Engineering a Platform to Harness Pluripotent Stem Cell-Derived Paracrine Factors

Abstract

The results of initial stem cell transplantation studies indicate that many of the observed functional improvements are due to transient paracrine actions of the transplanted stem cells, rather than the stem cells permanently engrafting and replacing the damaged cellular material. Thus, research on the identity and potency of paracrine factors secreted by stem cells has become an increased area of focus in the regenerative medicine field. Due to the mitogenic and morphogenic roles of embryonic stem cells (ESCs) during the early stages of development, they are an underexplored cell population which likely possess a unique and potent secretome. A potential application for the milieu of mitogens and morphogens produced by pluripotent stem cells is the restoration of the proliferative and regenerative capacity of adult stem cell populations, as these multipotent cells have a limited ability for expansion outside the body and are also negatively regulated by dysfunctional signals in vivo which are implicated in the reduced capacity for regeneration with injury or aging.

To take advantage of the stimulatory potential of pluripotent cell-derived signals, the goal of this project was to develop a controlled means of harnessing and delivering soluble factors derived from pluripotent stem cells. This objective was accomplished through the (1) development of a microencapsulation-based culture system for ESC aggregates, (2) design of a novel upstream bioreactor for encapsulated ESC culture which enabled the concentration and delivery of stem cell secreted products, (3) characterization of the global expression profile of ESC-secreted factors, and (4) investigation of the influence of ESC-derived factors on adult stem and progenitor populations. Ultimately, this project established pluripotent stem cells as a unique source of potent growth factors and cytokines which can be regulated and concentrated using engineering design parameters to enable multiple applications in the field of regenerative medicine.