CAREER: Understanding the Interdependence of the Microenvironment and Nuclear Organization in Stem Cell Aging

The dramatic increase in the elderly population presents new challenges for our society, and a critical effector of healthy lifespan is functioning skeletal muscle. Despite the significant personal and societal costs of age-related muscle atrophy and weakness, only modest progress has been made in understanding this degenerative process. One critical factor is a reduction in number and function of adult stem cells with aging.

Hence, a mechanistic understanding of how muscle stem cells become dysfunctional in old age is needed. The research objective of this Faculty Early Career Development (CAREER) project is to establish systems to study how stem cells receive and store information in their nuclei (which contain genetic information and controls and regulates cell activities) during aging.

The outcome will be enhanced understanding of the stem cell aging process in a unified and controllable manner. The primary educational objective of this project is to develop a series of stories that focus on introducing concepts of stem cells and genomics to under-represented minority (URM) students in K-3. These stories aim to increase scientific literacy and reduce the language barrier for URM students to engage with STEM principles and genomics at an early age, and positively portray underrepresented Minorities using Integrative Genomics, Human stem cells, and TechnologY (MIGHTY).

The investigator's long-term research goal is to develop and optimize technologies and therapeutics that prevent or delay age-related declines in skeletal muscle function that occur in the elderly population. A known critical contributor of sarcopenia (age-induced skeletal muscle wasting) is muscle stem cell dysfunction, which is regulated by the packaging of the genome in the nucleus.

Thus, in keeping with the long-term goal, this NSF CAREER project aims to elucidate the sensitive relationship between nuclear organization and the stem cell microenvironment in aging using in situ genome editing, microfluidics, biomaterials and integrative genomic assays. The Research Plan is organized under two objectives. The FIRST Objective is to demonstrate that muscle stem cell dysfunction observed in aging is driven by 3D genome misfolding.

An in-situ genome editing (CRISPR-Cas9) system in muscle stem cells will be used to manipulate heterochromatin and hierarchical nuclear organization. High-resolution 3D imaging coupled with epigenomic mapping will be used to contrast the effects of these perturbations with muscle stem cells isolated from different stages of life (youth, middle-age and old age).

Successful completion of these experiments will demonstrate how intrinsic alterations through genome folding engender stem cell dysfunction and remodeling of the microenvironment as well as expose the relative susceptibility of each part of the genome to deleterious changes that occur in aging. The SECOND Objective is to establish that the aberrant extracellular matrix produced during aging engenders chromatin defects that regulate muscle stem cell expansion.

Envelope muscle stem cells on myofibers with engineered biomaterials that replicate aspects of an aging endomysium will be used to assess the effect on chromatin architecture and stem cell expansion. Extracellular matrix density, elastic moduli, composition and structure surrounding muscle stem cells will be varied to determine how different types of modifications converge onto nuclear organization and impact clonal dynamics.

Successful completion of these experiments will reveal how muscle stem cells transduce alterations in their microenvironment into chromatin remodeling during aging and how these adjustments drive variations in proliferative behavior. The ability to make meaningful connections between these innovative engineering systems and critically important biological process in aging will facilitate construction of a molecular-scale, integrated understanding of the stem cell aging process that can help advance therapeutics, and fulfill knowledge gaps.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.