Cell Adaptation - Discussing Hypothrophy, Hyperplasia, Metaplasia, and Dysplasia

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Metaplasia is a type of cellular adaptation where one differentiated cell type is replaced by another differentiated cell type. Cells undergo a lot of stress which could be as a result of their environment which could be toxic or have components that can possibly destroy the cells, but then the cells learn to adapt to overcome those stress to remain in shape. For instance, we know that our stomach is made up of HCL and this acid is very corrosive that it can eat up the lining of our stomach but then our stomach finds a way to adapt, so we do not have acids in our body which could lead to death.

Organs tend to regulate themselves so as not to cause damage to the cells and the organs themselves, but when these organs undergo stress, it could lead to after effects which includes growth of the organ. The changes that these organ can experience will be as a result of the severity and the type of stress that they are undergoing and this adaptation can be done through Hypothrophy or hyperplasia. Let's quikly run through both.


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Hypotrophy is a growth adaptation that occurs as a result of an increase in the size of the cell as a result of stress causing the cells to grow. When the size increases, it leads t an increase in protein synthesis and increase in organelles. It occurs as a result of increasing gene activation. There are a few organs in the body that go through hypotrophy and they include the striated muscle cells of the heart and skeletal muscles.

Hyperplasia is a growth adaptation that doesn't have to do with the increase in size of the cell, rather it has to do with the increase in the number of the cells in the area. It will lead to multiple production of cells through the production of new stem cells which will produce more cells and tissues. Normally, the body experience hyperplasia and an example is the uterine lining during a normal menstrual cycle where hyperplasia occur in the endometrium but there can also be pathologic example of hyperplasia which usually lead to dysplasia or cancer. For instance Endometrial hyperplasia during menopause which causes the endometrial lining to grow without estrogen and when it is not treated, it can become endometrial carcinoma. When the body is put under a lot of stress, they usally underfo both hyperplasia and hypotrophy together, and these usually happen normally during scenario like pregnancy where the uterine lining increases and the uterus cells increase in number as well so as to accomodate the fetus.

When the body isn't going through these stress again, then the cells need to go back to their previously existing form, and this can be done with Atrophy. With Atrophy there is a reabsorption and breaking down of tissues, and it involves apoptosis. Atrophy can can be done through the decrease in the size of the cells and the decrease in the number of cells available. When the cell needs to be decreased in size, it requires the Ubiquitin-proteasome degradation pathway and autophagy. In Ubiquitin-proteasome degradation pathway, Ubiquitin binds to the intermidite filament of the cytoskeleton causing proteasome to destroy the cytoskeleton causing organelle autophagy where the organelles are destroyed. When it comes to decreasing the number of the cells that have been produced during hyperplasia, it is done through apoptosis where the cell is destroyed by programmed cell death.

Back to Metaplasia. With Metaplasia, the organs do not increase the number or size of cells they have, they change the type of cells they have as a result of stress changes. This usually occur during Cellular reprogramming in Stem cells, and it usually involves the surface epithilium of the skin. These changes occur to better handle the condition or type of stress they undergo. Metaplasia occurs in Barrett's Esophagus which is the metaplastic change in the mucosal cells lining of the esophagus where the normal stratified squamous epithlium becomes simple columnar epithelium with goblet cells, and this usually occur due to constant and/or untreated gastroesophageal reflux disease (GERD) and this when not treated can become Esophageal carcinoma. With Metaplasia, Barrett's esophagus can return back to normal. With Apocrine metaplasia, it doesn't lead to cancer and it is reversible. Vitamin A deficiency can lead to metaplasia such as keratomalacia where there is changess in the conjunctiva. If metaplasia or hyperplasia isn't corrected, it can lead to dysplacia which can then lead to cancer. Dysplasia is the abnormal growth or overdevelopment of cells which is usually a proliferation of pre-cancerous cells.

It is important to know that excessive stress to cells and organs, they expands to prevent death, if these cells and organs do not go back to normal, they can become carcinomas. In the case of pathological increase in size and amount, it is important to treat them to prevent them from becoming cancers.

Reference

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