Jarvie Journal - College of Dental Medicine - Columbia University

Volume 56, Spring 2013
Effects of Estrogen on Mandibular Condylar Cartilage Growth and Proliferation
Paola Annoni, Sunil Wadhwa, Jing Chen*
College of Dental Medicine, Columbia University, NY, NY * Faculty Mentor
Introduction:
The mechanisms that regulate the development and differentiation of the mandibular condylar cartilage are
intricate and currently not entirely understood. Estrogen plays a large role in regulating mandibular growth and
differentiation. For example, ovariectomy (estrogen deficiency) causes increased growth of mandibular
condylar cartilage that is reversed by estrogen supplementation. The mandibular cartilage is derived from the
outer surface of the mandibular bone, called the periosteum. The chondrocytes specifically derive from the
inner cambium layer of the periosteum, and then go on to proliferate into 4 chondral layers (superior articular [S
layer], polymorphic + flattened [F layer], and hypertrophic [H layer]). There are two classical estrogen receptors
here, and . Our central hypothesis is that estrogen acts through ER to inhibit chondrocyte maturation in the
mandibular condylar cartilage in female mice.
Objective:
The objective of this study is to examine the role of estrogen via the ER pathway in regulating mandibular
condylar growth in female WT and ER deficient mice. To achieve this aim, the mandibular condyle size along
with the polymorphic cell growth and maturation from sham or ovariectomized WT and ER deficient female
mice treated (or not treated) with estrogen has been analyzed and documented.
Materials & Methods:
Twenty-one day-old WT and ER deficient female mice were divided into three groups and sacrificed when
they are 49 days old. The groups consisted of:
1) Wild Type (sham), 2) Ovariectomy, 3) Ovariectomy+ Estrogen
Once the mice were sacrificed, histological slides of their temporomandibular joints were made and the cells
within the four chondral layers are then counted. In order to assess proliferation, BrdU immunohistochemistry
was performed and the percentage of BrdU positive cells over total cell numbers was calculated.
Results & Conclusions:
We found that ovariectomy caused a significant increase in total cell numbers in the mandibular condylar
cartilage that was reversed with estrogen supplementation in WT mice.
On the other hand, ovariectomy plus estrogen replacement had no significant effects on female ER KO mice.
Ovariectomy causes significant decrease in proliferation in both WT and ER KO compared to sham operated
controls.
Discussion:
Previous studies have shown that ovariectomy causes a general increase in mandibular condylar cartilage size.
In our study, we found similar results. However, when we performed ovariectomies on ER KO mice, no
increase in condylar cartilage size was noted.
Taken together, these results suggest that the effects of estrogen on condylar cartilage size are mainly mediated
by ER receptor.
Paola Annoni was supported by a College of Dental Medicine Pre-Doctor al Summer Research Fellowship.
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