RFA #: 0901051121
|Optimizing Dynamic Interactions Between hESC-Derived Cardiac Patch and Inflammatory Cells
|The Rockefeller University
|Regulation of Hair Follicle Stem Cell Maintenance and Activation
|Determining the Effects and Mechanisms of Id1 on Leukemia Stem Cells
Donald Freytes, PhD
Heart muscle cannot regenerate itself following myocardial infarction. Cardiac function can only be restored by new cardiomyocytes injected into the heart or implanted in the form of a tissue-engineered graft. Remarkable progress has been made in recent years in developing functional cardiomyocytes from human stem cells. However, the environment into which these cells will be placed – an ischemic heart undergoing inflammation and remodeling – is completely overlooked. We recently found that the progression of heart repair by human stem cells in an animal model can be both enhanced and suppressed by the inflammatory response of the host.
We propose to investigate the recruitment of monocytes and macrophages by repair cardiac cells at different stages of maturity using a high-throughput platform for cell co-culture under normoxic and hypoxic conditions. The two specific aims during the mentored phase are to: (1) quantify the recruitment of monocytes and macrophages when co-cultured with hESC-derived cardiomyocytes, and (2) determine the effects of monocytes and macrophages when co-cultured in direct contact with hESC-derived cardiomyocytes encapsulated in different matrices that could enhance the survival and function of implanted cells. Aim 3 (independent phase) will help determine the optimum time to deliver the cardiac repair cells within the context of the inflammatory cells and validate conclusions obtained from Aims 1 and 2.
Our goal is to understand the effects of environmental conditions on the recruitment and interactions of different subsets of macrophages and monocytes, by taking a fundamentally novel approach to this important aspect of cell-based therapy. If successful, this work would fill a major gap in our current knowledge of heart tissue repair by establishing principles for choosing optimal time for cell implantation, identifying the possibilities to modulate (or even harness) the inflammatory response, and developing strategies to enhance the survival and function of the implanted cells.
Ting Chen, PhD
The Rockefeller University
Many tissues have the ability to maintain proper function and structure in the face of environmental insults. The variable capacity of different tissues to renew themselves during normal development or respond to injury has been shown to depend upon populations of resident stem cells (SCs). In the adult skin, hair follicles (HFs) undergo cycles of new hair growth followed by destruction and rest. The process is fueled by follicle SCs that reside in a permanent niche (bulge) and undergo cycles of quiescence and activation. During injury, HF-SCs participate with basal interfolliclular epidermal SCs to repair damaged epidermis and sebaceous glands. Understanding the signaling pathways and intrinsic factors that regulate SCs is not only relevant to basic SC biology, but also has clinical significance, particularly in human cancers, where these mechanisms go awry. The goal of my study is to understand the mechanisms that establish, maintain and activate HF-SCs during tissue development in order to develop treatments for diseases and cancers. My preliminary studies show that HF regeneration happens as a two-step process involving two distinct epithelial compartments: bulge and hair germ (HG). Our findings suggest a model where HG cells fuel initial hair regrowth, while the bulge is the engine maintaining the process. In addition, our findings raise the following key questions: (1) Are the differences that define bulge SCs and HG cells intrinsic or extrinsic? (2) Of the genes whose expression is preferentially up/downregulated in HF-SCs or HG cells in vivo, which are functionally important to the features of SCs and their progenitor cells? By addressing these issues, we expect to uncover new insights into understanding how skin SCs possess and maintain their proliferative/tissue regenerative potential and are kept in an undifferentiated state until mobilized to generate tissue.
Lan Wang, PhD
Sloan Kettering Institute
Blood cells are generated by a group of immature cells in the bone marrow called hematopoietic stem cells (HSCs). HSCs are proposed to be the cell of origin in leukemia and we are studying how their behavior goes awry when the cells become transformed into acute leukemia. Leukemia stem cells show loss of normal growth control mechanisms, leading to abnormal cell division, survival and expansion. The development of acute leukemia is commonly associated with aberrant transcriptional regulation, where genes are inappropriately turned on or off. In most cases, correcting these abnormalities would block the development or progression of leukemia in patients. Our recent work showed that a specific gene, Id1, is required for maintaining HSC self-renewal. As a key regulator of blood cell production, Id1 could serve as a target for attacking leukemia stem cells, because eliminating the ability of Id1 to maintain the immaturity of leukemia stem cells should lead to their death. Here we propose to study the relevance of Id1 in turning normal blood cells into leukemia stem cells using mouse models of human leukemia. We plan to study the effect of Id1 on leukemia stem cells by eliminating its presence using genetic means or RNA interference. We also will test the effects of inhibitors of Id1 function, with or without chemotherapy, on the formation of leukemia stem cells and the progression to leukemia. Our prediction is that blocking Id1 will inhibit the development of leukemia stem cells. The information generated by this study may be useful for developing targeted therapeutics for human leukemia.