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Human embryonic stem (hES) cells are capable of differentiation into virtually all cell types and hold tremendous potential as cell sources for regenerative therapies. However, teratoma formation can be the main obstacle for hES cells therapy. In order to understand the biology and physiology of hES cells teratoma formation, we investigated the angiogenic process within teratomas and characterized teratoma cells. In this study, hES cells transduced with double fusion reporter gene that consists of firefly luciferase and enhanced green fluorescent protein (Fluc-eGFP) were injected into hind limbs of SCID mice and performed longitudinal bioluminescence imaging on these animals. To test angiogenic contribution of teratoma from host or hES cells, human and mouse endothelial cells marker CD31 was stained respectively. To further explore the characterization of teratoma derived cells, flow cytometry analysis was carried out and GFP+/SSEA-4+ cells were isolated and subcultured. Then, we re-injected the isolated GFP+/SSEA-4+ teratoma cells into SCID mice and observed by imaging. Our results show that the reporter gene imaging is an ideal technology for monitoring long-term stem cell viability, death, and proliferation. Teratomas contained vasculatures are from hES cells and host. hESCs derived teratomas express a high level of undifferentiated marker SSEA-4 and CD56, and subcultured GFP+/SSEA-4+ cells had similar expression pattern comparing to undifferentiated hES cells, except for a very high level of CD56 and a little lower expression of undifferentiated markers, such as SSEA-3, SSEA-4, TRA-1-60, and TRA-1-81. Moreover, the SSEA-4+ teratoma cells can form teratomas in SCID mice, and this type teratomas grow at a lower rate compared to teratomas derived from hES cells, and are more differentiated.

Mesenchymal stem cells (MSCs) are pluripotent cells that can be applied to the treatment of immune disorders, including inflammatory bowel disease (IBD). The therapeutic effects of MSCs have been mostly attributed to the secretion of soluble factors with paracrine actions, such as extracellular vesicles (EVs), which may play a relevant role in the repair of damaged tissues. In the present study, a mouse model of colitis was induced with the use of trinitrobenzene sulfonic acid (TNBS). EVs derived from human placental mesenchymal stem cells (hP-MSCs) were used for the treatment of colitis by in situ injection. Clinical scores were applied to verify the therapeutic effects of EVs on mice with colitis. Inflammation in the colon was evaluated by measuring the levels of various inflammatory cytokines. The content of reactive oxygen species (ROS) was detected by the use of molecular imaging methods for real-time tracking and the therapeutic effects of EVs on mucosal healing in mice with colitis were evaluated. The results revealed that the injection of EVs regulated the balance of pro-inflammatory and anti-inflammatory cytokines in colon tissue. Treatment with EVs also suppressed oxidative stress by decreasing the activity of myeloperoxidase (MPO) and ROS. Histological analysis further confirmed that the EVs significantly promoted mucosal healing, as reflected by the promotion of the proliferation of colonic epithelial cells and the maintenance of tight junctions. Taken together, the findings of the present study demonstrated that EVs derived from hP-MSCs alleviated TNBS-induced colitis by inhibiting inflammation and oxidative stress. These findings may provide a novel theoretical basis for the EV-based treatment of IBD.

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