Urothelial progenitor cells: regional differences in the rat bladder

OBJECTIVES

Because the trigone is a unique region in the caudal bladder with a higher risk of neoplasia, we hypothesized that this area would have a high proportion of progenitor cells. As yet there is no marker nor methodology to specifically isolate urothelial stem cells, and thus demonstrate multi-potential differentiation and self-renewal. Here, our goal was to evaluate the distribution of progenitor cells that carry two general major attributes of stem cells: clonogenicity and proliferative capacity.

MATERIALS AND METHODS

The bladders of Fisher rats were divided into caudal and cephalic segments and primary cultures were established from the harvested urothelial cells.

RESULTS

We found that colony-forming efficiency was almost 2-fold higher for cells from the caudal bladder compared to the cephalic bladder. Doubling time was significantly faster for cells harvested from the caudal bladder at initial plating. This suggested that the caudal bladder harbours a higher density of urothelial progenitor cells. With passage to p4, the differences between the upper and lower bladder were lost, suggesting selection of proliferative cells with serial passage. Based on Ki-67 staining, there was no geographical difference in cell proliferation under normal homeostatic in vivo conditions.

CONCLUSIONS

These results demonstrate geographical sequestration of urothelial progenitor cells to the area of the bladder that encompasses the bladder neck and trigone, which may be a factor in pathological disparities between the trigone and remaining bladder.

Economical LED based, real-time, in vivo imaging of murine corneal wound healing

An optimal system for monitoring in vivo corneal wound healing is inexpensive, has utility for wounding and imaging, and is able to provide previews before photography. We outline such an imaging system that takes advantage of a consumer digital camera and an LED-based light source for fluorescein excitation. Using FVB/NJ mice, 2mm diameter, circular, axial corneal epithelial defects were created using a crescent blade. The corneal wounds were imaged every four hours until healed using a Nikon Coolpix 5400 camera attached to a Nikon SMZ-10A stereomicroscope, using the illumination from a 16 LED 464nm flashlight. The wound area was calculated, and the linear regressions of the linear phase of wound healing were compared using the F-test. The slopes of the linear regressions for the 6 trials of 4 mice/trial had an average of -52.95microm/h (SEM=0.55microm/h) and were statistically equivalent (p>0.05). The mean of the R(2) values for the linear regressions was 0.9546 (SEM=0.0121). The equivalent linear regressions and R(2)>0.90 suggest that the imaging system could precisely monitor the wound healing of multiple trials and of animals within each trial, respectively. Using a consumer digital camera and LED-based illumination, we have established a system that is economical, is used in both wounding and imaging, is operated by a single person, and is able to provide real-time previews to monitor corneal wound healing precisely.

Wound dressings alter the colony-forming efficiency of keratinocytes in cultured sheet grafts

Cultured keratinocyte grafts transplanted for skin wound repair are often affixed to a wound dressing to facilitate handling. In this study, the ability of five different types of wound dressings to support cell viability and maintain stem cell populations in the cultured grafts was determined. Postconfluent keratinocyte (NHK) sheets were attached to wound dressings for 24 h and then released by trypsinization. Cell viability was determined and NHKs were assessed for clonogenic capacity by colony-forming efficiency (CFE) assays. CFEs for NHKs exposed to a collagen-bonded, bilaminate membrane and a polyurethane film were significantly less than control. On the other hand, CFEs for NHKs exposed to a collagen/alginate dressing and to petrolatum-impregnated gauze were significantly greater than control. The choice of a wound dressing carrier has implications for maintaining long-term viability of the transplanted sheet of epithelium.

Cyclic AMP-dependent protein kinase A plays a role in the directed migration of human keratinocytes in a DC electric field

Skin wound healing requires epithelial cell migration for re-epithelialization, wound closure, and re-establishment of normal function. We believe that one of the earliest signals to initiate wound healing is the lateral electric field generated by the wound current. Normal human epidermal keratinocytes migrate towards the negative pole, representing the center of the wound, in direct currents of a physiological strength, 100 mV/mm. Virtually nothing is known about the signal transduction mechanisms used by these cells to sense the endogenous electric field. To elucidate possible protein kinase (PK) involvement in the process, PK inhibitors were utilized. Two important findings have been described. Firstly, addition of 50 nM KT5720, an inhibitor of PKA, resulted in a 53% percent reduction in the directional response of keratinocytes in the electric field, while not significantly affecting general cell motility. The reduction was dose-dependent, there was a gradual decrease in the directional response from 5 to 50 nM. Secondly, addition of 1 microM ML-7, a myosin light chain kinase inhibitor, resulted in an approximate 31% decrease in the distance the cells migrated without affecting directional migration. The PKC inhibitors GF109203X at 4 microM and H-7 at 20 microM and W-7, a CaM kinase inhibitor, did not significantly alter either directed migration or cell migration, although they all resulted in a slight reduction in directional migration. D-erythro-sphingosine at 15 microM, a PKC inhibitor, had virtually no effect on either migration distance or directed migration. These findings demonstrate that divergent kinase signaling pathways regulate general cell motility and sustained directional migration and highlight the complexity of the signal transduction mechanisms involved. The inhibitor studies described in this paper implicate a role for PKA in the regulation of the directional migratory response to applied electric fields, galvanotaxis.

Divergent responses of ras-transfected and non-ras-transfected human keratinocytes to extracellular calcium

Raising extracellular calcium (Ca(o)) induces terminal differentiation in cultured epidermal keratinocytes. The introduction of the ras oncogene into keratinocytes results in resistance to Ca(o)-mediated differentiation. To understand the signaling mechanism involved, we examined the Ca(o)-induced formation of inositol triphosphate (IP3) and changes in intracellular Ca2+ (Ca(i)) concentration in non-ras-transfected and ras-transfected HaCaT lines of human keratinocytes. When switched from 0.05- to 1.5-mM Ca(o) medium, the non-ras HaCaT line showed a rapid twofold increase in IP3 formation, whereas the IP3 level in the ras-transfected I-7 line was slightly affected. G-protein-coupled activation of phospholipase was intact in both lines, as evidenced by the generation of similar amounts of IP3 in response to addition of bradykinin or guanosine 5'-[gamma-thio]-triphosphate. Addition of 1.0 mM Ca(o) evoked similar Ca(i) responses in both non-ras- and ras-transfected cells: a transient elevation, followed by a sustained lower plateau. However, the two lines differed in their later responses: after being maintained in 1.0 mM Ca2+ for 24 h, the Ca(i) level was significantly lower in ras-transfected cells than in non-ras-transfected HaCaT cells. The Ca(o)-induced increase in Ca(i) in both lines was inhibited by the Ca2+ entry blocker SK&F 96365 or depolarization in high K+ bathing solution, demonstrating its dependence of calcium influx. The results suggest fundamental differences in the early signal that are generated in response to an increase in Ca(o) in ras-transfected keratinocytes, with the absence of a Ca(o)-induced rise in IP3--a signaling pathway defect that may play a role in the differentiation block the cells exhibit. In addition, the inability of ras-transfected cells to sustain a prolonged Ca(i) plateau may also contribute to their inability to differentiate in response to the Ca(o) signal.

Ultraviolet B-mediated phosphorylation of the small heat shock protein HSP27 in human keratinocytes

Exposure of human keratinocytes to environmental stress is known to induce changes in the expression, phosphorylation, and subcellular relocalization of the 27 kDa heat shock protein. This study demonstrates that ultraviolet B (280-320 nM) irradiation with physiologic doses induces a dose-dependent phosphorylation of 27 kDa heat shock protein, generating the more acidic 27 kDa heat shock protein B, C, and D isoforms. Ultraviolet B also induces perinuclear cytoplasmic relocation and nuclear translocation of 27 kDa heat shock protein and caused aggregation of cytoplasmic actin filaments into a broad perinuclear distribution. The ultraviolet B-induced phosphorylation is reversible, returning to baseline levels 4 h after exposure, and this coincides with the reversal of ultraviolet B-induced actin reorganization. The ultraviolet B-induced phosphorylation is not affected by the protein kinase C inhibitor, GF 109203X, is partially inhibited by epidermal growth factor receptor tyrosine kinase inhibitor, PD 153035, and is substantially inhibited by the specific p38 mitogen-activated protein kinase inhibitor, SB 203580. In addition, pretreatment of cells with the anti-oxidant N-acetyl cysteine partially inhibits ultraviolet B-and oxidant-induced 27 kDa heat shock protein phosphorylation. The p38 mitogen-activated protein kinase cascade is thus the major transduction pathway for ultraviolet B-induced 27 kDa heat shock protein phosphorylation, and reactive oxygen species generated in response to ultraviolet B also contribute to this phosphorylation. As 27 kDa heat shock protein phosphorylation and relocalization has been associated with increased cell survival after environmental insult, our data suggest that ultraviolet B, in addition to initiating recognized cytotoxic events in keratinocytes, also initiates a signaling pathway that may provide cellular protection against this ubiquitous environmental insult.

Successful transplantation of bioengineered tissue replacements in patients with ocular surface disease

PURPOSE

To bioengineer a corneal surface replacement using ex vivo expanded, cultured corneal epithelial stem cells seeded on a matrix derived from amniotic membrane and use this bioengineered graft to manage difficult ocular surface disease.

METHODS

Fourteen patients with ocular surface disease unresponsive to standard medical and surgical treatments, including seven patients with presumed limbal stem cell deficiency were chosen for transplantation of a bioengineered composite corneal surface in eye each. Presumed corneal stem cells were harvested from either the patient's or related donor's limbus, expanded ex vivo, and cultivated on a carrier of modified human amniotic membrane. The resulting composite cultured tissue was transplanted to the ocular surface of the diseased eye, from which the abnormal tissue had been surgically removed. Ten patients received autologous grafts, and four received allogeneic grafts.

RESULTS

A successful outcome, defined as restoration or improvement of vision, along with maintenance of corneal re-epithelialization and absence or recurrence of surface disease was obtained in 6 of the 10 patients with autologous procedures and in all 4 allogeneic transplants. Follow-up ranged 6-19 months with a mean of 13 months.

CONCLUSIONS

This novel technique documents that presumed corneal epithelial stem cells can be harvested safely from the limbus, expanded successfully in vitro, and grown on denuded amniotic membrane. The resultant composite cultured tissue can be transplanted and appears to successfully manage eyes with difficult ocular surface disease, including those with stem cell deficiency. This technique minimizes the threat of damage or depletion to the contralateral or donor limbus.

DC electric fields induce rapid directional migration in cultured human corneal epithelial cells

After an epithelium is wounded, multiple soluble and extracellular matrix-associated signals induce a repair response. An often-overlooked signal is the endogenous electrical field established in the vicinity of the wound immediately upon disruption of epithelial integrity. Previous studies have detected lateral electric fields of approximately 42 mV mm-1 near bovine corneal wounds. In addition, electric fields on the order of 100-200 mV mm-1 have been measured lateral to wounds in mammalian epidermis. Here we report the migratory response of human corneal epithelial cells to DC electric fields of similar, physiologic magnitude. Our findings demonstrate that in a 100 mV mm-1 DC field, corneal epithelial cells demonstrate directed migration towards the cathode. The migratory speed and distances traversed by cultured human corneal epithelial cells is remarkably similar to those of cultured skin-derived keratinocytes under similar conditions; however, corneal epithelial cells demonstrate a more rapid directional response to the field than keratinocytes. These findings suggest that endogenous, wound-induced electric fields present in the cornea play an important role in human corneal wound healing, by orienting the directional response of migratory cells so that they efficiently re-epithelialize the wounded area.

Involucrin-positive keratinocytes demonstrate decreased migration speed but sustained directional migration in a DC electric field

When skin is wounded, keratinocytes from the cut edges of the epidermis migrate over the wounded area to re-epithelialize the wound. It is not clear which cells of the epidermis have the capacity to migrate and contribute to this re-epithelialization: the less differentiated cells of the basal layer, or the more differentiated, involucrin-positive suprabasilar cells. Here we demonstrate that both involucrin-negative and involucrin-positive cells are able to respond to a directional cue for migration with sustained directional migration. When cultured keratinocytes are exposed to a physiologic DC electric field of 100 mV per mm as a cue to guide migration (galvanotaxis) they migrate toward the cathode with equivalent directionality. The involucrin-positive cells, however, display mean migration speeds approximately one half (23.6 microm per h) of the mean rate achieved by involucrin-negative cells (46.5 microm per h). Despite their decreased migration rates, involucrin-positive cells appear to possess an intact mechanism for sensing a directional signal, transducing that signal, and responding with sustained directional migration. Because electric fields are endogenous in skin wounds, it is likely that both the basal, involucrin-negative cells and the involucrin-positive suprabasilar cells respond to this cue with directional migration. The new observation that involucrin-positive cells can indeed migrate suggests that these cells may also contribute to wound re-epithelialization in vivo.

Epidermal growth factor receptor relocalization and kinase activity are necessary for directional migration of keratinocytes in DC electric fields

Human keratinocytes migrate towards the negative pole in DC electric fields of physiological strength. This directional migration is promoted by epidermal growth factor (EGF). To investigate how EGF and its receptor (EGFR) regulate this directionality, we first examined the effect of protein tyrosine kinase inhibitors, including PD158780, a specific inhibitor for EGFR, on this response. At low concentrations, PD158780 inhibited keratinocyte migration directionality, but not the rate of migration; at higher concentrations, it reduced the migration rate as well. The less specific inhibitors, genistein, lavendustin A and tyrphostin B46, reduced the migration rate, but did not affect migration directionality. These data suggest that inhibition of EGFR kinase activity alone reduces directed motility, and inhibition of multiple tyrosine kinases, including EGFR, reduces the cell migration rate. EGFR redistribution also correlates with directional migration. EGFR concentrated on the cathodal face of the cell as early as 5 minutes after exposure to electric fields. PD158780 abolished EGFR localization to the cathodal face. These data suggest that EGFR kinase activity and redistribution in the plasma membrane are required for the directional migration of keratinocytes in DC electric fields. This study provides the first insights into the mechanisms of directed cell migration in electric fields.

Migration of human keratinocytes in electric fields requires growth factors and extracellular calcium

Currents that leak out of wounds generate electric fields lateral to the wound. These fields induce directional locomotion of human keratinocytes in vitro and may promote wound healing in vivo. We have examined the effects of growth factors and calcium, normally present in culture medium and the wound fluid, on the directional migration of human keratinocytes in culture. In electric fields of physiologic strength (100 mV per mm), keratinocytes migrated directionally towards the cathode at a rate of about 1 microm per min. This directional migration requires several growth factors. In the absence of these growth factors, the cell migration rate decreased but directionality was maintained. Epidermal growth factor alone restored cell migration rates at concentrations as low as 0.2 ng per ml. Insulin at 5-100 microg per ml or bovine pituitary extract at 0.2%-2% vol/vol also stimulated keratinocyte motility but was not sufficient to fully restore the migration rate. Keratinocyte migration in electric fields requires extracellular calcium. Changes in calcium concentrations from 3 microM to 3.3 mM did not significantly change keratinocyte migration rate nor directionality in electric fields; however, addition of the chelator ethyleneglycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid to migration medium reduced, and eventually abolished, keratinocyte motility. Our results show that (i) growth factors and extracellular calcium are required for electric field-induced directional migration of human keratinocytes, and (ii) keratinocytes migrate equally well in low and high calcium media.

Intracellular calcium oscillations in cell populations of ras-transfected I-7 subline of human HaCaT keratinocytes

We have observed oscillations of intracellular Ca2+ (Ca[i]) concentration in populations of ras-transfected HaCaT keratinocytes of I-7 subline. In postconfluent monolayers of I-7 keratinocytes, an increase in extracellular Ca2+ (Ca[o]) concentration to 0.25-0.5 mM induced sinusoidal Ca(i) oscillations, which persisted longer than 1 h with amplitudes of 50-150 nM and periods of 5-10 min. Thapsigargin, which depletes internal Ca2+ stores, did not prevent Ca(o)-induced Ca(i) oscillations, and it also induced Ca(i) oscillations in the ras-transfected I-7 line. Removal of extracellular Ca2+ or addition of Ca2+-entry blocker La3+ or SK&F 96365 inhibited Ca(i) oscillations, suggesting that Ca(i) oscillations in ras-transfected HaCaT keratinocytes were dependent on Ca2+ influx across the plasma membrane. Because the Ca(o)-induced Ca(i) oscillations have been observed only in ras-transfected I-7 subline and not in its nontransfected parental HaCaT line, this may provide a partial explanation for the divergent responses of ras-transfected and nontransfected keratinocytes to Ca(o) signal for control of growth and differentiation.

Thapsigargin induces phosphorylation of the 27-kDa heat shock protein in human keratinocytes

In the human keratinocyte line HaCaT, the nonphosphorylated 27-kDa heat shock protein (HSP27) isoform A (pI 6.5) is constitutively expressed. Application of thapsigargin, which inhibits Ca2+-ATPase in the endoplasmic reticulum, results in the rapid formation of the phosphorylated HSP27 isoform B (pI 6.0) and reduction of HSP27 A without affecting the synthesis of HSP27. The thapsigargin-dependent HSP27 isoform change is similar to that induced by 43 degrees C heat shock, but different from that induced by arsenite, where the biphosphorylated isoform HSP27 C (pI 5.7) is observed. The receptor agonist bradykinin, which increases intracellular Ca2+ (Ca(i)) level, shows no effect on the distribution of HSP27 isoforms. The responses of HSP27 isoforms to thapsigargin are independent of Ca(i) concentration in HaCaT cells. These observations suggest that the thapsigargin-induced change in HSP27 isoforms is dependent on the depletion of internal Ca2+ stores rather than on the increase in Ca(i) concentration. The thapsigargin-induced change in HSP27 isoforms is reduced by the tyrosine kinase inhibitor, genistein, but not the protein kinase C inhibitor, H-7. We propose that the modulation of HSP27 phosphorylation status by Ca(i) homeostasis may be mechanistically linked to control of keratinocyte growth and differentiation and responses of keratinocytes to extracellular stresses.

Imposition of a physiologic DC electric field alters the migratory response of human keratinocytes on extracellular matrix molecules

Outwardly directed ionic currents have been measured leaving skin wounds in vivo. These currents generate physiologic electric fields of approximately 100 mV/mm, which may function to direct keratinocyte migration toward the healing wound. We investigated whether the substrate on which the keratinocyte migrates modulates the galvanotactic response to an electric migratory signal. Cultured human keratinocytes were plated on different matrices; types I and IV collagen, fibronectin, laminin, and tissue culture plastic. The effect of an applied direct current (DC) electric field on directional migration was monitored by time-lapse video microscopy over a 2-h period. Directionality was quantitated by calculating the cosine of the angle of migration in relation to anodal-cathodal orientation. Migration toward the negative pole was observed on all matrices as compared with controls (no applied field), which displayed random migration. No significant increase in directional response occurred when the field strength was increased by 100 mV/mm (physiologic levels) to 400 mV/mm. The degree of directionality and the average net cell translocation however, varied significantly with the substrate. The greatest cathodal migration in response to a DC electric field was observed with keratinocytes plated on types I and IV collagens and plastic. The directional migratory response was least on a laminin substrate, whereas cells on fibronectin demonstrated a response that was intermediate between those of collagen and laminin. These results suggest that physiologic ionic currents in concert with underlying matrix may influence the rate of reepithelialization of skin wounds.

Human keratinocytes migrate to the negative pole in direct current electric fields comparable to those measured in mammalian wounds

Previous measurements of the lateral electric fields near skin wounds in guinea pigs have detected DC fields between 100–200 mV/mm near the edge of the wound. We have studied the translocation response of motile primary human keratinocytes migrating on a collagen substrate while exposed to similar physiological DC electric fields. We find that keratinocytes migrate randomly on collagen in fields of 5 mV/mm or less, but in larger fields they migrate towards the negative pole of the field, exhibiting galvanotaxis. Since these cells have an average cell length of 50 microns, this implies that they are able to detect a voltage gradient as low as 0.5 mV along their length. This cath-odally-directed movement exhibits increased directedness with increasing field strengths between 10 and 100 mV/mm. We observe a maximally directed response at 100 mV/mm with half of the cells responding to the field within 14 minutes. The average speed of migration tended to be greater in fields above 50 mV/mm than in smaller fields. We conclude that human keratinocytes migrate towards the negative pole in DC electric fields that are of the same magnitude as measured in vivo near wounds in mammalian skin.

Increased expression of a high molecular weight (130 KD) protein kinase C isoform in a differentiation-defective ras-transfected keratinocyte line

The role of ras on protein kinase C (PKC) signaling was examined in two keratinocyte cell lines. Increasing the level of extracellular calcium from 0.15 mM to 1.0 mM induces some features of differentiation in the spontaneously immortalized HaCaT line, but fails to do so in a c-H-ras-transfected subline (ras-HaCaT). Raising extracellular calcium also induced a transient increase in membrane-associated PKC activity 5 min after calcium addition, in HaCaT, but not in the ras-HaCaT cells. Partial purification of PKC from the membrane/particulate fraction revealed the major isoform expressed in HaCaT to be an 80 KD species recognized by the anti-PKC alpha antibody. In ras-HaCaT, the major expressed isoform is a 130 KD species recognized by the PKC beta antibody. The kinase activity of the partially purified high molecular weight PKC is phospholipid dependent but calcium independent. Further evaluation of PKC in the HaCaT and ras-HaCaT membrane/particulate cell fraction by immunoblotting using affinity-purified antibodies against PKC alpha, beta, delta, epsilon and zeta revealed a 130 KD band reacting with the PKC delta antibody. Increased expression of this high molecular weight protein was observed in ras-HaCaT. Immunoprecipitation of PKC in ras-HaCaT using the PKC delta antibody also revealed a 130 KD species. Analysis of the PKC delta immunoprecipitate demonstrated a phospholipid, but not calcium-dependent kinase which autophosphorylated. These results suggest that the 130 KD protein may be a novel (calcium-independent) PKC (nPKC) isoform and increased expression in the ras-transfected HaCaT may be a consequence of oncogenic ras expression. This 130 KD species may also play a role in the ras-associated inhibition of differentiation in HaCaT.

Amiloride blocks a keratinocyte nonspecific cation channel and inhibits Ca(++)-induced keratinocyte differentiation

Proliferation and differentiation in many cells are linked to specific changes in transmembrane ion fluxes. Previously, we have identified a nonspecific cation channel in keratinocytes, which is permeable to and activated by Ca++. To test whether this cation channel might serve as a pathway for Ca++ entry, we examined the effect of blocking this channel on membrane currents, markers of differentiation, and intracellular Ca++. In patch clamp studies, 10(-8) to 10(-6) M amiloride decreased the single-channel open probability. The same concentrations of amiloride inhibited the calcium-induced formation of cornified envelopes and activity of transglutaminase in a dose-dependent fashion. Amiloride inhibited the long-term rise of intracellular Ca++ induced by raised extracellular Ca++, without blocking the initial increase of intracellular Ca++. Amiloride at concentrations of 10(-7) to 10(-3) M did not change the resting intracellular pH of keratinocytes, although concentrations of 10(-6) M or greater inhibited the recovery from NH4(+)-induced acidification. To test whether the effect of amiloride was toxic, we measured DNA synthesis in the presence or absence of amiloride. DNA synthesis was unchanged, suggesting that amiloride's actions were not due to toxic effects. Although the exact mechanisms of amiloride's action remains to be determined, these experiments suggest that this compound may inhibit keratinocyte differentiation by blocking the nonspecific cation channel.

Immunolocalization of low-molecular-weight stress protein HSP 27 in normal skin and common cutaneous lesions

Stress proteins, which are found ubiquitously in mammalian cells, appear to be implicated in the regulation of cell growth and protection from environmental insult. Although we previously demonstrated the expression of low-molecular-weight stress protein, HSP 27, in cultured keratinocytes, HSP 27 has not yet been identified in human skin. Using standard immunohistochemistry on routinely processed paraffin sections, we examined specimens of common epidermal lesions and normal skin with a monoclonal antibody to HSP 27. Normal skin from the breast, foreskin, and lower extremity demonstrated strong cytoplasmic staining in the suprabasal epidermis. There was no change in the intensity of staining or cellular localization related to age, body location, or gender. Sections of actinic keratosis, superficial basal cell carcinoma, seborrheic keratosis, and psoriasis also exhibited strong cytoplasmic staining in the suprabasal layers of the epidermis. In contrast, cutaneous squamous cell carcinoma demonstrated only weak cytoplasmic staining throughout the infiltrating tumor. This is of particular interest, since other investigators have reported a loss of HSP 27 expression in oncogenically transformed cells that exhibit a tumorigenic phenotype. To our knowledge, this study provides the first demonstration of HSP 27 expression in human skin.

Dynamic changes in intracellular localization and isoforms of the 27-kD stress protein in human keratinocytes

We have begun to characterize the low molecular weight, 27-kD heat shock or stress protein (HSP27) in normal keratinocytes and in HaCaT, a spontaneously transformed keratinocyte line. The presence and location of HSP27 was determined by indirect immunofluorescence on fixed whole cells and immunoblot analysis of cytosolic, membrane, nuclear, and cytoskeletal cell fractions. HSP27 is localized throughout the cytoplasm of cells at 37 degrees C. After heating at 42 degrees C, there is a rapid (within 10 min) increase in nuclear HSP27. Two-dimensional gel analysis of whole cell HaCaT lysates identified multiple isoforms of HSP27 with different isoelectric points. The function of HSP27 is largely unknown but its presence throughout the cytoplasm of cells at 37 degrees C, its translocation to the nucleus after cellular stress, and the presence of multiple isoforms suggest a biologic role in both stressed and unstressed human keratinocytes.

Properties of enzymes hydrating epoxides in human epidermis and liver

1. Cytosolic and microsomal epoxide hydrolyzing enzymes of human skin and liver were compared and found to be different. 2. Epidermal and hepatic cytosolic epoxide hydrolases were different in terms of substrate selectivity, pI, inhibitor sensitivity and affinity chromatographic properties. 3. Microsomal epoxide hydrolases had the same pIs but different substrate selectivities. 4. Cytosolic epoxide hydrolase from adults had higher specific activity than that from neonates or cultured epidermis, but lower activity than adult hepatic enzymes. 5. The sizes of cytosolic epoxide hydrolase from epidermis and liver were similar and lower than that from cultured fibroblasts. 6. Cytosolic epoxide hydrolase from all sources shared similar antigenic determinants.

Focal dermal hypoplasia: four cases with widely varying presentations

We describe four patients with focal dermal hypoplasia (FDH): a girl with classic FDH, a boy with cutaneous findings, an infant with severe multisystem disease, and the infant's mother, who had previously undiagnosed FDH. These patients illustrate the classic cutaneous manifestations of FDH and the variations that can exist within a family.

Ion channels are linked to differentiation in keratinocytes

In vivo and in vitro, keratinocyte differentiation is linked with increased extracellular Ca2+. In order to correlate ion channels with cell differentiation and investigate keratinocyte membrane responses to Ca2+, keratinocyte single channel currents were studied using the patch-clamp technique. The most frequently observed channel was a 14 pS nonspecific cation channel. This channel was permeable to Ca2+ and activated by physiological concentrations of Ca2+. We also found a 35 pS Cl- channel whose open probability increased with depolarization. Finally, a 70 pS K+ channel was seen only in cell-attached or nystatin-permeabilized patches. We correlated channel types with staining for involucrin, an early marker of keratinocyte differentiation. While the nonspecific cation channel and Cl- channel were seen in both involucrin positive and involucrin negative cells, all channels in which the K+ channel activity was present were involucrin positive. Membrane currents through these channels may be one pathway by which signals for keratinocyte proliferation or differentiation are sent.

Low-energy helium neon laser irradiation does not alter human keratinocyte differentiation

There are reports that low-energy HeNe irradiation can enhance wound healing in vivo. We have previously demonstrated that HeNe irradiation increases the motility of human epidermally derived keratinocytes in vitro. Here we investigate whether HeNe irradiation alters normal keratinocyte differentiation, which is essential for the formation of a normal, functioning epidermis. Subconfluent keratinocyte cultures were irradiated three times within 24 h with either 0, 0.8, 3, or 7.2 J/cm2. After cultures reached post-confluence, parameters of growth and differentiation, such as cell number, cornified envelope (CE) formation, and transglutaminase activity were measured. No significant differences were found between the control (0 J) and irradiated cultures in these assays. We also examined the pattern of newly synthesized keratins in cultures irradiated with 7.2 J/cm2 three times within a 24-h period. Both control and irradiated cultures exhibited similar keratin patterns. These results provide evidence that HeNe irradiations of up to 7.2 J/cm2 have no direct deleterious effect on normal keratinocyte differentiation needed for the formation of a functional epidermis. Hence, it is anticipated that the clinical use of the HeNe laser irradiance that enhances keratinocyte migration in vitro (0.8 J/cm2) to promote wound healing in vivo will not alter the ultimate integrity or differentiated function of the epidermis that migrates to cover the wounded area.

Dyskeratosis congenita associated with elevated fetal hemoglobin, X-linked ocular albinism, and juvenile-onset diabetes mellitus

An 11-year-old boy had dyskeratosis congenita, elevated fetal hemoglobin level, X-linked ocular albinism, and juvenile-onset diabetes mellitus. A review of the international literature revealed that elevated fetal hemoglobin has been noted in 15 reported cases of dyskeratosis congenita. It is a previously unrecognized, commonly associated finding in dyskeratosis congenita that may provide insight into the location and function of the gene for dyskeratosis congenita.