Researchers reveal cause of inner-ear bone loss

OSAKA [Japan]: A group of researchers revealed how a person’s hearing and balance may be compromised by a variety of disorders and difficulties caused by prolonged middle ear inflammation. A typical problem is the formation of cholesteatomas, which are abnormal ear collections of cells that, if not treated, can lead to bone erosion. As a result, symptoms such as vertigo, facial paralysis, hearing loss, and even brain infection can occur.

Researchers from Osaka University have uncovered the aetiology of cholesteatomas in a paper published in Nature Communications, which may aid in the development of novel therapeutics for individuals suffering from this disease.

Cholesteatomas are made up of cysts or bumps in the ear that consist of skin, collagen fibers, skin cells, fibroblasts, keratin, and dead tissue. There are many theories on how these cholesteatomas can cause bone erosion, including the activation of cells responsible for the breakdown of the minerals and matrix of the bone, the presence of inflammatory markers and enzymes, and the accumulation and pressure from dead cells and tissues in the ear; however, the exact mechanism for the creation of cholesteatomas remains unknown.

“A cholesteatoma can still return or happen again even after its surgical removal, so it is important to know what is actually causing it,” says lead author Kotaro Shimizu.

To investigate this, researchers looked at human cholesteatoma tissues that were surgically removed from patients. A process called single-cell RNA sequencing analysis was employed to identify cells responsible for triggering bone erosion; these were called osteoclastogenic fibroblasts.

This study demonstrated how these fibroblasts expressed an abundant amount of activin A, a molecule that regulates different physiologic functions of the body. The presence of activin A is said to cause bone erosion through a process in which specialized cells initiate bone resorption through a process wherein the minerals and matrix of the bones are broken down and absorbed by the body.