- Melatonin dose-dependently augmented proteins that are incorporated into the bone
matrix, like procollagen type I c-peptide. Osteoprotegerin, an osteoblastic protein that
inhibits the differentiation of osteoclasts is also augmented by melatonin in vitro
- Another possible target cell for melatonin is the osteoclast, which degrades bone
partly by generating free radicals. Melatonin through its free radical scavenger
and antioxidant properties may impair osteoclast activity and bone resorption
Role of Cholesterol in the Regulation of Growth Plate
Chondrogenesis and Longitudinal Bone Growth
Hormonal Regulation of Bone Growth
The majority of the long bones of the body (including the tibia) form through a process called
endochondral ossification. A cartilage template is first formed in development and is then
replaced by bone. For continued growth of these bones, a cartilaginous growth plate persists
until the end of puberty in humans, and is responsible for longitudinal growth. A multitude of
hormones and other proteins regulate these processes and can increase or decrease growth
Glucocorticoids, cholesterol and melatonin all have varying effects in the body, including the
regulation of bone growth. To study the effect of these compounds, students will learn to
dissect embryonic tibia from mice, grow them in tissue culture and administer the
compounds. Longitudinal growth will then be assessed and the end of the culture period.
Objectives: In the lab you will…
1. Learn and be able to describe how the growth plate controls longitudinal growth of
2. Research the known molecular effects of various compounds on chondrocytes (the cell
type of cartilage) and then predict the effect on longitudinal growth.
3. Learn how to microdissect tibia from embryonic mice.
4. Learn and practice sterile technique for culturing tissues.
5. Examine the effects of compounds on longitudinal growth of long bones.
Purpose/Hypothesis – The purpose of this experiment was to study the effects of
dexamethasone, melatonin, and cholesterol on the regulation of embryonic tibia growth. We hypothesized that dexamethasone would inhibit bone growth while melatonin and
cholesterol would promote bone growth.
Method– After arresting CD1 embryonic mice at day 15.5 of gestation, tibia were
microdissected and isolated on individual growth plates. Within each independent trial,
tibia were subdivided into 5 treatment groups: DMSO cont