Influence of antenatal steroids and sex on maturation of the epidermal barrier in the preterm infant

Low-dose antenatal betamethasone treatment achieves preterm lung maturation equivalent to that of the World Health Organization dexamethasone regimen but with reduced endocrine disruption in a sheep model of pregnancy

BACKGROUND

The intramuscular administration of antenatal steroids to women at risk of preterm delivery achieves high maternal and fetal plasma steroid concentrations, which are associated with adverse effects and may reduce treatment efficacy. We have demonstrated that antenatal steroid efficacy is independent of peak maternofetal steroid levels once exposure is maintained above a low threshold.

OBJECTIVE

This study aimed to test, using a sheep model of pregnancy, whether the low-dose antenatal steroid regimen proposed as part of the Antenatal Corticosteroids for Improving Outcomes in Preterm Newborns trial would achieve preterm lung maturation equivalent to that of the existing World Health Organization dexamethasone treatment regimen, but with reduced risk of adverse outcomes.

STUDY DESIGN

Following ethical review and approval, date-mated ewes with single fetuses received intramuscular injections of either (1) four 6-mg maternal intramuscular injections of dexamethasone phosphate every 12 hours (n=22), (2) 4 2-mg maternal intramuscular injections of betamethasone phosphate every 12 hours (n=21), or (3) 4 2-mL maternal intramuscular injections of saline every 12 hours (n=16). Of note, 48 hours after first injection, (124±1 day), lambs were delivered, ventilated for 30 minutes, and euthanized for sampling. Arterial blood gas, respiratory, hematological, and biochemical data were analyzed for between-group differences with analysis of variance according to distribution and variance, with P<.05 taken as significant.

RESULTS

After 30 minutes of ventilation, lambs from both steroid-treated groups had significant and equivalent improvements in lung function relative to saline control (P<.05). There was no significant difference in arterial blood pH, pO₂, pCO₂, lung compliance, ventilator efficiency index, or lung volume at necropsy with a static pressure of 40 cmH₂O. The messenger RNA expression of surfactant protein (Sp)a, Spb, Spc, Spd, aquaporin (Aqp)1, Aqp5, and sodium channel epithelial 1 subunit beta (Scnn1b) was equivalent between both steroid groups. Maternal and fetal plasma neutrophil, glucose, and fetal plasma C-peptide levels were significantly elevated in the dexamethasone group, relative to the betamethasone group. Fetal plasma insulin-like growth factor 1 was significantly reduced in the dexamethasone group compared with the betamethasone group (P<0.05). Fetal adrenocorticotropic hormone (r=0.53), maternal glucose value (r=-0.52), and fetal glucose values (r=-0.42) were correlated with maternal weight in the betamethasone group (P<.05), whereas fetal pCO₂ and pO₂ were not correlated. There was no significant difference between male and female lamb outcomes in any groups for any of the items evaluated.

CONCLUSION

This study reported that in preterm lambs, a low-dose treatment regimen of 8 mg betamethasone achieves lung maturation equivalent to that of a 24-mg dexamethasone-based regimen, but with smaller perturbations to the maternofetal hypothalamic-pituitary-adrenal axis. These data suggested that given steroid pharmacokinetic differences between sheep and humans, a betamethasone dose of 2 mg may remain above the minimum dose necessary for robust maturation of the preterm lung. Maternal weight-adjusted betamethasone doses might also be a key to reducing perturbations to the maternofetal hypothalamic-pituitary-adrenal axis.

The effects of antenatal glucocorticoid exposure on fetal and neonatal skin maturation

AIMS

The use of antenatal glucocorticoids in women with preterm labor has dramatically improved outcomes for premature infants. The most commonly used antenatal glucocorticoids are betamethasone and dexamethasone. Glucocorticoids accelerate fetal lung growth by several mechanisms, including the maturation of type II pneumocytes enabling surfactant production. Furthermore, the lipids in the lung share similarity with those in the skin. Therefore, antenatal administration of glucocorticoids may have effects on the structure and function of the developing epidermal barrier in fetuses and neonates.

METHODS

We performed a systematic review to characterize these effects, identifying 11 studies (six animal and five human studies).

RESULTS

Five out of the six animal studies used a rodent model for investigating the effects of antenatally administered glucocorticoids, while the other used an ovine model. Antenatally administered glucocorticoids accelerated skin maturation in animal studies, but studies of human fetuses found conflicting results. None of the reviewed studies compared the effects of different types of glucocorticoids.

CONCLUSIONS

More human studies are needed to fully understand the effects of antenatal steroids. However, as the antenatal use of glucocorticoids in preterm pregnancies has become part of standard clinical practice, it would be unethical to carry out a large randomized controlled trial. We may have to rely on animal models to improve our understanding of the effects of antenatal glucocorticoid exposure on the fetal and neonatal skin maturation.

Significance of antenatal glucocorticoid exposure for pressure injury prevalence in neonates

AIMS

Studies have highlighted that antenatal steroids could have an effect on neonatal skin maturation. This study examined if there was a relationship between the administration of antenatal glucocorticoids for mothers and the skin injuries in their neonates. Data from skin injury audit were extracted from the neonatal database and analyzed to determine differences in the prevalence of neonates with pressure injuries [cases] whose mothers had received antenatal steroids, compared to those without pressure injuries [control].

RESULTS

Of 247 neonates audited, 77 [31%], had documented pressure injuries, 170 [69%] had no documented injury. The median birth weight and gestation were 1400 g [IQR 893-2268 g] and 30.3 weeks [IQR 26.3-40.0 weeks] respectively. Of the neonates born less than 34 weeks, 80% were exposed to antenatal steroids and were equally distributed across patient genders. Within the 77 cases, 53 [66%] were exposed to antenatal steroids compared to controls in which 88 [53%] had not. The effect between cases and controls was not statistically significant [χ2 = 2.81, P = 0.09]. However a difference was noted between genders, as female neonates benefited from the exposure to steroids [OR = 0.317, 95% [CI 0.105-0.956], p value -0.041].

CONCLUSION

Antenatal glucocorticoids appear to be beneficial in reducing pressure injury prevalence in female neonates.

Consistency of the proteome in primary human keratinocytes with respect to gender, age, and skin localization

Keratinocytes account for 95% of all cells of the epidermis, the stratified squamous epithelium forming the outer layer of the skin, in which a significant number of skin diseases takes root. Immortalized keratinocyte cell lines are often used as research model systems providing standardized, reproducible, and homogenous biological material. Apart from that, primary human keratinocytes are frequently used for medical studies because the skin provides an important route for drug administration and is readily accessible for biopsies. However, comparability of these cell systems is not known. Cell lines may undergo phenotypic shifts and may differ from the in vivo situation in important aspects. Primary cells, on the other hand, may vary in biological functions depending on gender and age of the donor and localization of the biopsy specimen. Here we employed metabolic labeling in combination with quantitative mass spectrometry-based proteomics to assess A431 and HaCaT cell lines for their suitability as model systems. Compared with cell lines, comprehensive profiling of the primary human keratinocyte proteome with respect to gender, age, and skin localization identified an unexpected high proteomic consistency. The data were analyzed by an improved ontology enrichment analysis workflow designed for the study of global proteomics experiments. It enables a quick, comprehensive and unbiased overview of altered biological phenomena and links experimental data to literature. We guide through our workflow, point out its advantages compared with other methods and apply it to visualize differences of cell lines compared with primary human keratinocytes.

Functional skin adaptation in infancy - almost complete but not fully competent

Early postnatal life is a period of active functional reorganization and cutaneous physiological adaptation to the extrauterine environment. Skin as the outermost organ of mammalians is endowed of multiple functions such as protection, secretion, absorption and thermoregulation. Birth stimulates the epidermal barrier maturation and the skin surface acidification especially in premature infants. In full-term infants the developed stratum corneum accomplishes competent barrier function, in contrast to prematures. Complete barrier maturation in preterm infants is fulfilled by 2-4 weeks of the postnatal life. However, in preterms with 23-25 weeks gestational age this process takes longer. Versatile regulatory mechanisms, namely skin surface acidity, calcium ion gradient and nuclear hormone receptors/ligands are interrelated in the complex postnatal newborn adaptation. The skin of newborns is adjusting quickly to the challenging environmental conditions of the postpartum. However, certain functions, for example, microcirculation, continue to develop even beyond the neonatal period, that is, up to the age of 14-17 weeks. Different environmental factors (for instance, dry and cold climate, diapers and cosmetic care procedures) influence the postnatal development of skin functional parameters such as stratum corneum hydration and the permeability barrier especially in premature infants. The aim of this article is to summarize the current knowledge on skin physiology in newborn and infants with a practical approach and to discuss the possible clinical consequences. This review offers the readership a critical and practical overview of skin physiology in newborns and infants. It emphasizes possible new research fields in neonatal and infantile skin physiology.

Ambient humidity influences the rate of skin barrier maturation in extremely preterm infants

OBJECTIVES

To test the hypothesis that the level of relative humidity (RH) in which preterm infants are nursed might influence their postnatal skin maturation.

STUDY DESIGN

In 22 preterm infants (GA 23-27 weeks), transepidermal water loss (TEWL) was determined at postnatal ages (PNA) of 0, 3, 7, 14, and 28 days. At a PNA of 7 days, the infants were randomized to care at either 50% or 75% RH.

RESULTS

TEWL decreased at a slower rate in infants nursed at the higher RH. At a PNA of 28 days, TEWL was about twice as high in infants nursed at 75% RH (22 +/- 2 g/m2 h) than in those nursed at 50% RH (13 +/- 1 g/m2 h; P < .001).

CONCLUSIONS

The results indicate that the level of RH influences skin barrier development, with more rapid barrier formation in infants nursed at a lower RH. The findings have an impact on strategies for promoting skin barrier integrity in extremely preterm infants.

Antenatal steroids and fluid balance in very low birthweight infants

OBJECTIVES

To determine if insensible water loss (IWL) differed between infants exposed or not exposed antenatally to corticosteroids and to explore possible mechanisms for the early postnatal diuresis associated with antenatal steroid exposure.

DESIGN

Retrospective analysis of prospectively collected data.

SETTING

Level three neonatal intensive care unit.

PATIENTS

Ninety six infants, median gestational age 27.5 weeks (range 23-33).

MAIN OUTCOME MEASURES

Comparison of the IWL, urine output and osmolality, fluid input, electrolyte imbalance, respiratory illness severity (as assessed by surfactant requirement, maximum peak inspiratory pressure, and inspired oxygen concentration), and cardiovascular status (as assessed by inotrope requirement) between infants with antenatal corticosteroid exposure and gestational age matched controls.

RESULTS

The infants exposed to antenatal steroids differed significantly from the controls in having both a lower IWL (p = 0.0135) and a higher urine output (p = 0.0036) on day 1, and fewer developed hyponatraemia (p = 0.027) on day 2. Fewer of those exposed to antenatal steroids required inotropes (p = 0.06), but their respiratory status was similar to that of the controls.

CONCLUSIONS

Infants exposed to antenatal corticosteroids have a lower IWL. The results suggest that greater skin maturation, but also better perfusion rather than less severe respiratory status, explains the early diuresis in infants exposed to antenatal steroids.

Besonderheiten der Haut des Neugeborenen und jungen Säuglings

Detailed knowledge of the special features of neonatal and infant skin is a prerequisite for adequate skin care in this age group. Immediately postpartum, the newborn baby's skin assumes vital functions regarding water and electrolyte homeostasis and thermoregulation, as well as innate and adaptive host defense. Due to its functional and structural immaturity, premature skin requires special care. Mature neonates demonstrate benign, transient skin lesions that do not require specific therapy but have to be distinguished from serious and potentially life-threatening illnesses.

Improved outcome of extremely low birth weight infants with Tegaderm application to skin

OBJECTIVE

Significant fluid and electrolyte disturbances occur in extremely low birth weight (ELBW) infants in the first few days of life. We investigated the effect of semipermeable polyurethane membrane (Tegaderm) applied to the skin shortly after birth on fluid and electrolyte status and the clinical outcome in these infants.

STUDY DESIGN

We reviewed charts of ELBW infants (BW<1.0 kg) born during 24 months prior to Tegaderm application and 19 months after starting Tegaderm. Data were collected daily from the first week of life and additional clinical morbidities were compared.

RESULTS

A total of 39 infants from pre-Tegaderm period (NOTEG) (mean+/-SD, BW 756+/-158 g, GA 26.1+/-1.9 weeks) were compared to 30 infants with extensive Tegaderm application to chest, abdomen and extremities (TEG) (BW 802+/-160 g, GA 26.3+/-1.8 weeks). The groups were similar in maternal demographics as well as postnatal surfactant use. Throughout the first week of life, serum Na levels, daily fluid intake and daily weight loss were significantly higher in the NOTEG infants (all P< or =0.04) while BUN/Serum creatinine levels were similar. Hypernatremia (Na>150 mEq/l) developed in 51% of NOTEG infants compared to 17% of TEG (P=0.0005) and daily fluid intake > or =170 ml/kg/day was required in 54 vs 13% (P=0.0008), respectively. The mean time to regain BW was significantly longer in NOTEG vs TEG infants, 20.7+/-7.4 vs 15.8+/-6.3 days, respectively (P<0.02). There were no statistical significant differences among the groups in incidence of IVH, NEC, PDA or nosocomial sepsis; however, respiratory outcome was better in TEG infants. They had significantly less BPD (58% in NOTEG vs 22% TEG (P=0.01)) and fewer infants in the TEG group required supplemental oxygen at discharge (58% vs 22% (P=0.01)). Survival was significantly higher in TEG 90% vs 64% in NOTEG infants (P=0.02).

CONCLUSIONS

Semipermeable polyurethane membrane application to skin of ELBW infants shortly after birth decreased postnatal fluid and electrolyte disturbances and significantly improved their outcome by reducing severity of lung disease and decreasing mortality.

Neonatal skin barrier: structure, function, and disorders

The development of the human skin from intrauterine to extrauterine life is a balletic interplay of maturing layers and interlocking structures. We discuss this transition and then branch out to touch on issues of premature infant as well as neonatal skin care. Disruption of the barrier function due to toxins and development errors are expounded upon. Staph scalded skin syndrome, collodion membrane, bullous congenital ichthyosiform erythroderma, autosomal recessive ichthyosis (lamellar and congenital ichthyosiform erythroderma), and harlequin fetus are used as examples of these disruptions. Discussion of therapy with the authors' experience highlights each disease.

Stratum corneum maturation. A review of neonatal skin function

The importance of the stratum corneum and its barrier function for infants, especially for newborns, is clinically evident. Research regarding the maturation of the stratum corneum in neonates, i.e. when full barrier function is obtained, has produced varying results. Based on transepidermal water loss and percutaneous absorption studies, term infants seem to possess stratum corneum with adult barrier properties. Additionally, postnatal life is thought to accelerate stratum corneum maturation, so that even preterm infants have barrier function similar to term infants at 2-3 weeks of gestational age. However, a look at other parameters, such as skin thickness, skin pH and stratum corneum hydration, shows that neonatal skin is always adjusting to the extrauterine environment in contrast to the steady state of adult skin. This suggests that barrier stabilization may be dependent on achieving a balance between different parameters. However, it is still in question, which parameters, what balance and what timing. This paper provides an up-to-date overview on the neonatal skin barrier based on the review of current literature.

Management of fluid balance in the very immature neonate

Preterm birth requires rapid adaptation from a liquid to a gaseous, low humidity environment. There are several ways in which this can be facilitated. The management of sodium and water balance is considered here.

Barrier function of the skin: "la raison d'être" of the epidermis

The primary function of the epidermis is to produce the protective, semi-permeable stratum corneum that permits terrestrial life. The barrier function of the stratum corneum is provided by patterned lipid lamellae localized to the extracellular spaces between corneocytes. Anucleate corneocytes contain keratin filaments bound to a peripheral cornified envelope composed of cross-linked proteins. The many layers of these specialized cells in the stratum corneum provide a tough and resilient framework for the intercellular lipid lamellae. The lamellae are derived from disk-like lipid membranes extruded from lamellar granules into the intercellular spaces of the upper granular layer. Lysosomal and other enzymes present in the extracellular compartment are responsible for the lipid remodeling required to generate the barrier lamellae as well as for the reactions that result in desquamation. Lamellar granules likely originate from the Golgi apparatus and are currently thought to be elements of the tubulo-vesicular trans-Golgi network. The regulation of barrier lipid synthesis has been studied in a variety of models, with induction of several enzymes demonstrated during fetal development and keratinocyte differentiation, but an understanding of this process at the molecular genetic level awaits further study. Certain genetic defects in lipid metabolism or in the protein components of the stratum corneum produce scaly or ichthyotic skin with abnormal barrier lipid structure and function. The inflammatory skin diseases psoriasis and atopic dermatitis also show decreased barrier function, but the underlying mechanisms remain under investigation. Topically applied "moisturizers" work by acting as humectants or by providing an artificial barrier to trans-epidermal water loss; current work has focused on developing a more physiologic mix of lipids for topical application to skin. Recent studies in genetically engineered mice have suggested an unexpected role for tight junctions in epidermal barrier function and further developments in this area are expected. Ultimately, more sophisticated understanding of epidermal barrier function will lead to more rational therapy of a host of skin conditions in which the barrier is impaired.

Scar quality and physiologic barrier function restoration after moist and moist-exposed dressings of partial-thickness wounds

BACKGROUND

There is growing evidence of improved healing of full- and partial-thickness cutaneous wounds in wet and moist environments. Retention of biologic fluids over the wound prevents desiccation of denuded dermis or deeper tissues and allows faster and unimpeded migration of keratinocytes over the wound surface. It allows also the naturally occurring cytokines and growth factors to exert their beneficial effect on wound contracture and re-epithelialization. Despite all of these documented benefits, applying the moist healing principles to large surface areas, in particular to large burns, is hindered by the major technical handicap of creating and maintaining a sealed moist environment over these areas.

METHODS

From January to September 2001, healing of partial-thickness skin graft donor sites was studied in a prospective comparative study of two types of moist dressings, Tegaderm (3M Health Care, St. Paul, MN), a semipermeable membrane occlusive dressing, and moist exposed burn ointment (MEBO) (Julphar; Gulf Pharmaceutical Industries, United Arab of Emirates), an ointment that can provide a moist environment without the need of an overlying occlusive dressing. Healing was assessed both clinically and with serial measurements of transepidermal water loss (TEWL) and moisture. Following healing, scar quality was evaluated by two members of the team separately using a visual analog scale. Results were statistically analyzed.

RESULTS

Faster healing was observed clinically with MEBO application. Physiologic healing as determined by TEWL measurements occurred at an extremely significant earlier stage for MEBO, and this was associated with better scar quality, demonstrating a positive relationship between function and cosmetic appearance. Moreover, the ointment is definitely easier to apply than the occlusive self-adhesive membrane, which requires some degree of dexterity and expertise.

CONCLUSION

MEBO application is an effective and valid alternative to conventional occlusive dressings. Moreover, the observed improved anatomic and physiologic healing indicates that MEBO may have a positive effect on healing more that the mere fact of passive moisture retention.

[Use of a polyethylene bag: a way to improve the thermal environment of the premature newborn at the delivery room]

BACKGROUND

Early interventions, such as occlusive wrapping of very low birth weight infants at delivery reduce postnatal temperature fall. This new intervention was implemented in our hospital on January 2000. The aim of this study was to investigate retrospectively the effect of polyethylene wrap, applied immediately at birth, on thermoregulation.

PATIENTS AND METHODS

Matched pair analysis was conducted for 60 infants delivered inborn at less than 33 weeks' gestation and 60 premature infants who were born during the second half of 1999 fulfilling the same criteria. The only difference in the management (medical and environmental) was wrapping with a polyethylene bag in the delivery room. Rectal temperature and other vital parameters were taken, after removal of wraps, on admission to NICU.

RESULTS

The perinatal characteristics of both groups were comparable. Use of wrapping resulted in a significantly higher admission rectal temperature (difference in means = 0.8 degree C, p < 0.0001), this difference was also significant in infants < 30 weeks. The incidence of hypothermia (< 35.5 degrees C) was less frequent in infants enclosed in plastic bags (8.3% vs 55%). No side effects (skin burns, infection or hyperthermia) were attributable to the intervention. The heart rate was higher in the wrapping group (163 +/- 16 vs 150 +/- 17 b/min, p < 0.01), as well as the capillary glycemia (62 +/- 26 vs 45 +/- 30 mg/dl, p < 0.01). There was no significant difference on arterial pressure.

CONCLUSION

Occlusive wrapping with a polyethylene bag at birth prevented low rectal temperature in premature infants in the immediate postnatal period. This method is easy, practical and effective, and does not interfere with current practice for resuscitation.