In the most severe cases, a ruptured eardrum can require surgery to put it right, but tissue-engineering techniques might provide a much simpler solution.
How the ear works
As sound waves enter the ear canal they make the eardrum vibrate. This vibration is transmitted by the ossicle bones — the malleus, incus and stapes — in the middle ear to the cochlea, which converts the vibrations into nerve impulses that are transmitted to the brain.
The eardrum is a thin membrane, just a fraction of a millimetre thick. Attached to the surrounding bone by a fibrocartilaginous ring, it separates the ear canal and the middle ear. It not only acts as a physical barrier, keeping foreign bodies such as bacteria out of the middle ear, but it also performs an essential role in hearing.
Pain in the membrane
Like a stubbed toe or a paper cut, a ruptured eardrum (also known as a tympanic membrane perforation or perforated eardrum) is a fairly common complaint. It is usually caused by an infection in the middle ear, which leads to a build up of pressure and, subsequently, a tear. But there are many other causes of membrane perforation, including a sudden change of pressure or inserting a cotton bud too far into the ear. A perforated eardrum is painful and associated with hearing loss, which is largely determined by the size of the tear: the larger the hole, the greater the hearing loss.
Few small ruptures are reported clinically, and most of these will heal naturally over several weeks. But for the small proportion of tears that fail to heal properly, surgery is the only option.
The standard operation, called a tympanoplasty, requires a specialist surgeon to harvest a skin graft from the patient and use this to patch over the damaged eardrum. As with all surgical procedures, cost and a shortage of surgeons — particularly in developing countries — can limit access to treatment. The procedure is effective in 80–90% of patients2, relieving pain, reducing the risk of infections and improving hearing. But the surgery does have potential complications, including nerve damage and the risks associated with anaesthesia.
An engineered solution
Tissue engineering could be a quick, convenient and effective alternative to surgery. The technique provides cells with a scaffold to grow on and a growth factor to encourage them to proliferate. Researchers in Japan have trialled a technique that infuses basic fibroblast growth factor (bFGF) into a gelatin-sponge scaffold to help the eardrum to regenerate.
From ear to a new era
The results of a phase III trial completed in July 2016 should reveal whether this simple, outpatient procedure can supplant tympanoplasty. The approach looks set to transform other areas of surgery as well. Preclinical studies have shown that a similar technique using gelatin and bFGF helps vocal-cord scarring to heal4, and sheets of gelatin and bFGF can reduce healing time for skin grafts5.
1. Neurological Regeneration (ed. Pham, P. V.) (Springer, 2017).
2. Indorewala, S., Adedeji, T. O., Indorewala, A. & Nemade, G. Iran J. Otorhinolaryngol. 27, 101–108 (2015).
3. Kanemaru, S. et al. Otol. Neurotol. 32, 1218–1223 (2011).
4. Hiwatashi, N. et al. J. Tissue Eng. Regen. Med. 11, 1598–1609 (2017).
5. Thilagar, S., Jothi, N. A., Omar, A. R., Kamaruddin, M. Y. & Ganabadi, S. J. Biomed. Mater. Res. B. Appl. Biomater. 88, 12–16 (2009).