ELECTRONIC ARTICLE |









* Department of Pediatrics
|| Nephrology and Dialysis
¶ Pathology, Kitano Hospital, Tazuke Kofukai Medical Institute, Osaka, Japan
Departments of Pediatrics
Pathology, Kishiwada City Hospital, Kishiwada, Osaka, Japan
# Department of Dermatology, Hirosaki University School of Medicine, Hirosaki, Japan
** Department of Dermatology and Cutaneous Biology, Thomas Jefferson University, Philadelphia, Pennsylvania

Department of Pathology, Institute of Clinical Medicine, University of Tsukuba, Tsukuba, Japan
Division of Cell Biology, Kihara Institute for Biological Research, Yokohama City University, Yokohama, Japan
| ABSTRACT |
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Key Words: Herlitz junctional epidermolysis bullosa laminin-5 nephrotic syndrome proteinuria glomerular basement membrane
Abbreviations: H-JEB, Herlitz junctional epidermolysis bullosa PTC, premature termination codon GBM, glomerular basement membrane TBM, tubular basement membrane NAG, N-acetylglucosaminidase mAb, monoclonal antibody PCR, polymerase chain reaction
Junctional epidermolysis bullosa is a group of autosomal recessive diseases characterized by profound skin fragility, with blister formation resulting from dermal-epidermal disadhesion at the level of the lamina lucida within the basement membrane zone. The most severe form, Herlitz junctional epidermolysis bullosa (H-JEB), manifests with generalized blistering and erosions of the skin, with extracutaneous involvement, and is usually lethal during the first 1 year of life.1
Immunohistochemical and molecular genetic studies have demonstrated that the underlying cause of H-JEB is absent expression of laminin-5, a component of anchoring filaments traversing the lamina lucida of the dermal-epidermal basement membrane zone. A characteristic genetic lesion is a premature termination codon (PTC)-causing mutation in both alleles of 1 of the 3 genes (LAMA3, LAMB3, and LAMC2) encoding the subunit polypeptides of laminin-5 (ie, the
3, ß3, and
2 chains, respectively). Because all 3 chains are necessary for the structural assembly of trimeric laminin-5 macromolecules, defects in any of the 3 genes can result in complete absence of laminin-5.2,3 Laminin-5 is expressed in multiple tissues, including the skin and the respiratory and gastrointestinal tracts,2 and its absence in tissues other than skin accounts for the repertoire of extracutaneous manifestations.
Laminins are heterotrimeric extracellular matrix proteins that are composed of
, ß, and
chains. At least 15 isoforms are assembled from 5
, 3 ß, and 3
chains.4 In the kidney, laminin-11 (
5ß2
1) and laminin-1 (
1ß1
1)/laminin-10 (
5ß1
1) are the major laminin components of the glomerular basement membrane (GBM) and the renal tubular basement membrane (TBM), respectively.5 Findings for laminin ß2-null mice showing lethal congenital nephrotic syndrome suggested that laminin-11, which includes the laminin ß2 chain, plays an important role in glomerular function.6 Although a few studies have shown that laminin-5 is also expressed in the murine,7 rat,8 and human911 kidney, the functional importance of laminin-5 in the kidney is unknown.
In this article, we describe an infant with H-JEB complicated by nephrotic syndrome, compositional changes in laminin isoforms of the GBM, and no detectable laminin-5 protein in the renal TBM. This case suggests that laminin-5 may play an important role in renal function and that, in addition to the protein loss from denuded skin and mucous surfaces, massive proteinuria, a previously unreported complication of H-JEB, may contribute to the high mortality rate for H-JEB in early postnatal life.
| CASE REPORT |
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At the time of admission, extensive denudation and erosion were present on the patients occiput, back, buttocks, and extremities, with erosions of the oral mucosa. The fingernails and toenails were absent. Blood examination showed leukocytosis (11500 cells per mm3 [11.5 x 109 cells per L]), anemia (hemoglobin: 8.6 g/dL [86 g/L]), positive C-reactive protein results (12.1 mg/dL [0.121 g/L]), and hypoalbuminemia (2.6 g/dL [26 g/L]). Blood culture results were negative. The patient was wrapped in silicon gauze impregnated with hydrated petrolatum, dimethylisopropylazulene, or topical antibiotics when necessary and was reared in a temperature- and humidity-controlled unit. He received intravenous hyperalimentation and repeated intravenous albumin transfusions. On the 11th hospital day, intravenous antibiotic therapy was started because of suspected sepsis. Despite repeated intravenous albumin transfusions and gradually healing skin lesions, hypoalbuminemia (2.5 g/dL [25 g/L] on the 13th hospital day) persisted, which suggested significant protein loss from sites other than the denuded skin. Subsequently, urinalysis showed massive albuminuria of 2.1 g/d, a high level of ß2-microglobulin (104 mg/L [0.104 g/L]; normal range: <0.5 mg/L [<0.5 x 103 g/L]), and a high level of ß-N-acetylglucosaminidase (NAG) (38.4 IU/L; normal range: <7 IU/L), suggesting renal glomerular and tubular involvement. Despite the repeated albumin transfusions, hypoalbuminemia progressed (1.1 g/dL [11 g/L]) and massive proteinuria continued (albuminuria: 18.9 g/d; urinary NAG level: 99.3 IU/L) on the 21st hospital day. Throughout his hospitalization, the patient remained critically ill, with persistent suspected sepsis, disseminated intravascular coagulation, severe anemia, electrolyte imbalance, and severe hypoproteinemia. The clinical condition continued to deteriorate, and the patient died on the 25th hospital day.
Light-microscopic examination of a skin biopsy specimen taken from a newly developed blister on the dorsum of the right foot demonstrated a split at the dermal-epidermal junction, without associated inflammatory cell infiltrates. Electron-microscopic examination showed subepidermal cleft formation arising within the lamina lucida, as well as hemidesmosomal hypoplasia (Fig 1).
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2 chains was examined through immunostaining with specific monoclonal antibodies (mAbs) (Fig 5). Although these chains were clearly localized to the TBM in the control specimen (Fig 5, c and e), they were completely absent in the patients kidney (Fig 5, d and f), which confirmed the lack of laminin-5 expression at the tissue level. Expression of the laminin
3 chain was also examined through immunostaining with a specific mAb (Fig 5, a and b). Interestingly, the control kidney stained positively for the
3 chain in Bowmans capsule (Fig 5a), whereas staining in the GBM was apparent in the patients kidney (Fig 5b). Because the laminin
3 chain is the subunit polypeptide not only of laminin-5 but also of laminin-6 and laminin-7, expression of the
3 chain in the GBM of the patients kidney might indicate the expression of laminin-6 or laminin-7 or the presence of an unreported novel laminin.
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5 chain, a subunit polypeptide of laminin-11, the major laminin component of the GBM, was examined through immunostaining with a mAb specific for this chain (Fig 5, g and h). Expression of the laminin
5 chain was lower in the GBM of the patients kidney than in the control kidney, which suggests that the defect in laminin-5 might lead to compositional changes in the GBM by altering the expression of laminin-11, which is essential for the structure of the GBM. | METHODS |
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Materials
Renal tissue was obtained from the patient at autopsy and was used with the informed consent of the parents. The renal tissue was fixed in 20% buffered formalin and embedded in paraffin. Sections (4 µm) cut from the paraffin-embedded tissue were used for immunohistochemical detection of the laminin
2 and
5 chains. For immunohistochemical detection of the laminin
3 and ß3 chain epitopes, fresh renal tissue was snap-frozen in OCT compound (embedding medium; Sakura Finetek, Tokyo, Japan) and stored at 80°C until use. Renal tissue from a 1-year-old male subject was prepared in a parallel manner and used as a control specimen.
Antibodies
The following mAbs were used in this study: mAb to the laminin
3 chain (P3H9) (Chemicon, Temecula, CA), mAb to the laminin ß3 chain (29E), mAb to the laminin
2 chain (D4B5), and mAb to the laminin
5 chain (4C7) (Life Technologies, Gaithersburg, MD). The mAbs 29E and D4B5 were raised against purified human laminin-5 and human recombinant laminin
2 chain (amino acid residues 382608), respectively, in our laboratory.10,14
Immunohistochemical Analyses
For immunohistochemical analyses, the paraffin sections were deparaffinized, rehydrated, immersed in 0.3% hydrogen peroxide-containing methanol for inactivation of intrinsic peroxidase, and treated with protease XXIV (Sigma, St Louis, MO) for 20 minutes at room temperature. The frozen sections were immersed in 0.3% hydrogen peroxide-containing methanol and treated with protease XXIV for 5 minutes. The paraffin sections were incubated with the anti-
2 mAb (D4B5) or the anti-
5 mAb (4C7) at 4°C overnight, whereas frozen sections were incubated with anti-
3 mAb (P3H9) or anti-ß3 mAb (29E) for 20 to 30 minutes at room temperature. The labeled antigen was detected with a HistoFine kit (Nichirei Pharmaceutical, Tokyo, Japan) and observed through the 3,3-diaminobenzidine reaction. Other experimental conditions were as described previously.15
| RESULTS AND DISCUSSION |
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1 chains are found in all nephron basement membranes. At the capillary loop stage, laminin ß2 chain begins to accumulate in the developing GBM; as the GBM matures, laminin ß1 is eliminated gradually. Through these developmental transitions of laminin isoforms, laminin-11 (
5ß2
1) becomes the major laminin of the mature GBM, whereas laminin-1 (
1ß1
1) and laminin-10 (
5ß1
1) become the major laminins found in the mature TBM. Interestingly, some studies showed that laminin-5 is expressed in fetal and newborn mouse kidney,7 as well as human fetal9,10 and neonatal11 kidney, but not in human adult kidney.9 However, the function of laminin-5 in the kidney is unknown.
For the infant with H-JEB, we demonstrated that laminin-5 was completely absent in the TBM, apparently because of the LAMB3 mutations 2379delG and Q995X, in contrast to the apparent expression in the TBM of the control kidney. The laminin
3 chain was also expressed aberrantly in the GBM, compared with expression in Bowmans capsule in the control kidney. Moreover, we demonstrated diminished expression of the
5 chain of laminin-11 in the GBM, compared with the control kidney. Our immunohistopathologic findings depicting the altered expression of laminin
chains in the GBM and the lack of laminin-5 in the TBM of the patients kidney may account for the massive albuminuria attributable to failure of the glomerular filtration barrier and the extraordinarily high urinary levels of NAG, indicating renal tubular involvement, respectively. We were unable to detect laminin-5 in the GBM of normal kidney, likely because of the restricted expression in the fetal kidney, as reported previously.9 We speculate that the laminin-5 defect in fetal nephrogenesis might influence the complex developmental transitions of laminin isoforms in the GBM. It is well established that a deficiency of the laminin
2 chain is accompanied by compensatory upregulation of the laminin
4 chain in mouse skeletal muscle cells17 and a deficiency of the laminin
5 chain causes a striking defect in mouse glomerulogenesis.18 In addition, it has been shown that laminin ß2-null mice exhibit a severe nephrotic syndrome in the first postnatal week; although the GBM appears ultrastructurally normal and, at a molecular level, laminin ß1 substitutes for ß2 in the GBM, the ß1 subunit seems to be functionally inadequate.6 The findings for the ß2-null mice are consistent with our present findings, which suggest that compositional changes in laminin isoforms in the GBM can result in failure of the glomerular filtration barrier. It was reported recently that human laminin ß2 deficiency causes congenital nephrosis with mesangial sclerosis and distinct eye abnormalities.19 Our report is the second case study demonstrating that a defect in a laminin subunit causes dysfunction of human renal basement membranes. It is probable that massive proteinuria among patients with H-JEB has been overlooked, although the possibility that the massive proteinuria for our patient is an unusual presentation of H-JEB has not been excluded completely. Collection of urine samples with urine collection bags is almost impossible, because the bag attachment would hurt the fragile skin. We used soft gauze for collection of urine samples. The histomorphologic findings for our patients kidney seem more serious than those observed for the kidneys of laminin ß2-null mice or human patients with laminin ß2 deficiency, which might result from the additional effects of many infectious, metabolic, and/or pharmacologic insults on the fragile GBM of our patient.
The importance of GBM composition for glomerular function is also illustrated by Alports syndrome, a human hereditary glomerular nephritis in which a mutation in the collagen
3,
4, or
5 chain gene leads to progressively altered glomerular function. It has been shown that type IV collagen isolated from human Alports syndrome kidney containing
1 and
2 chains is more susceptible to endoproteolysis than type IV collagen isolated from normal kidney containing
1 to
6 chains. This observation suggests that the Alports syndrome GBM could be more vulnerable to deterioration than the normal GBM.20 It is likely that the GBM in H-JEB could also be more susceptible to many insults to the patient, such as sepsis, disseminated intravascular coagulation, anemia, malnutrition, hypoxia, and antibiotics, compared with that of normal kidney. Throughout the patients clinical course, blood urea nitrogen and creatinine levels, as well as creatinine clearance, remained at normal levels despite massive albuminuria. It is of interest to note that compositional changes in laminin isoforms and collagen isoforms in the GBM cause different types of nephropathy (ie, nephrosis and nephritis, respectively), but the precise mechanisms remain to be explored. Studies of mutant mice that genetically lack laminin-5 could elucidate the underlying mechanism.21
Proteinuria and mild hypoalbuminemia (not in the nephrotic range), secondary to focal segmental glomerulosclerosis, have been reported in epidermolysis bullosa with pyloric atresia, an autosomal recessive disease caused by mutations in the genes encoding either 1 of the 2 subunits of
6ß4 integrin, which are expressed in the hemidesmosomes of a variety of epithelial tissues, including human skin and the gastrointestinal tract.22 In the case of epidermolysis bullosa with pyloric atresia, reduced ß4 integrin expression was demonstrated in glomerular podocytes.22 The finding that
6ß4 integrin functions as a receptor for laminin-523 supports the functional importance of laminin-5 in human kidney. It has been shown that both laminin-5 and laminin-binding integrins play a role in kidney development and ureteric bud branching morphogenesis in embryonic rats.24
From the therapeutic point of view, the observations for our patient strongly suggest that H-JEB should be considered not only a hereditary skin disease but also one of the congenital nephrotic syndromes. Currently, H-JEB among affected infants is invariably lethal within the first 1 year of life. A potential approach for treatment may be combination therapy with meticulous skin care and the treatment protocol proposed for infants with congenital nephritic syndromes, ie, massive intravenous albumin supplementation and nutritional support (to make normal growth and development possible), followed by bilateral nephrectomy and peritoneal dialysis (to stop protein loss from the kidney) and finally by renal transplantation. Because keratinocyte gene therapy for H-JEB is now under investigation,25,26 combination therapy with gene therapy for skin lesions and the aforementioned treatment protocol for congenital nephrotic syndromes might be worth investigating for H-JEB in the near future.
| ACKNOWLEDGMENTS |
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| FOOTNOTES |
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Address correspondence to Daisuke Hata, MD, Department of Pediatrics, Kitano Hospital, Tazuke Kofukai Medical Institute, 2-4-20 Ohgimachi, Kita-ku, Osaka, 5308480, Japan. E-mail: d-hata{at}kitano-hp.or.jp
Drs Hata and Miyazaki contributed equally to this work.
No conflict of interest declared.
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