Summary The mammalian hair follicle arises during embryonic development from coordinated interactions between the epidermis and dermis. It is currently unclear how to recapitulate hair follicle induction in pluripotent stem cell cultures for use in basic research studies or in vitro drug testing. To date, generation of hair follicles in vitro has only been possible using primary cells isolated from embryonic skin, cultured alone or in a co-culture with stem cell-derived cells, combined with in vivo transplantation. Here, we describe the derivation of skin organoids, constituting epidermal and dermal layers, from a homogeneous population of mouse pluripotent stem cells in a 3D culture. We show that skin organoids spontaneously produce de novo hair follicles in a process that mimics normal embryonic hair folliculogenesis. This in vitro model of skin development will be useful for studying mechanisms of hair follicle induction, evaluating hair growth or inhibitory drugs, and modeling skin diseases.

The pathogenesis of chronic rhinosinusitis (CRS) remains unclear to date. The tissue remodeling in nasal polyps may be the result of inflammatory mediators and may involve epithelial-mesenchymal transition (EMT) and EMT-associated features such as cell motility in nasal epithelial cells (NECs). We determined whether NEC in nasal polyps of CRS already display features of EMT in vivo or respond with EMT to growth factor stimulation in vitro. Nasal polyp tissues expressed both epithelial and mesenchymal markers. Primary NEC from inferior turbinates and nasal polyps responded to the EMT-inducing agents transforming growth factor (TGF)-β1 and epidermal growth factor (EGF) with different expression patterns of EMT markers (E-cadherin, N-cadherin, Snail, Slug, Twist), however, only NEC from nasal polyps were susceptible to TGF-β1 and EGF-dependent cell migration. Our data suggest that a partial EMT is associated with the pathogenesis of nasal polyps in CRS patients. Furthermore, we show for the first time that epithelial cells from both nasal polyps and inferior turbinates were able to undergo an EMT-like process following exposure to TGF-β1 or EGF in vitro but that only NEC from nasal polyps responded with enhanced cell motility. Our data suggest that NEC from CRS patients have undergo partial EMT and that this process may be involved in the pathogenesis of CRS.

The signaling pathways that sustain the disease process of chronic rhinosinusitis with nasal polyps (CRSwNP) remain poorly understood. We sought to determine the expression levels of Wnt signaling genes in CRSwNP and to study the role of the Wnt pathway in inflammation and epithelial remodeling in the nasal mucosa. Microarrays and real time-quantitative polymerase chain reaction comparing gene expression in matched NPs and inferior turbinates revealed that WNT2B, WNT3A, WNT4, WNT7A, WNT7B, and FZD2 were up-regulated and that FZD1, LRP5, LRP6, and WIF1 were down-regulated in NPs. Immunolabeling showed robust expression of Wnt ligands, nuclear β-catenin, and Axin-2 in NP tissue, suggesting that Wnt/β-catenin signaling is activated in NPs. We used primary human nasal epithelial cell (HNEpC) cultures to test the functional consequences of Wnt pathway activation. Monolayer HNEpCs treated with recombinant human WNT (rhWNT) 3A, but not with rhWNT4, had altered epithelial morphology and decreased adhesion, without loss of viability. We found that neither rhWNT3A nor rhWNT4 treatment induced proliferation. The expression and release of inflammatory cytokines IL-6 and granulocyte-macrophage colony-stimulating factor were increased after rhWNT3A exposure of HNEpCs. When differentiated at an air-liquid interface, rhWNT3A- and WNT agonist-, but not rhWNT4-treated HNEpCs, had abnormal epithelial architecture, failed to undergo motile ciliogenesis, and had defective noncanonical Wnt (planar cell polarity) signaling. On the basis of these results, we propose a model in which Wnt/β-catenin signaling sustains mucosal inflammation and leads to a spectrum of changes consistent with those seen during epithelial remodeling in NPs.

Experimental autoimmune encephalomyelitis (EAE) in rats is a highly valuable model of multiple sclerosis (MS) because it mimics major hallmarks of the human disease. EAE induced with myelin-oligodendrocyte-glycoprotein (MOG) in DA rats is relapsing/ remitting, and lesions in the central nervous system show inflammation, demyelination, and axonal and neuronal loss. Recently, bone marrow transplantation (BMT) was introduced as a novel strategy to treat MS, but its efficiency and the underlying mechanism are debatable. In MOG-induced EAE we found that BMT at the peak of EAE but not in the chronic phase leads to disease attenuation. In both settings, rats receiving bone marrow (BM) transplants were protected from subsequently induced relapses. These findings could be confirmed by histopathology in which rats receiving BM transplants did not have lesions compared with controls not receiving transplants. Importantly, the protective effect was achieved by allogeneic, syngeneic, and BM grafts from diseased rats. BMT resulted in increased numbers of CD4 ؉ CD25 bright regulatory T cells, increased IntroductionMultiple sclerosis (MS) is a chronic inflammatory autoimmune disease of the central nervous system (CNS) that is characterized by demyelinating plaques and axonal loss. 1 Although MS is highly prevalent in Northern Europe and the United States, 2 no cure is presently available and the clinical management of the disease is unsatisfactory. 1 The etiology of MS is unknown. However, it is generally believed that both genetic and environmental factors contribute to the development of its pathology. 3 The onset of MS is presumably characterized by autoreactive T cells crossing the blood brain barrier (BBB) and initiating an inflammatory response that results in an opening of the BBB. This allows influx of additional immune cells such as granulocytes, macrophages, natural killer (NK) cells, and B cells as well as antibodies and complement. 4 Subsequently, this process leads to myelin destruction, induction of oligodendrocyte death, axonal degeneration and, ultimately, to the functional deficits seen in MS patients. 5 Experimental autoimmune encephalomyelitis (EAE) is a frequently used animal model for MS that can be induced in rodents and monkeys. 6 In particular, myelin-oligodendrocyte-glycoprotein (MOG)-induced EAE in DA rats mimics major hallmarks of the human disease. These include the relapsing/remitting type of disease course, the occurrence of demyelinated plaques in the brain and spinal cord, axonal loss, and the involvement of both antibodies and complement in the pathogenesis. [7][8][9][10][11] Autologous bone marrow transplantation (BMT) and hematopoietic stem cell transplantation (HSCT) are presently discussed as novel options for the treatment of patients with MS with fast progressive disease courses that do not respond to conventional treatment. 12,13 Clinical trials were to some extent inconclusive because they arrived at divergent results. [14][15][16] Preclinical studies were performed in EAE that assessed...