Optimised growth of human epidermal cells in vitro without the use of a feeder layer or collagen substrate

The titanium surface texture effects adherence and growth of human gingival keratinocytes and human maxillar osteoblast-like cells in vitro

The adhesion, orientation and proliferation of human gingival epithelial cells and human maxillar osteoblast-like cells in primary and secondary culture were studied on glossy polished, sandblasted and plasma-sprayed titanium surfaces by scanning electron microscopy and in thin sections. The primary cultured explants of human gingival epithelial cells attached, spread and proliferated on all titanium surfaces with the greatest extension on the polished and the smallest extension on plasma-sprayed surfaces. In secondary suspension cultures of gingival keratinocytes, attachment spreading and growth was only observed on polished and plasma-sprayed surfaces, but not on sandblasted surfaces. Moreover, the attachment of these cells depended on the seeding concentration as well as on the coating with fetal calf serum. Cells on polished surfaces developed an extremely flat cell shape, but on sandblasted and plasma-sprayed surfaces a more cuboidal shape. In contrast human maxillar osteoblasts seeded as secondary suspension cultures attached very well to all three differently textured titanium surfaces and showed identical growth patterns independent of the titanium surface structure. These findings suggest that cell morphology, orientation, proliferation and adhesion of human gingival epithelial cells in primary or secondary culture are dependent on the texture of the titanium surface whereas no such differences were observed for maxillar osteoblast-like cells. In conclusion, the soft tissue integration and response is more influenced by the surface texture than the process of osseointegration.

Production of TNF-alpha by primary cultures of human keratinocytes challenged with loxosceles gaucho venom

Primary cultures of human keratinocytes were challenged with increasing doses from 10 ng/mL to 2 &mgr;g/mL of Loxosceles gaucho venom, responsible for dermonecrotic lesion in humans. TNF-alpha was investigated by bioassay and ELISA in the supernatant of the cultures challenged with 100 ng/mL, 500 ng/mL, 1 and 2 &mgr;g/mL of venom. TNF-alpha was detected by bioassay in the supernatant of cultures challenged with 100 ng/mL, after 6 h. The cytokine was detected by ELISA in the supernatant of the cells challenged with doses of l &mgr;g/mL, after 6 and 12 h. The results point out the capacity of this venom to activate the keratinocytes in primary cultures to produce TNF-alpha. The production of cytokines could contribute to the local inflammatory process in patients bitten by Loxosceles sp.

Cultivation and transplantation of epidermal keratinocytes

Transplantation of autologous cultured keratinocytes is the most advanced area of tissue engineering which has clinical application in restoration of skin lesions. In vitro, disaggregated keratinocytes undergo activation and after adhesion and histogenic aggregation form three-dimensional epithelial sheets suitable for grafting on prepared wounds that provide a reparative environment. Epidermal stem cells survive and proliferate in culture, retaining their potential to differentiate and to produce neoepidermis. Reconstructed skin is physiologically compatible to split-thickness autografts. Autotransplantation of cultured keratinocytes is a promising technique for gene therapy. In many cases allografting of cultured keratinocytes promotes wound healing by stimulation of epithelialization. Banking of cryopreserved keratinocytes is a significant improvement in usage of cultured keratinocytes for wound healing. Skin substitutes reconstructed in vitro that have morphological, biochemical, and functional features of the native tissue are of interest as model systems that enable extrapolation to situations in vivo.

Effects of ultraviolet irradiation on human skin-derived epidermal cells in vitro

The effects of UVA, mixed UVA + B, and solar-simulated irradiation were examined in human keratinocytes and melanocytes cultured in vitro. Irradiation with UVA, UVA + B, or the solar simulator caused a dose-dependent decrease in keratinocyte cell numbers and thymidine incorporation at 24 hours, with recovery after 48 and 72 hours. Divided dose regimens reduced the inhibitory effect of ultraviolet (UV) irradiation on cell numbers measured 24 hours after the last irradiation. Exposure to both UVA and UVA + B increased formation of cornified envelopes. Similar irradiance doses of UVA 80 minutes (1.12 J/cm2) and UVA + B 40 minutes (1.04 J/cm2) caused 2.4- and 3.3-fold increases in cornified envelope formation, respectively. With solar-simulated irradiation, the cornified envelope formation was increased by 3.5-fold after exposure of 8 minutes (2.6 J/cm2). Irradiation of melanocytes with UVA, UVA + B, or solar-simulated irradiation resulted in a dose-dependent decrease in melanocyte numbers after 24 hours compared with sham-irradiated controls. As a result of UV irradiation, tyrosinase activity of melanocytes measured at 24 hours was stimulated. UVA + B irradiation (1.04 J/cm2) increased tyrosinase activity approximately twofold, while UVA alone (1.1 J/cm2) increased tyrosinase four to sixfold and solar-simulated irradiation (1.3 J/cm2) increased tyrosinase approximately twofold compared to the control cells. Melanin content increased in cells after both UVA and mixed UVA + B irradiation. These results indicate that both UVA and mixed UVA + B irradiation had qualitatively similar effects on the proliferative and functional activity of skin-derived cells but that the type of irradiation and the dosage regimen affect the dose-response relationship.

Serial cultivation of normal human keratinocytes: A defined system for studying the regulation of growth and differentiation

We have developed a defined method for human epidermal keratinocyte culture. The minimally supplemented basal medium supported establishment of primary cultures from neonatal foreskin in a defined environment. It also supported serial cultivation and rapid expansion of cell number. Casein replaced serum for defined cryopreservation. Cells were serially cultivated in medium containing 0.08 mM calcium. The rate of cell division however remained high after addition of 1.8 mM calcium. The particulate transglutaminase activity of the cultures was low at confluence, even in the presence of 1.88 mM calcium, indicating an enrichment of the basal cell population. Culture with small amounts (0.3%) of chelated serum increased particulate transglutaminase activity approximately 2.2-fold in low calcium cultures and approximately 3.5-fold in high calcium cultures. A gradual reduction in growth rate of serum-treated cultures upon serial cultivation also indicated a depletion of cells with basal cell character. Bovine hypothalamic extract and cholera toxin were able to avert, in part, the differentiation-promoting effects of serum. Keratinocytes serially cultivated in the defined medium maintained the ability to develop normally into a morphologically differentiated epidermis.

Effects of extra- and intracellular calcium concentration on DNA replication, lateral growth, and differentiation of human epidermal cells in culture

Variation in the extra- and intra-cellular concentration of calcium ([Ca]e and [Ca]i) affected the 3H-thymidine labeling pattern of sorted S-phase cells in human epidermal cultures. A lowering of [Ca]e resulted in retarded lateral growth but, unless [Ca]e was extremely low, caused an increase in the proportion of strongly labelled (rapidly cycling) S-phase cells. An increased desquamation of superficial cells due to a reduced cellular cohesiveness was also observed in low calcium medium. Thus, a lowering of [Ca]e might stimulate the proliferation of a pool of cycling cells destined for rapid terminal differentiation and tissue regeneration, whereas proliferation destined for lateral growth is inhibited. Attempts to decrease the [Ca]i with the calcium chelator quin-2 at low [Ca]e seemed to elevate the proportion of strongly labelled S-phase cells, whereas an increased [Ca]i obtained with the ionophore A23187 caused a dramatic decrease in the proportion of S-phase cells that showed strong 3H-thymidine incorporation. This implies that variation in both [Ca]i and [Ca]e may play a role in the regulation of proliferation and differentiation, in keratinocytes.

In vitro culture of disaggregated rabbit keratinocytes

A technique is described for the culture of disaggregated rabbit keratinocytes and the production of confluent sheets of immunologically pure keratinocytes suitable for use in transplantation studies. The benefits of various feeder layers, nutrients and growth hormones were examined by the use of paired controls. The ability of the cultured keratinocyte sheets to be removed from the culture vessel intact and survive as viable autografts was demonstrated, thus establishing a new animal model for the investigation of allograft rejection responses to cultured keratinocytes. The benefits of using the rabbit model for such studies and the advantages of this culture technique over a previously described method of rabbit keratinocyte cell culture are discussed.

Cultivation of keratinocytes derived from epidermal explants of sheep skin and the roles of growth factors in the regulation of proliferation

Procedures to promote the growth of primary cultures of keratinocytes derived from sheep epidermis through several passages are described. Rapid epithelial outgrowth was obtained from explants of epidermis isolated from trypsinized inguinal skin biopsy specimens. Following initiation and attachment, cells displayed the polygonal morphology typical of keratinocytes in culture and survived a number of passages before terminally differentiating and sloughing from the surface of the culture vessel. Proliferation occurred in the absence of a feeder layer and was attained in a medium supplemented with foetal bovine serum and hydrocortisone or cholera toxin. Growth was stimulated by the addition of epidermal growth factor or fibroblast growth factor (FGF) to the culture medium. The detection of basic-FGF immunoreactivity in Western immunoblots of extracts of fresh tissues suggests a role for this factor in autocrine or paracrine growth regulation of skin cell populations in vivo.

Review of keratinocyte culture techniques: problems of growing skin

Keratinocyte cell culture has been studied by a large number of investigators, resulting in an extensive body of often contradictory literature. The advantages and disadvantages of the two major techniques, explant and disaggregated culture, will be examined, followed by a critical evaluation of the major technical variables. Suggested standardized methods for both explant and disaggregated culture, and the indications for the use of each, will be proposed. Finally, further directions for basic research will be suggested in order to improve this useful tool.

The clinical management and laboratory assessment of anal warts

The results of a clinical and virological survey of anal warts from 85 predominantly homosexual or bisexual men is presented, together with an improved technique for the surgical treatment of these lesions. Two types of anal warts, which were classified as either "acute" or "chronic" on the basis of their appearance and clinical behaviour, were recognized commonly. However, our laboratory investigations--which consisted of the routine histopathological examination of all specimens, together with immunohistochemical testing for the common wart antigen of specimens from 30 patients and papillomavirus typing by human papillomavirus DNA probing of 27 specimens--failed to reveal any significant differences between the two classes of anal warts. By means of a dot hybridization technique with mixed human papillomavirus DNA probes for types 6 and 11 and types 16 and 18, all wart biopsy specimens that were tested were shown to contain human papillomavirus types 6/11; two specimens also contained human papillomavirus types 16/18. Southern blot hybridization studies of eight specimens revealed that five warts contained human papillomavirus type 6 only and three warts contained human papillomavirus type 11 only. Although the surgical technique that is described was successful in terms of patient acceptance and the eventual eradication of anal warts, there was a high rate of recurrence of the lesions, which necessitated repeat operations in two-thirds of the patients. The need for counselling before surgery and for regular follow-up examinations after surgery is discussed.

Cell biology of cultured anogenital warts

A simple, reliable culture system for keratinocytes from anogenital warts is described. Using this technique we found that it was possible to produce multiple confluent keratinocyte cultures from two-thirds of the surgically-excised anogenital wart specimens received in our laboratory. Some morphological and cultural differences between these cells and normal keratinocytes derived from neonatal foreskins were observed, although there was no evidence that wart-derived keratinocytes were 'transformed'. The cultures were tested for evidence of HPV-DNA replication using 32P-labelled HPV-DNA probes, for the production of viral capsid proteins using peroxidase-antiperoxidase staining and for whole virus particles using electron microscopy. Fifty-seven per cent (8 of 14) of the wart cultures tested showed persistence of HPV-DNA (5-100 copies HPV-DNA/cell genome equivalent). However, no viral proteins or particles were detected in any culture. This system may prove to be a useful in vitro model for the study of virus-cell interaction and the role of HPV in the malignant conversion of epithelial cells.

Expression of blood group antigens by cultured human epidermal cells

The presence of blood group antigens on the surface of cultured human epidermal cells has been demonstrated using monoclonal antibody supernatants in indirect immunoperoxidase and immunofluorescence tests. An isoantigen pattern, consistent with the blood group of the donor infant, was detected in cultures derived from 10 different foreskin specimens, and in sections of the epidermis of 5 of these specimens. The A, B, and H antigens were found on the surface of cultured keratinocytes which resembled those of the spinous and granular cell layers of the in vivo epidermis. These antigens were readily detectable throughout the majority of the lifespan of the cells in vitro. This finding may be of relevance to those contemplating allograft transplantation of cultured human epidermis.