Taste Bud Regeneration Research Articles

舌の化学的損傷に関する病理組織学的研究 低濃度酸，アルカリによる創傷治ゆについて

Tongue injuries are caused mechanically, thermically, chemically and radiologically, etc., but these lesions and healing processes seem to have been less studied.The authors examined tongue injuries by acid or alkali substances, and discussed some problems about the healing process.Experimental methods:Six-week-old Wistar strain male rats were used as experimental animals. HC1 was used as acid, while NaOH used as alkali. The concentration of each chemical used in this study was 10, 20 and 30% diluted aqueous solution with application time of 1 minute. These experimental animals were generally anesthesized with Nembutal and the afilter paper sufficiently soaked with HCl or NaOH was applied to the anterior 2/3 part of tongue dorsal surfae.Thirty day-research was made on tongue damage and recovery which were examined by light and scanning electron microscope.Experimental results:Macroscopically, no remarkable change occurred by HCl or NaOH, but light and scanning electron microscopic examinations revealed the tongue injured by increased drug concentration and considerably destroyed taste buds of fungiform papillae. One or two weeks after the tongue injury, these damaged areas showed healing of the filiform and fungiform papillary wounds, and 30 days after the injury they showed regeneration with an almost normal structure of the taste bud. In this case, however, though usually a fungiform papillary taste bud has a taste pore, some of the regenerated taste buds had several taste pores, a very intresting finding in terms of the regeneration mechanism.

Regeneration of taste buds after surgical excision of human vallate papilla

We examined regenerative capabilities of vallate papilla and taste buds in a human adult after complete surgical excision of the papilla and underlying glands and muscle. Although trenchlike invaginations were observed in the healed epithelium biopsied 18 months after papilla removal, no normal papilla, characterized by definite boundaries and circular trench, could be found. A few regenerated taste buds, totaling slightly more than 7% of the number counted in the excised papilla, were present on the top surface of the regenerated epithelium. They were longer and narrower than the original buds, but otherwise appeared normal and most had distinct taste pores. Our findings confirm earlier reports that vallate papillae fail to reform if surgical excision is complete, but that taste buds can develop and will regenerate in tongue epithelium of nonhuman species without the presence of the original papilla.

Regeneration of taste buds after surgical excision of human vallate papilla

Abstract We examined regenerative capabilities of vallate papilla and taste buds in a human adult after complete surgical excision of the papilla and underlying glands and muscle. Although trenchlike invaginations were observed in the healed epithelium biopsied 18 months after papilla removal, no normal papilla, characterized by definite boundaries and circular trench, could be found. A few regenerated taste buds, totaling slightly more than 7% of the number counted in the excised papilla, were present on the top surface of the regenerated epithelium. They were longer and narrower than the original buds, but otherwise appeared normal and most had distinct taste pores. Our findings confirm earlier reports that vallate papillae fail to reform if surgical excision is complete, but that taste buds can develop and will regenerate in tongue epithelium of nonhuman species without the presence of the original papilla.

Trophic Specificity of the Gustatory Fibers upon Taste Bud Regeneration

24 adult dogs were classified into six groups; in 2 animals of each group the lingual nerve was transected distal to the point of entry of the chorda tympani and its proximal end was sutured to the distal end of the glossopharyngeal nerve. In the other 2 animals transtympanic chorda tympani neurectomy was performed before suturing the lingual and glossopharyngeal nerves. Invasion of the papillae by regenerating fibers from the 8th postoperative week onwards was followed by reappearance of taste buds only in lingual glossopharyngeal anastomosis with intact chorda tympani. The difference in number of taste buds, size and number of constituent cells between the two operative procedures was statistically significant from the 8th week onwards. The significance of these findings was discussed.

Regeneration of the vallate papilla in the rat with special reference to the origin of the taste bud-bearing epithelium.

The regeneration of the vallate papilla in the rat was studied by both light and electron microscopy. The papillae were excised and regeneration was studied at time intervals of 3 to 45 days. It was found that the vallate papilla is capable of regeneration after both partial and total papillectomies. The regenerated papillae were asymmetrical in shape. Several invaginations, independent of one another, were the equivalent of the original sulcus. Regeneration of the gustatory system occurred at circumscribed portions of the associated Von Ebner glands. The amounts of newly formed taste buds were proportional to the amount of nerve fibers in the subepithelial plexus. The regenerated taste buds showed normal histochemical and fine-structural characteristics. The results support the contention of some degree of specificity concerning the epithelium where taste bud regeneration occurs.

ラット舌神経の再生に関する実験的研究

In our clinical practice, we occasionally severed nerve fibers in treating the lingual diseases or traumatic injury of the tongue. In such cases, it seems to be very interesting how the functional disturbance was recovered physiologically or pathohistologically. The rat's lingual nerve, which was cut off at the peripheral portion in the root of the tongue, was used for the experiment. The results obtained are summarized as follows. A. Physiological findings : 1. By the 18th day after the unilateral cutting of the lingual nerve, the afferent impulses were not elicited from cutting side by tactile and chemical stimulus of the tongue surface. 2. In one of two cases on 21th day after the operation, the afferent impulses in cutting side were elicited by tactile stimuli. 3. In two cases on 31th day after the operation, the afferent impulses in cutting side were elicited by tactile and chemical stimulus. 4. Among 11 cases which lapsed from 30th to the 35th day after the operation, 3 cases showed responses to both tactile and chemical stimulus, 3 cases only to tactile stimuli. 5. Both frequency and amplitude of the afferent impulses were slowly increased as time elapsed. B. Patho-histological findings : 1. The nerve fibers in the fungiform papillae showed a slight degeneration by 24 hours after the operation. 2. The degenerative process of the taste buds in the fungiform papillae continued to be seen until about the 7th day, while the nerve fibers in connective tissue and muscular layer showed a picture of degeneration, which was swelling, laceration, granular decomposition and rosary-degeneration. 3. Taste buds had completely disappeared by the 10th day and were replaced by normal cells by 14th day. 4. Regenerated nerve fibers along Schwann's cell were observed in connective tissue and muscular layer on 17th day after the operation. 5. Regeneration of taste buds was observed in one case on 23th day after the operation. 6. The number of regenerated nerve fibers and taste buds increased as time elapsed. C. Relation between physilogical and patho-histological findings : 1. Patho-histologically, regenerated nerve fibers in connective tissue and muscular layer were observed on 17th day after the operation, while the afferent impulses were elicited on 21th day by tactile stimuli. 2. Regenerated taste buds in the fungiform papillae were observed on 23th day after the operation, while the afferent impulses were elicited on 31th day by tactile and chemical stimulus. 3. In unilateral cutting of the lingual nerve, functional recovery was obtained after morphological one, which was indicative for this experiment that the taste regained a partial recovery functionally and morphologically.

The long‐term fate of neurons in allografts of ganglia in AG‐B‐compatible normal and immunologically tolerant rats

AbstractNeurons in Ag‐B‐incompatible allografts of ganglia are acutely rejected while those in Ag‐B‐compatible grafts are able to survive the immune reaction directed against them. The present study was undertaken to determine the long‐term fate of neurons in allografts of ganglia in Ag‐B‐compatible rats. Isogenic strains of Ag‐B‐compatible adult Lewis (LE) and Fischer (FR) rats were used. The sensory nodose ganglia were reciprocally exchanged between normal LE and FR and between LE and FR animals rendered immunologically tolerant of each other's histocompatibity antigens. The findings were similar in both rat strains and revealed that although neurons and glial cells (i.e., satellite and Schwann cells) could survive for prolonged periods they were nevertheless eventually rejected by normal (nonimmunosuppressed) recipients. On the other hand, neurons and glial cells survived indefinitely in allografts in tolerant rats. Moreover, these neurons were functional because they regenerated nerve fibers into cotransplanted isografts of tongue and exerted the neurotrophic influence of inducing taste bud regeneration. The results demonstrate that, unlike kidney and heart, neurons in ganglia allografts cannot survive indefinitely without immunosuppression in Ag‐B‐compatible animals. Nevertheless, the permanent survival and function of neurons in Ag‐B‐compatible grafts can be achieved, as it is in Ag‐B‐incompatible ganglia grafts, by rendering the recipient immunologically tolerant.

Regeneration of taste buds in tongue grafts after reinnervation by neurons in transplanted lumbar sensory ganglia

Taste buds disappear after denervation and reappear after nerve regeneration. Sensory neurons are responsible since reinnervation by motor or autonomic fibers of peripheral nerve fail to induce bud regeneration. However, we do not know whether some neurons in all sensory ganglia can support buds or whether gustatory (i.e., taste bud inducing) neurons are localized to specific cranial ganglia. The present study was therefore pefrormed to determine whether neurons in transplanted spinal ganglia could support taste buds similarly to those in transplanted cranial ganglia. Grafts of lumbar or vagal nodose ganglia were combined with grafts of tongue's vallate papillae in the anterior chamber of rats' eyes and the papillae examined for taste buds 35 days later. Neurons were present in all transplanted ganglia, and all papillae reinnervated by them contained regenerated taste buds. Nerve fibers could be traced from the transplanted ganglia to the epithelium of the tongue grafts which bore the regenerated taste buds. Papillae transplanted without ganglia lacked buds. These findings indicate that some neurons in all sensory ganglia can induce taste bud formation. The present results could occur if gustatory neurons are intrinsically present in all sensory ganglia, but an alternative interpretation is that the tongue grafts transformed some neurons into gustatory neurons and, hence, that neuronal plasticity is involved.

Regeneration of taste buds after transplantation of tongue and ganglia grafts to the anterior chamber of the eye

Although many neurons can survive after transplantation of rat sensory ganglia to the anterior chamber of the eye, the function of these neurons has not been studied. In the present study, nodose ganglia and vallate papillae were isografted to the same eye to see if the surviving neurons could regenerate nerve fibers into the papilla and cause taste buds to develop. Similarly, skin and nodose ganglia were isografted together to determine whether there was any preference for taste buds to appear in tongue or skin epithelium. After 90 days, papillae that were transplanted alone contained no taste buds but buds were present in papillae that had been combined with ganglia. The buds appeared not only in their normal position along the trench walls of the papilla but also in the epithelium on the top of the papilla, adjacent to the papilla, and in filiform papillae. No buds were found in skin epithelium. Many neurons were present in the transplanted ganglia from which nerve fibers were traced to the lingual epithelium that bore regenerated taste buds. These results show that sensory neurons transplanted to the anterior chamber of the eye are functional and that taste buds can develop in a variety of lingual epithelia but not in skin grafts.

Prolonged survival and trophic function of neurons in homologous transplants of sensory ganglion in vivo

Neurons in gustatory ganglia which survive autologous transplanatation in vivo retain their trophic effectiveness and can cause taste bud regeneration. In the present study homologous ganglion transplanatation in vivo was performed to see if these neurons would also survive and induce bud regeneration. The vagus nodose ganglion was transplanted in adult male rats and, 30 weeks later, studied for the presence of neurons, the nerves for nerve fiber growth, and the tongue's vallate papilla for taste buds. A small number of neurons was found in all nine transplanted ganglia; these neurons appeared morphologically and histochemically normal. Furthermore, some of these surviving neurons gave rise to nerve fibers which caused taste bud regeneration; after removal of the ganglion these buds degenerated. A mild cellular reaction consisting of large-nucleated cells, neutrophilic leucocytes, and small lymphocytes was present around but not within the transplanted ganglia and its nerve fibers; a cellular reaction was not seen in the papilla. The results demonstrate that neurons can survive homologous transplantation in vivo and still perform a trophic function, and it therefore seems that neurons may not evoke, or be adversly affected, by an immune reaction.

Trophic influence of in vivo transplanted sensory neurons on taste buds

Neurons in spinal ganglion can survive in vivo transplantation. The present study was performed to determine if in vivo-transplanted sensory neurons could regenerate their nerve fibers and retain the trophic property of inducing taste bud regeneration. The vagal nodose ganglion (innervates buds in the pharynx) of adult rats was transplanted and anastomosed to the cut distal glossopharyngeal nerve, and the vallate papilla of the tongue examined for taste buds 24 weeks later. Regenerated taste buds were present in four of the six papillae that were studied. Although the total number of buds present was small, each bud appeared normal. Similarly, although the number of neurons in the transplanted ganglia was diminished, they appeared normal and varied from small to large in diameter as in normal ganglia. The results demonstrate that some neurons in the vagal nodose ganglion can survive transplantation, regenerate their nerve fibers, and cause the development and maintenance of taste buds. I conclude that neurons surviving in vivo transplantation retain their trophic property.

Regeneration of taste buds after reinnervation by peripheral or central sensory fibers of vagal ganglia

Denervation causes the degeneration and disappearance of taste buds in the rat's vallate papilla. Buds will, however, reappear after reinnervation by the glossopharyngeal (self-reinnervation), vagus, or chorda tympani nerves. In all previous reinnervation studies, the anastomosis of the reinnervating nerve was performed distal to the sensory ganglia, that is, with peripheral fibers of the ganglia. The present experiment was performed to determine whether buds would reappear after reinnervation by central fibers of the gustatory ganglia. The vallate papilla of adult male rats was studied after denervation and after reinnervation by peripheral (superior and nodose) or central (nodose) sensory fibers of the vagus nerve. All taste buds disappeared from the papilla within 2 weeks after denervation and, in the absence of innervation, none reappeared. Buds were found, however, 5 months after reinnervation by peripheral or central sensory fibers of the vagus nerve. The regenerated buds were found only in their normal location in the trench walls, and not in the epithelium on the top of the papilla or in the epithelium surrounding it. Although more buds were present after peripheral than after central reinnervation, the results demonstrate that either peripheral or central sensory fibers of gustatory ganglia can cause taste bud regeneration. Despite the known morphological and physiological differences between peripheral and central fibers of gustatory sensory ganglia, each can exert a trophic influence sufficient to cause bud regeneration.

Combined effects of testosterone and motor, sensory, or gustatory nerve reinnervation on the regeneration of taste buds

Taste buds in the rat's vallate papilla degenerate after bilateral glossopharyngeal nerve transection and reappear after unilateral or bilateral nerve regeneration. The present experiment was performed to determine whether they would rcappear after unilateral reinnervation by motor (hypoglossal), sensory (auriculotemporal), or different gustatory (chorda tympani, vagus) nerves. Since testosterone treatment causes taste buds to appear in new locations in the normal papilla, additional groups of reinnervated animals were given this hormone. Adult male rats were studied 3 months after nerve regeneration; the hormonally treated animals received 2.0 mg. testosterone daily for 3 weeks before being examined. Buds were found in the trench walls (normal location) after glossopharyngeal, chorda tympani, or vagal reinnervation. In the testosterone-treated animals, buds were also found in new locations, namely the top of the papilla and adjacent to it. No buds were found after denervation, unilateral or bilateral auriculotemporal reinnervation, or unilateral hypoglossal reinnervation, even after testosterone treatment. The results indicate that taste bud regeneration is dependent on a property of gustatory nerves that is not shared by general sensory or motor nerves. The appearance of buds in new sites demonstrates that under appropriate conditions additional regions of tongue epithelium can form taste buds.