Evaluation of autologous cultured epithelium as replacement skin after tattoo excision: correlation between skin texture and histological features

BACKGROUND

Cultured epidermal autographs (CEAs) are currently used as a coverage treatment for burn wounds, for disfiguring burn scars involving depigmentation and in restoring the elasticity of the skin. The advantage of CEAs is that epidermal sheets prepared from small skin pieces can be enlarged sufficiently to cover large burn areas.

OBJECTIVES

We examined the correlation between recovery of skin texture, and elastic fibre formation and keratinocyte differentiation (assessed by immunohistochemistry) in CEAs used as replacement skin after tattoo excision in a Japanese patient.

METHODS

The tattooed skin was excised down to the deep dermal layer and then CEA was transplanted onto the patient. The skin textures were evaluated by taking replicas of the skin surface, and histological changes of filaggrin, transglutaminase, involucrin, fibrillin and elastin in the autograft skin were examined by immunohistochemistry.

RESULTS

The skin texture improved with time after grafting the CEA, and appeared similar to that of normal skin at 39 months. Among keratinocyte differentiation markers, filaggrin recovered to a normal pattern at around 6 months, and transglutaminase did so at 39 months, whereas involucrin expression remained abnormal at 39 months. Fibrillin expression appeared similar to that of normal skin by 39 months, except for sparse candelabra-like structures of short fibres. Elastin expression remained at a low level throughout.

CONCLUSIONS

Our results show that the recovery of skin texture after application of CEAs following tattoo excision is associated with the normalization of epidermal differentiation markers, except involucrin, and with the regeneration of elastic fibres in the dermis.

The importance of laminin 5 in the dermal-epidermal basement membrane

The skin consists of two main layers, epidermis and dermis, separated by the basement membrane. Epidermal-dermal communication through the basement membrane is important for skin homeostasis. The basement membrane contains specialized structures, called the anchoring complex, which ensure the stability of connection and communication between these two tissue compartments. The proteins within the anchoring complex provide links to both the intracellular cytoskeletal keratins in keratinocytes and connective tissue proteins of the dermis. One of the key components of the complex is laminin 5, which is essential to epidermal cell attachment. The biological function of laminin 5 has been investigated by using a skin equivalent model in vitro and during keratinocyte sheet grafting in vivo. As a major link between the epidermal basal cells and the papillary dermis, laminin 5 initiates hemidesmosome formation and provides stable attachment of the epidermis to the dermis. Laminin 5 also accelerates the assembly of basement membranes and may enhance the recovery of damaged skin. An intact basement membrane at the epidermal-dermal junction is essential to stability of the skin.

Pretreatment of human keratinocyte sheets with laminin 5 improves their grafting efficiency

Laminin 5 is essential in epithelial attachment to stromal tissues, suggesting that it might improve keratinocyte attachment in a variety of clinical situations. In this study, we examined the effect of exogenous laminin 5 upon the efficiency of transplantation of keratinocyte sheets in animal models. Keratinocyte sheets were prepared according to the method of Rheinwald & Green (1975). Purified laminin 5 was added to the sheets of group 1 (1.0 microg per cm2), Dulbecco's modified Eagle's medium alone was added to group 2. The sheets were grafted to the panniculus carnosus of nude mice (BALB/C nu/nu) (n = 12) and nude rats (Fisher 344) (n = 15). The take rate was assessed by measurement of the area of surviving epithelium at 7 d postgrafting. Laminin 5 bound the keratinocyte sheets of group 1. At 7 d postgrafting, the area of epithelialization of group 1 was significantly larger than that of group 2. Immunohistochemistry staining showed that collagen IV, laminin 5, and collagen VII stained more strongly at the dermal-epidermal junction in group 1 than in group 2. Integrin chains alpha6 and beta4 were similar in both groups. Electron microscopy at day 3 after grafting, showed the lamina densa of group 1 to be more continuous than in group 2. Pretreatment of cultured human keratinocyte sheets with laminin 5 improved the extent of epithelial coverage and increased the rate of neobasement membrane formation. The results suggest that laminin 5 promotes epithelial attachment by increasing the rate of basement membrane assembly.

Laminin 5 can promote assembly of the lamina densa in the skin equivalent model

Skin equivalents were prepared by culturing human keratinocytes on the surface of type I collagen gel contracted by human skin fibroblasts (dermal equivalents) and by raising the gel to an air-liquid interface. A stratified squamous epithelium was formed with a well-differentiated cornified layer at the top of keratinocyte layers within 7 days after plating of the keratinocytes on the dermal equivalents. Although major basement membrane components such as collagens IV and VII and laminin 5 were detected immunohistochemically at the dermal-epidermal junction, a lamina densa was rarely observed by electron microscopy even in 14-day skin equivalents. When laminin 5 (1, 5 or 20 microg/ml) was added to the culture medium on day 7 through day 14, types IV and VII collagens at the dermal-epidermal junction stained more strongly by immunohistochemistry compared with the control. Patches of lamina densa were present along the epidermal-dermal junction, and vesicles containing electron-opaque sheets approximately 0.6 microm in diameter that reacted with anti-collagen IV antibody were also observed in basal keratinocytes in 14-day skin equivalents by electron microscopy. Morphometric analysis showed that the total length of lamina densa along the dermal-epidermal junction as well as in the vesicles increased up to 180%, 230% or 520% of control cultures by the addition of laminin 5 (1, 5 or 20 microg/ml, respectively). These results suggest that laminin 5 accelerates formation of the lamina densa along the dermal-epidermal junction of the skin equivalents, depending on the concentration of laminin 5 supplemented exogenously.

Growth and differentiation properties of normal and transformed human keratinocytes in organotypic culture

The growth and differentiation of human normal keratinocytes and their transformed counterparts were examined in organotypic cultures in which the keratinocytes were grown at the air-liquid interface on top of contracted collagen gel containing fibroblasts. We developed a modified culture procedure including the use of a mixed medium for keratinocytes and fibroblasts. Normal keratinocytes formed a three-dimensional structure of epithelium that closely resembled the epidermis in vivo, consisting of basal, spinous, granular and cornified layers. Cells synthesizing DNA were located in the lowest basal layer facing the collagen gel. Expressions of proteins involved in epidermal differentiation were examined by immunohistochemical staining and compared with those in skin in vivo. In the organotypic culture, transglutaminase, involucrin and filaggrin were expressed, as in the epidermis in vitro, most prominently in the granular layer. Type IV collagen, a component of basement membrane, was expressed at the interface between the keratinocyte sheet and the contracted collagen gel. Keratinocytes transformed by simian virus 40 or human papilloma virus (HPV) exhibited a highly disorganized pattern of squamous differentiation. In particular, HPV-transformed cells invaded the collagen gel. Organotypic culture is unique in that regulatory mechanisms of growth and differentiation of keratinocytes can be investigated under conditions mimicking those in vivo.

Dissociation of actin microfilament organization from acquisition and maintenance of elongated shape of human dermal fibroblasts in three-dimensional collagen gel

Actin microfilaments of the fibroblasts cultured in a collagen gel were distributed along the inner surface of the entire cell membrane, in either spherical shape at an initial stage of culture or elongated shape at a later stage. The distribution was quite different from that of the fibroblast cultured on a two-dimensional surface, where actin microfilaments were found to be aligned essentially along the inner membrane which is in contact with a flat surface. Timing of morphological change from spherical shape to spread shape or elongated shape was also greatly affected by contact with substrates whether in two-dimension or in three-dimension: distinct morphological change was observed within 6 h on glass or on the collagen gel, and at 30 h or later within the collagen gel. The retardation of cell elongation in the gel was antagonized by a low dose (0.2 microM) of cytochalasin D, although the drug kept the cells in round shape at a concentration of 2 microM. Since a low concentration of cytochalasin was reported to induce actin polymerization in vitro, the organization of actin microfilaments was examined by rhodamine-phalloidin staining. It was found that actin filaments in elongated cells by low cytochalasin D were disrupted. These results suggest that accelerated acquisition of elongated shape by the treatment of a low dose of cytochalasin D might be initiated by destabilization of the actin microfilaments that may scaffold the spherical shape of the cell in the collagen gel. The elongated shape thus formed returned to spherical upon washing of the added free cytochalasin D.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of hyaluronate on physicochemical and biological properties of collagen solution which could be used as collagen filler

The effect of hyaluronate (HA) on the physiochemical and biological properties of collagen solution was examined for two preparations of collagen with different rates of fibril formation. The addition of HA to the collagen preparation with the slower rate of fibril formation caused a prominent acceleration of fibril formation. A differential scanning calorimetric measurement of the collagen preparation demonstrated a stabilizing effect of HA on collagen solution after incubation at 37 degrees C. Histochemical examination of rat dermis after injection of the collagen solution into the tissue revealed the migration of fibroblast-like cells into the region occupied by the injected collagen. The addition of HA to collagen preparation S (slower rate of fibril formation) shortened the time-to-appearance of fibroblast-like cells to a similar value to that observed when collagen preparation F (faster rate of fibril formation) was used. The timing of cell appearance was in accord with the rate of fibril formation in vitro. Fibrils newly formed by injected collagen might provide sites for cell attachment, migration and proliferation.

Identification of lamin B2 as a substrate of protein kinase C in BALB/MK-2 mouse keratinocytes

Protein phosphorylation by activation of protein kinase C was examined using quiescent cultures of the mouse epidermal keratinocyte line BALB/MK-2. Treatment with phorbol ester caused rapid phosphorylation of five proteins with molecular weights of 80,000, 70,000, 40,000, 34,000, 28,000. Of these proteins, the 70,000 molecular weight one (p70) was studied further. Its position on two-dimensional gel suggested that p70 is nuclear envelope lamin B. This possibility was confirmed by the co-migration of p70 with the lamin fraction of mouse liver and its immunoprecipitation with antinuclear lamina antibody. The lamin B fraction consists of lamin B1 and lamin B2. Evidence that p70 is lamin B2 was obtained by peptide mapping and amino acid sequencing. Lamin B2 is the only lamin that shows a substantial increase in phosphorylation on treatment of BALB/MK-2 cells with phorbol ester.

Purification and identification of creatine phosphokinase B as a substrate of protein kinase C in mouse skin in vivo

We previously described epidermal proteins with molecular weights of 40,000 (p40) and 34,000 (p34) as target proteins of protein kinase C in mouse skin carcinogenesis in vivo. In the present work, p40 was purified from mouse brain by the use of 32P-labeled p40 of BALB/MK-2 cells as a tracer. Following four lines of evidence indicate that p40 is creatine phosphokinase B. 1) The amino acid sequences of all peptide fragments of p40 from mouse brain were located in the primary structure of creatine phosphokinase B. 2) p40 of BALB/MK-2 cells was immunoprecipitated with goat antibody against human creatine phosphokinase B. 3) p40 of BALB/MK-2 cells was absorbed to and eluted from a creatine affinity column. 4) Purified creatine phosphokinase B was phosphorylated in vitro by purified protein kinase C, but not by cAMP-dependent kinase or casein kinase II.

Regulation of creatine phosphokinase B activity by protein kinase C

We previously reported that topical application of 12-o-tetradecanoylphorbol-13-acetate to mouse skin causes phosphorylation of epidermal proteins with molecular weights of 40,000 (p40) and 34,000 (p34). In the accompanying paper, p40 was identified as creatine phosphokinase B. Here we report that both in intact cells and in a cell-free system, phosphorylation of creatine hosphokinase B by protein kinase C resulted in an increase in its ability to catalyze the transfer of the high-energy phosphate of phosphocreatine to ADP, thereby producing ATP. H-7, a specific inhibitor of protein kinase C was found to abolish the increase in enzyme activity. Lineweaver-Burk plot analysis indicated that the increased activity was mostly due to a decreased Km for phosphocreatine. Phosphorylation and activation of creatine phosphokinase B may be a physiological response to maintain ATP balance when a protein kinase C pathway is stimulated.

Growth rate of human fibroblasts is repressed by the culture within reconstituted collagen matrix but not by the culture on the matrix

Effect of reconstituted type I collagen gel on in vitro growth of fibroblasts was examined. A prolonged lag period was observed by culture either on the surface of three-dimensional collagen gel ("on-gel") or within the gels ("in-gel") as compared with the culture on plastic dishes. The rate of cell proliferation in logarithmic phase growth was repressed by the culture "in-gel" but not by the culture "on-gel". The differential growth rates between "in-gel" culture and "on-gel" culture should be ascribed to difference in distributions of interacting sites between cell and collagen fibrils. The repression of cell growth was more marked in a contracting collagen gel which contains higher density of collagen fibrils. The cell density in contracted gel per unit cross-section area was found to be much lower than that of confluent monolayer culture. These results suggest that the repression of cell growth by collagen fibrils in the three-dimensional gels is not due to direct cell-cell contact, but due to the distribution and number of contact sites between a cell and collagen fibrils.

Unfolding and refolding of a type kappa immunoglobulin light chain and its variable and constant fragments

By limited proteolysis of a type kappa immunoglobulin light chain (Oku) with clostripain, both the VL and CL fragments were obtained with a high yield. The unfolding and refolding by guanidine hydrochloride of light chain Oku and its VL and CL fragments were studied at pH 7.5 and 25 degrees C with circular dichroism and tryptophyl fluorescence. The concentration of guanidine hydrochloride at the midpoint of the unfolding curve was 1.2 M for the VL fragment and 0.9 M for the CL fragment. As in the case of the CL fragment of light chain Nag (type lambda) [Goto, Y., & Hamaguchi, K. (1982) J. Mol. Biol. 156, 891-910], the unfolding and refolding kinetics of the CL fragment could be explained in principle on the basis of the three-species mechanism U1 in equilibrium U2 in equilibrium N, where N is native protein and U1 and U2 are the slow-folding and fast-folding species, respectively, of unfolded protein. The unfolding and refolding kinetics of the VL(Oku) fragment were described by a single exponential term. Double-jump experiments, however, showed that two forms of the unfolding molecule exist. The equilibrium and kinetics of unfolding of light chain Oku were explained by the sum of those of the VL and CL fragments. On the other hand, the refolding kinetics of light chain Oku were greatly different from the sum of those of the VL and CL fragments.(ABSTRACT TRUNCATED AT 250 WORDS)

Conformation of the constant fragment of the immunoglobulin light chain: effect of cleavage of the polypeptide chain and the disulfide bond

In order to understand the conformations and stabilities of the immunoglobulin domains, a derivative of the type-lambda constant fragment in which the peptide bond Arg190-Ser191 is cleaved and a derivative of the type-kappa constant fragment in which the peptide bond Arg142-Glu143 is cleaved were prepared by limited proteolysis with the proteinase from mouse submaxillary gland, endoproteinase Arg-C [EC 3.4.21.40]. The cleaved peptide bond of each derivative is located in the loop formed by the intrachain disulfide bond and the two peptides formed are linked by the disulfide bond. The two nicked CL fragments did not assume any ordered conformation. On the other hand, a derivative in which the intrachain disulfide bond is reduced had a conformation very similar to that of the intact CL fragment, although the stability was considerably low. Since the entropy of the nicked fragment should be nearly the same as that of the reduced CL fragment in the unfolded state, a destabilizing effect of cleavage of the polypeptide bond in the folded state in addition to the entropic effect in the unfolded state seems necessary to account for the conformations of the nicked CL fragments.