Cutis Laxa Patients Research Articles

In vivo skin biophysical behaviour and surface topography as a function of ageing

Normal skin ageing is characterised by an alteration of the underlying connective tissue with measurable consequences on global skin biophysical properties. The cutis laxa syndrome, a rare genetic disorder, is considered as an accelerated ageing process since patients appear prematurely aged due to alterations of dermal elastic fibres. In the present study, we compared the topography and the biomechanical parameters of normal aged skin with an 17 year old cutis laxa patient. Skin topography analyses were conducted on normal skin at different ages. The results indicate that the skin relief highly changes as a function of ageing. The cutaneous lines change from a relatively isotropic orientation to a highly anisotropic orientation. This reorganisation of the skin relief during the ageing process might be due to a modification of the skin mechanical properties, and particularly to a modification of the dermis mechanical properties. A specific bio-tribometer, based on the indentationtechnique under light load, has been developed to study the biophysical properties of the human skin in vivo through two main parameters: the physico-chemical properties of the skin surface, by measuring the maximum adhesion force between the skin and the bio-tribometer; and the bulk mechanical properties. Our results show that the pull-off force between the skin and the biotribometer as well as the skin Young's modulus decrease with age. In the case of the young cutis laxa patient, the results obtained were similar to those observed for aged individuals. These results are very interesting and encouraging since they would allow the monitoring of the cutis laxa skin in a standardised and non-invasive way to better characterize either the evolution of the disease or the benefit of a treatment.

Mutations in LTBP4 Cause a Syndrome of Impaired Pulmonary, Gastrointestinal, Genitourinary, Musculoskeletal, and Dermal Development

We report recessive mutations in the gene for the latent transforming growth factor-beta binding protein 4 (LTBP4) in four unrelated patients with a human syndrome disrupting pulmonary, gastrointestinal, urinary, musculoskeletal, craniofacial, and dermal development. All patients had severe respiratory distress, with cystic and atelectatic changes in the lungs complicated by tracheomalacia and diaphragmatic hernia. Three of the four patients died of respiratory failure. Cardiovascular lesions were mild, limited to pulmonary artery stenosis and patent foramen ovale. Gastrointestinal malformations included diverticulosis, enlargement, tortuosity, and stenosis at various levels of the intestinal tract. The urinary tract was affected by diverticulosis and hydronephrosis. Joint laxity and low muscle tone contributed to musculoskeletal problems compounded by postnatal growth delay. Craniofacial features included microretrognathia, flat midface, receding forehead, and wide fontanelles. All patients had cutis laxa. Four of the five identified LTBP4 mutations led to premature termination of translation and destabilization of the LTBP4 mRNA. Impaired synthesis and lack of deposition of LTBP4 into the extracellular matrix (ECM) caused increased transforming growth factor-beta (TGF-beta) activity in cultured fibroblasts and defective elastic fiber assembly in all tissues affected by the disease. These molecular defects were associated with blocked alveolarization and airway collapse in the lung. Our results show that coupling of TGF-beta signaling and ECM assembly is essential for proper development and is achieved in multiple human organ systems by multifunctional proteins such as LTBP4.

Autosomal recessive cutis laxa syndrome revisited

The clinical spectrum of the autosomal recessive cutis laxa syndromes is highly heterogeneous with respect to organ involvement and severity. One of the major diagnostic criteria is to detect abnormal elastin fibers. In several other clinically similar autosomal recessive syndromes, however, the classic histological anomalies are absent, and the definite diagnosis remains uncertain. In cutis laxa patients mutations have been demonstrated in elastin or fibulin genes, but in the majority of patients the underlying genetic etiology remains unknown. Recently, we found mutations in the ATP6V0A2 gene in families with autosomal recessive cutis laxa. This genetic defect is associated with abnormal glycosylation leading to a distinct combined disorder of the biosynthesis of N- and O-linked glycans. Interestingly, similar mutations have been found in patients with wrinkly skin syndrome, without the presence of severe skin symptoms of elastin deficiency. These findings suggest that the cutis laxa and wrinkly skin syndromes are phenotypic variants of the same disorder. Interestingly many phenotypically similar patients carry no mutations in the ATP6V0A2 gene. The variable presence of protein glycosylation abnormalities in the diverse clinical forms of the wrinkled skin-cutis laxa syndrome spectrum necessitates revisiting the diagnostic criteria to be able to offer adequate prognosis assessment and counseling. This paper aims at describing the spectrum of clinical features of the various forms of autosomal recessive cutis laxa syndromes. Based on the recently unraveled novel genetic entity we also review the genetic aspects in cutis laxa syndromes including genotype-phenotype correlations and suggest a practical diagnostic approach.

A p.C217R Mutation in Fibulin-5 from Cutis Laxa Patients Is Associated with Incomplete Extracellular Matrix Formation in a Skin Equivalent Model

Cutis laxa (CL) is a rare genodermatosis, which is clinically and genetically heterogeneous. It is characterized by redundant, loose, sagging, and inelastic skin. In a consanguineous family from Lebanon with autosomal-recessive transmission, we identified a homozygous missense mutation (c.649T --> C; p.C217R) in the fibulin-5 gene (FBLN5), which was, to our knowledge, previously unreported. Small skin biopsies were performed, which permitted isolation of skin fibroblasts harboring this FBLN5 mutation; they exhibited a deficit in cell growth. A CL skin equivalent (CL-SE) model compared with control SE was successfully developed to define the behavior of CL fibroblasts in a three-dimensional model. There was increased cell death and a global extracellular matrix deficiency in the dermis of this CL-SE model, and a low level of the main elastic fiber expression. There was no basement membrane evident at the ultrastructural level, and type-VII collagen could not be detected at the histological level. This model reproduced some defects of the extracellular matrix and highlighted other defects, which occurred at the time of the basement membrane formation, which were not evident in skin from patients. This CL-SE model could be adapted to screen for therapeutically active molecules.

Fibulin-5 mutations: mechanisms of impaired elastic fiber formation in recessive cutis laxa

To elucidate the molecular mechanisms of impaired elastic fiber formation in recessive cutis laxa, we have investigated two disease-causing missense substitutions in fibulin-5, C217R and S227P. Pulse-chase immunoprecipitation experiments indicated that S227P mutant fibulin-5 was synthesized and secreted by skin fibroblasts at a reduced rate when compared with the wild-type protein. Both mutants failed to be incorporated into elastic fibers by transfected rat lung fibroblasts. Purified recombinant fibulin-5 with either mutation showed reduced affinity for tropoelastin in solid-phase binding assays. Furthermore, S227P mutant fibulin-5 also showed impaired association with fibrillin-1 microfibrils. The same mutation triggered an endoplasmic reticulum (ER) stress response, as indicated by the strong co-localization of this mutant protein with folding chaperones in the ER, including calreticulin, immunoglobulin-binding protein and protein disulfide isomerase, and by increased rates of apoptosis in patient fibroblasts. Histological analysis of skin sections from a cutis laxa patient with a homozygous S227P mutation showed a lack of fibulin-5 in the extracellular matrix and a concomitant disorganization of dermal elastic fibers. By electron microscopy, elastic fibers in the skin of this patient showed a failure of elastin globules to fuse into a continuous elastic fiber core. We conclude that recessive cutis laxa mutations in fibulin-5 result in misfolding, decreased secretion and a reduced interaction with elastin and fibrillin-1 leading to impaired elastic fiber development. These findings support the hypothesis that fibulin-5 is necessary for elastic fiber formation by facilitating the deposition of elastin onto a microfibrillar scaffold via direct molecular interactions.

A combined defect in the biosynthesis of N- and O-glycans in patients with cutis laxa and neurological involvement: the biochemical characteristics

Based on our preliminary observation of abnormal glycosylation in a cutis laxa patient, nine cutis laxa patients were analyzed for congenital defects of glycosylation (CDG). Isoelectric focusing of plasma transferrin and apolipoproteinC-III showed that three out of nine patients had a defect in the biosynthesis of N-glycans and core 1 mucin type O-glycans, respectively. Mass spectrometric N-glycan analyses revealed a relative increase of glycans lacking sialic acid and glycans lacking sialic acid and galactose residues. Mutation analysis of the fibulin-5 gene (FBLN5), which has been reported in cases of autosomal recessive cutis laxa, revealed no mutations in the patients' DNA. Evidence is presented that extracellular matrix (ECM) proteins of skin are likely to be highly glycosylated with N- and/or mucin type O-glycans by using algorithms for predicting glycosylation. The conclusions in this study were that the clinical phenotype of autosomal recessive cutis laxa seen in three patients is not caused by mutations in the FBLN5 gene. Our findings define a novel form of CDG with cutis laxa and neurological involvement due to a defect in the sialylation and/or galactosylation of N- and O-glycans. Improper glycosylation of ECM proteins of skin may form the pathophysiological basis for the cutis laxa phenotype.

Plasma zinc and copper in primary and secondary immunodeficiency disorders

Plasma copper and zinc concentrations were measured in 58 patients with a laboratory-confirmed primary or secondary immunodeficiency. Patients with severe combined immunodeficiency, collagen vascular disease with depressed cell-mediated immunity, and acquired or congenital acrodermatitis enteropathica had mean plasma zinc concentrations substantially below the lower limit of normal. In contrast, patients with primary humoral and polymorphonuclear leukocyte defects had normal plasma zinc concentrations. Patients with primary polymorphonuclear leukocyte defects had a mean plasma copper concentration substantially above the upper limit of normal. Those subjects with primary humoral immunity defects also had significantly elevated plasma copper concentrations in comparison to controls. Plasma copper concentrations in patients with severe combined immunodeficiency or acrodermatitis enteropathica were normal. Cutis laxa patients had low plasma zinc and copper concentrations. These data demonstrate that zinc and copper homeostasis are altered in come immunodeficiency disorders and may be important factors in host defenses. Since it is known that cellular immunity is impaired by zinc deficiency, patients with primary and secondary immunodeficiency states with appropriately documented mild or severe zinc deficiency should receive zinc supplements.