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Inflammation is central in intervertebral disc (IVD) degeneration/regeneration mechanisms, and its balance is crucial to maintain tissue homeostasis. This work investigates the modulation of local and systemic inflammatory response associated with IVD degeneration/herniation by administration of PRO- versus ANTI-inflammatory treatments. Chitosan/poly-γ-glutamic acid nanocomplexes, known as pro-inflammatory (PRO), and soluble diclofenac, a non-steroidal anti-inflammatory drug (ANTI), were intradiscally administered in a rat IVD injury model, 24 h after lesion. Two weeks after administration, a reduction of disc height accompanied by hernia formation was observed. In the PRO-inflammatory treated group, IL-1β, IL-6 and COX-2 IVD gene expression were upregulated, and loss of nucleus pulposus (NP) structure and composition was observed. Systemically, lower T-cell frequency was observed in the lymph nodes (LN) and spleen (SP) of the PRO group, together with an increase in CD4+ T cells subset in the blood (BL) and LN. In contrast, the ANTI-group had higher proteoglycans/collagen ratio and collagen type 2 content in the NP, while an increase in the frequency of myeloid cells, M1 macrophages and activated macrophages (MHCII+) was observed at the systemic level. Overall, this study illustrates the dynamics of local and systemic inflammatory and immune cell responses associated with intradiscal therapies, which will contribute to designing more successful immunomodulatory treatments for IVD degeneration.

Study Design: Ex vivo experimental study., Objective: To investigate the effect of proinflammatory/degenerative intervertebral disc (IVD) microenvironment on the regenerative and immunomodulatory behavior of mesenchymal stem/stromal cells (MSCs), using an ex vivo model from bovine origin., Summary of Background Data: Low back pain is a cause of disability worldwide, most frequently associated with IVD degeneration and inflammation, and characterized by increased levels of inflammatory mediators, often disregarded. MSC-based therapies to low back pain have been advocated, but the involvement of inflammation in IVD remodeling mechanism, promoted by MSCs has not yet been explored., Methods: Bovine IVD organ cultures of nucleus pulposus punches were stimulated with needle puncture and culture medium supplementation with 10 ng/mL of interleukin (IL)-1β, to induce a proinflammatory/degenerative environment, as previously established. Human bone marrow-derived MSCs were cultured on top of transwells, placed above nucleus pulposus punches, for up to 16 days. MSCs were analyzed by screening cell viability/apoptosis, metabolic activity, migration, and inflammatory cytokines production in response to the proinflammatory environment. IVD extracellular matrix (ECM) remodeling, gene expression profile of IVD cells, and inflammatory cytokine profile in the presence of MSCs in basal versus proinflammatory conditions were also evaluated., Results: Proinflammatory/degenerative IVD conditions did not affect MSCs viability, but promoted cell migration, while increasing IL-6, IL-8, monocyte chemoattractant protein-1, and prostaglandin E2 and reducing transforming growth factor-β1 production by MSCs. MSCs did not stimulate ECM production (namely type II collagen or aggrecan) in neither basal nor inflammatory conditions, instead MSCs downregulated bovine proinflammatory IL-6, IL-8, and TNF-α gene expression levels in IL-1β-stimulated IVDs., Conclusion: The present study provides evidence for an immunomodulatory paracrine effect of MSCs in degenerated IVD without an apparent effect in ECM remodeling, and suggest an MSCs mechanism-of-action dependent on a cytokine feedback loop., Level of Evidence: 5.

Anticancer immune responses depend on efficient presentation of tumor antigens and co-stimulatory signals provided by antigen-presenting cells (APCs). However, it is described that immature dendritic cells (DCs) and macrophages at the tumor site may have an immunosuppressive profile, which limits the activity of effector T cells and supports tumor progression. Therapeutic targeting of these innate immune cells, either aiming at their elimination or re-polarization towards an immunostimulatory profile, has been pointed as an attractive approach to control tumor progression. In the present work, we assessed the potential of Chitosan (Ch)/Poly(γ-glutamic acid) (γ-PGA) nanoparticles (NPs) to modulate macrophages and DCs inflammatory profile and to impair their ability to promote cancer cell invasion. Interestingly, Ch/γ-PGA NPs, prepared by co-acervation method, induced an immunostimulatory DCs phenotype, enhancing the expression of the co-stimulatory molecules CD86, CD40 and HLA-DR, and the secretion of the pro-inflammatory cytokines TNF-α, IL-12p40 and IL-6. Furthermore, Ch/γ-PGA NPs re-educated IL-10-stimulated macrophages towards a pro-inflammatory profile, decreasing the expression of CD163 and promoting the secretion of IL-12p40 and TNF-α. These alterations in the immune cells phenotype promoted CD4 + and CD8 + T cell activation/proliferation and partially inhibited APCs' ability to induce colorectal cancer cell invasion. Overall, our findings open new perspectives on the use of Ch/γ-PGA NPs as an immunomodulatory therapy for antigen-presenting cells reprogramming, providing a new tool for anticancer therapies., Statement of Significance: The immune system is responsible to detect and destroy abnormal cells preventing the development of cancer. However, the immunosuppressive tumor microenvironment can compromise the immune response favoring tumor progression. Thus, immune system modulation towards an immunostimulatory profile can improve anticancer therapies. This research focus on the development of chitosan/poly(γ-glutamic acid) nanoparticles (NPs) to modulate human antigen-presenting cells (APCs) phenotype and to counteract their pro-invasive capacity. Interestingly, Ch/γ-PGA NPs had a prominent effect in inducing macrophages and dendritic cells immunostimulatory phenotype, thus favoring T cell proliferation and inhibiting colorectal cancer cell invasion. We propose that their combination with other immunomodulatory drugs or conventional anticancer therapies can improve patients' outcome., (Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.)

Unlabelled: Intervertebral disc (IVD) degeneration is one of the most common causes of low back pain (LBP), the leading disorder in terms of years lived with disability. Inflammation can play a role in LPB, while impairs IVD regeneration. In spite of this, different inflammatory targets have been purposed in the context of IVD regeneration. Anti-inflammatory nanoparticles (NPs) of Chitosan and Poly-(γ-glutamic acid) with a non-steroidal anti-inflammatory drug, diclofenac (Df), were previously shown to counteract a pro-inflammatory response of human macrophages. Here, the effect of intradiscal injection of Df-NPs in degenerated IVD was evaluated. For that, Df-NPs were injected in a bovine IVD organ culture in pro-inflammatory/degenerative conditions, upon stimulation with needle-puncture and interleukin (IL)-1β. Df-NPs were internalized by IVD cells, down-regulating IL-6, IL-8, MMP1 and MMP3, and decreasing PGE2 production, compared with IL-1β-stimulated IVD punches. Interestingly, at the same time, Df-NPs promoted an up-regulation of extracellular matrix (ECM) proteins, namely collagen type II and aggrecan. Allover, this study suggests that IVD treatment with Df-NPs not only reduces inflammation, but also delays and/or decreases ECM degradation, opening perspectives to new intradiscal therapies for IVD degeneration, based on the modulation of inflammation., Statement of Significance: Degeneration of the IVD is an age-related progressive process considered to be the major cause of spine disorders. The pro-inflammatory environment and biomechanics of the degenerated IVD is a challenge for regenerative therapies. The novelty of this work is the intradiscal injection of an anti-inflammatory therapy based on Chitosan (Ch)/Poly-(γ-glutamic acid) (γ-PGA) nanoparticles (NPs) with an anti-inflammatory drug (diclofenac, Df), previously developed by us. This drug delivery system was tested in a pro-inflammatory/degenerative intervertebral disc ex vivo model. The main findings support the success of an anti-inflammatory therapy for degenerated IVD that not only reduces inflammation but also promotes native IVD matrix production., (Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.)

Intervertebral disc (IVD) degeneration is one of the major causes of low back pain, a problem with a heavy economic burden, which has been increasing in prevalence as populations age. Deeper knowledge of the complex spatial and temporal orchestration of cellular interactions and extracellular matrix remodelling is critical to improve current IVD therapies, which have so far proved unsatisfactory. Inflammation has been correlated with degenerative disc disease but its role in discogenic pain and hernia regression remains controversial. The inflammatory response may be involved in the onset of disease, but it is also crucial in maintaining tissue homeostasis. Furthermore, if properly balanced it may contribute to tissue repair/regeneration as has already been demonstrated in other tissues. In this review, we focus on how inflammation has been associated with IVD degeneration by describing observational and in vitro studies as well as in vivo animal models. Finally, we provide an overview of IVD regenerative therapies that target key inflammatory players., (© 2015 The Author(s) Published by the Royal Society. All rights reserved.)

Tissue engineering and regenerative medicine have created a demand for biomaterials with specific functions such as the ability to modify the host immune response. The objective of this study was to evaluate the effect of two different pro-resolution lipid mediators, lipoxin A4 (LxA4) and resolvin D1 (RvD1), in the modulation of the inflammatory response to biomaterials through M2 macrophage polarization. This was investigated in vivo using a mouse air-pouch model of inflammation. Our results demonstrated that both LxA4 and RvD1 are able to shift the macrophage response to implanted Ch scaffolds to an M2 reparative response. The injection of these pro-resolution mediators caused a decrease in inflammatory cells recruited to the implant site together with higher numbers of F4/80(+)/CD206(+) cells (M2 macrophages) and lower numbers of F4/80(+)/CCR7(+) cells (M1 macrophages); it also induced a general decrease in several pro-inflammatory cytokines; and caused a significant decrease in the thickness and area of the fibrous capsule formed around the implanted scaffolds. In conclusion, the use of either LxA4 or RvD1 allowed the in vivo control of macrophage phenotypic profile and thus may play a significant role in regenerative medicine applications, namely through modulation of the inflammatory response., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

In our search for immunomodulatory biomaterials capable of modulating the inflammatory response through M2 macrophage polarization, we report here on a new strategy that resulted from the incorporation of resolvin D1 (RvD1), a pro-resolution lipid mediator in porous 3D chitosan (Ch) scaffolds, followed by its lyophilisation. We have investigated the inflammatory response caused by this biomaterial in vivo using a mouse air-pouch model of inflammation. We found that this developed material caused a decrease in inflammatory cells recruited to the implant site, together with higher numbers of F4/80(+)/CD206(+) cells (M2 macrophages) and lower numbers of F4/80(+)/CCR7(+) cells (M1 macrophages). It also induced a general decrease in pro-inflammatory cytokines, and caused a decrease in the inflammatory cells observed around and within the implanted scaffolds, when compared with Ch alone or Ch not submitted to lyophilisation after RvD1 incorporation. Our results demonstrate that we were able to develop an immunomodulating biomaterial that triggers a shift in the macrophage response towards a M2 reparative response that will be advantageous for the host., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Recent studies have pointed towards a decisive role of inflammation in triggering tissue repair and regeneration, while at the same time it is accepted that an exacerbated inflammatory response may lead to rejection of an implant. Within this context, understanding and having the capacity to regulate the inflammatory response elicited by 3-D scaffolds aimed for tissue regeneration is crucial. This work reports on the analysis of the cytokine profile of human monocytes/macrophages in contact with biodegradable 3-D scaffolds with different surface properties, architecture and controlled pore geometry, fabricated by 3-D printing technology. Fabrication processes were optimized to create four different 3-D platforms based on polylactic acid (PLA), PLA/calcium phosphate glass or chitosan. Cytokine secretion and cell morphology of human peripheral blood monocytes allowed to differentiate on the different matrices were analyzed. While all scaffolds supported monocyte/macrophage adhesion and stimulated cytokine production, striking differences between PLA-based and chitosan scaffolds were found, with chitosan eliciting increased secretion of tumor necrosis factor (TNF)-α, while PLA-based scaffolds induced higher production of interleukin (IL)-6, IL-12/23 and IL-10. Even though the material itself induced the biggest differences, the scaffold geometry also impacted on TNF-α and IL-12/23 production, with chitosan scaffolds having larger pores and wider angles leading to a higher secretion of these pro-inflammatory cytokines. These findings strengthen the appropriateness of these 3-D platforms to study modulation of macrophage responses by specific parameters (chemistry, topography, scaffold architecture)., (Copyright © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.)

The effect of the degree of acetylation (DA) of 3D chitosan (Ch) scaffolds on the inflammatory reaction was investigated. Chitosan porous scaffolds with DAs of 4 and 15% were implanted using a subcutaneous air-pouch model of inflammation. The initial acute inflammatory response was evaluated 24 and 48 h after implantation. To characterize the initial response, the recruitment and adhesion of inflammatory cells to the implant site was studied. The fibrous capsule formation and the infiltration of inflammatory cells within the scaffolds were evaluated for longer implantation times (2 and 4 weeks). Chitosan with DA 15% attracted the highest number of leukocytes to the implant site. High numbers of adherent inflammatory cells were also observed in this material. For longer implantation periods Ch scaffolds with a DA of 15% induced the formation of a thick fibrous capsule and a high infiltration of inflammatory cells within the scaffold. Our results indicate that the biological response to implanted Ch scaffolds was influenced by the DA. Chitosan with a DA of 15% induce a more intense inflammatory response when compared with DA 4% Ch. Because inflammation and healing are interrelated, this result may provide clues for the relative importance of acetyl and amine functional groups in tissue repair and regeneration.

We have used self-assembled monolayers (SAMs) of alkanethiolates on gold to study the contribution of methyl terminal functional groups in implant-triggered inflammation. The CH3-coated biomaterials were inserted in an air-pouch cavity of the BALB/c mouse and the in situ inflammatory response was monitored 4, 24, 48 and 72 h later. Flow cytometry was applied to define surface expression of the adhesion receptor Mac-1 (CD11b/CD18), a marker of activated leukocytes, and also of CD3 and B220 antigens (T and B lymphocytes). The CH3-coated surfaces caused a significant enhancement in the number of Mac-1+ cells in the implant. The only significant change in T and B lymphocytes was a transient increase in T cells detected 48 h after the implantation. Peak numbers of Mac-1+ phagocytes were observed 24 h after implantation. We conclude that if CH3 is present at the surface of implants, this chemical group will trigger a significant enhancement of activated phagocytes involved in the inflammatory reaction, and this phenomenon may extend the local phlogistic event.

The contribution of methyl groups in implant-triggered inflammation was investigated in vivo using self-assembled monolayers (SAMs) of alkanethiols on gold. The CH(3)-coated implants were inserted in an air-pouch cavity induced in BALB/c mice. The in situ inflammatory response was monitored 24, 48, and 72 hours later. Inflammatory cells recovered from the air pouches were counted and observed by light microscopy. The cellularity of the implant surfaces was defined by scanning electron microscopy (SEM). In comparison with gold implants, the CH(3)-coated SAMs recruited a significantly higher number of inflammatory cells. Polymorphonuclear leukocytes (PMN) were more numerous than mononuclear cells (Mo) in the exudates recovered from the air pouches with CH(3)-coated SAMs. The opposite PMN/Mo proportion was observed in air pouches of the two control groups (mice receiving gold implants or sham-operated animals). A low density of adherent cells was seen on CH(3)-coated implants, with no significant quantitative differences during the time course of the study. In contrast, the gold-coated surfaces were covered with numerous cells during all of the 3 days of the inflammation. In conclusion, implants with CH(3) surfaces are likely to induce PMN-dominated local acute inflammation but these surfaces are not associated with a significant adherence of leukocytes to the implant., (Copyright 2005 Wiley-Liss, Inc.)

The acute inflammatory response and the adhesion of cells to self-assembled monolayers (SAMs) of well-defined surface chemistry was studied in vivo using a rodent air-pouch model of inflammation. SAMs with three different terminal functional groups (OH, COOH and CH3) were implanted in subcutaneous air pouches induced in BALB/c mice. After 24 h, inflammatory cells were recovered from the air pouches and the implants were removed and prepared for observation by scanning electron microscopy (SEM). The implants coated with OH and CH3, were found to cause the highest recruitment of inflammatory cells into the subcutaneous pouches. Polymorphonuclear neutrophils (PMNs) leukocytes predominated over mononuclear cells in inflammatory exudates of SAMs-coated implants, the opposite being found in uncoated implants (controls). CH3-coated implants induced the highest number of inflammatory cells and also the largest percentage of PMNs seen in the subcutaneous pouches. Control and OH-covered implants presented the higher densities of attached inflammatory cells detected by SEM. In contrast, the CH3-coated implants showed a very low density of cells adherent to the implant surface. We conclude that the chemical nature and the degree of hydrophobicity of the surface of implants modulate both the local acute inflammatory reaction and the adhesion of leukocytes.

Background: Inflammation has been implicated in core features of depression pathophysiology and treatment resistance. Therefore, new challenges in the discovery of inflammatory mediators implicated in depression have emerged. MicroRNAs (miRNAs) have been found aberrantly expressed in several pathologies, increasing their potential as biomarkers and therapeutical targets. In this study, the aim was to assess the changes and biomarker potential of inflammation-related miRNAs in depression patients. Methods: Depression diagnosis was performed according to the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5). 40 healthy controls and 32 depression patients were included in the study. The levels of inflammatory cytokines were measured in plasma, and expression levels of cytokines and inflammation-related miRNAs were evaluated in peripheral blood mononuclear cells (PBMCs). Results: Depression patients were found to have a pro-inflammatory profile in plasma, with significantly higher levels of TNF-α and CCL2 compared with controls. In PBMCs of depression patients, TNF-α and IL-6 expression levels were significantly up and downregulated, respectively. Moreover, miR-342 levels were found upregulated, while miR-146a and miR-155 were significantly downregulated. miR-342 expression levels were positively correlated with TNF-α. Importantly, when analyzed as a diagnostic panel, receiver operating characteristics (ROC) analysis of miR-342, miR-146a, miR-155 in combination, showed to be highly specific and sensitive in distinguishing between depression patients and healthy controls. Conclusion: In summary, these findings suggest that inflammation-related miRNAs are aberrantly expressed in depression patients. Moreover, we show evidences on the potential of the combination of dysregulated miRNAs as a powerful diagnostic tool for depression. [ABSTRACT FROM AUTHOR]

The burden of chronic inflammatory diseases of joints and the spine is increasing with population ageing and unhealthy lifestyles. Articular cartilage and intervertebral discs (IVDs) are avascular and aneural tissues with abundant extracellular matrix, low cell density, and reduced regenerative capacity after damage or degeneration. The most advanced in vitro and ex vivo cell‐/tissue‐/biomaterial‐based models and technologies to improve physiological mimicry are discussed, focusing on the impact of inflammation on articular repair/regeneration. In addition, in vivo models, developed to study cartilage and IVD repair/regeneration are addressed. While animal models continue to provide crucial mechanistic and preclinical data, more advanced and robust in vitro/ex vivo cartilage and IVD models, with appropriate extracellular matrix cues and allowing for cellular crosstalk, have seen an exponential growth in the last decade. Due to the complexity of articular microenvironments, adequate in vitro/ex vivo/in vivo models are essential to study the molecular mechanisms underlying articular diseases and develop new therapies for repair/regeneration. [ABSTRACT FROM AUTHOR]

In recent years, evidence supporting a link between inflammation and neuropsychiatric disorders has been mounting. Autism spectrum disorders (ASD) and schizophrenia share some clinical similarities which we hypothesize might reflect the same biological basis, namely, in terms of inflammation. However, the diagnosis of ASD and schizophrenia relies solely on clinical symptoms, and to date, there is no clinically useful biomarker to diagnose or monitor the course of such illnesses.The focus of this review is the central role that inflammation plays in ASD and schizophrenia. It spans from pre-clinical animal models to clinical research and excludes in vitro studies. Four major areas are covered: (1) microglia, the inflammatory brain resident myeloid cells, (2) biomarkers, including circulating cytokines, oxidative stress markers, and microRNA players, known to influence cellular processes at brain and immune levels, (3) effect of anti-psychotics on biomarkers and other predictors of response, and (4) impact of gender on response to immune activation, biomarkers, and response to anti-psychotic treatments. [ABSTRACT FROM AUTHOR]

Dendritic cells (DC) are promising targets for inducing tolerance in inflammatory conditions. Thus, this study aims to investigate the effects of the natural anti-inflammatory molecule resveratrol on human DC at phenotypic and functional levels, including their capacity to recruit mesenchymal stem/stromal cells (MSC). Primary human monocyte-derived DC and bone marrow MSC were used. DC immunophenotyping revealed that small doses of resveratrol (10 µM) reduce cell activation in response to tumor necrosis factor (TNF)-α, significantly decreasing surface expression of CD83 and CD86. Functionally, IL-12/IL-23 secretion induced by TNF-α was significantly reduced by resveratrol, while IL-10 levels increased. Resveratrol also inhibited T cell proliferation, in response to TNF-α-stimulated DC. The underlying mechanism was investigated by Western blot and imaging flow cytometry (ImageStreamX), and likely involves impairment of nuclear translocation of the p65 NF-κB subunit. Importantly, results obtained demonstrate that DC are able to recruit MSC through extracellular matrix components, and that TNF-α impairs DC-mediated recruitment. Matrix metalloproteinases (MMP) produced by both cell populations were visualized by gelatin zymography. Finally, time-lapse microscopy analysis revealed a significant decrease on DC and MSC motility in co-cultures, indicating cell interaction, and TNF-α further decreased MSC motility, while resveratrol recovered it. Thus, the current study points out the potential of resveratrol as a natural anti-TNF-α drug, capable of modulating DC phenotype and function, as well as DC-mediated MSC recruitment. [ABSTRACT FROM AUTHOR]

Rheumatoid arthritis (RA) is a systemic disease that affects the osteoarticular system, associated with bone fragility and increased risk of fractures. Herein, we aimed to characterize the systemic impact of the rat collagen-induced arthritis (CIA) model and explore its combination with femoral bone defect (FD). The impact of CIA on endogenous mesenchymal stem/stromal cells (MSC) was also investigated. CIA induction led to enlarged, more proliferative, spleen and draining lymph nodes, with altered proportion of lymphoid populations. Upon FD, CIA animals increased the systemic myeloid cell proportions, and their expression of co-stimulatory molecules CD40 and CD86. Screening plasma cytokine/chemokine levels showed increased tumor necrosis factor-α (TNF-α), Interleukin (IL)-17, IL-4, IL-5, and IL-12 in CIA, and IL-2 and IL-6 increased in CIA and CIA+FD, while Fractalkine and Leptin were decreased in both groups. CIA-derived MSC showed lower metabolic activity and proliferation, and significantly increased osteogenic and chondrogenic differentiation markers. Exposure of control-MSC to TNF-α partially mimicked the CIA-MSC phenotype in vitro. In conclusion, inflammatory conditions of CIA led to alterations in systemic immune cell proportions, circulating mediators, and in endogenous MSC. CIA animals respond to FD, and the combined model can be used to study the mechanisms of bone repair in inflammatory conditions. [ABSTRACT FROM AUTHOR]

Abstract: We have used self-assembled monolayers (SAMs) of alkanethiolates on gold to study the contribution of methyl terminal functional groups in implant-triggered inflammation. The CH3-coated biomaterials were inserted in an air-pouch cavity of the BALB/c mouse and the in situ inflammatory response was monitored 4, 24, 48 and 72 h later. Flow cytometry was applied to define surface expression of the adhesion receptor Mac-1 (CD11b/CD18), a marker of activated leukocytes, and also of CD3 and B220 antigens (T and B lymphocytes). The CH3-coated surfaces caused a significant enhancement in the number of Mac-1+ cells in the implant. The only significant change in T and B lymphocytes was a transient increase in T cells detected 48 h after the implantation. Peak numbers of Mac-1+ phagocytes were observed 24 h after implantation. We conclude that if CH3 is present at the surface of implants, this chemical group will trigger a significant enhancement of activated phagocytes involved in the inflammatory reaction, and this phenomenon may extend the local phlogistic event. [Copyright &y& Elsevier]

Inflammation is a complex and highly regulated biological process, crucial for a variety of functions in the human body, from host response against infectious agents to initiation of repair/regeneration of injured tissues. In the context of tissue repair, the action of different immune cell populations and their interplay with tissue specific cells, including stem cells, is still being uncovered. Extracellular Vesicles (EV) are small membrane vesicles secreted by cells in a controlled manner, which can act locally and systemically. The ability of EV to influence tissue repair and regeneration has been proposed as a physiologically intelligent and targeted strategy of cell communication. Herein, the role of EV in tissue repair is reviewed, summarising first their contribution to the regulation of immune cell function, and discussing the implications for the resolution of inflammation during repair. Next, the impact of EV on cell proliferation and differentiation, and on extracellular matrix remodelling, key aspects of the subsequent phases of tissue repair, is addressed. Finally, EV-based therapies are discussed, focusing on the application of naturally produced EV, and the use of EV as delivery vehicles. [ABSTRACT FROM AUTHOR]

The hypothesis behind this work is that fibrinogen (Fg), classically considered a pro-inflammatory protein, can promote bone repair/regeneration. Injury and biomaterial implantation naturally lead to an inflammatory response, which should be under control, but not necessarily minimized. Herein, porous scaffolds entirely constituted of Fg (Fg-3D) were implanted in a femoral rat bone defect and investigated at two important time points, addressing the bone regenerative process and the local and systemic immune responses, both crucial to elucidate the mechanisms of tissue remodelling. Fg-3D led to early infiltration of granulation tissue (6 days post-implantation), followed by bone defect closure, including periosteum repair (8 weeks post-injury). In the acute inflammatory phase (6 days) local gene expression analysis revealed significant increases of pro-inflammatory cytokines IL-6 and IL-8, when compared with non-operated animals. This correlated with modified proportions of systemic immune cell populations, namely increased T cells and decreased B, NK and NKT lymphocytes and myeloid cell, including the Mac-1+ (CD18+/CD11b+) subpopulation. At 8 weeks, Fg-3D led to decreased plasma levels of IL-1β and increased TGF-β1. Thus, our data supports the hypothesis, establishing a link between bone repair induced by Fg-3D and the immune response. In this sense, Fg-3D scaffolds may be considered immunomodulatory biomaterials. [ABSTRACT FROM AUTHOR]

Abstract: Macrophages are a key cell in the host response to implants and can be polarized into different phenotypes capable of inducing both detrimental and beneficial outcomes in tissue repair and remodeling, being important in tissue engineering and regenerative medicine. The objective of this study was to evaluate the macrophage response to 3D porous chitosan (Ch) scaffolds with different degrees of acetylation (DA, 5% and 15%). The M1/M2 phenotypic polarization profile of macrophages was investigated in vivo using a rodent air-pouch model. Our results show that the DA affects the macrophage response. Ch scaffolds with DA 5% induced the adhesion of lower numbers of inflammatory cells, being the M2 the predominant phenotypic profile among the adherent macrophages. In the inflammatory exudates F4/80+/CD206+ cells (M2 macrophages) appeared in higher numbers then F4/80+/CCR7+ cells (M1 macrophages), in addition, lower levels of pro-inflammatory cytokines together with higher levels of anti-inflammatory cytokines were found. Ch scaffolds with DA 15% showed opposite results, since M1 were the predominant macrophages both adherent to the scaffold and in the exudates, together with high levels of pro-inflammatory cytokines. In conclusion, Ch scaffolds with DA 5% induced a benign M2 anti-inflammatory macrophage response, whereas Ch scaffolds with DA 15% caused a macrophage M1 pro-inflammatory response. [Copyright &y& Elsevier]