Effects of cryopreservation and deconstruction on the dermal glycosaminoglycan content of human skin.

Since the concept of a fabricated skin replacement was first proposed, it has been recognized that a permanent skin replacement must contain a functional complex structure consisting of epidermis integrated with dermis. Although a practical solution for the replacement of missing epidermis exists through the culture expansion of the autologous epidermis, a practical solution for permanently replacing missing dermis has not been achieved. While it is generally recognized that the insoluble matrix components--largely collagen and elastin--are essential, the role of other matrix components such as glycosaminoglycans (GAGs) and proteoglycans remains undefined. This article describes both the qualitative and quantitative GAG composition of fresh and cryopreserved human dermis. Through the use of 2 different colorimetric assays and cellulose acetate electrophoresis, we found the following: 1) the principal dermal GAGs are those of the heparin family; 2) dermatan sulfate is the second most predominant GAG component; 3) chondroitin-6-sulfate is found at concentrations of 2 orders of magnitude less than the heparins; and 4) hyaluronan and keratan sulfate were both found as only minor constituents. When the GAG composition of fresh skin was compared with that of cryopreserved skin, no significant differences were observed. This study also examined the time course of GAG leaching during the preparation of deconstructed human dermis, which is human dermis reduced to the native insoluble matrix components by exhaustive saline soaking. We found that GAG leaching was readily detectable even within the first day. Sixty percent of total GAG leaching occurred by day 7. These investigations establish a benchmark for the reproduction of GAGs in synthetic dermal constructs. Further, the results of the leaching study generate important considerations for short-term skin storage and long-term skin banking. Because GAG leaching commences immediately, appropriate precautions must be taken to minimize the potential functional compromise of cryopreserved human dermis.

Critical role of phosphagens in the energy cascade of cutaneous ischemia and protective action of phosphocreatine analogues in skin flap survival.

A general understanding of the pivotal role of phosphocreatine (PCr) as the principal determinant of skin flap survival is now emerging. Definitive metabolic investigations using phosphorus (31P) and proton (1H) magnetic resonance spectroscopy (MRS) have established that the inability to replenish metabolically exhausted PCr reserves predictably correlates with skin flap necrosis. Furthermore, postoperative parenteral administration of PCr has been shown to augment effectively skin flap survival. We hypothesized that creatine kinase, the enzyme controlling the utilization of the high-energy phosphate component of PCr, is a critical determinant of the tolerance of a skin flap to ischemic insult. In other words, if the rate of utilization of PCr is too rapid, PCr stores will rapidly deplete, and the flap will not be able to withstand a period of ischemia. Alternatively, if the rate of dephosphorylation of PCr is reduced, survival of skin flaps during periods of ischemia could be extended. To test this hypothesis, we investigated the metabolic distribution and fate of cyclocreatine (cCr), a competent creatine analogue with a lower affinity for the creatine kinase enzyme. When administered as 1.5 percent (w/w) of the normal diet of laboratory rats, cCr accumulates in skin as the competent phosphagen, phosphocyclocreatine (PcCr). Cutaneous flaps elevated in these animals, and studied by 31P and 1H MRS, demonstrate that once depletion of PCr has occurred, PcCr continues to sustain ATP levels. This results in significant enhancement of skin flap survival (p < 0.005). These observations confirm the importance of the creatine kinase enzyme in cutaneous flap ischemia and suggest new approaches to augment skin flap survival.

The burn camp experience: variables that influence the enhancement of self-esteem.

Since 1982, there have been summer camps for children and adolescent burn survivors. Although the primary focus of camp is to have "fun," the principal goal is psychosocial readjustment through peer interactions and the resulting enhancement of self-esteem (SE). This study was initiated to test the hypothesis that the burn camp experience enhances the SE of campers. Forty-three campers at the Connecticut Burns Care Foundation Summer Camp were invited to participate in this study with the Rosenberg Self-Esteem Scale. The age range was 8 to 18 years (mean 12 years). The extent of previous burn injury ranged from 10% to 98% total body surface area (mean 40%). The interval between hospital discharge and camp experience was 4 to 144 months (mean 54 months). Thirty-seven percent of the children demonstrated an increase in SE to varying degrees, whereas 30% showed no change, and 3% exhibited a decrease in SE. This study failed to support the working hypothesis.

A reliable and cost-effective in vitro assay of skin viability for skin banks and burn centers.

The tetrazolium salt, MTT (3-[4,5-Dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide), was used to evaluate the viability of fresh native human skin and cryopreserved human skin under a wide variety of conditions. Viability of fresh and cryopreserved skin was determined with our modification of the MTT assay, and compared with the well-described tetrazolium reductase assay. The MTT assay provides a precise and reproducible index of viability for both fresh and cryopreserved skin. In comparison, the tetrazolium reductase assay (1) is subject to higher levels of variability and, (2) underestimates the viability of fresh native skin. The precision, simplicity, and economy of the MTT assay support its utility in the routine assessment of skin viability in skin banks, burn centers, and skin biology research units.

The carpal boss. A 20-year review of operative management.

Between 1969 and 1989, 116 patients were evaluated and treated surgically for symptomatic carpal boss. Their mean age was 32 years and male and female patients were equally affected. 28 patients gave a history of previous injury. Surgical treatment consisted of excision of the localized bony abnormality and the associated degenerative arthritic process to the level of normal articular surfaces and normal adjacent cancellous bone. The mean follow-up period for the patients in this study was 42 months. Complete symptomatic relief was observed in 94% of the patients undergoing surgical treatment. Recurrence or persistence of symptoms developed in seven surgical patients. Six had a second operation with more extensive removal of sclerotic bone and degenerate cartilage, and all patients had relief of symptoms.

Localized in vivo 31P NMR spectroscopy of skin flap metabolism.

We have used a rectangular surface coil and chemical shift imaging to conduct in vivo localized 31P NMR metabolic studies in a rat dorsal skin flap model. This approach permits regional comparisons without manipulation of either coil position or subject within the magnet bore. Both the PCr:Pi ratio (reflecting ischemia insult) and the PCr:ATP ratio (reflecting phosphagen reserves) decreased as functions of time and distance from the vascular pedicle. The maximum change was nearly 6-fold for the PCr:Pi ratio, and 3-fold for the PCr:ATP ratio. Signal contamination from subjacent muscle is constant and does not interfere with the metabolic evaluations of skin flaps. This technique may facilitate a better understanding of cutaneous metabolic derangements, such as burns and skin flaps used in reconstructive surgery, as well as studies of pharmacologic regimens developed for their treatment. It also holds potential for application in the study of congenital and neoplastic metabolic disorders of skin.

Chemiluminescent restriction fragment length polymorphism analysis (DNA fingerprinting) to identify keratinocytes from two donors in co-culture.

The transplantation of allogeneic cells such as pancreatic islet cells, bone marrow, and keratinocytes for skin replacement is in growing use clinically. Present techniques which are used to distinguish transplanted allogeneic cells from phenotypically identical host cells in chimeric tissue have serious limitations. This study assesses the feasibility of using chemiluminescent restriction fragment length polymorphism (RFLP) analysis to distinguish between keratinocyte cell lines from 2 different donors grown in co-culture. We evaluated the sensitivity of this technique in tissue cultured cells in order to define its usefulness in clinical situations. RFLP analysis readily detects heterologous DNA comprising only 10% of a 5 micrograms sample. This was a detection threshold of 500 ng of high molecular weight DNA. With standard extraction methods, this represents the DNA obtained from 4000 cells. This new chemiluminescent technique is as sensitive as older techniques which employ radioactive probes, but avoids the hazards of handling radioactive material. Using this RFLP analysis, the presence of transplanted allogeneic cells can be readily detected in small biopsy specimens. This technique has wide potential application in allogeneic cellular transplantation investigations.

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.

In vitro reconstitution of skin: fibroblasts facilitate keratinocyte growth and differentiation on acellular reticular dermis.

Extensive full-thickness burns require replacement of both epidermis and dermis. We have described a method in which allogeneic dermis from engrafted cryopreserved cadaver skin was combined with cultured autologous keratinocytes. In the present study we combined human keratinocytes and fibroblasts, and acellular human dermis in vitro and transplanted this "reconstituted skin" into athymic mice. Both human papillary dermis in which the basement membrane zone has been retained and human reticular dermis that has been repopulated with human dermal fibroblasts are good substrates for keratinocyte attachment, stratification, growth, and differentiation. Both of these dermal preparations can be lyophilized and stored at room temperature without losing their ability to support keratinocyte growth. In contrast, human papillary dermis that has been treated with trypsin lacks laminin and collagen type IV in the BMZ and supports keratinocyte attachment and differentiation less well.

Amelioration of renal ischemic injury by phosphocreatine.

Phosphocreatine (PCr) is a critical intracellular energy reservoir used in the regeneration of ATP. The aim of this study was to determine the efficacy of exogenously added PCr on preservation of renal function in an in vitro model. The renal artery and ureter of a rat were cannulated and the kidney was subjected to 45 min of normothermic in vivo ischemia. The kidneys were then perfused ex vivo with either a Krebs-bicarbonate solution (Krebs) or a Krebs solution containing 3 mM PCr or an osmotically balanced solution containing 3 mM PCr. Our results indicate that the perfusion of kidneys subjected to 45 min of warm ischemia with solutions containing PCr resulted in significant improvements in GFR, RPF, and V, FRNa and FRH2O compared to KREBS alone. This suggests that the important factor in preservation of kidney function after an initial ischemic insult may be the addition of PCr rather that the electrolyte solution used.

Double-Z rhombic technique for reconstruction of facial wounds.

The double-Z rhombic technique of repair of excisional defects is characterized by borrowing the required tissue from two nonadjacent opposite sides of the defect. Most other flaps borrow the required tissue from a single adjacent region or all adjacent directions. The "sharing" of tissue from two opposite regions minimizes tension in that direction, while not borrowing from the remaining regions prevents the distortion of anatomic landmarks located along that direction. The orientation of the final scar and direction of tissue tension can be controlled by rotating the rhombic defect about its central axis. This study was undertaken to assess the utility of the double-Z rhombic technique in terms of cosmesis and avoidance of displacement of mobile anatomic landmarks such as eyelids, eyebrows, nasal alae, and lips. Excisional defects resulting from removal of skin neoplasms in 30 patients in whom primary closure or reconstruction with direct tissue advancement was not feasible and displacement of facial landmarks was undesirable were reconstructed using the double-Z rhombic technique. No considerable asymmetry or facial anatomic landmark deformity was observed in any of the 30 patients. Our results are presented along with representative illustrations.

Upper extremity entrapment neuropathy and tourniquet use in patients undergoing hemodialysis.

Patients with end-stage renal disease, undergoing hemodialysis, have been shown to have an increased prevalence of carpal tunnel syndrome. From mid-1981 through 1986, 21 patients undergoing hemodialysis were operated on for 33 cases of clinically diagnosed entrapment of the median and/or ulnar nerves, including 14 extremities with functioning vascular access. All patients report improvement in symptoms and function in the affected extremity. Preoperative tourniquet use did not have a permanent adverse effect on any access site. Electrophysiologic studies were not reliable predictors of clinically resolvable nerve entrapment.

Reconstitution of structure and cell function in human skin grafts derived from cryopreserved allogeneic dermis and autologous cultured keratinocytes.

Grafts of allogeneic dermis plus autologous epidermal cell cultures were used to replace extensively burned skin. Cryopreserved split-thickness cadaveric skin was grafted onto debrided burn wound, and autologous keratinocytes were cultured from uninjured donor sites. Several weeks later, allograft epidermis was abraded and replaced with the keratinocyte cultures. The final grafts were thus composites of autologous cultured epidermis and allogeneic dermis. In a case with 28 months follow-up, reconstitution of the dermal-epidermal (BMZ.1) and microvascular (BMZ.2) basement membrane zones was studied immunohistochemically and ultrastructurally. Immediately before grafting, thawed cryopreserved skin reacted with antibodies against laminin and type IV collagen in normal patterns. Twenty-nine days after grafting, BMZ.1 reacted weakly with both antibodies, and anticollagen type IV reactivity was absent from BMZ.2. Antilaminin reactivity of BMZ.2, however, was moderately intense, consistent with recent neovascularization. On day 29, the allograft epidermis was replaced with autologous keratinocyte cultures. Twenty-five days later (54 d after allografting), staining of both BMZs was intense with both antibodies. Ultrastructurally, at day 76 (47 d after culture placement) BMZ.1 revealed only small hemidesmosomes, few incipient anchoring fibrils, and a discontinuous lamina densa. BMZ.2, however, was fully reconstituted. By 124 d, both BMZs appeared normal. Observations in the dermis at 76 d included the presence of lymphocytes, organellar debris, and hyperactive collagen fibrillogenesis, all indicative of dermal remodelling. The microvasculature was well differentiated, but no elastic fibers or nerves were found. In the epidermis, melanocytes and evidence of melanosome transfer were seen at 5, 47, and 95 d after grafting of keratinocyte cultures. We conclude that the composite procedure reconstitutes skin with excellent textural and histologic qualities.

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.

Immunologic alterations following excisional wounding and immediate repair with syngeneic or allogeneic skin grafts.

Immunosuppression and its associated infectious complications have long been recognized as consequences of major thermal trauma, though the factors that mediate this suppression remain unclear. A murine split-thickness skin graft model was developed to investigate the role of a large surface area wound in the initiation of immunosuppression in the absence of burn injury. Significant T cell-mediated immunosuppression was demonstrated following wounding and immediate repair with either syngeneic or allogeneic split-thickness skin grafts. These results are consistent with previous experiments in a murine burn model treated by escharectomy and resurfacing with syngeneic composite full-thickness skin. Data also supports the concept that mediators of inflammation at the wound site play an important role in postburn immunosuppression. Furthermore, these results suggest that the use of skin allografts during the early postburn period does not adversely affect cell-mediated immunity in any way that could be abrogated by primary autografting.

The role of topical treatment as a determinant of infection in outpatient burns.

Up to 95% of all burned patients are treated as outpatients. While uniform guidelines exist to evaluate the severity of an outpatient's burn, treatment forms vary greatly. Furthermore, the relative merits of one treatment modality over another have not been demonstrated. This study reviews 262 patients with uncomplicated, thermal partial-thickness burns. All of these patients were treated with either a petrolatum fine-mesh gauze (FMG = 102), a topical penetrating antibacterial agent (TPA = 58), or a topical nonpenetrating antibacterial agent (TNA = 102). The size of the injury along with its location and etiology, the age of the patient, the time from injury to treatment, and comorbid factors were comparable among the major treatment groups. On follow-up, a wound was classified as infected if it exhibited erythema, tenderness, increased warmth, and edema (cellulitis). Infection rates were 2.0% (2/102) in the FMG group, 5.2% (3/58) in the TPA group, and 2.0% (2/102) in the TNA group. The differences among the rates did not reach statistical significance (P = 0.41). Given the cost of treatment, frequency of dressing changes and overall patient comfort, we advocate FMG as the optimal method for the care of uncomplicated partial-thickness outpatient burns.