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ORIGINAL ARTICLE
Year : 2020  |  Volume : 21  |  Issue : 4  |  Page : 287-293

The epidermal growth pattern in human fetuses


1 Department of Anatomy, Uttar Pradesh University of Medical Sciences, Etawah, Uttar Pradesh, India
2 Department of Anatomy, All India Institute of Medical Sciences, Patna, Bihar, India

Date of Submission15-Apr-2019
Date of Acceptance26-Apr-2020
Date of Web Publication30-Sep-2020

Correspondence Address:
Dr. Adil Asghar
Department of Anatomy, All India Institute of Medical Sciences, Phulwari Sharif, Patna - 801 507, Bihar
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ijpd.IJPD_42_19

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  Abstract 


Background: The estimation of fetal epidermal thickness has clinical significance for dermatological investigation and diagnosis of fetal prematurity. Objective: We aimed to collect baseline data of fetal epidermal thickness and secondarily to study the correlation of gestational age (GA) from epidermal thickness. Materials and Methods: Thirty fetuses were selected for the study aged from 11 to 40 weeks. They were divided into six groups at a 4-week interval. The mean epidermal thickness was measured at four sites such as the abdomen, interscapular region, scalp, and palm. The histometric analysis was done with the help of amscope 5MP Aptina MT9P001. Results: The mean age of gestation was 25.67 ± 8.45 weeks. The mean epidermal thickness of the abdominal, interscapular, scalp, and palmar region was 21.9 ± 12.9 μm (3.41–42.48), 111.21 ± 74.39 μm (7.9–214.51), 27.58 ± 13.26 μm (11.7–46.2), and 139.73 ± 96.40 μm (7.3–280.51), respectively. The growth pattern of the epidermis of the different region was significantly variable based on the ANOVA (P = 1.98E-13 P < 0.05 significant) and paired t-test of interregion comparison. Conclusions: The epidermal thickness has a significant positive correlation with GA and anatomical sites. We emphasize that epidermal thickness is a newborn maturity marker at birth.

Keywords: Fetal maturity, gestational age, histometry, mean epidermal thickness


How to cite this article:
Dhingra S, Verma JK, Asghar A. The epidermal growth pattern in human fetuses. Indian J Paediatr Dermatol 2020;21:287-93

How to cite this URL:
Dhingra S, Verma JK, Asghar A. The epidermal growth pattern in human fetuses. Indian J Paediatr Dermatol [serial online] 2020 [cited 2020 Oct 19];21:287-93. Available from: https://www.ijpd.in/text.asp?2020/21/4/287/296860




  Introduction Top


Fetal and neonatal skin is more sensitive and prone to injury but heals without a scar. The development of dermal and epidermal layers is continuous and shows sequential changes even at light microscopy level till getting maturity.[1] Layers of dermis and epidermis are differentiable and can be mapped to study the developmental dynamics of the skin. Of two layers, the epidermal layer is well defined and has a distinct border and its thickness can be measured more accurately than the dermis. The intrauterine stratification and keratinization of the epidermis are sequential.[2] The differentiation of the epidermal layer into five layers increases thickness. The epidermal thickness and skin maturity are linked with gestational age (GA). The epidermal thickness is a key biophysical parameter which has several important aspects of medicine such as dermatology, plastic, and cosmetic surgery and biophysical study. The biophysical behaviours such as transepidermal water loss, skin hydration, and skin acidity (pH) vary according to the thickness of the epidermis.[3] These biophysical behaviors are deranged in psoriasis and atopic and allergic dermatitis due to an alteration of epidermal structure. The skin thickness varies with location, age, gender, and underlying pathologies. However, many skin diseases affect the epidermal thickness, for example, an increase in thickness is called acanthosis in dermatitis and psoriasis or a decrease or atrophy in lichen sclerosus or scars.[4],[5] The chronic actinic disorder may proceed to acanthosis and hyperkeratosis due to epidermal hyperplasia.[6] Currently, noninvasive modalities are the investigation of choice for skin disorder by imaging of human skin in vivo. These modalities are either optical techniques such as confocal laser microscopy, optical coherence tomogram (OCT), and multiphoton microscopy or high-frequency ultrasound.[7],[8],[9] These modalities are noninvasive and provide repeatability, but they lack accuracy and need to be standardized with baseline data. Skin histometry still be considered the “gold standard” for the measurement of epidermal thickness, and the baseline data may be retrieved for comparison with other methodologies. Sometimes, it has major lacuna which is a distortion of skin morphology, nonrepeatable, and iatrogenic trauma.[10]

Many authors measured epidermal thickness by noninvasive techniques but were unable to standardize due to the unavailability of baseline data. Similarly, the comparatives among noninvasive techniques in the computation of fetal epidermal thickness are unconvincing due to the lack of baseline data of fetal epidermal histometry. The connection of an age-related histomorphometrics of the fetal skin was previously underreported with a high concordance with the chronology of gestation.[11],[12] The epidermal thickness is also a nutritional marker and its sequential chronology helps to diagnose fetal or newborn prematurity. While the GA estimation by current approaches faces challenges, fetal maturity may be indirectly determined based on their organs and tissues. By standardizing the newer modalities by histometry to estimate GA and diagnose prematurity will be more convincing. These data may be utilized for comparisons at the community level, mainly in low- and medium-income countries for the policymaker.[11]

The secondary motivation of this study is the importance of accurate GA determination from epidermal thickness which will reduce the prematurity-related adverse outcomes at birth. Unplanned pregnancy and late prenatal care are situations not exclusive to low- and medium-income countries which challenge the existing GA markers at birth. However, accurate estimation of GA at birth is difficult in the congenital anomaly of major organs. Hidden neonatal prematurity is the clinical target that needs to be identified, considering that high-risk newborns are often affected by inadequate postnatal nutrition. This study was aimed to capture baseline data and to investigate the relation and association between the length of pregnancy and fetal epidermal thickness as a secondary objective.


  Materials and Methods Top


This cross-sectional study was conducted on fetuses obtained from medically terminated pregnancy from January 2017 to June 2018 according to the inclusion and exclusion criteria. The protocol of research was approved by the institutional ethics committee E. C. No 2017/131. Written informed consent was obtained from each mother. The medically terminated fetuses of 11–40 weeks of GA without any gross anomaly were collected from the department of obstetrics and gynecology. The skin samples were collected from the abdomen, interscapular region, palm, and scalp. The size of tissue taken was roughly 5 mm × 5 mm. The skin samples were fixed in 10% buffered formalin and labeled properly for the transportation to histology laboratory for histometry. The age of the fetus was computed with the help of crown-rump length, biparietal diameter, and femur length and matched with ultrasonography (USG) scan and menstrual history given by the mother. The fetuses with the gross difference between calculated age and USG determined age were excluded from the study.

The inclusion criteria for the selection of fetuses were 11–40 weeks of gestation, no visual abnormalities on gross morphology, and medical termination of pregnancy (MTP) done for the eugenic or medical causes. The fetuses were classified into six groups according to the period of gestation at 4-week interval [Table 1]. The exclusion criteria for the study were gross abnormalities visible, the difference of >7 days between calculated and USG determined age, and the mother with a history of diabetes, hypertension, immunological disorder or vasculitis, chronic dermatological disorder, hydrops fetalis, genodermatoses, and history of intrauterine infection and oligohydramnios.
Table 1: Mean epidermal thickness±standard deviation in different regions in μm ×10 H and E stain

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Only thirty sets of samples were selected for the study based on the aforementioned criteria. Skin samples were processed by paraffin-embedding method. The histological processing was done in following steps: fixation, dehydration, clearing, wax impregnation, embedding, section cutting, and staining with hematoxyline- eosin. The section so stained was mounted with Dibutylphthalate Polystyrene Xylene (DPX) and coverslip. The slide was examined under the light microscope.

Measurement

Amscope 5MP Aptina MT9P001 [CMOS; Color; Resolution: 2592 × 1944 (approx. 5,040,000 pixels), Reduction Lens: X0.5 Pixel Size: 2.2 μm × 2.2 μm, G Sensitivity: 0.53 v/lux-sec (550 nm) Frame Rate: 60fps at 640 × 480, 18fps at 1280 × 960, 5fps at 2592 × 1944 Exposure: 0.21–2000 ms, ROI] was used for measuring epidermal thickness. Epidermal thickness was measured from the dermoepidermal junction to the topmost intact keratin layer [Figure 1]. Epidermal thickness was assessed by two-blinded examiners, with a single measurement being acquired by each interrater agreement. The coefficient of variations of epidermal thickness between raters was 1.3% (95% confidence interval [CI] of the mean: 0.4 ± 2.9%).
Figure 1: Measurement of epidermal thickness. H and E stain ×40 (scalp; 25 weeks). The scale bar represents 50 μm

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Statistical analysis

Statistical analysis was done by SPSS v22.0 (IBM Corp., Armonk, N.Y., USA) and MS Excel 2007. ANOVA was used to compare all groups and paired t-test was applied to compare between the two groups. To study the relation of epidermal thickness with GA and weight, the correlation coefficient was measured and the least count regression model was executed.


  Results Top


On microscopy, in Group 1 (11–15 weeks of gestation), the epidermis was found to be thin and only two-layered thick in all the regions (abdomen, interscapular, scalp, and palm) with no hair follicle present, no capillary was seen. In Group 2 (16–20 weeks), the fetus started showing multilayered epidermis in all the regions with developing capillaries appreciable and developing hair follicles (absent in palm) were delineated. The epidermal layers increased in size along with hair follicles (absent in the palm), sebaceous glands were appreciable, and well-developed capillaries were observed in Groups 3–6 [Figure 2] and [Figure 3].
Figure 2: The growth of epidermal thickness in the abdomen in all groups. H and E stain ×10. The scale bar represents 50 μm. Group I – shows the periderm layer and few dome-like cells, Group II – Appearance of rete ridges, Group III – Granular cell layer thickens, Group IV – Keratin layer develops, Group V – Maturation of the epidermis and well-developed rete ridges, Group VI – Mature epidermis with thick keratin layer

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Figure 3: The growth of epidermal thickness in scalp in all groups. H and E stain ×10. The scale bar represents 50 μm. Group I – shows periderm layer and few dome-like cells, Group II – Appearance of rete ridges, Group III – Granular cell layer thickens, Group IV – Keratin layer develops, Group V – Maturation of the epidermis and well-developed rete ridges, Group VI – Mature epidermis with thick keratin layer. The sequence of hair follicles development visible

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The mean age of gestation was 25.67 ± 8.45 weeks. The mean epidermal thickness of abdominal, interscapular, scalp, and palmer region was 21.9 ± 12.9 μm (3.41–42.48), 111.21 ± 74.39 μm (7.9–214.51), 27.58 ± 13.26 μm (11.7–46.2), and 139.73 ± 96.40 μm (7.3–280.51), respectively. The growth pattern of the epidermis of different regions was significantly variable based on the statistical test applied, i.e., ANOVA (P = 1.98E-13 P < 0.05 significant) and paired t-test for interregion comparison. The epidermal thickness in each group is shown in [Table 1] and comparisons of intergroup were also significantly varying with GA [Figure 4]. The GA has more than 80% of prediction for the epidermal thickness of all four regions with a strong association (r > 0.9 in all regions) [Table 2] and [Figure 5], [Figure 6].
Figure 4: The comparative of epidermal thickness in four regions

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Table 2: Correlation of epidermal thickness with gestational age

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Figure 5: Regression plot of epidermal thickness of different region predicted versus observed value

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Figure 6: Correlation of epidermal thickness with gestational age in four regions

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  Discussion Top


Skin development has a layered organization, including the avascular epidermis and vascularized dermis. The epidermal thickness analysis based on assessments to verify the intrauterine fetal growth effects is a novel approach. The birth-weight patterns did not influence the epidermal and dermal thicknesses.[13] The epidermal layer is essentially formed by keratinocytes from 20 weeks of gestation and becomes functional late in fetal life and similar evidence was found by us. The cellular epidermal is supplemented with age in adults, but the same is narrowed due to the flattening of the dermoepidermal junction in elderly individuals.[14],[15],[16] A significant thinning of epidermis was observed in elderly on histometric analysis of skin in 64 individuals aged 20-80 years.[17],[18] The epidermal thinning in old age is primarily because of retraction of rete pegs and loss of villous cytoplasmic serration of the basal layer, resulting in a flattened interface of the epidermis and dermis. By contrast, Sandby-Møller et al. reported that epidermal thickness was not correlated to age. This result might be due to the narrow and unbalanced age range.[11]

Comparison of the epidermal thickness with previous studies

The thickness of the epidermis is variable and ranges from 60 to 100 μm which is relatively constant over the body except in the palm and sole in adults[Table 3].[19] Gambichler et al. measured epidermal thickness at the interscapular region in 16 healthy adult individuals and found a mean value of 79.4 ± 21.9 μm by histometry. The same measurement was taken by them using optical coherence tomogram (OCT) with a mean thickness of 106 ± 15.4 μm, and the observed correlation coefficient was 0.29 (P = 0.27). These two techniques were not comparable and needed further standardization.[10] Rajadhyaksha et al. reported a maximum thickness of the epidermis of approximately 130 μm at the forearm, whereas Neerken et al. obtained a much smaller epidermal thickness 89 ± 8 and 75 ± 7 μm in younger and older individuals, respectively.[16],[20] Lock-Andersen et al. measured epidermal thickness in buttock tissue with different fixation techniques – formalin fixed and freeze-dried. The epidermal thickness was significantly lowered in freeze technique (71.4 ± 21.8 μm) as compared to formalin and fixed tissue (74.02 ± 22.8 μm) with P = 0.04.[21] Robertson and Rees measured the epidermal thickness with the help of confocal microscopy at the back of the hand (62.5 μm), center of the calf (60.5 μm), outer forearm (60.3 μm), inner forearm (59.4 μm), inner upper arm (58.2 μm), upper back (55.6 μm), chest (56 μm), abdomen (61.3 μm), corner of the eye (56.8 μm), and temple (61.4 μm). They did not measure epidermal thickness at the palm or sole and scalp.[22] Sandby-Møller et al. observed that the mean epidermal thickness all over the body was 83.7 ± 16.6 μm in the adult volunteers. They found mean epidermal thickness at the buttock (96.5 ± 16.1 μm), shoulder (81.3 ± 13.5 μm), and dorsal of the forearm (74.9 ± 12.7 μm) by skin reflectance meter ultraviolet (UV).[11] Whitton and Everall studied the mean epidermal thickness in 22 different anatomic sites in Caucasian volunteers aged 15–89 years which ranged from 37.6 (front of the upper trunk) to 221.8 μm (finger) by light microscopy. Epidermal thickness at the forehead, abdomen, upper back, and palm were 50.3 ± 20.2 μm, 37.6 ± 11.1 μm, 43.4 ± 13.4 μm, and 221.8 ± 122.1 μm, respectively.[23] Vitral et al. analyzed the correlation of neonatal skin thickness of the forearm and planter surface with a gestational period in two hundred twenty-two-term and preterm infants by high-frequency ultrasound. They used multivariate regression model to observe the relation of epidermal thickness with GA and the number of days neonate was kept in an incubator. They were formulated as follows:
Table 3: Comparison of techniques of epidermal thickness measurement

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GA (weeks) = −28.0 + 12.8 Ln (epidermal thickness) −4.4 ncubator stay; R2 = 0.604 (P < 0.001). The mean epidermal thickness of the forearm was as follows: 172.2 ± 19.8 μm inadequate for GA, 171.4 ± 20.6 μm in small for GA, and 177.7 ± 15.2 μm in large for GA (P = 0.525,). They hypothesized that the epidermal thickness was not influenced by the standard of fetal growth, and skin maturity can contribute to clinical applications.[24] Our finding was similar to previous studies.[23],[24] Our data clearly support that epidermal thickness has a strong correlation with GA. However, in the elderly age group, the mean epidermal thickness decreases with age might be due to chronic exposure of UV in the older individual.[12] We did not find any sexual dimorphism in the epidermal thickness like Moragas et al. and Whitton and Everall.[23],[25] However, Sandby-Møller et al. have revealed the greater thickness of viable epidermis without the stratum corneum in male than female.[11] Gambichler et al. have reported the smaller epidermal thickness of facial skin in the elderly female.[12],[23]

Strengths and limitations

During recent years, the epidermis has been studiedin vivo by means of noninvasive modalities such as high-frequency ultrasound, confocal microscopy, optical coherence tomogram (OCT), and a skin reflectance meter. The undulation of the dermoepidermal junction and low penetration and resolution of these newer modalities pose technical difficulties in the differentiation of epidermal layers, especially acellular stratum corneum. The optical techniques such as OCT or confocal microscopy and skin reflectance meter utilized the absorption of light by nuclei of keratinocytes. Their results were influenced by the content of melanin and thickness of acellular stratum corneum. High-resolution ultrasound puts some contact pressure on the skin and gives faulty value. These explorative studies included only small sample sizes and were not appropriately designed for definitive epidermal thickness in relation to GA or postneonatal age. The newer modalities have less reliability and are unable to provide baseline data. The histometry is the gold standard for morphological investigation of the skin but has no repeatability, and biopsy alters the morphology due to tissue shrinkage and tissue dehydration during processing.


  Conclusions Top


The epidermal thickness has a significant positive correlation with GA and anatomical sites. We emphasize epidermal thickness as a newborn maturity marker at birth, without the influence of the fetal growth standard. These baseline data will help to diagnose hidden prematurity at birth. We believe that epidermal maturity can contribute to clinical applications that aid in improving the classification of neonates into groups with low birth weight, prematurity, and intrauterine growth restriction, which are directly linked to the accurate prediction of GA. After standardization, these newer noninvasive modalities may be utilized for nutritional monitoring of neonates as a future perspective.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]
 
 
    Tables

  [Table 1], [Table 2], [Table 3]



 

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