A humanized mouse model to study human immune response in xenotransplantation

Development of a humanized mouse model with functional human materno-fetal interface immunity

Materno-fetal immunity possesses specialized characteristics to ensure pathogen clearance while maintaining tolerance to the semiallogeneic fetus. Most of our understanding on human materno-fetal immunity is based on conventional rodent models that may not precisely represent human immunological processes owing to the huge evolutionary divergence. Herein, we developed a pregnant human immune system (HIS) mouse model through busulfan preconditioning, which hosts multilineage human immune subset reconstitution at the materno-fetal interface. Human materno-fetal immunity exhibits a tolerogenic feature at the midgestation stage (embryonic day [E] 14.5), and human immune regulatory subsets were detected in the decidua. However, the immune system switches to an inflammatory profile at the late gestation stage (E19). A cell-cell interaction network contributing to the alternations in the human materno-fetal immune atmosphere was revealed based on single-cell RNA-Seq analysis, wherein human macrophages played crucial roles by secreting several immune regulatory mediators. Furthermore, depletion of Treg cells at E2.5 and E5.5 resulted in severe inflammation and fetus rejection. Collectively, these results demonstrate that the pregnant HIS mouse model permits the development of functional human materno-fetal immunity and offers a tool for human materno-fetal immunity investigation to facilitate drug discovery for reproductive disorders.

Tissue-engineered vascular microphysiological platform to study immune modulation of xenograft rejection

Most of the vascular platforms currently being studied are lab-on-a-chip types that mimic capillary networks and are applied for vascular response analysis in vitro. However, these platforms have a limitation in clearly assessing the physiological phenomena of native blood vessels compared to in vivo evaluation. Here, we developed a simply fabricable tissue-engineered vascular microphysiological platform (TEVMP) with a three-dimensional (3D) vascular structure similar to an artery that can be applied for ex vivo and in vivo evaluation. Furthermore, we applied the TEVMP as ex vivo and in vivo screening systems to evaluate the effect of human CD200 (hCD200) overexpression in porcine endothelial cells (PECs) on vascular xenogeneic immune responses. These screening systems, in contrast to 2D in vitro and cellular xenotransplantation in vivo models, clearly demonstrated that hCD200 overexpression effectively suppressed vascular xenograft rejection. The TEVMP has a high potential as a platform to assess various vascular-related responses.

Humanized Mouse Models for Transplant Immunology

Our understanding of the molecular pathways that control immune responses, particularly immunomodulatory molecules that control the extent and duration of an immune response, have led to new approaches in the field of transplantation immunology to induce allograft survival. These molecular pathways are being defined precisely in murine models and translated into clinical practice; however, many of the newly available drugs are human-specific reagents. Furthermore, many species-specific differences exist between mouse and human immune systems. Recent advances in the development of humanized mice, namely, immunodeficient mice engrafted with functional human immune systems, have led to the availability of a small animal model for the study of human immune responses. Humanized mice represent an important preclinical model system for evaluation of new drugs and identification of the mechanisms underlying human allograft rejection without putting patients at risk. This review highlights recent advances in the development of humanized mice and their use as preclinical models for the study of human allograft responses.

Imaging preclinical tumour models: improving translational power

Recent developments and improvements of multimodal imaging methods for use in animal research have substantially strengthened the options of in vivo visualization of cancer-related processes over time. Moreover, technological developments in probe synthesis and labelling have resulted in imaging probes with the potential for basic research, as well as for translational and clinical applications. In addition, more sophisticated cancer models are available to address cancer-related research questions. This Review gives an overview of developments in these three fields, with a focus on imaging approaches in animal cancer models and how these can help the translation of new therapies into the clinic.