Developing Predictive Indicators of Cell Maturation as Measures of Cell Therapy Product Efficacy and Safety

Principal Investigator: Deborah Hursh, PhD
Office / Division / Lab: OCTGT / DCGT / CTTB

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General Overview

Living cells are being used both directly and to engineer whole tissues for the repair and regeneration of diseased, damaged or aging tissues. In order for the therapies derived from this important and promising new field of medical research to be both safe and effective, scientists must learn how to reliably predict how these living cellular products will mature and integrate into the body after they are administered to patients. Cells and tissues that do not grow and mature in a predictable way will not provide effective treatment; they can also cause serious adverse consequences, such as tumors.

After a cell therapy product is administered to a patient, the fate of those cells depends largely on their ability to efficiently communicate with their environment. Both the cells and their host environment carry out this communication by releasing signaling molecules called growth factors. These growth factors can work in collaboration or opposition to each and guide the maturation of the transplanted cells so they can repair or regenerate target tissues.

To ensure that cell and tissue therapy products manufactured outside an organism will work effectively after they are administered to a patient, we are trying to de-code the complex communications used by cells during maturation. This knowledge will help us to predict how transplanted cell and tissue products will respond to the specific environment into which they are transplanted within patients.

This research program uses a simple organism as a model to study communication among cells. We focus on communication networks known to be active in embryonic development and regeneration: the Bone Morphogenetic Protein, Wnt, and Hedgehog pathways. We are able to screen the entire set of genes (complete genome) of our organism to identify molecules involved in cell-cell communication networks. By this method, we identify genes that can serve as predictive indicators of cell fate.

The cell communication networks we study have been shown to be identical among all animals, so we expect that the data acquired in our model system is applicable to humans. Promising candidates can be tested in human cells or in mouse models to establish whether the candidate proteins will serve as markers whose activity can help us to predict how the cells and tissues will behave in a patient. Lack of identified markers is a current hurdle to the development of safe and effective cell therapies.

We are also beginning to study which aspects of cell communication are most critical for predicting the survival of cells. The cells in most current cell therapies die soon after administration, thus preventing them from replacing or regenerating patient tissues. Our data suggests that cells undergo premature cell death when cell-to-cell communication is disrupted or mis-regulated.

An additional project in our laboratory aims at developing methods to examine genome stability in cultured stem cells, since abnormal changes (e.g., mutations) can reduce the safety and effectiveness of products made from these cells.

Developing markers that help us to predict cell fate, cell behavior, and cell survival is critical to our role in ensuring the safe and effective use of all cell therapy products, including the emerging area of stem cell therapy.

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Scientific Overview

This research program focuses on the role of intercellular communication via peptide growth factors in cell differentiation and the formation of tissues. Using the tools of genetics and molecular biology, our goal is to describe biochemical pathways through which growth factors act to modulate morphology, gene expression and cell behavior. Our major focus is the Transforming Growth Factor beta family, with lesser focus on the Wnt and Hedgehog signaling pathways. Results are relevant to the use of growth factors as cytokines in the manufacture of cellular and tissue products as well as therapeutic agents in and of themselves.

Furthermore, understanding the stability of differentiated cells and their capacity to be reprogrammed by their environment is a major concern in use of cellular therapies, particularly those using stem cells and the nascent area of engineered tissues. Our work uses the fruitfly Drosophila melanogaster as a model system. Drosophila is one of the premier systems for rapid genome-wide in vivo screens to analyze protein function. A completed, annotated genome, and extensive resources for loss of expression and tissue specific over-expression in the context of the intact organism also make Drosophila among the most powerful model systems for analysis of cell and tissue interactions. All signal transduction pathways (TGF-beta, Wnt, Hedgehog, FGF, EGF, MAP kinase, JNK (SAPK) kinase) are highly conserved between Drosophila and mammals, therefore results from Drosophila can be extended to higher animals. However, where mammals often have multiple genes for individual signal transduction pathway members, the simpler fruitfly typically has single gene representatives of critical signaling proteins, thus the issue of genetic redundancy, which often obscures genetic analysis in mammals, is avoided.

The lab has developed a sensitized genetic model of TGF-beta activity to carry out genetic interaction screens to identify markers of growth factor activity. Using this screen, we have identified proteins whose expression is correlated with TGF-beta activity, and are examining their relationship with TGF-beta action. We have also uncovered previously unknown interactions between the TGF-beta pathway and other critical growth factor pathways.

Our genetic screen is based on TGF-beta action in a specific morphogenetic event: the fusion of epithelial sheets called imaginal discs to form the ectodermal derivatives of the adult head. This model of TGF-beta action allows investigation of signaling within and across tissues, in the context of an intact organism. As we further understand this growth factor regulated system, we are beginning to use it to analyze the role of growth factor delivery across tissue layers. We have also observed that loss of growth factor signaling results in apoptotic cell death, most likely though the JNK kinase pathway, and we are looking for the triggers by which inadequate or inappropriate growth factor signaling induces cell death. As most cells administered for therapeutic effect currently undergo cell death rapidly after administration, a better understanding how improper cell communication induces apoptosis may lead to better predictive tools to ensure that cells administered to patients will survive.

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Publications

Dev Biol 2012 Sep 15;369(2):362-76
Hox proteins coordinate peripodial decapentaplegic expression to direct adult head morphogenesis in Drosophila.
Stultz BG, Yeon Park S, Mortin MA, Kennison JA, Hursh DA

Dev Biol 2010 Jul 1;343(1-2):167-77
Odd paired transcriptional activation of decapentaplegic in the Drosophila eye/antennal disc is cell autonomous but indirect.
Sen A, Stultz BG, Lee H, Hursh DA

Tissue Eng Part A 2009 Mar;15(3):455-60
Synopsis of the Food and Drug Administration-National Institute of Standards and Technology Co-Sponsored "In Vitro Analyses of Cell/Scaffold Products" Workshop.
McCright B, Dang JM, Hursh DA, Kaplan DS, Ballica R, Benton KA, Plant AL

Development 2007 Apr;134(7):1301-10
The Zic family member, odd-paired, regulates the Drosophila BMP, decapentaplegic, during adult head development.
Lee H, Stultz BG, Hursh DA

Dev Biol 2006 Aug 15;296(2):329-39
Decapentaplegic head capsule mutations disrupt novel peripodial expression controlling the morphogenesis of the Drosophila ventral head.
Stultz BG, Lee H, Ramon K, Hursh DA

Dev Biol 2006 Feb 15;290(2):482-94
Transcriptional activation by extradenticle in the Drosophila visceral mesoderm.
Stultz BG, Jackson DG, Mortin MA, Yang X, Beachy PA, Hursh DA

Oncogene 2005 Dec 15;24(56):8229-39
Drosophila caliban, a nuclear export mediator, can function as a tumor suppressor in human lung cancer cells.
Bi X, Jones T, Abbasi F, Lee H, Stultz B, Hursh DA, Mortin MA

Genesis 2005 Jun 28;42(3):181-92
Analysis of the shortvein cis-regulatory region of the decapentaplegic gene of Drosophila melanogaster.
Stultz BG, Ray RP, Hursh DA