Extracellular Matrix Function

Introduction

The extracellular matrix (ECM) is a collection of proteins and polysaccharides secreted by cells outside the cell membrane. The three-dimensional structure has molecules made from fibrous proteins and lipids inside the ECM.

The ECM is a dynamic structure that provides cells with support, protection, and signaling functions. This post will focus on what the ECM does and how it interacts with other structures in our body to promote homeostasis.

What Makes the Extracellular Matrix?

The extracellular matrix is a collection of macromolecules and polysaccharides secreted outside the cell membrane.

The components of the ECM are arranged in an organized fashion to offer cell protection, signalling, and structural support.

The ECM consists mostly of collagen fibres made from amino acid chains. These chains branch out into other structures like proteoglycans, glycoproteins, and other ECM proteins.

The Animal Extracellular matrix

The animal extracellular matrix is made up of structural and signalling molecules and proteoglycans that tell cells to turn off immune responses.

Inside the ECM, some proteins bind to specific receptors on cells and initiate signalling cascades to promote homeostasis.

The ECM also drapes around epithelial cells and creates a physical barrier to prevent infection by viruses or bacteria. The animal ECM consists of the basement membrane and the interstitial matrix.

The basement membrane.

The basement membrane is the layer that is closest to the cells, and it consists mostly of collagen. It provides mechanical support to cells while also providing signalling molecules that tell cells when it is time for them to die.

Basement membranes have an important role in the development of organs and tissues. It also helps with maintaining the balance between unhealthy and healthy cells.

This membrane is structured so that there’s an epithelial layer/endothelial cells on the outermost part. The basement membrane follows the epithelium and then the dermis.

Other functions of this matrix membrane are to keep the organs from sliding while expanding and contracting and prevent bacteria or viruses from entering through the skin.

The Interstitial matrix

The interstitial matrix is the second layer of the ECM, and it consists mostly of proteoglycans, glycoproteins, and other proteins.

• The interstitial matrix is mainly found in connective tissues, and it functions to maintain the shape of these tissue types by giving them support.
• It also provides space for cells to grow and divide so that there is no cell contact with other developing cells. The created space also ensures that cells do not touch the basement membranes.
• The interstitial matrix also enables cells to move through the tissue. The movement is regulated by the proteoglycans and glycoproteins in this layer.
• It also initiates the immune response by activating and recruiting proteins to help remove any foreign material (e.g., bacteria).

The interstitial matrix resides between larger spaces in tissues called the interstitium. It consists of proteoglycans.

Plant extracellular matrix

The plant extracellular matrix is made up of proteoglycans that are organized into microfibrils.

Although the Extracellular matrix (ECM) does not play as many structural roles for plant cells, they use the ECM to bind to moisture and create a surface on which cell walls can grow.

The Extracellular matrix (ECM) also binds to minerals to help plants uptake them from their environment. It consists of cell wall elements like cellulose and signalling molecules.

It also provides mechanical support and a barrier to protect cells from infection by viruses or bacteria. The main macromolecules in this ECM are cellulose fibres and pectin.

The plant extracellular matrix is located between the epidermal layer and the ground. It’s also found in the roots, leaves, and petals of plants.

It is fluid but still provides structural support to cells below it by maintaining their shape (e.g., preventing leaves from being crushed or petals to droop).

The plant ECM also helps with cell signaling by activating and recruiting proteins. It does this through the use of proteoglycans, which are found in its intercellular structure.

Components of the Extracellular Matrix Explained

Proteoglycans

A proteoglycan is a type of glycosaminoglycan that helps to regulate water balance. It also provides mechanical support for cells and the ECM. There are two types of proteoglycans: glycosaminoglycan and Versican.

Glycosaminoglycan proteoglycans are mainly found in the animal extracellular matrix. They have a protein core that is linked to glycosaminoglycan chains.

Versican proteoglycans are mainly found in the plant extracellular matrix. They are more heavily modified than glycosaminoglycan proteoglycans.

Proteoglycans are important for cell signaling. They activate and recruit proteins to help remove any foreign material (e.g., bacteria).

The three sulfate compounds found in the extracellular matrix are chondroitin, keratan, and heparan sulfates.

Chondroitin

Chondroitin is a glycosaminoglycan that helps regulate water balance and provides mechanical support for cells and the ECM.

It is often found in the animal extracellular matrix and has a protein core linked to glycosaminoglycan chains.

Chondroitin contributes to the tendons, cartilage, and ligament strength. It is also found in the lungs and helps to decrease the risk of asthma.

Keratan

Keratan sulphate is another glycosaminoglycan that helps to regulate water balance and tissue repair. It also provides mechanical support for cells and the ECM.

It is often found in the animal extracellular matrix and has a protein core linked to glycosaminoglycan chains.

Keratan is found in the skin, teeth, and hair. Keratin can also be used as a natural protein filler for wound healing or tissue repair. It replaces a damaged stem cell to facilitate healing.

This sulfate compound gives hair its strength and is found in all these other tissues because it provides mechanical support.

Heparan

It is found in the animal extracellular matrix and has a protein core linked to glycosaminoglycan chains.

Heparan sulfate also helps regulate water balance and provides mechanical support for cells and the ECM.

Heparan is attached to proteins and is used to signal the extracellular environment, cells, or tissues. It also regulates cell growth and division.

It is found in the epidermis and can bind to bacteria. It is also an important part of blood vessels, which it helps in cell signalling and blood cell movement.

Fibronectin

Another one of the many ECM components is fibronectin. This one provides mechanical support for cells and the ECM. Fibronectin is often found in animal mesenchymal tissues but can also be found in the skin and certain blood cells.

Fibronectin is a protein that binds to various other proteins, including collagen. It also interacts with other cells and helps to create a network.

These extracellular matrix proteins are secreted in inactive forms and are activated by proteases (enzymes that break down proteins) in the matrix.

Fibronectins help in wound healing by assisting in the formation of new blood vessels and repairing cells.

Extracellular Vesicles

Extracellular vesicles are also found in the extracellular matrix. They can help regulate water balance, provide mechanical support for cells and the ECM, or play a role in immune system defence. They have a protein core that is linked to glycosaminoglycan chains.

Vesicle proteoglycans have a protein core linked to an amyloid saccharide instead of chains. It links cells together by surrounding them. Amyloid can also help with cell signalling.

Other cellular functions of these vesicles include the regulation of water balance, metabolic support for cells and the extracellular matrix, and immune defence.

Laminin

These are extracellular proteins found in the animal extracellular matrix. They have a protein core linked to glycosaminoglycan chains.

Laminin helps maintain water balance in tissues, regulates cell movement and differentiation (e.g., during development), and provides mechanical support for cells and ECM components like proteoglycans, collagen fibres, and elastin.

Laminin is also found in the epidermis, regulates cell communication during development, and helps with water balance.

The laminin helps regulate extracellular matrix components by wrapping around other proteins to bind them together. It can also wrap around cells or tissues through chemical interactions that make up the ECM (e.g., proteoglycans).

Laminin is a modular protein with different combinations of proteins to bind with, including collagen IV and V or types IX and X, depending on location in the extracellular matrix.

Elastin

Elastin is a glycoprotein and provides mechanical support for cells. It also helps regulate water balance by maintaining the shape of cells below it (e.g., preventing leaves from being crushed or petals drooping).

The plant ECM has this as well, but elastin does not provide much support in the animal ECM.

Elastin is found in the skin, lungs, liver, and many other tissues of an animal. It starts as a long fibre when it first develops but breaks down into smaller pieces over time.

Also, elastin can be synthesized in a lab and used to help a tissue heal. It is a natural protein filler for wounds or tissue repair.

Collagen

Collagen is a part of the extracellular matrix proteins. It is the most abundant protein in animals, and without it, we would not have skin. It interacts with other proteins to create a strong structural framework found in the skin, bone, and cartilage.

Collagen also helps to provide a barrier for keeping moist tissues moist and dry tissues from drying out. It is also found in the eye’s cornea, which helps to keep water in and protects it from drying out.

Protein collagen also controls the skin’s elasticity, cartilage, ligaments, tendons, hair follicles, and blood vessels. It is what gives these structures their strength and helps to make them elastic.

Tenascins

These ECM proteins manifest in five different forms: TN-R, TN-C, TN-X, TN-W, and TN-Y. They are all important in maintaining the extracellular matrix and other cell functions.

Tenascins provide mechanical support for cells by binding to other ECM proteins and cells. They also help regulate water balance by maintaining the shape of cells below them (e.g., preventing leaves from being crushed or petals drooping).

Tenascin X has a role in the development of cancer and can be used to promote tumour growth and help prevent tumor cells from dying.

Tenascin Y is found in the brain and helps with neural activity, specifically in the cerebral cortex. Tenascin X is also found in the brain but does not have a role in neural activity.

Tenascin-C absence will interfere with the regeneration of the bone tissue. Tenascin-R is found in the heart and can help to regulate blood pressure.

Tenascin W is responsible for tissue repair and is found in the skin, lungs, liver, and brain.

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How Does The Process of Tissue Regeneration Happen?

The process of tissue regeneration can happen in a few different ways, such as by scar formation or through the addition of new cells. Scar formation is the process of forming a fibrous network over the site where tissue is lost.

The new cells are either added through cell migration and proliferation or by differentiation of cells that already exist in the area. Scar tissue is not as strong or resilient as native tissue, but it can still be functional.

There are two types of scars: hypertrophic and atrophic. Hypertrophic scars are raised, red, thickened areas that can lead to keloids. Atrophic scars are depressions in the skin and can be caused by burns, acne, or surgery.

Fibroblasts determine how a wound heals. They produce collagen that links to the wound and then fills in the gap where the tissue was lost. They can also be used in tissue engineering.

Tissue engineering is a process of rebuilding damaged tissue. It is done using synthetic biological and natural materials that closely resemble the original cells or tissues being repaired.

Different cells have different roles in wound healing:

• Fibroblasts produce collagen that links to the wound and then fills in the gap where the tissue was lost.
• Macrophages eat any dead cells and bacteria, as well as any other foreign objects.
• Inflammation prevents infection and heals wounds with the help of macrophages, fibroblasts, and neutrophils.
• Immune cells are also found in a wound but do not participate in healing, as they help fight infection.
• Epithelial cells attach to the wound and begin growing over it, creating a protective layer of skin that can prevent bacteria from entering.
• Neurons release chemicals that help with the healing process, such as nerve growth factors and thyroxine.

What Factors Prolong the Wound Healing Process?

The wound healing process can be prolonged for a few different reasons:

• If the injury is deep, there may not be enough tissue to cover the wound. Deep wounds can also get infected, and the infection can disrupt the healing process.
• In case there is damage to other nearby tissue, it may slow down or stop the wound from healing.
• If the wound is kept open for a long period, it can delay healing. This could happen if there are stitches or staples in the wound.
• If there is a chronic infection, it can interfere with the healing process and cause it to take longer than usual.
• If the wound is not kept clean, it will be more difficult for cells to attach and start healing.

ECM and Gene Expression

The extracellular matrix has a role in gene expression. Genes are activated by the ECM and other cells, as well as the extracellular proteins.

There are a few different Extracellular matrix types: collagen, elastin, and proteoglycans.

Proteoglycans are proteins that have sugar chains attached to them. They help cells bind together, and they also regulate cell growth, differentiation, and movement.

Collagens are found all over the body, from internal support structures to skin tissue. They provide strength and structure in tissues.

Protein elastin is found in places that need to stretch, such as skin and lungs. They help the cells maintain their elasticity so that they can return to their original shape.

Gene expression is the process of producing RNA from DNA. It is a complicated process that involves multiple steps.

The ECM triggers gene expression and provides signals to the cells to control the process.

What’s the Role of the Extracellular Matrix Cell Differentiation?

Cell differentiation is the process of certain cell types changing to resemble and function as others. This process happens in three steps:

1. The first step is called proliferation, which means that the cells will divide and produce more cells of the same type.
2. The next step is called determination, which means that some of the cells will change into different cells and stop dividing.
3. The final step is called maturation, which means that the cells will change their shape and function like well-established mature cells.

Extracellular matrix has a role in cell differentiation by providing signals to the cells. It tells them when they should start dividing and when they should stop.

The ECM also provides signals to cells in the differentiation process, telling them what type they should become and how to change.

Examples of cells that are differentiated by the extracellular matrix include keratinocytes, adipose cells, and osteoblasts. Others are smooth muscle cells and leukocytes.

Extracellular Matrix and Cancer plasticity

The extracellular matrix is made up of proteins, RNA, and DNA. These are the basic building blocks for cells, and they help regulate cell growth and differentiation. This means that the ECM plays a role in cancer because it signals cells about when they should grow, change shape, or differentiate.

Cancer cells adapt to the environment and can use different signals around them to grow, change shape, or differentiate.

Cancer cells can use signals from the Extracellular matrix to do these things, so cancer cells are considered plastic and adaptable.

Cell death can create a signal to other nearby cancer cells to start dividing. This process is called necroptosis.

Necroptosis can lead to cancer cells spreading and becoming more invasive in the body. To prevent necroptosis, the Extracellular matrix needs to have a signal that tells the cells not to divide.

We still don’t know what triggers necroptosis, but there are many possibilities. In one study, researchers found that the ECM has a role in cancer plasticity and necroptosis by providing signals to the cells.

You may expand your knowledge by familiarizing with common biochemical terms!

Take Away

The extracellular matrix (ECM) is a complex network that surrounds every cell in the human body. It provides structural support for cells, as well as protection and nourishment to those cells.

ECMs are made up of proteins, glycoproteins, lipids, proteoglycans, water-soluble molecules like sugars or ions, and other substances found in tissues such as collagen fibers. Understanding how this system works will help you better understand your health, making sure you research further! However, in case you are still in doubt regarding that assignment, our professional writers for hire will be glad to help.

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