الفهرس 
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Abstract
Osteoporosis is one of the most common chronic diseases associated with progressive
bone loss. The prevalence of osteoporosis increases with an aging population, particularly in
postmenopausal women. It is characterized by excessive bone resorption and diminished
bone formation due to the impaired orchestrating activities of osteoblasts and osteoclasts,
leading to the decrease of bone mass.
Ovariectomy (OVX) is the most appropriate model for postmenopausal osteoporosis
research that causes estrogen deprivation. It causes a decrease in estrogen’s bone-protective
effects which are followed by a fast loss of trabecular bone.
Melatonin is a pineal neuroendocrine hormone that possesses anti-aging, antiinflammatory, and antioxidant properties. Therefore, it has been scientifically tested for the
prevention of chronic diseases such as inflammatory bowel disease, obesity with insulin
sensitivity, neurological diseases, and respiratory diseases.
Bone tissue is a dynamic mineralized connective tissue that contains cells, extracellular
matrix, and other connective tissue elements such as hematopoietic tissue and adipose tissue.
Bone’s capacity to provide structural support and hardness to the tissues is due to the
mineralization process.
The present work aimed to assess the biochemical and histological changes in the
lumbar vertebrae after OVX-induced osteoporosis in adult female albino rats. The possible
protective effect of melatonin against OVX-induced osteoporosis was evaluated as well.
The current study was conducted on 24 adult female albino rats (5-6-months-old) that
were randomly divided into two groups as follows:
group I (sham-operated control group): included 12 rats that were subjected to
transverse abdominal incisions without ovarian removal, which were then subdivided into
two subgroups:
Subgroup IA: six rats; each received subcutaneously (S.C) the normal saline (the
vehicle of MLT) for a period of four successive weeks.
Subgroup IB: six rats; each received 0.4 ml of the freshly prepared MLT solution at a
concentration of 10 mg/kg body weight S.C daily between 4:00 and 6:00 pm for a period of
four successive weeks.
group II (OVX group): included 12 rats that were subjected to bilateral OVX and
were then subdivided into two subgroups:
Subgroup IIA (Induced osteoporosis subgroup): six rats; each received the normal
saline S.C.
Subgroup IIB (MLT-treated subgroup): six rats; each received the same dose of the
freshly prepared MLT solution S.C at the same concentration and time as subgroup IB.
Summary
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At the end of the experiment, the following studies were conducted:
I- Histological study: the lumbar vertebrae of all animals were dissected out carefully and
then were subjected to the following procedures:
1. Light microscopic examination:
The vertebral bodies of L4 were immediately fixed in 10% neutral buffered formalin
and further decalcified by formic acid for the subsequent studies:
• Hematoxylin and eosin (H&E) stain.
• Masson’s trichrome stain.
2. Scanning electron microscopic examination (SEM):
The vertebral bodies of L5 were immediately fixed in glutaraldehyde solution, further
prepared for examination.
II- Morphometric study:
1. The mean area percentage of collagen fibers in Masson’s trichrome-stained sections
were measured.
2. The mean trabecular thickness from SEM imaged sections were measured.
III- Biochemical study: blood samples were collected to assess serum E2, Ca2+, PO4
3-
,
ALP and RANKL.
IV- Statistical analysis: The collected data were analyzed statistically.
The results of this work can be summarized as follows:
I- Subgroup IA and IB of the sham-operated control group revealed similar biochemical
and histological results:
• Histological examination showed normal cancellous bone structure, regular
meshwork of anastomosing bone trabeculae with connected bone marrow cavities and
the regularly aligned collagen lamellae of bone matrix enclosing lacunae of
osteocytes. SEM showed numerous regions of resting surfaces with well-organized
bone lamellae and flattened osteoblasts lining the smooth endosteum.
• Morphometric measurements of the mean area % of collagen fibers from trichromestained sections and the mean thickness of trabeculae from SEM specimens were
statistically similar.
• Serum measurements of E2, Ca2+, PO4
3-
, ALP and RANKL were within normal
control levels.
II- Subgroup IIA (Induced osteoporosis subgroup): the results of this subgroup
demonstrated the following features of osteoporosis:
• Histological examination showed discontinuous thin bone trabeculae with
microfractures and cracks and wide bone marrow cavities. Ragged endosteal surfaces
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that were seeded with numerous osteoclasts lying within wide resorption bays were
also seen.
• Morphometric measurements showed a statistically significant decrease in the mean
area % of collagen fibers as well as the mean thickness of bone trabeculae as
compared to subgroups IA and IB.
• Statistically significant decrease of E2, Ca2+ and PO4
3- with statistically significant
increase of ALP and RANKL as compared to subgroups IA and IB.
III- Subgroup IIB (MLT-treated subgroup): the results of this subgroup revealed the
features of ameliorated osteoporosis as evidenced by:
• Histological examination in most of the specimens showed interconnected bone
trabeculae that were lined mostly by cuboidal osteoblasts with scattered osteoclasts
in between. Sweeping formative bone lamellae bridging the disconnected bone ends
were also depicted by SEM, alternating with other areas of disorganized, separated
lamellae.
• Morphometric measurements showed a statistically significant increase in the mean
area % of collagen fibers as well as the mean thickness of bone trabeculae as
compared to OVX subgroup IIA.
• Statistically significant increase of E2, Ca2+ and PO4
3- with a statistically significant
decrease of ALP and RANKL as compared to OVX subgroup IIA.
Obviously, the present results revealed that melatonin possesses the potential to protect
against OVX-induced osteoporosis