Isolation, detection, and amplification of intact mRNA from dermatome strips, epidermal sheets, and sorted epidermal cells

Three different strategies for isolating RNA from epidermal cells were compared. Starting with dermatome sections frozen or disaggregated epidermal cells purified by fluorescence activated cell sorting (FACS), RNA was isolated with a guanidinium thiocyanate technique. Specific mRNA were detected by Northern blot analysis (involucrin, keratin 5, actin), or by reverse transcription and amplification with the polymerase chain reaction (PCR), using primers specific for keratinocyte products (keratins 1 and 14) and Langerhans cells (CD1a). Messenger RNA's characteristic of Langerhans cells and of keratinocytes at different stages of differentiation were detected in dermatome and epidermal sheet preparations as well as in FACS-separated cells. The use of snap-frozen dermatome sections allows the isolation of RNA from epidermis that has undergone minimal trauma and is very close to its in vivo state, but that includes RNA from some dermal cells. Extraction of RNA from Dispase-separated sheets involves slightly more manipulation of the epidermis but provides a sample free from dermal contaminants. PCR analysis of sorted epidermal cells is both sensitive and specific, but involves still greater manipulation. This final technique, however, allows the investigation of mRNA produced by small groups of epidermal cells that are still much closer to their in vivo state than if they had been cultured. By combining these techniques it is possible to determine the baseline production of specific mRNA in the skin in vivo and to assign their production to specific groups of cells with a sensitivity and specificity greater than any approach previously described.

Paracrine stimulation of melanocytes by keratinocytes through basic fibroblast growth factor

Melanocytes cultured in the presence of keratinocytes survive for weeks without added basic fibroblast growth factor (bFGF) and cyclic-adenosine-monophosphate (cAMP), the two factors needed for their proliferation in vitro. We show here that the growth factor for melanocytes produced by human keratinocytes is bFGF because its activity can be abolished by neutralizing antibodies to bFGF and by a bFGF synthetic peptide that inhibits the binding of the growth factor to its receptor. The melanocyte mitogen in keratinocytes is cell-associated and increases after irradiation with ultraviolet B (UVB). Northern blots reveal bFGF gene transcripts in keratinocytes but not melanocytes. These studies demonstrate that bFGF elaborated by keratinocytes in vitro sustains melanocyte growth and survival, and they suggest that keratinocyte-derived bFGF is the natural growth factor for normal human melanocytes in vivo.

Basic fibroblast growth factor from human keratinocytes is a natural mitogen for melanocytes

To survive and proliferate in pure culture, human melanocytes require basic fibroblast growth factor (bFGF) and cAMP. Without these factors, even in the presence of serum, the cells die. Melanocytes cultured in the presence of keratinocytes, however, survive for weeks without added bFGF and cAMP. We show here that the growth factor for melanocytes produced by human keratinocytes is bFGF because its activity can be abolished by neutralizing antibodies to bFGF and by a bFGF synthetic peptide that inhibits the binding of the growth factor to its receptor. The melanocyte mitogen in keratinocytes is cell associated and increases after irradiation with ultraviolet B. Northern blots reveal bFGF gene transcripts in keratinocytes but not melanocytes. These studies demonstrate that bFGF elaborated by keratinocytes in vitro sustains melanocyte growth and survival, and they suggest that keratinocyte-derived bFGF is the natural growth factor for normal human melanocytes in vivo.

Toxic epidermal necrolysis: an approach to management using cryopreserved allograft skin

Toxic epidermal necrolysis is an acute exfoliation of skin simulating a scald injury. Drug-induced toxic epidermal necrolysis has a mortality of greater than 50%. We report an 8-year-old girl with drug-induced toxic epidermal necrolysis who was treated with cryopreserved cadaver skin, with good outcome. The allograft was clinically and histologically viable. Graft keratinocytes demonstrated epiboly as reepithelialization by the host occurred along the host/graft interface. Host epidermis regenerated rapidly, presumably from adnexae, and displaced the viable allograft along the plane of the host/graft interface. The new epidermis appeared normal in all respects.

Use of cultured epidermal autografts and dermal allografts as skin replacement after burn injury

An adult with burns over 55% of body surface area (80% of which were third degree) was treated with cadaver skin allografts. The allografts were later abraded to remove allogeneic epidermis and resurfaced with autogenous keratinocyte cultures. Complete reconstitution of skin, consisting of epidermal autograft and dermal allograft, was achieved.

Epidermolysis bullosa: current concepts and management of the advanced hand deformity

A current classification of the types of epidermolysis bullosa is reviewed, in conjunction with some etiological concepts. The pathomechanics of the advanced hand deformity are discussed, and applied to a sequential plan of reconstructive surgery. The objective is the restoration of elementary hand function. Two illustrative cases are presented.