Tissue specific stem and progenitor cells exist to replenish the tissue it resides during normal homeostasis or during regeneration from a wound. Disease and aging leads to a depletion of these stem and progenitor cells, which can impede the ability of the body to regenerate itself. Thus, an understanding of the mechanisms of how tissue specific stem and progenitor cells self-renew and differentiates is key to being able to maintain these cells for life and to use these cells therapeutically. Stem and progenitor cells reside in specific niches in our bodies, which interact with neighboring cells and extracellular proteins. Unfortunately, this type of interaction is difficult to model in cultured cells. We have previously developed methods to regenerate 3D intact human epidermis on immune compromised mice, which allows us to investigate the factors important for tissue regeneration. Potential regulators of epidermal stem cell self-renewal and differentiation include epigenetic factors. Epigenetic factors are proteins that modify either DNA or histone. Alterations in DNA or histone can lead to heritable changes in gene expression, which may lead to a stem cell determining whether to differentiate or proliferate. We propose to determine the function of modifiers of DNA and histone methylation in epidermal stem cell self-renewal and differentiation. This will lead to a fundamental understanding of how tissue specific stem cells maintain a tissue for the duration of our lives.
Millions of Californians suffer from epidermal derived skin disorders, which range from psoriasis, squamous cell carcinomas, basal cell carcinomas to chronic wounds. These diseases are characterized by abnormalities in epidermal stem and progenitor cell growth and differentiation. For example, increased proliferation and failure to properly differentiate can lead to skin carcinomas. Currently not much is known about the mechanisms that govern epidermal stem cell growth and differentiation. This proposal seeks to understand the fundamental mechanisms of epidermal stem cell self-renewal and differentiation through the study of epigenetic factors, which may yield insights in the development of therapies for epidermal disorders. Our proposed research will benefit California in several ways: 1) our research should provide epigenetic targets that can be modulated by small molecules that can potentially treat epidermal disorders; 2) provide a thorough understanding of how adult somatic stem cells regenerate tissue; 3) training the next generation of stem cell scientists.
This application is focused on the study of tissue homeostasis in the epidermis, which comprises the outer layers of the skin. The investigator has established a system in which human epidermal cells are experimentally manipulated in culture and then used to reconstitute skin on immune-compromised mice. The applicant will use this system to study the function of specific epigenetic regulators in maintaining normal human stem/progenitor cell self-renewal and differentiation in the epidermis.
Significance and Innovation
- Tissue homeostasis is an issue of central medical importance, and it is likely that most, if not all, homeostasis systems, like the one under investigation here, involve adult stem cells and their niches.
- The investigator utilizes an elegant model system in which to study human adult stem cells, it is based on one of the classic, well-established systems for the investigation of tissue homeostasis.
- While many investigators have identified transcription factors that regulate genes in developmental pathways, the fundamental mechanisms of epigenetic regulation, as addressed in this proposal, have not yet been clearly elucidated.
- Since the epigenetic regulators under investigation are of general importance in cellular processes, some reviewers expressed doubt they exert specific functions in tissue homeostasis, and thus questioned the underlying rationale for the proposed studies. Others, however, pointed out that studies published by the applicant in high impact journals and compelling preliminary data indicate that the chosen molecular targets do play specific roles in epidermal homeostasis, justifying their functional analysis in this system.
Feasibility and Experimental Design
- Preliminary data and publications provide confidence in the applicant’s proficiency in the use of the human epidermis model system.
- The proposal is well organized, clearly written, and experiments are well conceived.
- Some reviewers thought the proposed research was overly ambitious in the scope of the proposed activities and therefore could not be accomplished in the three-year time frame.
- One of the proposed studies, the structure/function analysis, is not strongly justified and it is not clear it will lead to important new insights.
Principal Investigator (PI) and Research Team
- The PI is a very promising young investigator and the research team is outstanding.
- The PI’s ability to direct independent research remains to be proven. However, the strong publication record and training in top-level laboratories provide confidence that the applicant will become an effective PI.
- The environment is excellent for the proposed studies, and the PI has identified several senior mentors who should help guide the proposed efforts.
Responsiveness to the RFA
-The application is responsive to the RFA as it addresses basic mechanisms of cell differentiation.