Symposium summary: The crucial role of the extracellular matrix in meat marbling and tenderness
Scientists used to think the extracellular matrix (ECM) was simply a kind of scaffolding. That was partly true; the ECM is a non-living mix of proteins that sits between cells and provides structural support. But research has revealed that the ECM also plays a crucial role in the development of new cells in the body. Scientists now think that signals in the ECM can spark the transformation of immature cells into muscle and fat cells.
“Such a radical change in view owes to the efforts of countless biologists,” wrote Washington State University professor Min Du in a paper for the Journal of Animal Science.
In his paper, Du summarized four presentations given at the 2011 Joint Annual Meeting “Extracellular matrix in muscle growth and meat quality symposium.” Du explained that growth of connective tissue, which contributes to toughness in meat, could be controlled by the ECM. The ECM also plays a role in the growth of fat cells that lead to marbling in meat. Du called marbling and tenderness the “top two quality problems” in meat production because producers want to increase marbling and decrease toughness. Perhaps research into the ECM can help.
In the first symposium presentation, wrote Du, Purdue University animal scientist Shihuan Kuang focused on muscle stem cells, called “satellite cells,” in the ECM. When signals between cells and muscle fibers pass through the ECM, those signals can prompt satellite cells to develop into mature muscle cells. Huang said his lab uses this knowledge to regenerate cells in “bioactive scaffolds” that mimic the properties of the ECM. This research could mean better treatments for injuries in humans and a better understanding of how satellite cells led to muscle development.
“It’s important for human health, but it’s important for agriculture too,” Du said.
In the second presentation, Sandra Velleman from The Ohio State University discussed how proteins in the ECM, called proteoglycans, regulate skeletal muscle growth. Different types of proteoglycans create pathways for signals from proteins like fibroblast growth factor-2, which is one protein that controls muscle growth. Studying communications between cells through the ECM pathways could help scientists understand how the ECM affects muscle growth and meat production in livestock.
In the third presentation, Gary Hausman from the USDA Agricultural Research Service described the properties of cells called stromal-vascular cells. Stromal-vascular cells are embedded in the ECM and contain a collection of stem cells, fat cells and muscle fiber cells at different stages of differentiation. When a fat cell, or adipocyte, is still developing, it is called a preadipocyte. Preadipose cells in the ECM become the intramuscular fat cells that give meat its valuable “marbled” taste.
In the final presentation, food scientist Peter Purslow from the University of Guelph discussed turnover of connective tissue in skeletal muscle. Connective tissue is partially made up of the ECM. When meat contains mature connective tissue, it become less tender when cooked. Purslow showed that degradation of mature connective tissue cells can lead to the growth of newer, more tender connective tissue cells.
Research into cell development and signals from the ECM could improve the quality of the meat we consume. Du said that the symposium was just a glimpse into a growing field of research. He said there will be a new symposium at the 2012 Joint Annual Meeting in Phoenix, Arizona on this topic. In the future, Du hopes to see more research into how stem cell differentiation affects marbling and tenderness.
The symposium summary was written by Min Du and Kasey Carlin. It can be read in full at: journalofanimalscience.org
Min Du, PhD
Washington State University
American Society of Animal Science