is well known that pericytes from different organs may have distinct embryonic sources. Yamazaki et al. (2017) using several transgenic mouse model reveal by cell-lineage tracing that pericytes are even more heterogeneous than previously appreciated. This study shows that pericytes from within the same tissue may be heterogeneous in their origin. Remarkably, a subpopulation of embryonic dermal pericytes derives from the hematopoietic lineage, an unexpected source. Reconstructing the lineage of pericytes is central to understanding development, and also for the diagnosis and treatment of diseases in which pericytes play important roles.