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Expansion of human Treg cells in vivo: Flt3L takes centre stage

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  2. Expansion of human Treg cells in vivo: Flt3L takes centre stage
  3. Vascularized tissue from an injectable in vitro prototype

FoxP3+ regulatory T (Treg) cells constitute an important component of the immune regulatory network which prevents autoimmunity and restrains overwhelming inflammatory reactions. A better understanding of the mechanisms involved in the homeostasis of human Treg cells could lead to therapeutic applications by modulating the frequency and activity of this cell population. In this issue, Klein et al. demonstrate that, in keeping with previous pre-clinical studies, administration of the hematopoietic growth factor Flt3L leads to an expansion of FoxP3+ Treg cells in human subjects. This is an indirect effect, whereby the Flt3L-expanded pool of CD1c+ myeloid dendritic cells induces proliferation of pre-existing Treg cells. These findings suggest that Flt3L, which already has a well-established clinical safety profile, could be used as a therapeutic agent in the treatment of autoimmune conditions and in the setting of transplantation medicine, by promoting the establishment of Treg-cell-mediated tolerance towards autoantigens and allografts.

Klein et al., Eur J Immunol 2013;43:533–539.

Vascularized tissue from an injectable in vitro prototype

  1. Top of page
  2. Expansion of human Treg cells in vivo: Flt3L takes centre stage
  3. Vascularized tissue from an injectable in vitro prototype

In vivo revascularization is the bottle-neck problem that hinders the development of tissue engineering and regeneration. It is now very difficult, if not impossible, for in vitro engineered blood vessel networks to become functional and generate anastomosis with host blood vessels. In this work, instead of trying to fabricate blood vessel networks directly, Yao and her coworkers developed a highly biomimetic and injectable prototype based on microsphere co-cultures and stem cell differentiation. The gap among the microspheres and endothelial cell layer was designed to facilitate host blood vessel growth and anastomosis. The prototype resembled the natural adipose tissue in many aspects and successfully developed into adipose tissue with functional blood vessel networks. The vasculature formed within the injections benefited the formation, maturity, and long-term maintenance of newly generated adipose tissue. Further work is ongoing in the laboratory to study the mechanism behind the phenomena and apply the prototype to larger animal models.

Yao et al., Biotechnol Bioeng 2013;110: 1430–1443