DNA hydroxymethylation, TET enzymes and regulation of stem cell activity during skin regeneration and wound healing

Biological mechanisms that regulate the development of mammals, including humans, continue during the lifespan of individuals and are altered during ageing. As an organ that covers the body, the skin protects us from a variety of environmental insults, such as mechanical injury, ultraviolet irradiation, and variations in temperature.

The skin also provides a unique system for studying the mechanisms that control organ development, regeneration and ageing. Skin development results in formation of the epidermis, a stratified self-renewing epithelium. Additional structures of the skin include hair follicles, nails and glands. After birth, the epidermis continuously regenerates using the ability of epithelial stem cells to supply progeny cells that form all epidermal cell layers. Meanwhile, epidermal regeneration, following skin injury, is controlled by stem cells derived from the hair follicle.

Data obtained during the last decade has revealed that many cellular biochemical pathways controlling skin development and its postnatal regeneration are of particular importance. Recent data demonstrate that activity of these biochemical pathways is governed by epigenetic regulatory mechanisms. These mechanisms include covalent modifications of the DNA molecule and methylation/hydroxymethylation of the cytosine nucleotides, which play important roles in the control of gene activation and repression.

This project will look at how enzymes called Tet1/2/3 that regulate DNA hydroxymethylation impact normal physiological skin regeneration and when induced by injury. This project will also explore how Tet1/2/3 regulate different molecular signals in epithelial stem cells and their progenies (that form skin and hair follicle epithelium), and their involvement in wound healing.

Studying the skin as a model system in this way, will cast light on the mechanisms that control the development and regeneration of other epithelial tissues, such as the epithelia of the intestine, teeth, kidney and lung. The knowledge gained from this study will also provide new opportunities for the development of novel epigenetic therapies to cure aberrant tissue growth and regenerative conditions, such as impaired wound healing in diabetic patients and in elderly individuals.

Epigenetic mechanisms play an important role in the control of stem cell activity during development and regeneration and understanding how and why these mechanisms are altered in many disorders (cancer, autoimmunity, impaired wound healing, etc.) has become a growing priority in biomedical research.

The long-term goals of this collaborative project are to understand the mechanisms that control the establishment of lineage-specific patterns of gene expression and chromatin organisation in adult stem cells during the process of differentiation into specialised cell types in normal and regenerating epithelia.

TET1/2/3 enzymes are a group of recently discovered epigenetic regulators that promote oxidation of methylated DNA and conversion of 5-methylcytosine (5mC) into 5-hydroxymethylcytosine (5hmC). 5mC DNA oxidation is required for gene activation in mammals and plays an essential role in many biological processes including development, cell differentiation and cancer.

Here, we will test the hypothesis that Tet1/2/3 proteins are critical determinants that control gene expression programmes in adult epithelial stem cells and their progenies during skin regeneration and wound healing via two Specific Aims:
1) Define the common features and differential impact of the distinct Tet proteins on the self-renewing and differentiation potentials of epithelial stem cells and their progenies during physiological hair cycle-dependent skin regeneration.
2) Identify the role of Tet proteins in the control of activity of skin epithelial stem cells and their lineage-committed progenies (epidermal keratinocytes) during wound healing.

This project will provide new important insights into fundamental mechanisms that regulate stem cell activity inside and outside of the skin, and will serve as an important platform for the development of novel epigenetic drugs to target stem cells for the needs of regenerative medicine and stem cell-based therapy.

An understanding of biological mechanisms regulating stem cell activity is highly important for better understanding the changes that occur during life, and affect the health status and longevity of individuals. This project will look at how Tet1/2/3 proteins, epigenetic regulators that control DNA methylation/hydroxymethylation status and gene expression, impact stem cell activity during skin regeneration and wound healing.

SCIENTIFIC COMMUNITY
This project will provide substantial new knowledge for the scientific community and will contribute to an advance in public health benefits. Delineating the functions of Tet1/2/3 proteins in the control of stem cells and their lineage-committed progenies during skin postnatal regeneration, and wound healing will help to advance knowledge for investigators working in the following areas of fundamental research (developmental biology, molecular biology, stem cell biology and tissue regeneration, hair follicle biology), in addition to clinical (dermatology, regenerative medicine) and veterinary medicine.

PUBLIC HEALTH & AWARENESS
This project will have significant health implications and will benefit the public sector, including health professionals and their patients. Chronic wounds represent a substantial public health problem. In the UK, chronic wounds affect approximately 200,000 patients, with an estimated 3% of the annual healthcare budget spent on chronic wound care alone.

The information generated by this project will provide new opportunities for therapeutic interventions to cure chronic epithelial wounds. It will also influence the generation of new therapeutics for specific forms of hair loss. This will ultimately contribute to the enhancement of quality of life.

INDUSTRY
Business/industry will benefit from this project by expanding our understanding of molecular mechanisms that control skin and hair regeneration. This is vital for development of new approaches to improve diagnosis and for treatment of skin and hair disorders, leading to substantial economical benefits in related life science industries. Knowledge transfer activities with industrial partners will be actively implemented for those areas of the results that can be used for new therapeutic product development. The newly generated knowledge will also be used in the relevant higher education courses for basic scientists and health professionals.

To ensure that the results of the proposed project will be made available to the general public and to the specific groups mentioned above, several approaches will be pursued. The results will be presented at prestigious international conferences. In April 2012, we organised an International Symposium "Epigenetic Control of Skin Development and Regeneration" (http://www.skin.brad.ac.uk/SkinEpigenetics-2012/), which we aim to hold annually. This symposium represents a unique opportunity to bring skin biologists together with scientists studying epigenetic regulatory mechanisms and provides platform for establishing intradisciplinary collaboration. We plan to organize second symposium in 2015 with a focus on more translational approaches and development of novel epigenetic therapies for modulation of stem cell activity for the needs of regenerative medicine and stem cell-based therapy. Our data will be published in international peer-reviewed journals with the widest possible audience. Information on the project outcomes will also be made available to relevant Health and Wound-healing charities.

Overall, this project will provide information of strategic importance for researchers, the business/industrial sector, and health professionals within the NHS, whilst longer term will contribute to better public health.