ABSTRACT
BACKGROUND:
The changes in
trabecular bone microarchitecture in
osteoporosis have aroused much
attention. The decrease in the number of trabecular nodes and increase in the number of free ends are found in
osteoporosis, but the mechanism is still unclear.
OBJECTIVE:
To observe the trabecular
remodeling process in ovariectomized
rats as the
osteoporosis models
electron microscopically, and to explore the reasons for the decrease in the number of trabecular nodes and increase in the number of free ends.
DESIGN:
Randomized and controlled
animal trial.
SETTING:
Department of
Orthopedics, Third
Hospital of
Peking University.MATERIALS The experiment was conducted in the
Animal Laboratory, Third
Hospital of
Peking University from September 1999 to February 2000. Thirty-six
female Wistar rats of 3 months old and 240-280 g were selected and randomly divided into ovariectomized group and
control group with 18
rats in each group. The
rats were observed at 4,8, and 12 weeks postoperatively with 6
rats at each
time point.
METHODS:
The
rats of ovariectomized group were subjected to
ovariectomy 1 week after
feeding, but the
control group was not. The changes of proximal
tibia trabecular microarchitecture was observed under scanning
electron microscope at 4, 8 and 12 weeks, respectively, and the
osteoclast,
osteoblast, and structure of
cell organs were observed under
transmission electron microscope.MAIN OUTCOME
MEASURES:
[1]The re modeling process after
ovariectomy by
electron microscope; ②morphological changes of
trabecular bone.
RESULTS:
[1]Scanning
electron microscope
observation showed that
trabecular bone remodeling was distributed in every region of trabecular microarchitecture, especially St and Nd-St region. After
ovariectomy, the transverse trabecular was easier to be perforated and broken; the trabecular network was almost intact at 4 weeks, but gradually damaged at weeks 8 and 12; moreover, the
collagen fibers on the surface of
trabecular bone were scrappy, disorder and thinner. ②By the
transmission electron microscopic study, the tibial
osteoclast were found active at 12 weeks. When absorbing
cancellous bone,
osteoclast closely adhered to its surface, and digitations stretched into the
cancellous bone. The shape and size of digitations were significantly different, and around them, lucent area was observed.
Osteoclast was polynucleation with abundant kytoplasm, and there were plenty of
Golgi complex,
smooth endoplasmic reticulum and mitochondrium.
Lysosome inclusion compounds with different sizes and
electron density were found in
cells.
Osteoblast was rarely found, and
cell edge was rough, with
bone lacuna.
CONCLUSION:
Bone remodeling is significantly active in St and Nd-St region of
trabecular bone in ovariectomized
rats.This may be the reason for the decrease in the number of trabecular nodes and increase in the number of free ends.