We found that sensory organs critically rely on a signal, the Sonic hedgehog (Shh) protein, that is delivered to the tongue epithelium by ganglion neurons that send projections from their cell bodies into the tongue. Beachy and Lu studied laboratory mice to learn that drugs or genetic manipulations that block the response to the Hedgehog signal delivered by the nerves stops the regeneration of taste receptor cells, leading to an eventual die-off of the cells and a loss of taste. In fact, it has long been known that the maintenance of the taste receptor cells requires this connection to the ganglion. But information also flows in the other direction.
These taste receptors relay the taste information they sense to the brain via connections to a cranial ganglion (a cluster of nerve cells behind the ear). Due to their role on the frontline of our digestive system, the taste receptor cells undergo a fairly high turnover rate - dying and being replaced within a period of just a few days or weeks.
They're meant to let us know not just when things taste good, but also when something is spoiled or potentially toxic (no, I don't think you can count your cousin's noxious green bean casserole). Our sense of taste relies on taste receptor cells clustered in taste buds along our tongues. In addition to the widespread loss of taste from traditional cancer therapy, a particularly interesting manifestation of taste disturbance occurs in cancer patients treated with Hedgehog (Hh) pathway antagonists, which our lab discovered and helped develop. Loss of taste sensation occurs in about 85 percent of cancer patients receiving chemotherapy and is a significant clinical issue because it causes loss of appetite, unwanted weight reduction, and complications in recovery. They published new findings on taste last week in the Proceedings of the National Academy of Sciences. Previous work in Beachy's lab showed that the Hedgehog signaling pathway is often misregulated in cancers, and treatment of certain tumors involves specifically blocking the Hedgehog pathway. Stanford stem cell biologist Philip Beachy, PhD, and instructor Wan-Jin Lu, PhD, wondered about the role of a critical developmental signaling protein called Hedgehog in this loss of taste. Not only can the treatment lead to nausea, many patients also lose their sense of taste and struggle to eat enough to support their recovery. Not so for cancer patients recovering from chemotherapy. You might be thinking fondly right about now of a fantastic meal from last week (prime rib, anyone?) or eagerly anticipating a quiet lunch of leftovers.
The holidays are a time of feasting for many people.
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