Mesenchymal stem cells occupy niches in stromal tissues where they provide sources of cells for specialized mesenchymal derivatives during growth and repair. The origins of mesenchymal stem cells have been the subject of considerable discussion, and current consensus holds that perivascular cells form mesenchymal stem cells in most tissues. The continuously growing mouse incisor tooth offers an excellent model to address the origin of mesenchymal stem cells. These stem cells dwell in a niche at the tooth apex where they produce a variety of differentiated derivatives. Cells constituting the tooth are mostly derived from two embryonic sources: neural crest ectomesenchyme and ectodermal epithelium. It has been thought for decades that the dental mesenchymal stem cells giving rise to pulp cells and odontoblasts derive from neural crest cells after their migration in the early head and formation of ectomesenchymal tissue. Here we show that a significant population of mesenchymal stem cells during development, self-renewal and repair of a tooth are derived from peripheral nerve-associated glia. Glial cells generate multipotent mesenchymal stem cells that produce pulp cells and odontoblasts. By combining a clonal colour-coding technique with tracing of peripheral glia, we provide new insights into the dynamics of tooth organogenesis and growth.

Deregulation of microRNAs (miRNAs) contributes to the development and progression of many cancer types; however, their functions in the pathogenesis of testicular germ cell tumor (TGCT) remain unclear. Here, we determined miRNA expression profiles of TGCTs and normal testes using small RNA sequencing, and identified several deregulated miRNAs in TGCTs, including the miR-506~514 cluster. In functional studies in vitro we demonstrated that miR-514a-3p induced apoptosis through direct regulation of the paternally expressed gene 3 (PEG3), and ectopically expressed PEG3 could rescue the apoptotic effect of miR-514a-3p overexpression. Silencing of PEG3 or miR-514a-3p overexpression reduced nuclear accumulation of p50 and NF-κB reporter activity. Furthermore, PEG3 was co-immunoprecipitated with tumor necrosis factor receptor-associated factor 2 (TRAF2) in TGCT cell lysates. We propose a model of PEG3-mediated activation of NF-κB in TGCT. Loss of miR-514a-3p expression in TGCT increases PEG3 expression that recruits TRAF2 and activates the NF-kappa B pathway, which protects germ cells from apoptosis. Importantly, we observed strong expression of PEG3 and nuclear p50 in the majority of TGCTs (83% and 78%, respectively). In conclusion, our study describes a novel function for miR-514a-3p in TGCT and highlights an unrecognized mechanism of PEG3 regulation and NF-κB activation in TGCT.

We have previously shown that human embryonic stem cell (hESC) therapy to injured rabbit vocal folds (VFs) induces human tissue generation with regained VF vibratory capacity. The aims of this study were to test the sustainability of such effect and to what extent derivatives of the transplanted hESCs are propagated in the VFs. The VFs of 14 New Zealand rabbits were injured by a localized resection. HESCs were transplanted to 22 VFs which were analyzed for persistence of hESCs after six weeks and after three months. At three months, the VFs were also analyzed for viscoelasticity, measured as dynamic viscosity and elastic modulus, for the lamina propria (Lp) thickness and relative content of collagen type I. Three months after hESC cell therapy, the dynamic viscosity and elastic modulus of the hESC treated VFs were similar to normal controls and lower than untreated VFs (p ≤ 0.011). A normalized VF architecture, reduction in collagen type I, and Lp thickness were found compared with untreated VFs (p ≤ 0.031). At three months, no derivatives of hESCs were detected. HESCs transplanted to injured rabbit VFs restored the vibratory characteristics of the VFs, with maintained restored function for three months without remaining hESCs or derivatives.

Abstract. Embryonic neural tumors are responsible for a disproportionate number of cancer deaths in children. Although dramatic improvements in survival for pediatric malignancy has been achieved in previous years advancements seem to be slowing down. For the development of new enhanced therapy and an increased understanding of the disease, pre-clinical models better capturing the neoplastic niche are essential. Tumors of early childhood present in this respect a particular challenge. Here, we explore how components of the embryonic process in stem-cell induced mature teratoma can function as an experimental in vivo microenvironment instigating the growth of injected childhood neuroblastoma (NB) cell lines. Three human NB cell lines, IMR-32, Kelly and SK-N-BE(2), were injected into mature pluripotent stem cell-induced teratoma (PSCT) and compared to xenografts of the same cell lines. Proliferative NB cells from all lines were readily detected in both models with a typical histology of a poorly differentiated NB tumor with a variable amount of fibrovascular stroma. Uniquely in the PSCT microenvironment, NB cells were found integrated in a non-random fashion. Neuroblastoma cells were never observed in areas with well-differentiated somatic tissue i.e. bone, muscle, gut or areas of other easily identifiable tissue types. Instead, the three cell lines all showed initial growth exclusively occurring in the embryonic loose mesenchymal stroma, resulting in a histology recapitulating NB native presentation in vivo. Whether this reflects the 'open' nature of loose mesenchyme more easily giving space to new cells compared to other more dense tissues, the rigidity of matrix providing physical cues modulating NB characteristics, or if embryonic loose mesenchyme may supply developmental cues that attracted or promoted the integration of NB, remains to be tested. We tentatively hypothesize that mature PSCT provide an embryonic niche well suited for in vivo studies on NB. IntroductionKey knowledge is still missing for the successful cure of aggressive neuroblastoma (NB), representing one of the most deadly pediatric malignancies (1-4). Neuroblastoma is a small round cell tumor of childhood and is considered to arise from dedifferentiation of primordial neural crest cells that populate the sympathetic trunks and the adrenal medulla (reviewed in ref. 5). During this process, an aberrant response to microenvironment cues may play an important role in modulating the tumor phenotype, and hence also lead to the variable clinical presentations of NB in patients. The clinical presentation spans from a benign type with the ability to spontaneously regress to a variant with a high rate of recurrence, metastatic spread and a high frequency of therapy-resistance. Current consensus supports the importance of a strong interplay with the surrounding tissue promoting tumor growth and spread (6). Thus, pre-clinical studies of childhood NB would for increased relevance benefit from in vivo models better matching the embryonic neoplastic niche i...