PubMed Health⌕ Search

Biomedical subjects

H A Navsaria

Publications and source records attributed to H A Navsaria.

32 records · Page 2Linked to original sources
PubMed1994

An animal model to study the significance of dermis for grafting cultured keratinocytes on full thickness wounds.

Autologous cultured keratinocytes grafted onto full thickness wounds take poorly, and any epidermal cover that is produced is unstable. However, a more stable epidermis has been reported when keratinocytes are grafted onto a dermal surface. We have developed a skin grafting model using a polytetrafluoroethylene (PTFE) skin graft chamber in the domestic pig. The chambers isolate individual wounds and prevent epithelial migration from the wound edge. Dermal grafts were prepared by enzymatic separation of the epidermis from split skin to leave a de-epidermalized dermis (DED). Full thickness wounds were initially grafted with autologous DED and, subsequently, 7 days later with cultured autologous keratinocytes. The wounds were biopsied serially over 6 weeks, and processed for histology, immunocytochemistry and electron microscopy. Clinically, the grafts were seen to mature over the 6-week period. In 14/20 wounds, 40-72 per cent of the wound areas (as assessed by image analysis) had acquired epidermal cover at day 14. In 6/20 wounds, the epidermal cover was 0-27 per cent. The skin surface was stable at day 21. At this time electron microscopy and immunohistochemistry demonstrated a continuous, well formed basement membrane. The epidermis was initially acanthotic, but was histologically mature by day 14. Surprisingly, the dermal grafts were broken down by day 14. However, a neodermis formed beneath all areas with epithelial cover 21 days after grafting the keratinocytes. In this model, we have demonstrated the advantage of providing a dermal bed for cultured keratinocytes.

Animals↗
PubMed1994

Mutations in the rod 1A domain of keratins 1 and 10 in bullous congenital ichthyosiform erythroderma (BCIE).

Bullous congenital ichthyosiform erythroderma is a human hereditary skin disorder in which suprabasal keratinocytes rupture. Recent reports have implicated keratins K1 and K10 in this disease. Here we describe four diverse keratin mutations that are all significantly associated with this disease. Two of these are in the helix 1A subdomain of the type II keratin 1, giving a serine-to-proline substitution in codon 185 and an asparagine-to-serine substitution in codon 187. In the analogous region of type I keratin 10, an arginine-to-proline and an arginine-to-serine transition in codon 156 have been identified. All four mutations create restriction fragment length polymorphisms that were used exclude the mutations from 120 normal chromosomes. Insertional polymorphism (in the V2 subdomains of the non-helical tails of K1 and K10) was excluded as the cause of the phenotypic heterogeneity observed within one family.

Amino Acid Sequence↗
PubMed1993

Skin graft storage and keratinocyte viability.

The viability of human split skin grafts stored in four solutions has been assessed by monitoring the percentage of viable keratinocytes in the stored grafts. Skin grafts stored in RM+ (Ready Mix) tissue culture medium remained more viable than those stored in Hartmann's, Marshall's or saline solutions. By day 10 (postoperative), the percentage of viable keratinocytes of those grafts stored in RM+ was around 85%, compared to a value of around 10% for the other media. By day 30, RM+ achieved a value of around 60% keratinocyte viability compared to a value approaching 1% in the other storage media under investigation. RM+ provides mitogens, nutrients, growth factors and physiological pH, all of which are important factors for successful skin graft storage.

Adolescent↗
PubMed1993

Restoration of basement membrane structure in pigs following keratinocyte autografting.

The attachment of grafts of keratinocyte sheets is mediated in part by the presence and organisation of basement membrane components. The reappearance of basement membrane following keratinocyte autografting was examined in pigs. These studies showed that there was rapid expression of anchoring fibrils and hemidesmosomes, which reached normal numbers at 10 days. However, the length of hemidesmosomes did not reach normal size during the period of study. Weakness of attachment of keratinocyte autografted epidermis was found to lie between the basement membrane and the granulation tissue. This suggests that reported clinical problems with keratinocyte graft attachment may be mediated not only by delay in maturation of the basement membrane but also by its poor integration with collagen of the wound bed.

Animals↗
PubMed1993

A porcine model using skin graft chambers for studies on cultured keratinocytes.

In wound healing research, animal models permit an extensive tissue analysis which is not normally possible in clinical studies. A morphological comparison of human and porcine skin was made in order to identify those aspects of the wound healing process where a porcine model may help our understanding of clinical problems. We describe a porcine model for evaluating the growth of cultured keratinocytes on a variety of wound beds. Polytetrafluoroethylene skin graft chambers were used to isolate wounds and prevent epidermal healing from the skin edge. The chambers remained in situ for 5-7 weeks. We detail the surgical technique, the method of porcine keratinocyte culture and highlight some practical measures that were taken to optimise the "take" of the cultured keratinocyte grafts.

Animals↗
PubMed1993

Kerato-dermal grafts: the importance of dermis for the in vivo growth of cultured keratinocytes.

In a porcine model, we studied the benefit of dermis for the growth of cultured autologous keratinocytes (CAK) on full-thickness wounds isolated within skin graft chambers. Kerato-dermal grafts were prepared in a two stage process using autologous de-epidermalised dermis (DED) and CAK (Group 1). Control wounds were prepared by grafting either CAK only (Group 2) or DED only (Group 3). The median epidermal cover of 34 wounds in Group 1 was 47% and was significantly greater (p < 0.001) than the epidermal cover of 12 wounds in Group 2 (4%) and 14 wounds in Group 3 (12%). The epidermis in Group 1 was durable whereas it was fragile in the control wounds. Histologically rête ridges were present at 2 weeks in Group 1, but not in the control wounds. These data indicate that a dermal wound bed significantly improves the in vivo growth of cultured keratinocytes.

Animals↗
PubMed1993

The effect of backing materials on keratinocyte autograft take.

A porcine model has been established to study keratinocyte autografts as a model of human keratinocyte grafting. Keratinocyte autografts were placed on 104 full thickness wounds in 13 pigs and backed with 3 dressings which varied in their ability to maintain an occlusive environment. Sixteen control wounds were ungrafted. No take was found using a backing of woven viscose and cotton gauze. Take was 20% at day 16 using a backing of woven viscose and paraffin gauze. Serial biopsies showed that keratinocytes frequently attached to the interstices of the viscose dressing and difficulty in detaching the viscose caused loss of epidermis. Hydrogel sheet backing made assessment at day 10 difficult because of wound hydration but dressing removal, enabling exudate evaporation, produced 22% take at day 13. The development of improved dressing techniques is certainly necessary for improved graft take.

Animals↗
PubMed1992

Replication of varicella zoster virus in primary human keratinocytes.

The ability of varicella zoster virus (VZV) to infect and replicate in human keratinocytes in culture was examined. Primary human keratinocytes derived from the abdomen, breast, and foreskin were plated as monolayers and infected by co-cultivation with VZV infected fibroblasts (MRC-5 cells). Replication and spread of the virus was assayed by plaque assay and immunofluorescence of infected cells using a VZV specific monoclonal antibody. Although all three types of keratinocytes tested were capable of supporting productive VZV infection, the keratinocytes showed a 1.5 to 2 log reduction in virus yield as compared to infection of monolayer cultures of MRC-5 cells. Results from immunofluorescence studies and plaque assays indicate a slower rate of cell-to-cell spread of the virus. Testing of an anti-VZV compound in this novel assay system demonstrated an interesting sensitivity compared to that observed in conventional assay systems.

Antigens, Viral↗
PubMed1990

Interferon-gamma activates co-ordinate transcription of HLA-DR, DQ, and DP genes in cultured keratinocytes and requires de novo protein synthesis.

The purpose of this study was to determine the effect of interferon-gamma on keratinocyte major histocompatibility complex class II gene transcription. Transformed human foreskin keratinocytes (SVK14 cells) were incubated with recombinant IFN-gamma in the presence or absence of the protein synthesis inhibitor cycloheximide. Total cellular RNA was extracted from the cells and Northern blot analysis carried out using cDNA probes for all the functional class II genes. We report that 1) there is co-ordinate activation of all the class-II genes; 2) the rate of transcription varies between gene loci after activation; and 3) de novo protein synthesis is required for IFN-gamma activation of class II transcription.

Cell Line, Transformed↗
PubMed1988

Gamma-interferon induced human keratinocyte HLA-DR synthesis: the role of dermal activated T lymphocytes.

Experiments were performed to examine the hypothesis that the surface expression of HLA-DR by keratinocytes in certain disease states is conferred by the activity of gamma-interferon, derived from dermal activated T lymphocytes. In vivo studies revealed a spatial relationship between keratinocyte HLA-DR expression and activated T lymphocytes within the dermal inflammatory infiltrate. In vitro studies confirmed that gamma-interferon can induce keratinocyte synthesis of HLA-DR. These results suggest that, in vivo, gamma-interferon produced by activated T lymphocytes induces keratinocyte HLA-DR synthesis and expression.

Adult↗
PubMed1987

Treatment of chronic venous ulcers with sheets of cultured allogenic keratinocytes.

Cultured keratinocytes were used as allografts to treat 51 patients with chronic venous ulceration or rheumatoid ulcers unresponsive to all previous conventional treatments including split skin grafts. Although early epithelialization could be seen in the centre of some ulcers, a major effect appeared to be healing from the previously indolent edge. This treatment appears to provide some clinical benefit in healing of chronic ulceration.

Aged↗
PubMedDate not supplied

A hyaluronic acid membrane delivery system for cultured keratinocytes: clinical "take" rates in the porcine kerato-dermal model.

The clinical take rates of cultured keratinocyte autografts are poor on a full-thickness wound unless a dermal bed is provided. Even under these circumstances two important problems are the time delay in growing autografts and the fragility of the grafts. A laser-perforated hyaluronic acid membrane delivery system allows grafting at early confluence without requiring dispase digestion to release grafts from their culture dishes. We designed this study to investigate the influence of this membrane on clinical take rates in an established porcine kerato-dermal grafting model. The study demonstrated a significant reduction in take as a result of halving the keratinocyte seeding density onto the membrane. The take rates, however, of grafts grown on the membrane at half or full conventional seeding density and transplanted to a dermal wound bed were comparable, if not better, than those of keratinocyte sheet grafts.

Animals↗