Ear Melanocytes Research Articles

There is no evidence of cochlear and vestibular melanocyte damage in patients with alopecia areata.

Follicular melanocytes are known to be damaged in alopecia areata (AA). However, it is not clear whether melanocytes are the primary target of autoimmunity and whether melanocytes in the inner ear are affected. This study aimed to detect possible cochlear and/or vestibular melanocyte damage in AA patients. Thirty-two AA patients and 35 sex- and age-matched healthy volunteers were evaluated between November 2018 and March 2020 at the Karabük University Training and Research Hospital. The conventional pure tone audiometry test and distortion product otoacoustic emission test were performed to evaluate hearing. To evaluate the vestibular function, the following tests were performed: the vestibulospinal reflex tests (Romberg test, tandem stance test and tandem walking test); positional balance tests (Dix-Hallpike test, supine roll test and head hanging test); vestibulo-ocular reflex tests (caloric test, head shake test) and oculomotor tests (saccade, smooth pursuit and optokinetic). The mean age of AA patients was 31.94±11.86years (range, 15-67years). There were no significant differences in the results of the hearing and balance tests between the groups. Furthermore, disease parameters (duration of the last attack, recurrence, positive family history, positive pull test, the severity of the disease, etc) were not associated with hearing loss and vestibular damage. AA patients did not exhibit hearing loss or balance abnormalities that would indicate cochlear and vestibular melanocyte damage. The lack of damage to the inner ear melanocytes in AA patients may indicate that follicular melanocytes are affected secondary to autoimmune damage in the hair bulb, and melanocytes are not the primary target in the pathogenesis of AA.

Dhh-expressing Schwann cell precursors contribute to skin and cochlear melanocytes, but not to vestibular melanocytes.

For a long time, melanocytes were believed to be exclusively derived from neural crest cells migrating from the neural tube toward the developing skin. This notion was then challenged by studies suggesting that melanocytes could also be made from neural crest-derived Schwann cell precursors (SCPs) on peripheral nerves. A SCP origin was inferred from lineage tracing studies in mice using a Plp1 promoter-controlled Cre driver transgene (Plp1-CreERT2) and a fluorescent Rosa26 locus-controlled Cre reporter allele (Rosa26FloxSTOP-YFP ). However, doubts were raised in part because another SCP-directed Cre driver controlled by the Dhh promoter (Dhh-Cre) was apparently unable to label melanocytes when used with a non-fluorescent Rosa26 locus-controlled Cre reporter (Rosa26FloxSTOP-LacZ ). Here, we report that the same Dhh-Cre driver line can efficiently label melanocytes when used in a pure FVB/N background together with the fluorescent instead of the non-fluorescent Rosa26 locus-controlled Cre reporter. Our data further suggest that the vast majority of skin melanocytes are SCP-derived. Interestingly, we also discovered that SCPs contribute inner ear melanocytes in a region-specific manner, extensively contributing to the cochlea but not to the vestibule.

Vitiligo and its association with hypoacusis: A case control study

Vitiligo is a pigmentary disorder with absence of functional melanocytes in the affected area. Melanocytes originate from neural crest and migrate to rest of the body in a cephalo-caudal manner in the embryonic life. Apart from epidermis and hair bulb in skin, they are also present in leptomeninges, inner ear, retina and uveal tract. In the inner ear melanocytes are present in endolymphatic sac, hair cells, vestibular organ and striavascularis. Vitiligo is not just skin deep and is also responsible for subclinical hypoacusis in majority of patients. Patients suffering from vitiligo affecting the head and neck region at the time of origin are more prone to the auditory dysfunction. Leucotrichia is another association with asymptomatic sensori-neural hypoacusis. This is due to the loss of melanocytes which have a protective role in inner ear. TEOAE and Pure tone audiometry can be used effectively for screening patients and these patients should be informed regarding the noise exposure and ototoxic drugs.

Audiovestibular disorders as autoimmune reaction in patients with melanoma

Melanoma is an aggressive form of cancer derived from neuroectodermal melanocytes. Melanocytes are present in the skin and hair follicles, as well as in the eye (iris and choroids), the leptomeninges, the anal canal and the inner ear. In the inner ear melanocytes are found both in the intermediate layer of the stria vascularis of the cochlea and in the dark cells of the vestibular organs. They are believed to play an important role in the production of endolymphatic potentials and in the maintenance of normal volumes of the inner ear fluids. Recently, audiovestibular dysfunctions have been demonstrated in patients treated with immunotherapy for metastatic melanoma and have been related to an autoimmune attack on the normal melanocytes of the inner ear.Melanoma is an immunogenic tumor type frequently associated with spontaneous autoimmune manifestations which seem to be associated with better prognosis. The melanoma-associated antigens are also expressed in normal melanocytes in the skin, eye and ear. We hypothesize that inner ear melanocytes could be a target of an autoimmune process in patients affected by melanoma. The immune system could produce antibodies that cross-react with both the melanoma cells and the labyrinth melanocytes causing an altered homeostasis of endolymphatic liquids and provoking some labyrinthic disorders such as vertigo, hearing loss, aural fullness and tinnitus resembling or influencing Ménière’s disease. In this perspective, audiovestibular disorders could be interpreted as an attempt by the individual immune system to develop anti-tumor response. In patients affected by melanoma an autoimmune genesis has already been advocated for ocular symptoms in melanoma-associated retinopathy, where the cross-reaction happens against retinal cells.A possible role of inner ear melanocytes should be considered as a potential cause of audiovestibular disorders. Further research is needed to demonstrate a connection between melanoma and labyrinth dysfunctions such as in melanoma-associated retinopathy.

In vitro Isolation and Cell Culture of Vestibular Inner Ear Melanocytes

Introduction: Melanocytes of the membranous labyrinth of the inner ear have been described morphologically in various contexts. Nature and functions of these cells are as yet not completely clear, even though several hypotheses exist regarding the same. The limited knowledge is due in part to a lack of methods regarding in vitro cell culture. The aim of this study was to describe conditions for the successful cell culture of vestibular inner ear melanocytes (VIEM), to compare their growth properties with those of epidermal melanocytes, and to characterize them immunohistochemically. Materials and Methods: Membranous labyrinth cells from freshly slaughtered sheep were isolated, and melanocytes and fibroblasts subsequently cultured. In addition, melanocytes from the skin of the same sheep were cultured. Antibodies specific to tyrosinase, tyrosinase-related protein 1 (TRP-1/Mel-5), and melanoma-specific antigen A (Melan A) were used to analyze the cultured cells. Results: The proliferation of VIEM was retarded in comparison to epidermal melanocytes. After 14 days, VIEM began to proliferate for the first time, whereas epidermal melanocytes proliferated already after 7 days. In contrast to epidermal melanocytes, the culturing process of VIEM seemed to be dependent on the presence of fibroblasts, and VIEM often accumulated in the vicinity of fibroblasts forming three-dimensional clusters. Moreover, VIEM showed a higher ratio of highly pigmented cells with a round cell shape and small dendrites in comparison to epidermal melanocytes. Immunohistochemical techniques proved the VIEM to be positive for Melan A, TRP-1 and, in the majority of cases, also for tyrosinase. Conclusion: We successfully cultured melanocytes of the inner ear vestibular labyrinth for the first time and demonstrated melanocytic characteristics of these cells. This accomplishment will provide the opportunity to investigate VIEM in more detail in future experiments.

Inner ear melanocytes: Ethnic differences

Inner ear melanocytes: Ethnic differences

Melanocytes in the stria vascularis and vestibular labyrinth of the Mongolian gerbil (Meriones unguiculatus).

Inner ear melanocytes are mainly present in the cochlea, vestibular organ, and endolymphatic sac, but their exact biological function has not been determined. In this investigation, we study the pigment cells in the membranous labyrinth of the gerbil. The inner ear melanocytes of M. unguiculatus show an irregular dendritic shape with cytoplasmic processes. These cells are disposed following the distribution of strial marginal and vestibular dark cells that have an important metabolic activity. Gerbil inner ear melanocytes are characterized by the presence of melanosomes, which are homogeneously dense organelles, of variable size and shape, that are surrounded by a membrane. In these cells, the Golgi apparatus plays a important role in melanin synthesis. When melanocytes were incubated in L-DOPA solution, the vesicles and cisterns of the Golgi apparatus exhibited a positive tyrosinase reaction. An interesting observation is the relation between melanocytes and inner ear capillaries. Sometimes, near to sensory vestibular areas, the melanocytes were in contact with Schwann cells and with myelinated fibres of vestibular nerve. The ultrastructural findings of this investigation are consistent with the hypothesis that melanocytes may have functional significance in the inner ear.

The determination and intracellular distribution of intermediate filaments of cultured inner ear melanocytes

The determination and intracellular distribution of intermediate filaments of cultured inner ear melanocytes