Medicine

Mannan from yeast induces psoriasis-like inflammation in the skin of inbred mouse strains. Limitations of available models led us to develop a new psoriasis model with a rapid disease onset, severe disease course, short duration, and a simple and easy-to-induce protocol with much more practically convenient features and cost-benefits. Mannan-induced skin inflammation (MISI) is more severe than the classical imiquimod (IMQ)-induced skin inflammation (IISI), with characteristic features resembling human plaque psoriasis but with relatively fewer toxicity issues. Epicutaneous application of mannan (5 mg) in incomplete Freund’s adjuvant or Vaseline induces severe psoriasis in BALB/c female mice. Psoriasis area and severity index (PASI) and histological evaluation of the skin could help assess the disease development. MISI mimics natural environmental factors affecting the skin relatively more closely than IISI. This disease model can be used to dissect inflammatory pathways in the skin, identify genetic and environmental factors affecting psoriasis, and test potential pharmacological agents or new combinations of available drugs for treatment before designing clinical trials.

Key features

• S. cerevisiae mannan induces psoriasis-like skin inflammation(MISI) when applied on the skin of inbred mice.

• The MISI model has a rapid onset, severe disease, short duration, and simple and easy-to-induce protocol.

• MISI is more severe than imiquimod-induced skin inflammation (IISI).

• Female mice had a more severe disease than males in the MISI model, thereby allowing the study of sex-dependent disease mechanisms.

• The MISI model identifies skin inflammatory pathways and genetic/environmental factors affecting psoriasis.

• The MISI model can be used as a drug testing platform for potential pharmaceuticals to develop new therapeutics for psoriasis patients.

• The MISI model can be used to explore the relative contribution of different pattern recognition receptors in the development and severity of psoriasis.

Graphical overview

Tracking macrophages by non-invasive molecular imaging can provide useful insights into the immunobiology of inflammatory disorders in preclinical disease models. Perfluorocarbon nanoemulsions (PFC-NEs) have been well documented in their ability to be taken up by macrophages through phagocytosis and serve as ¹⁹F magnetic resonance imaging (MRI) tracers of inflammation in vivo and ex vivo. Incorporation of near-infrared fluorescent (NIRF) dyes in PFC-NEs can help monitor the spatiotemporal distribution of macrophages in vivo during inflammatory processes, using NIRF imaging as a complementary methodology to MRI. Here, we discuss in depth how both colloidal and fluorescence stabilities of the PFC-NEs are essential for successful and reliable macrophage tracking in vivo and for their detection in excised tissues ex vivo by NIRF imaging. Furthermore, PFC-NE quality assures NIRF imaging reproducibility and reliability across preclinical studies, providing insights into inflammation progression and therapeutic response. Previous studies focused on assessments of colloidal property changes in response to stress and during storage as a means of quality control. We recently focused on the joint evaluation of both colloidal and fluorescence properties and their relationship to NIRF imaging outcomes. In this protocol, we summarize the key assessments of the fluorescent dye–labeled nanoemulsions, which include long-term particle size distribution monitoring as the measure of colloidal stability and monitoring of the fluorescence signal. Due to its simplicity and reproducibility, our protocols are easy to adopt for researchers to assess the quality of PFC-NEs for in vivo NIRF imaging applications.

Graft-versus-host disease (GvHD) is a significant complication of allogeneic hematopoietic stem cell transplantation. In order to develop new therapeutic approaches, there is a need to recapitulate GvHD effects in pre-clinical, in vivo systems, such as mouse and humanized mouse models. In humanized mouse models of GvHD, mice are reconstituted with human immune cells, which become activated by xenogeneic (xeno) stimuli, causing a multi-system disorder known as xenoGvHD. Testing the ability of new therapies to prevent or delay the development of xenoGvHD is often used as pre-clinical, proof-of-concept data, creating the need for standardized methodology to induce, monitor, and report xenoGvHD. Here, we describe detailed methods for how to induce xenoGvHD by injecting human peripheral blood mononuclear cells into immunodeficient NOD SCID gamma mice. We provide comprehensive details on methods for human T cell preparation and injection, mouse monitoring, data collection, interpretation, and reporting. Additionally, we provide an example of the potential utility of the xenoGvHD model to assess the biological activity of a regulatory T-cell therapy. Use of this protocol will allow better standardization of this model and comparison of datasets across different studies.

Graphical abstract