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Bladder: Cell Types Composing the Tissue
Bladder: Cell Types Composing the Tissue
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Bladder: Cell Types Composing the Tissue
Human tissues are subject to permanent damage and injuries, and stem cells can help to regenerate these tissues. Understanding stem cells and their differentiation and regeneration process will help understand how they can be used in repair of bladder dysfunctions. To have an in-depth understanding of the use of stem cells in bladder tissue regeneration and therapy, it is also essential to understand the anatomy of the bladder.
Urinary Bladder
The hollow muscular organ in the pelvic area is known as the urinary bladder. It is spherical in shape and is approximately the size of a large grapefruit. The function of the urinary bladder is to collect and store the urine. The urinary bladder is connected to the kidneys by means of small tubular structures known as ureters. The base of the bladder is connected to the urethra, which helps in draining the urine.
Bladder Anatomy
The sphincter muscle coats the wall of the bladder and prevents leakage of fluid from the bladder. When the bladder is filled, the sphincter relaxes and the bladder contracts, thus emptying the urine.
Various Bladder Tissue Types
A smooth glistening tissue lines the inner surface of the bladder. This tissue is known as the mucosa and it is made up of transitional epithelial cells in a layer known as the urothelium.
A layer of connective tissue, nerves, and blood vessels form the layer next to the urothelium.
Next to this layer is the muscular bladder wall, which is formed by a layer of smooth muscle cells. The primary function of the muscular layer is to contract the bladder to excrete the stored urine. This layer is called the muscularis propria.
This layer of muscle cells is surrounded by the outermost layer of fat.
The transitional epithelial cells that line the interior of the bladder can transform into cancerous cells, thus leading to bladder cancer.
Bladder Dysfunctions and Cancers
About 90% of bladder cancers are derived from the transitional epithelial cells. The cancer type is determined based on the appearance of the cells.
Types of Bladder Cancers
1 Transitional cell carcinoma: This is the most common type of bladder cancer, and the cells of this type of cancer resemble those of urothelial cells. About 90% of bladder cancers in the United States are of this type. Transitional cell carcinoma can be either invasive or noninvasive.
2 Squamous cell carcinoma: The cells of this cancer appear like the flat cells on the surface of the skin. Only 1% to 2% of the bladder cancers in the United States are of this type. These are mostly invasive.
3 Small cell carcinoma: These types of cancer account only for 1% of the bladder cancers in the United States. The cells of this type of cancer appear like nerve cells.
4 Sarcoma: These are cancers that originate from the cells in the muscular layer of the bladder.
Other Bladder Dysfunctions
Spina bifida is the most common congenital bladder dysfunction in the United States. This leads to permanent, disabling birth defects. Children with this disability are unable to ambulate without the assistance of wheel chairs and crutches. The bladder and bowel functions are also out of control in these children.
These bladder cancers and dysfunctions can be treated using the inherent potential of adult stem cells or progenitor cells. To understand how these stem cells help in treating bladder cancers and dysfunctions, a brief understanding of stem cells is essential.
Stem Cells and Their Inherent Potential
Some stem cells are totipotent and form the biological source material for all cells, tissues, and organs. Stem cells are unspecialized cells that can self-renew and can differentiate into other cell types. Self-renewal is the ability to divide and produce more stem cells. Differentiation is the ability to develop into other types of cells.
There are cells in certain tissues of humans called adult stem cells. Adult stem cells have the capacity to self-renew (divide and produce more stem cells) or differentiate (divide and give rise to more mature cells that are not stem cells). Cells that have the capability to differentiate but not to self-renew are called progenitor cells. Progenitor cells are the progeny of stem cells.
Adult Stem/Progenitor Cells in the Bladder
Potential stem cells that can differentiate into bladder cells have been identified by researchers at the University of California–Davis Children’s Hospital. These human bladder stem/progenitor cells possess the ability of self-renewal. CD34+ CD45– cells are the progenitor cell types in the bladder. The discovery of these adult stem cells in the lining of the bladder paves the way for future research that will lead to artificial regeneration of entire bladder tissue.
Bladder Tissue Regeneration and Treatment of Bladder Dysfunctions and Cancers
Stem cell therapies for bladder cancers and for disabilities like spina bifida are in experimental stages. Here are few experiments that were conducted to demonstrate the ability of stem cells to regenerate into bladder tissue.
Ability to restore the underactive bladder.
In an experiment for treating underactive bladder in the rat, which was due to bladder outlet obstruction, Nishijima et al. demonstrated that an intra-bladder injection of unsorted bone marrow cells in rats with underactive bladder helped to restore bladder contractile function.
Treatment of overactive bladder (OAB).
Huang et al., in an experiment to correct overactive bladder, demonstrated that an intravenous injection of adipose-derived stem cells (ASCs) showed improvement in tissue parameters and the urodynamics in rat models.
Mesenchymal stem cells (MSCs) for partial bladder regeneration study.
