Muscle cell-derived cytokines in muscle regeneration

Adult skeletal muscle is capable of robust regeneration, mainly due to the presence of resident quiescent stem cells known as muscle satellite/stem cells (MuSCs). Upon injury the satellite cells are activated and undergo rapid proliferation. A small percentage of the newly proliferated myoblasts return to quiescence for future regeneration events, while the rest withdraw from the cell cycle and differentiate . Differentiated myoblasts fuse together to form new multinucleated myofibers or may repair an existing myofiber. With such a delicate and intricate process to maintain, it is important for the muscle to have many regulators to guide the regeneration successfully. Although research on muscle regeneration and its regulators has been extensive, many of the processes and regulators remain either incompletely understood or unknown. Cytokines make up an important group of regulators for muscle regeneration. The major source of cytokines in the regeneration niche is immune cells. Immune cells infiltrate muscle injury sites and secrete cytokines to promote inflammatory responses and also directly regulate muscle regeneration. However, another potentially important source of these cytokines is the muscle itself. Several years ago, our lab performed a functional RNAi screen, which identified numerous cytokines that could potentially regulate myogenic differentiation. Interestingly, those myokines are often produced also by the immune cell population, which raises the question: What is the role of the muscle-derived cytokines in muscle regeneration? This question was difficult to answer directly for a long time due to the inability to distinguish between cytokines derived from immune cells and those muscle-derived ones. In Chapter 2, I describe our lab’s successful generation of myogenic progenitor cell (MPC)-specific CRISPR-Cas9 mouse lines and how that enabled us to investigate the function of muscle-derived Chemokine (C-C) motif ligand-8 (Ccl8) as a negative regulator of skeletal myogenesis. We also mined publicly available muscle regeneration scRNA-seq data to create a new resource to predict relationships between regulators and various sub-populations within the muscle regeneration niche. In Chapter 3 I investigate two other Ccl family members, Ccl2 and Ccl7. Although both cytokines can share a common receptor with Ccl8, we believe that each cytokine can have a potentially unique role in regulating muscle regeneration. I find that depletion of Ccl2 and Ccl7 have different effects on myogenic differentiation from Ccl8, and their expression within the subpopulations of the regeneration niche, including MuSCs, fibro-adipogenic progenitor cells (FAPs), and macrophages, are different from one another. I also utilize an MPC-specific CRISPR-Cas9 mouse line to investigate the role of Ccl7 in muscle regeneration. Lastly, in Chapter 4, I investigate the function of interleukin-17B (IL-17B), a potential myogenic regulator that emerged from our lab’s RNAi screen. The knockdown of IL-17B enhances myogenic differentiation in a proliferation-independent manner. I again utilize our MPC-specific CRISPR-Cas9 mice to address the role of muscle derived IL-17B in regulating muscle regeneration. Muscle-cell derived cytokines are important for communicating and organizing responses during regeneration. If we can understand these systems, we can potentially manipulate them to improve muscle regeneration in muscle diseases or in aging. The establishment of the MPC-specific CRISPR-Cas9 mice has put us in a uniquely advantageous position to directly investigate the many muscle-derived cytokines for their roles in muscle regeneration. The potential for mechanistic understanding and therapeutic target identification is tremendous.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Cell and Developmental Biology

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2024

Author dc:creator

• Boss-Kennedy, Allison Ann

Contributors dc:contributor

• Chen, Jie
• Ceman, Stephanie
• Belmont, Andrew
• Boppart, Marni

• Myokines
• Skeletal Muscle Regeneration
• Myogenic Progenitor Cell
• Satellite Cell
• Il-17b
• Ccl8
• Ccl7

Statement dc:rights

• Copyright 2024 Allison Boss-Kennedy

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/127454

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F127454