Visual Properties of Striae Distensae of
Nkengne A1*, Halimi K1, Vié K1,Seroul P2 and Trevisan S2
1Laboratoires Clarins, 5 rue Ampère, 95300 Pontoise, France
2Newtone Technologies, 13 bis place Jules Ferry, 69006 Lyon, France
Submission: January 09, 2020;Published: January 23, 2020
*Corresponding author: Alex Nkengne, Laboratoires Clarins, 5 rue Ampère, 95300 Pontoise, France
How to cite this article: Nkengne A, Halimi K, Vié K,Seroul P, Trevisan S.Visual Properties of Striae Distensae of Chinese Women. JOJ Dermatol &
Cosmet. 2020; 2(2): 555582. 10.19080/JOJDC.2020.02.555582
Background: Striae Distensae (SD) or stretch marks are manifestations of epidermal atrophy that would arise from a combination of hormonal factors and mechanical stretching and that are characterized by distinct microstructural features. The objective of this in vivo study was to investigate the biophysical properties of recent versus old SD in a Chinese population.
Methods: A cohort of 110 Chinese women, aged between 21 and 45 years old, were recruited. Fifty-five presented recent and inflamed SD while the other 55 volunteers suffered old and scarred SD. Morphological characteristics and anatomical distribution of the SD were evaluated by a trained expert. Contrast, entropy and anisotropy of SD were obtained from cross-polarized images and skin glossiness was computed from parallel and cross-polarised images. Spectrocolorimetric data were used to calculate colour and estimate chromophores concentration in SD and in adjacent normal skin.
Results: 98.2% of the volunteers claimed their SD are due to pregnancy. They were mainly located on the abdomen (93.6% of women), the thighs (72.7%) and the hips (83.6%). The recent SD are significantly darker (L*) and redder (a*) than old ones. These colour differences correlate to a higher concentration of skin chromophores in recent SD. Texture contrast is also more important in recent SD but old SD are brighter while there in no differences in skin texture complexity nor in the directional properties between recent and old SD.
Conclusion: The visual contrast of SD can be related to chromophore distribution (recent) or light scattering (old).
Striae distensae (SD) or stretch marks are common linear skin scars accompanied by epidermal atrophy . They appear during pregnancy, adolescence, obesity, weight loss, bodybuilding, cachexia or in conditions associated with extensive corticosteroid use [1-4] Areas most commonly affected are the abdomen, breasts, buttocks, hips and thighs [1,5]. Despite being of no medical importance, they are an important cosmetic concern: their occurrence can be as high as 88% of pregnant women  and they cause significant psychological burden to many patients .
At the onset, the lesions appear as erythematous and inflammatory streaks (striae rubrae), oriented perpendicular to the direction of skin tension which, over months to year, mature into striae alba: atrophic, wrinkled, hypopigmented and permanent scars [7-9]. Even if the exact cause remains unclear, they would arise from a combination of hormonal factors and mechanical stretching due to rapid tissue expansion . This expansion results in the reduction, thinning and disorganisation of
the elastic fibre network due to elastolysis mediated by infiltrating mast cells and macrophages [11-13]. At early stages, SD formation also involve oedema in the dermis whilst striae albae are less vascularised .
Despite the advances made in the characterization of SD at the molecular level, their objective clinical grading by an easy to use, reproducible, and non-invasive methods is still a challenge . Therefore, the objective of this study is to better characterize the biophysical properties of recent versus old SD using objective non-invasive methods. We also decided to focus our study on Chinese women, a population for which only few data are available
A cohort of 110 Chinese women from the city of Wuhan and its surrounding (Hubei province, Central China) was recruited after signing a written informed consent. The age of the volunteers wasranging between 21 and 45 years old. Fifty-five of them (mean age
= 28.5 years old) suffered recent (less than a year in 95% of the
cases) and inflamed SD while the other 55 volunteers (mean age =
35.9 years old) presented old (more than a year-old in 85% of the
cases) and scarred SD.
Morphological characteristics and anatomical distribution of
the SD were evaluated by a trained expert. The study focused on
the abdomen, the breasts, the thighs, the hips and the arms where
the number, the length and the width of SD were determined. A
109 items questionnaire was also used to identify the origin of the
SD and their influence on self-appreciation of the volunteers’ body.
The visual properties were investigated with a digital camera
system using controlled polarised light conditions (Nomad,
Newtone Technologies, France). Texture of SD was evaluated
in term of roughness, regularity and isotropy. Roughness and
regularity are quantified using, respectively, the contrast and
entropy parameters described by Haralick . These parameters
are obtained by the computation of co-occurrence matrix. This
statistical tool measures the distribution of grey levels in the
image, or in a given region of interest, and highlights the frequency
and regularity of a colour to detect a possible pattern. The contrast,
which measures local variations of grey levels is defined according
to the following formula:
Where, Pi,j is the co-occuring value of a pair of pixels withspecific values (i and j) and in a specified spatial relationship occur
in an image; and where N the number of rows (i) and columns (j)
of the co-occurrence matrix. With this formula, contrast decreases
when the texture becomes smoother. It is equal to 0 when all
image intensities are identical.
Entropy reflects the complexity of texture. It decreases when
the texture becomes more regular and is defined as follow:
Skin texture anisotropy was measured to determine the
homogeneity in the orientation of the skin texture at the level
of SD. For this purpose, a tensor image is computed from the
cross-polarized image. This image allows visualization of skin
lines orientation from a 2D image. The anisotropic coefficient is
quantified according to Zahouani et al. :
To calculate specular glossiness, a gloss map was generated
by compensating parallel and cross polarized images exposition
and computing the difference between them. Glossy pixels were
extracted from the gloss map using an automatic threshold
method  (Figure 1). Their value was averaged to obtain the
specular glossiness value, value that increases when the skin
is glossier. Finally, reflexion spectra of SD and adjacent normal
skin were acquired using a CM 700d spectrocolorimeter (Konica
Minolta Sensing, Japan). Spectra were used to calculate the L*, a*,
b* colour parameters [19 and the ΔE colour difference parameter
. They were also used to calculate oxy , deoxy hemoglobin and
melanin concentrations  in SD and to compare to those of
Data are expressed as mean ± standard deviation. Statistical
comparisons were performed using paired or unpaired Student’s
t-test (significance level at a = 0.05) following confirmation of
normality of the data distribution using the Anderson–Darling
The SD of the 110 Chinese women volunteers were mainly
located on the abdomen (93.6% of the women), the hips (83.6%)and the thighs (72.7%). Only 6.4% of the women presented SD on
the breasts and 3.6% on the arms. For 98.2% of the volunteers, SD
were due to pregnancy. Only one woman claimed they were due to
body development and another one to weight gain.
Clinical grading (Table 1) reveals no differences between
women harbouring recent or old SD: the average number of SD
on each zone is similar as well as the length or the width of SD.
Finally, self-assessment of the impact of SD on appreciation of the
volunteers’ body confirms their negative influence: 58% of the
volunteers claimed having a rather negative image of their body,
SD bother 68% of them for the image they have of themselves
and 81% of them for the image they present to others. Finally, SD
influences the way 65% of the volunteers dress.
Initial comparison of the skin’s L*, a*, b* parameters obtained
by spectrocolorimetric analysis show that the two groups of
women have normal skin with significantly different colour L*, a*
and b* parameters (Figure 2 - ΔE = 2.65). Therefore, our analysis
focused on the colour difference between SD and adjacent normal
skin within each group. This analysis shows that while there is no
significant difference in the L*, a*, b* parameters between old SD
and adjacent normal skin, there are differences between recent SD
and adjacent normal skin (Figure 2). Recent SD are 5.4% darker
(p < 0.0001) and 35.3% redder (p < 0.0001) while there is no
significant difference in the yellow-blue b* parameter (p = 0,099).
To gain possible insight in the underlying colour differences
between recent and old SD we used the spectral data acquired
with the spectrocolorimeter to compute the concentration of
oxy-, deoxy-hemoglobin and melanin. Again, to avoid effect due to
normal skin colour variation between the two groups, the analysis
focused on the comparison between SD and adjacent normal
skin. Results show (Figure 3) that the amount of oxy-, deoxyhemoglobin
and melanin is respectively 12.1% (p = 0.0018), 5.7%
(p = 0.0005) and 8.6% (p = 0.029) higher in old SD than in adjacent
normal skin. For recent SD, the differences are more pronounced
and show higher significance with 61.2% (p < 0.0001) more oxyhemoglobin
in SD than in adjacent normal skin, 16.0% (p < 0.0001)
more deoxy-hemoglobin and 34.3% (p < 0.0001) more melanin.
We also studied the texture differences that exist between
recent and old SD using pictures taken under polarised light.
Results (Figure 4) show that the specular glossiness is higher in
old SD than in recent SD (+5.8%, p < 0.0001) while the texture
contrast is more important in recent SD compared to old ones
(+33.2%, p < 0.0001). In other words, if old SD reflect more light
than recent SD, the skin micro-relief of SD is more important when
they are recent. In addition, texture entropy and anisotropy are
similar in both recent and old SD, namely there is no significant
difference in skin texture complexity nor in the directional
properties between recent and old SD.
Since their first histological description , SD have been
described in many ethnic groups and where shown to have similar
clinical appearance. Still, their colour can vary [14,22]. On white
colour skin, recent SD are generally erythematous (striae rubrae)
and then turn white (striae albae). They can also be blackish in
dark-pigmented populations (striae nigrae) or bluish in case of
prolonged corticotherapy (striae caeruleae). Therefore, we were
interested in better characterising the appearance of SD in the
Chinese population for which little is known.
To circumvent the fact that the volunteers with recent and old
SD where presenting normal skin with different complexion, we
focused our analysis on the comparison of SD to adjacent normal
skin within each group. Results show that recent SD are slightly
darker and much redder than adjacent normal skin while the colour
of old SD does not differ to that of adjacent skin. The colour data
of recent SD are in agreement with the increased concentration of
oxy-, deoxy-hemoglobin and melanin we quantified in recent SD.
This increase in skin chromophore is also detected in old SD but to
a lower and less significant extend which probably explains why it
is not detected as a colour difference.
The results we obtained for the colour and chromophore
content of recent SD in the Chinese population we studied are
in agreement with previous studies performed on other ethnic
groups which relates the initial red and erythematous appearance
of recent SD to changes in microvasculature and melanocyte
activity [14,22,23]. We also show that, similarly to a Caucasian
population, old SD from Chinese women still present a slight
accumulation of melanin . Conversely, the increase of oxy-,
deoxy-haemoglobin we show in old SD differs from what has been
obtained in a Caucasian population where such an increase was
not detected . Indeed, old SD are generally described as being
lighter than surrounding skin  which most probably relates to
differences in methodology and the higher specular glossiness of
This high specular glossiness of old SD indicates a higher skin
glossiness, due to less variation in skin micro-relief, than in recent
SD. It also correlates to the lower texture contrast we found in old
SD compared to recent SD. Both results clearly relate to changesin skin structure. Indeed, SD are also known to be accompanied
by several microstructural changes. They are characterized by
gradual atrophy of the epidermis, including loss of rete ridges .
The mid-dermis undergoes elastolysis as evidenced by mast cell
degranulation and stimulation of macrophages . The elastic
fibre network breaks down, collagen fibres thicken, become more
densely packed and arranged in a parallel pattern [13,15]. The
fact that we do not observed any difference in texture entropy
or anisotropy suggest that, at the macroscopic level, underlying
changes in skin structure occurring in recent SD remains in old
SD. Still these differences are more visible, producing more microrelief
to skin texture, in recent SD.
If some differences might exist in populations with different
skin complexion, especially when darker, we show that, similarly
to the Caucasian population, the visual characteristics of recent
SD in Chinese women relates to colour. Darker and redder than
adjacent normal skin, the colour difference relates to an increased
concentration of oxy-, deoxy-hemoglobin and melanin. If old SD
also show higher concentration of chromophores than normal
skin, they show no colour difference and are characterised by their
glossiness that relates to changes in skin structure.
The authors thank Claire Sylvain / Pr Wenyao Yu from
COSderma for data acquisition and Pierre Seroul / Matthieu
Jomier from Newtone Technologies for the analysis of visual data.
They also wish to thank Dr Philippe Crouzet, Estium-Concept, for
scientific writing services.