Journal of immunology and regenerative medicine最新文献

Although considerable evidence exists supporting the use of mesenchymal stromal cells (MSCs) for treating immune diseases, successful clinical translation has been challenging and has led researchers to investigate cell-free alternatives. MSC-derived extracellular vesicles (MSC-EVs) have been shown to mediate a significant portion of the observed therapeutic effect, including immunosuppression. MSCs have been shown to respond to different aspects of the injury microenvironment such as inflammatory cytokines and hypoxia, although acidosis has not been investigated and different conditions have not been assessed in terms of their effects on MSC-EV function. This study investigated the effects of acidosis, hypoxia, and inflammatory cytokine priming on MSCs and MSC-EVs. We cultured MSCs in the presence of acidosis, hypoxia, or inflammatory cytokines (Interferon-gamma and Tumor Necrosis Factor-alpha) and compared the characteristics of their EVs as well as their uptake by and suppression of different T cell subsets. MSCs showed a greater effect on suppressing activated CD4⁺ and CD8⁺ T cells than MSC-EVs. However, MSC-EVs from MSCs primed with acidosis increased CD4⁺ and CD8⁺ regulatory T cell frequency in vitro. This functional response was reflected by MSC-EV uptake. MSC-EVs from acidosis-primed MSCs were the only EV group to be taken up significantly by CD4⁺ and CD8⁺ regulatory T cells. These data suggest that a simple low-cost alteration in MSC culture conditions, acidosis, can generate extracelluar vesicles that have a desirable influence on anti inflammatory T cell subtypes.

The lymphoid system protects the body from pathogens through organs that produce immune cells and facilitate immune surveillance. The study and treatment of a variety of pathologies affecting or interacting with the immune system can benefit from tissue engineering strategies. These designs can be implemented in vitro and in vivo through a variety of fabrication methods. Here we describe structure, cell types, and signaling found in the bone marrow niche, thymus, peripheral lymphoid organs, and lymphatic vasculature. We then summarize lymphoid tissue engineering studies from recent reports, and choice of design components including scaffolds, stromal cells, and chemical or physical signals. Finally, we discuss the current limitations and future of this field.

Cell therapies are currently used to treat many haematological diseases. These treatments range from the long-term reconstitution of the entire haematopoietic system using the most potent haematopoietic stem cells (HSCs) to the short-term rescue with mature functional end cells such as oxygen-carrying red blood cells and cells of the immune system that can fight infection and repair tissue. Limitations in supply and the risk of transmitting infection has prompted the design of protocols to produce some of these cell types from human pluripotent stem cells (hPSCs). Although it has proven challenging to generate the most potent HSCs directly from hPSCs, significant progress has been made in the development of differentiation protocols that can successfully produce haematopoietic progenitor cells and most of the mature cell lineages. We review the key steps used in the production of haematopoietic stem and progenitor cells (HSPCs) from hPSCs and the cell surface markers and reporter strategies that have been used to define specific transitions. Most studies have relied on the use of known markers that define HSPC production in vivo but more recently single cell RNA sequencing has allowed a less biased approach to their characterisation. Transcriptional profiling has identified new markers for naïve and committed hPSC-derived HSPC populations and trajectory analyses has provided novel insights into their lineage potential. Direct comparison of in vitro- and in vivo-derived RNA single cell sequencing datasets has highlights similarities and differences between the two systems and this deeper understanding will be key to the design and the tracking of improved and more efficient differentiation protocols.

This study evaluated the healing potential of free Cramoll, a xyloglucan membrane extracted from Hymenaea courbaril (HcXM) and Cramoll immobilized in HcXM (Cramoll-HcXM), in cutaneous wounds of diabetic mice induced by alloxan. Sixty male Swiss albino mice were randomly divided into four experimental groups (15 animals): Control; Cramoll; HcXM; and Cramoll-HcXM. Wounds, on the animals’ back after anesthesia and trichotomy, were treated daily, and clinical analysis was performed daily. Microbiological, wound retraction, histological and collagen I and III quantification analyses were performed on the 2nd, 7th and 12th days of treatment. During the 12 days of treatment no contamination was observed to any experimental wounds. Reepithelialization was accelerated in Cramoll, HcXM and Cramoll-HcXM groups and wound retraction was statistically superior in the Cramoll group. The Cramoll and HcXM groups, after 12 days of treatment, presented epidermis and dermis with typical characteristics of healthy skin, with greater deposition of type 1 collagen. The treatment of cutaneous wounds in diabetic mice with Cramoll and HcXM accelerates the healing process when used individually, however, inflammatory infiltrate and fibrovascular tissue persisted in the Cramoll-HcXM group. According to the results, this is the first report on the use of a lectin as a healer in induced diabetic mice; Cramoll and HcXM are excellent compounds for repairing skin wounds in diabetics.

Biomaterial characteristics such as topography and wettability have been shown to influence the immune response to implanted medical devices. Thus, appropriate surface design considering the immune system has moved more into focus. Previous in vitro studies have commonly employed simplistic immune models and as such, the role of different immune cell populations, particularly those of the adaptive immune system, is still poorly understood. Here, we employed a biologically complex human-based in vitro model consisting of peripheral blood mononuclear cells (PBMC) to examine interactions between cells of the innate and adaptive immune system in the context of clinically used implants. To achieve this, five differently treated titanium surfaces were characterised in terms of physicochemical properties using contact angle measurement, XPS and confocal scanning microscopy. Cytokine analysis revealed different material surface properties to result in different immune responses with SLActive surface showing low levels of IL-6 and IL-8 but high levels of MCP-1. Cytokine and surface marker analysis in isolated populations of monocytes and lymphocytes and defined ratios revealed lymphocytes alone to be unaffected by the SLActive biomaterial and except for a slight effect on HLA-DR expression indicated no activation of monocytes by lymphoid cells. On lymphocytes, CD16 and HLA-DR expression was unaffected by monocytes under physiological conditions but was elevated with high levels of monocytes present. Intracellular cytokine staining in whole PBMC cultures confirmed monocytes to be responsible for the observed immune response, with minimal involvement of lymphocytes. Expression of the pro-inflammatory cytokines IL-8 and TNF-α in monocytes peaked 12 h after biomaterial contact, while the expression of surface markers HLA-DR and CD86 continued to rise 72 h following contact. These results collectively suggest the immune response to titanium biomaterials in the first 72 h in vitro to be almost exclusively driven by the innate rather than the adaptive immune system.

Since the generation of human embryonic and induced pluripotent stem cells, regenerative cell-based approaches for the treatment of diabetes have gained popularity. One strategy is to generate an unlimited source of insulin-producing pancreatic β-cells from human pluripotent stem cells. As such, major effort continues to be placed in creating efficient differentiation protocols that generate functional β-like cells from human pluripotent stem cells. In this review, I provide the historical context of stem cell differentiation protocols towards the aim of generating functional β-like cells. I also highlight recent advancements in differentiation protocols, including enrichment of cell populations using cell surface markers, suspension culture to mimic in vivo development, and the importance of hippo signalling in endocrine cell fate. I conclude by suggesting future endeavors that have the potential to further improve differentiation protocols to achieve the ultimate goal of a cell-replacement therapy for diabetes.

Objectives

Biomaterials are routinely used in clinical applications. A key to the clinical success of implanted biomaterials is not eliciting detrimental immune responses. In this article, we provide an overview of immune responses to biomaterials, along with biomaterial-based approaches to mitigate the adverse host reactions while supporting pro-healing immune responses. We also review existing in-vitro models used to assess the biocompatibility of biomaterials.

Key findings

Once implanted, biomaterials are often detected as foreign bodies by the immune system, triggering detrimental immune responses. Such responses could damage host tissues and impair the function of implanted materials or devices. Therefore, there is substantial interest in developing new materials and tools with the ability to modulate immune responses to support tissue regeneration and healing processes. However, the bioengineering of immune responses through biomaterials requires detailed understanding of how the immune system typically responds to foreign materials. This knowledge can inform designing materials with bio-instructive chemistries and/or surface attributes. In this review, first we briefly discuss basic aspects of the foreign body response followed by different strategies for developing ‘immune-instructive’ biomaterials, models to test their efficacy and examples of their clinical applications.

Conclusions

Promising progress has been made in the field of biomaterial engineering however, how different immune cells interact with biomaterials is yet to be fully elucidated. A better understanding of cell-material interactions, and particularly the impact of inter-individual variations, will allow the development of new generation of more personalised ‘immune-instructive’ biomaterials and medical devices to modulate immune responses towards anti-inflammatory and pro-healing phenotypes.

Cancer immunotherapy is a unique treatment modality that uses the body's immune system to eliminate cancer cells. Immune checkpoint blockades, which inhibit immunosuppressive mechanisms to enhance cancer-reactive T-cell responses, have expanded cancer-treatment options because they can induce the regression of cancer that is refractory to existing treatments. However, many patients do not respond to immune checkpoint blockades, and new therapies are needed to overcome resistance to treatment. In recent years, researchers have begun developing methods to generate immune cells, which play an important role in eliminating cancer, from induced pluripotent stem cells (iPSCs) and have been administered to humans in clinical trials. This therapy can potentially replace existing cell-based cancer immunotherapies as the next generation of hybrid-cell therapies that combine immune cell therapy, regenerative medicine, and gene therapy. Previously, we constructed cytokine-dependent proliferating myeloid cells (induced pluripotent stem cell-derived proliferating myeloid cells; iPSC-pMCs) by inducing myeloid cell differentiation from iPSCs and subsequently introducing proliferation factors. Once constructed, the cells have proliferative potential, which eliminates the need for re-differentiating myeloid cells from iPSCs, resulting in an indefinite and stable supply of homogeneous cells with little investment of cost and effort. In this review, we discuss the potential of iPSC-pMC-based immune cell products as immune-stimulating agents for cancer that are refractory to checkpoint blockade.

In healing wounds, the regression of blood vessels during the resolution phase creates a significant number of apoptotic endothelial cells (ApoECs). Surprisingly few studies have investigated the fate of apoECs in wounds, or the consequence of their removal. The current study employed both in vitro and in vivo models to investigate if macrophages ingest apoECs and to determine if such phagocytosis alters macrophage phenotype. To examine the capability of macrophages to ingest apoECs in in vivo wounds, pHrodo green labeled apoECs were injected into skin wounds 6 days after injury. The results demonstrated that 2.2% of macrophages in the wounds had engulfed apoECs 24 h after injection. Macrophages that had engulfed apoECs expressed the markers CD80 (100%), CD86 (93.8%), and CD163 (22.8%), while no expression of CD206 marker was observed. In in vitro studies, 76.1% and 81.1% of PMA differentiated THP-1 macrophages engulfed apoECs at 6 and 24 h, respectively. mRNA expression levels of IL-1β, iNOS, and TGF-β1 decreased in THP-1 macrophages after exposure to apoECs, while the expression of IL-6 increased. THP-1 macrophages that were incubated with apoECs for 6 h expressed CD80 (30.2%), CD163 (62.9%), and CD206 (45.3%), while expression levels in untreated group were 0.5%, 45.0%, and 2.4%, respectively. Taken together, our studies showed that macrophages phagocytize dermal apoECs both in vitro and in vivo. The engulfment of apoECs leads to a unique macrophage phenotype, which has characteristics of both M1 and M2 macrophage phenotypes. These findings provide a new mechanism by which macrophage phenotypes can be modified during wound resolution.

The host immune response, specifically macrophage function, is a critical determinant of biomaterial success or failure post-implantation. Extracellular matrix (ECM) derived scaffolds have been shown to promote a pro-regenerative macrophage phenotype and a more constructive remodelling outcome. Here we demonstrate that macrophages adopt distinct phenotypes when exposed to articular cartilage (AC), ligament (LIG) and growth plate (GP) derived ECM scaffolds. Macrophages were generally unresponsive to LIG-derived ECM, adopted an M2-like phenotype when exposed to AC-derived ECM, and a hybrid M1-M2 phenotype when exposed to GP-ECM. Furthermore, macrophages expressed higher levels of pro-chondrogenic factors, such as FGF2, when exposed to AC-ECM, and higher levels of angiogenic and pro-osteogenic factors, such as VEGF, IL-6 and TNF, when exposed to GP-ECM. In addition, we observed that they can differentially direct the differentiation of skeletal stem cells, whereby AC-ECM promotes the chondrogenic differentiation and GP-ECM the osteogenic differentiation of multipotent stem/stromal cells (MSCs). In vivo characterisation of immune cell subsets following scaffold implantation into a large bone defect demonstrated that AC-ECM drives an M2 macrophage phenotype, while GP-ECM containing scaffolds promoted a hybrid M1-M2 phenotype and enhanced vascularisation and vessel maturation. This distinct response to the implantation of GP-ECM containing scaffolds was associated with increased CD45⁺ leukocyte and CD3⁺ T cell infiltration, accompanied by elevated concentrations of IFN-γ and IL-17. Taken together this work demonstrates that the source tissue of ECM scaffolds plays a key role in regulating the phenotype of both macrophages and skeletal stem cells. Furthermore, these ECMs can direct the cellular differentiation and production of growth factors essential for the regeneration of their source tissue. This work highlights the need for a more thorough characterisation of innate immune cell subsets post-biomaterial implantation.