References: Hair growth and hair loss
Exp Cell Res. 1991 Jun;194(2):218-27.
Restoration of the epidermal phenotype by follicular outer root sheath cells in recombinant culture with dermal fibroblasts.
Limat A, Breitkreutz D, Hunziker T, Boillat C, Wiesmann U, Klein E, Noser F, Fusenig NE.
Cosmital SA, Marly, Switzerland.
In order to better understand how outer root sheath (ORS) cells are able to reepithelialize superficial skin wounds, the level of epidermal differentiation achieved by isolated ORS cells in vitro was determined. Using postmitotic human dermal fibroblasts (HDF) as efficient feeder cells, large numbers of ORS cells from individual follicles were generated. Passaged ORS cells were grown exposed to air on HDF-populated collagen gels in the CRD device (Noser and Limat, In vitro 23, 541-545, 1987) which allows histiotypic tissue organization. In such recombinant organotypic cultures, ORS cells developed distinct epidermal strata comparable to interfollicular keratinocytes (NEK). Ultrastructurally, desmosomes and intermediate filaments increased in number toward the epithelial surface and small keratohyalin (KH) granules (but no large irregular KH granules as in NEK) were abundant, adjacent to an electrondense stratum corneum. Also, synthesis of epidermal suprabasal keratins (K1 and 10;2D gels) was lower in ORS cultures, but clearly visible suprabasally by immunofluorescence along with other epidermal markers (involucrin, filaggrin, surface glycoprotein gp80, pemphigus vulgaris antigen). Basement membrane components (laminin, type IV collagen, bullous pemphigoid antigen) were detectable in both ORS and NEK in these assays. Thus, phenotypic expression was largely comparable, but, whereas terminal differentiation (keratinization) was progressing in NEK cultures limiting their lifespan, this seemed to be better controlled in ORS cultures and viable cell layers persisted resulting in longer survival time.
online pharmacy ref. source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=1709101&dopt=Abstract
Exp Neurol. 1992 Jan;115(1):13-7.
The structural and functional aspects of hair cell regeneration in the chick as a result of exposure to intense sound.
Saunders JC, Adler HJ, Pugliano FA.
Department of Otorhinolaryngology, Head and Neck Surgery, University of Pennsylvania, Philadelphia 19104.
This paper summarizes the structural and functional damage caused by intense sound exposure in neonatal chicks. Scanning electron microscopy has been used to follow the structural changes to the papilla and their subsequent repair. Pure-tone exposures produced a localized lesion consisting of tectorial membrane destruction, changes in surface organization of the papilla, and hair cell loss. The papilla underwent significant repair following the exposure and new hair cells could be identified on the sensory surface after 4 days of recovery. In addition, various evoked-potential methods provided an objective assessment of auditory function and demonstrated that the peripheral ear was severely impaired by overstimulation. Auditory function returned to near normal levels within 3 days postexposure. The inescapable conclusion from these observations was that hair cell regeneration had little to do with the functional recovery observed during the first 3 days. Tectorial membrane regeneration and the restoration of cochlear micromechanics were combined to form a hypothesis to account for the restoration of auditory function.
online pharmacy ref. source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=1728559&dopt=Abstract
Hear Res. 1991 Nov;56(1-2):203-10.
Hair cell regeneration in the chicken cochlea following aminoglycoside toxicity.
Lippe WR, Westbrook EW, Ryals BM.
Department of Otolaryngology, University of Washington School of Medicine, Seattle 98195.
Hair cell loss in the avian cochlea partially recovers following both acoustic trauma and aminoglycoside intoxication. DNA labeling with tritiated thymidine has shown that the restoration of cell number following acoustic trauma results from the production of new hair cells by mitotic division. The purpose of the present study was to determine if mitosis also contributes to the recovery of hair cell number which occurs following aminoglycoside intoxication. Chickens received daily injections of either gentamicin sulfate or distilled water for 10 consecutive days. During the latter 7 days of this period, all birds were also injected with [3H]thymidine. Following postinjection survival periods of 3 or 6 days, one papilla from each bird was processed for autoradiography and the other for scanning electron microscopy (SEM). Incorporation of [3H]thymidine was seen over hair cells and support cells in experimental papillae in regions of hair cell loss. No labeling was seen outside of damaged regions or in the papillae of control birds. SEM showed that damaged regions in experimental birds contained cells similar in appearance to developing auditory hair cells in avian embryos. These results show that the restoration of hair cell number following aminoglycoside toxicity results from the production of new cells by mitosis.
online pharmacy ref. source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=1769915&dopt=Abstract
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