1. The study examined morphological changes in the ovine cervix in response to sex steroids using confocal microscopy. Ovariectomized ewes were treated with various sex steroid combinations and their cervical morphology was compared to intact ewes at different reproductive stages. 2. Confocal microscopy allowed visualization of subcellular changes in cervical epithelium associated with alterations in progesterone and estradiol levels. Differences in nuclear size, distribution and density could be detected between treatment groups. 3. The results demonstrate that confocal microscopy has potential for detecting hormonally-induced cellular changes in the cervix and may help diagnose cervical conditions.

1. Detection of morphological changes of the ovine
cervix in response to sex steroids using a
fluorescence confocal endomicroscope
Eleanor M. Bott,a
I. Ross Young, PhD,a
Graham Jenkin, PhD,a
Wendy J. McLaren, PhDb,c,
*
Departments of Physiologya
and Pharmacology,c
Monash University, Clayton, Victoria, Australia; Optiscan Pty. Ltd,
Notting Hill, Victoria, Australiab
Received for publication September 29, 2004; revised April 28, 2005; accepted June 3, 2005
KEY WORDS
Confocal microscopy
Fluorescence
Progesterone
Estradiol
Sheep cervix
Objective: This study examined morphological changes of the ovine cervix in response to sex
steroids using confocal microscopy.
Study design: Experimental animals were ovariectomized, and the hormonal status of 4 groups of
ewes (n = 5) was manipulated using sex steroids (no replacement, estradiol, progesterone,
estradiol, and progesterone). The results were correlated with control ewes (n = 7) in naturally
occurring reproductive states (estrus and midluteal).
Results: Plasma progesterone concentrations of experimental animals were comparable with
those observed during normal reproduction. Confocal microscopy enabled subcellular resolution
of the cervical epithelium and the detection of morphological changes associated with alterations
in progesterone and estradiol in both artificially manipulated and naturally cycling ewes.
Differences in nuclear size, distribution, and density could be differentiated in confocal images
and histologic sections of ectocervix from animals in estrus and in the presence of exogenous
estradiol.
Conclusion: Confocal microscopy has potential diagnostic value for the detection of cellular and
subcellular changes of the cervical epithelium.
Ó 2006 Mosby, Inc. All rights reserved.
Current methods used to detect malignant and pre-
malignant changes of the cervix rely on screening
programs (Papanicoloau test) and colposcopy. Both
methods, however, have limitations and are subject to
error. The Papanicoloau test does not always detect
early cellular changes that may lead to cancer of the
cervix. The false-negative rate (missed lesion) has been
reported at 15% to 40%.1
Sampling and reading errors
may allow a lesion to progress to more advanced disease
before it is detected. Moreover, a Papanicoloau test
cannot be used for diagnosis at the time of patient ex-
amination. Colposcopy enables visual assessment of the
size and location of changes on the cervical epithelium;
Supported by a National Health and Medical Research Council
(NHMRC) of Australia Program Grant No 143786 (to G.J.) and
Optiscan Pty Ltd. The study described in this article was conducted at
the Department of Physiology, Monash University, Clayton, Australia.
* Reprint requests: Dr. Wendy McLaren, Optiscan Pty. Ltd., 15-17
Normanby Road, Notting Hill, Victoria 3168, Australia.
E-mail: wendym@optiscan.com
0002-9378/$ - see front matter Ó 2006 Mosby, Inc. All rights reserved.
doi:10.1016/j.ajog.2005.06.023
American Journal of Obstetrics and Gynecology (2006) 194, 105–12
www.ajog.org

2. however, the accuracy for diagnosis ranges from 48% to
72%.2,3
If preliminary results show an abnormality, a
biopsy is performed to confirm diagnosis. Biopsies are
invasive, and the selection of biopsy sites in regions
of diffuse disease is challenging. The development of a
subsurface in vivo imaging technique as an adjunct to
colposcopy could potentially improve patient treatment
and outcome. Confocal microscopy allows the visuali-
zation of microscopic details of the cervix in real time
in vivo. The ability to assess cervical morphology at
the time of examination may eliminate or guide biopsy
excision.
The sheep is an appropriate animal model to study
hormonally induced changes in cellular morphology of
the cervical epithelium. The hormonal changes during
the estrus cycle can be equated with those in the human
menstrual cycle. Moreover, the ovine cervix is similar in
size to the human cervix, and there is an abrupt
transition between the ectocervix and endocervix, allow-
ing examination of specific tissue types. The occurrence
of normal, hormonally induced cellular changes of the
cervix in women may lead to misdiagnosis of pathology.
Conversely, real dysplastic changes in cellular morphol-
ogy may be incorrectly attributed to hormonally in-
duced physiological changes. Therefore, the aim of this
study was to identify and characterize steroid-dependent
changes in an animal model using a recently developed
prototype confocal probe for the examination of the
cervix.
Specifically, our aims were to describe and assess the
ability of untrained observers to detect:
1. Hormonally induced changes in the confocal ap-
pearance of the cervical epithelium from ovariecto-
mized (OVX) ewes receiving no replacement or
estradiol alone, progesterone alone, or estradiol
and progesterone.
2. Naturally occurring changes in the confocal ap-
pearance of the cervical epithelium from ewes at
estrus or in the midluteal phase of their ovarian
cycle.
Material and methods
Animal preparation
All experiments were approved by the institutional
animal ethics committee. Surgery was performed under
general anesthesia and aseptic conditions on Merino
ewes (n = 20). Ewes were OVX through a midline
laparotomy and the hormonal status was manipulated
with silicone implants containing sex steroids placed
subcutaneously on the medial aspect of the ewe’s hind
limb. Following surgery, ewes were kept at pasture until
required for experimentation.
Experimental protocol
The study design used 2 groups of ewes (OVX and intact
animals) to determine the effects of hormonal status on
the morphology of the cervix. OVX ewes were randomly
allocated to 4 treatment groups: no hormone replace-
ment, 17b-estradiol alone, progesterone alone, and
17b-estradiol C progesterone. Sex steroids were slowly
released from the subcutaneous implants. The length of
the implants was kept uniform to maintain a consistent
release rate using a previously described method of
hormone manipulation.4
The estrus cycles of the intact control animals were
synchronized using controlled intravaginal drug releas-
ers containing progesterone, which were implanted for 6
days to mimic luteal phase progesterone concentrations
and to stimulate follicle development. Following re-
moval of the controlled intravaginal drug releasers, ewes
were injected with 400 U of pregnant mare serum
gonadotropin to induce ovulation. Once the treatment
had ceased, the time to ovulation was approximately 54
hours (estrus). Ewes were deemed to be in the midluteal
phase of the estrus cycle 1 week later. The morphology
of the cervix in the intact ewes was examined at estrus
(n = 7) and the midluteal phase (n = 7) of the repro-
ductive cycle.
The changes in the morphology of the cervix in
response to hormonal status were examined using con-
focal microscopy and conventional histology. Animals
were killed humanely using an overdose of intravenous
sodium pentobarbitone. At necropsy, the reproductive
tract (uterus, cervix, and a minimal amount of vaginal
cuff) was removed and weighed before imaging. Venous
blood samples (20 mL) were collected from the OVX
and intact control animals immediately before postmor-
tem for hormone analysis. Plasma concentrations of
progesterone were measured as described by Rice et al,5
with modifications by Deayton et al.6
Confocal microscopy and conventional histology
Single-channel fluorescence confocal imaging of the
cervix was performed using an Optiscan F900e personal
confocal system (Optiscan P/L, Notting Hill, Victoria,
Australia) equipped with a rigid endomicroscope probe
and an argon ion laser (excitation wavelength 488 nm,
detection above 505 nm). The objective lens used for
imaging (Edmund Optics, Singapore; 20! magnification,
0.7 NA) was contained within the probe body, allowing
precise control over the imaging depth within the sample.
To remove mucus from the surface of the cervix and to
enhance the image resolution and contrast, acetic acid
(5% volume/volume) was applied to the mucosal epithe-
lium. Regions of the ectocervix were then imaged follow-
ing the topical application of the nuclear fluorophore
Acriflavine (0.05% in saline; Sigma Pharmaceuticals,
106 Bott et al

3. Clayton, Victoria, Australia). The probe tip was placed
against the mucosal epithelium to image cells in a plane
parallel to the tissue surface. Two-dimensional optical
sections (1 scan/image; 512 ! 512 pixel resolution; field
of view [FOV] = 400 mm) were observed in real time
and collected for data analysis.
Confocal image sites were excised and fixed in buff-
ered formalin (12 to 24 hours) for comparison with
conventional histology. Fixed tissue was processed and
embedded in paraffin wax. Sections (6 mm) of cervix
were cut parallel to the confocal image plane prior to
staining with hematoxylin and eosin.
Image analysis
Representative confocal images of the ectocervix were
selected for each animal for image analysis. Fourteen lay
observers were asked to evaluate the confocal images
(n = 60 for each tissue site) and to match them to the
treatment groups. Prior to scoring, observers received
sample images representative of each treatment regimen
or physiological state, together with a brief description
of the associated changes in morphology. The images
for scoring were arranged randomly and the results were
assessed as the number correctly identified for each
treatment group.
To enable correlation of the conventional histology
with the confocal image data, color photomicrographs
of the histological sections were mounted, scanned, and
digitized in monochrome. The images were then re-
versed to negative to allow comparison with the confo-
cal images. Ten homogeneous photomicrographs were
selected for each animal in the OVX treatment groups
and the intact control groups. The photomicrographs
were scored in the same manner as that described for the
confocal image data.
To calculate the relative density of nuclei in the con-
focal images, a 10-cm2
template was created and divided
into 1-cm2
units. The template was placed over each of
the 60 images used for image analysis and the number of
nuclei was counted. The results are presented as the
mean number of nuclei per square centimeter of image.
Statistical analysis
A c2
analysis was performed on results of individual
observers (frequency of correct identification for each
treatment group) to detect any association between the
treatment groups observers assigned to each image and
the actual treatment groups. The data from all observers
were then combined and analyzed. Data other than
frequencies (expressed as mean G SEM) were analyzed
by 1-way analysis of variance to detect significant
differences between treatment groups. A probability
level of 5% (P ! .05) was specified as significant. A
post hoc test of least significant difference was used to
identify differences between means of individual treat-
ment groups.
Results
Reproductive tract weight
The effect of hormonal status on the reproductive tract
weight is shown in Figure 1. There was no significant
difference in organ weight between the OVX ewes that
received no hormone replacement or progesterone im-
plants alone (P = .53). In contrast, ewes treated with
17b-estradiol or 17b-estradiol and progesterone com-
bined had higher reproductive tract weights (82.7g and
81.4 g, respectively) than those animals not exposed to
17b-estradiol (P ! .05). The tract weights were highest
in the intact animals at estrus (131 G 16.8 g). The uteri
of these ewes were pink and turgid, consistent with high
levels of estradiol. Intact animals in the midluteal phase
of the estrus cycle had a mean tract weight of 100 G 9.29 g.
This weight was not different from OVX ewes receiving
17b-estradiol treatment alone or combined 17b-estradiol/
progesterone replacement (P O .05).
Hormone concentrations
The arterial plasma concentrations of progesterone in
the experimental and control animals are shown in
Figure 2. In the OVX ewes that received no hormone
replacement or 17b-estradiol implants alone, progester-
one concentrations were low (0.31 G 0.4 ng/mL and
0.28 G 0.04 ng/mL, respectively). The mean concentra-
tions in these animals were not significantly different
from the intact animals at estrus (0.22 G 0.02 ng/mL;
P O .05). In contrast, intact ewes in the midluteal phase
of the reproductive cycle had mean progesterone con-
centrations of 4.36 G 1.03 ng/mL. In OVX ewes with
progesterone replacement, the mean level achieved was
0.61 C 0.1 ng/mL. Although this level did not mimic
peak luteal concentrations observed in the intact ani-
mals, the implants raised concentrations to levels that
were significantly higher than those observed for the
other OVX treatment groups (P ! .001). Plasma
estradiol concentrations could not be measured because
of a freezer malfunction with the samples remaining
thawed for an unknown period.
Confocal microscopy of the ectocervix
Changes in the morphology of the ectocervix in associa-
tion with hormone replacement or reproductive state
observed with confocal microscopy are shown in Figure 3.
In OVX animals with no hormone replacement, the
nuclei of the squamous epithelium stained strongly
with Acriflavine (Sigma Pharmaceuticals) and were
small and densely concentrated in the FOV (Figure 3A).
Bott et al 107

4. Conversely, in OVX animals treated with 17b-estradiol,
the number of nuclei in a FOV was reduced. The nuclei
were generally larger in size and did not fluoresce as
brightly as those in the no-replacement animals (Figure
3B). Confocal images from progesterone-treated ewes
demonstrated smaller and less rounded cell nuclei that
were less homogeneously distributed across the FOV than
in the estradiol-treated animals (Figure 3C). Treatment of
OVX ewes with combined 17b-estradiol and progesterone
implants resulted in variable image results (Figure 3D).
The ectocervical images of control ewes in estrus closely
resembled those of the OVX ewes receiving 17b-estradiol
replacement (Figure 3E). Similarly, the morphology of
the cervical epithelium of ewes in the mid-luteal phase of
the reproductive cycle (Figure 3F) was analogous to that
in the OVX ewes given progesterone implants.
Nuclear density of confocal images
Confocal images of the ectocervix of OVX ewes treated
with 17b-estradiol showed similar nuclear densities to
images of ectocervix from intact animals at estrus
(Figure 4; P = .493). This suggests that estradiol im-
plants raised plasma concentrations sufficiently to re-
produce the biological effects observed at estrus. OVX
animals treated with progesterone implants showed
similar nuclear densities to the intact animals at the
midluteal phase of the estrus cycle (8.25 G 0.33 nuclei/
cm2
and 8.74 G 0.60 nuclei/cm2
, respectively). The mean
nuclear density of these images was significantly higher
than in images from OVX ewes treated with 17b-
estradiol and progesterone (P ! .001) or ewes treated
with 17b-estradiol alone.
Evaluation of confocal images
Thirteen of 14 observers showed a significant associa-
tion between the treatment group selected for each
image and the actual treatment group of the image
(Figure 5, open bars). If the observer had guessed the
treatment group, approximately 17% of the images
would have been correctly identified. Instead, 48% of
the images were identified correctly (P ! .05). The
majority of significant c2
values for individuals resulted
from correct identification (more than 60%) of OVX
animals treated with 17b-estradiol or intact animals at
estrus. When these images were removed from the c2
test, only 8 of 14 observers showed a significant asso-
ciation (P ! .05) between the treatment group selected
for each image and the actual treatment group.
Histological photomicrographs
When lay observers were asked to assess the histological
photomicrographs, 12 of 14 observers showed a signif-
icant association (P ! .05) between the treatment group
selected and the actual treatment group (Figure 5, filled
bars). As was observed with the confocal data, more
than 50% of the images for animals treated with 17b-
estradiol or those animals in estrus could be correctly
identified. When the analysis was repeated with results
from estradiol-treated animals and those at estrus
grouped together, c2
analysis revealed that all 14
observers showed a significant association between the
treatment group selected and the actual treatment
group.
Comment
The present study aimed to characterize changes in the
morphology of the ovine cervix in relation to hormonal
status during the estrus cycle using confocal microscopy,
an optical imaging technique that enables real-time
imaging of microscopic structure both in vivo and
in vitro. The imaging device enabled subcellular resolution
Figure 1 The mean (G SEM) reproductive tract weights of
OVX ewes with and without hormone replacement and intact
ewes at estrus and the midluteal phase of the reproductive
cycle. Data points denoted by different letters represent
significant differences between means (P ! .05).
Figure 2 The mean (G SEM) concentrations of progesterone
(nanograms per milliliter) in the arterial plasma of OVX ewes
given hormone replacement and intact ewes at estrus or the
midluteal phase of the reproductive cycle. Data points denoted
by different letters represent significant differences between
means (P ! .05).
108 Bott et al

5. Figure 3 Single optical sections obtained by confocal microscopy from the surface of the squamous epithelium of the ovine
ectocervix following the topical application of Acriflavine (0.05%). A, OVX, no hormone replacement. B, OVX, 17b-estradiol
replacement. C, OVX, progesterone replacement. D, OVX, 17b-estradiol, and progesterone replacement. E, intact animals, estrus.
F, intact animals, midluteal phase. Bar, 100 mm.
Bott et al 109

6. of the epithelium. Morphological features associated
with estrogen-dominated states could be differentiated
reasonably well by untrained, lay observers, and we
suggest that these results would be exceeded by trained
clinicians. The results suggest that confocal endomicro-
scopy has the potential to be a useful imaging modality
for the detection of microscopic changes of the human
cervix.
The ability of lay observers to identify estradiol-
dominated states from the confocal images of the ecto-
cervix accords with the significant differences in nuclear
density between ewes exposed to estradiol and those
given no hormone replacement or progesterone implants
alone. Images of the ectocervix of ewes in an estradiol-
dominated state were characterized by sparsely distrib-
uted cell nuclei that were uniformly spread across the
FOV. Images from OVX animals given no hormone re-
placement or progesterone implants alone had cell nuclei
that were more densely concentrated in a given FOV,
closely resembling dysplastic conditions in humans.7-9
If
similar changes in cellular morphology are demonstrated
in humans throughout the reproductive cycle, the ability
to distinguish early dysplasia or neoplasia with confocal
microscopy would probably be greatest when the patient
is in an estrogen-dominated state.
The effect of estradiol on the cervical epithelium is
well documented. Estradiol is thought to initiate expan-
sion of the stromal cell cytoplasm10
and a change in the
shape and diameter of the cervix.11
Pinto et al12
found
that injection of estradiol in term pregnant women
promotes softening of cervical collagen fibers and dila-
tion of the external os, similar to the qualitative obser-
vations made in this study. Cervices from estradiol
treated ewes were bigger and had larger diameters
than those of the other treatment groups and were soft
and supple with a partially open external os, exposing
the endocervical canal. Estrogens also increase uterine
blood flow.13
Consistent with this suggestion, the repro-
ductive tracts of OVX ewes treated with estradiol were
pink and vascular.
The administration of estrogen to OVX ewes induces
changes to the reproductive tract similar to those found
at estrus or during the follicular stage of the menstrual
cycle. There is a rapidly developing hyperemia and an
increase in weight, which initially is due to the accumu-
lation of fluid but is later augmented by cellular growth
and proliferation.14
In the present study, the reproduc-
tive tract weights of OVX ewes given estradiol replace-
ment and intact ewes at estrus were high in comparison
with those in the other treatment groups. Estradiol
regulates epithelial cell proliferation in urogenital tract
tissue through a paracrine mechanism mediated via
stromal steroid receptors.15
Previous studies suggest
that cyclic changes in estrogen receptors may contribute
to the change in morphology of the squamous epithe-
lium in the human ectocervix; however, results are
contradictory because of difficulty in accurately defining
the stage of the reproductive cycle.16-19
Although estro-
gen receptors were not measured in the present study,
the use of an animal model enabled accurate control
over the endocrine status and satisfactory definition of
the stage of the reproductive cycle.
Optical technologies are being used increasingly for
assessment of tissue morphology. Techniques such as
fluorescence spectroscopy20
and reflectance spectros-
copy21
extract diagnostic information from tissue on
the basis of the interaction of light with endogenous
tissue chromophores (autofluorescence). The level of
contrast, however, between diagnostically important
structures such as the nucleus can vary significantly.
Figure 4 The mean (G SEM) nuclear density of confocal
images from the ectocervix of OVX ewes with and without
hormone replacement and intact ewes at estrus or the
midluteal phase of the reproductive cycle. Data points denoted
by different letters represent significant differences between
means (P ! .05).
Figure 5 The mean percentage of confocal images (open
bars) and photomicrographs (filled bars) obtained from OVX
and intact ewes that were correctly identified by lay observers.
110 Bott et al

7. The application of an exogenous fluorophore provides a
signal intensity that is stronger and more consistent than
is found with autofluorescence. This facilitates scanning
of large surface areas of tissue and the collection of
images with a high signal-to-noise ratio.
A significant advantage of confocal microscopy over
conventional imaging techniques for the cervix (ie, the
Papanicolaou test and colposcopy) is the collection of
data in real time without the need for tissue removal.
With further development, confocal microscopy has the
potential to offer noninvasive diagnosis of tissue mor-
phology and the development of a see-and-treat algo-
rithm for cervical dysplasia and neoplasia.7
The rapid
nature of fluorescence measurements allows examination
of a greater number of sites than can be feasibly excised.
The length of time to perform the procedure is signifi-
cantly less than conventional tissue sampling and pro-
cessing. Moreover, the noninvasive nature of the imaging
procedure allows multiple sites to be assessed without the
associated superficial bleeding and tissue damage asso-
ciated with biopsies. Previous studies using confocal
microscopy to image the human cervical epithelium (in
vivo and in vitro) have highlighted the clinical potential
for the detection of dysplasia.22-28
Further clinical inves-
tigation of this technique is warranted.
In conclusion, the results of the present study have
shown that fluorescence confocal microscopy is a useful
imaging technique for examination of the cervix.
Changes in the morphology relative to hormonal status
could be differentiated throughout the estrus cycle in
sheep. The results suggest that confocal microscopy may
be a useful adjunct to the Pap smear or colposcopy to
enhance diagnostic accuracy and patient outcome.
Acknowledgments
The expert technical assistance of Mr. Alex Satragno in
surgical techniques and Ms. Jan Deayton for assay
results and analysis is gratefully acknowledged. We are
also grateful to Mr. Ian Boundy (Department of Anat-
omy, Monash University) for histological expertise.
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