Bone Formation Lab Report

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MOLECULAR MECHANISM OF BONE FORMATION
Arunava Seth 16IP009
INTRODUCTION
Skeletal system is an integral part of vertebrates, and essential for crucial activities. It not only provides a hard frame to body and protects vital soft organs, it also is required for locomotion, storage of minerals, especially calcium in body and sheltering hematopoietic stem cell in body. Bone is actually a type of dense connective tissue, with honeycomb-like matrices, the reason behind it’s rigidity.
Ossification is the process of bone tissue formation. This can be formation of new bone during development. But it is also synonymous with bone remodeling, another important phenomenon of bone metabolism. Bone remodeling is removal of mature bone tissue from skeleton
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The most important being Wnt signaling pathway, prominently the Wnt canonical pathway (i.e. Wnt/B-catenin). It has been reported both in human and mice that loss of function mutation in co-receptor of Wnt (LRP5) causes osteoporosis, and gain of function mutation of same receptor causes high bone mass (15). This clearly indicates Wnt signaling is involved in bone formation. The exact mechanism is yet to be deciphered, in fact the identity of the Wnt ligand from the 19 Wnt ligands human produced is yet to be…show more content…
Beginning with commitment of mesenchymal cell to form cartilage cell. Factors involved in this are Pax1 and Scleraxis which are secreted by nearby mesodermal cells. The next stage is condensation of these committed cells to form compact nodules and form chondrocytes. Important molecule in this stage is N-cadherin. Also, there are some reports which points at involvement of SOX9. Next stage is endochondral ossification, the chondrocytes proliferate rapidly to form the model for the bone. The chondrocytes secrete a cartilage-specific extracellular matrix. Following stage, the chondrocytes stop dividing and increase their volume and become hypertrophic chondrocytes. These are large chondrocytes with altered the matrix they produce (adding collagen X and more fibronectin) and enable it to become mineralized by calcium carbonate. The finale phase is invasion of the cartilage model by blood vessels. The hypertrophic chondrocytes die by apoptosis. This space will become bone marrow. As the cartilage cells die, a group of cells that have surrounded the cartilage model differentiate into osteoblasts and started making bone matrix. Gradually all the cartilage is replaced by bone. Various bones are produced in this way, most notably the vertebral column, the pelvis, and the

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