- Stem cell therapies are being used in regenerative medicine like forming new adult bone, which usually does not regrow to bridge wide gaps. Successful attempts have now been made in this area because the same paracrine and endocrine factors were found to be involved in both endochondral ossification and fracture repair. Few methods to achieve the above are given
below.
A. Develop a collagen gel containing plasmids carrying the human parathyroid hormone gene and place in the gap between the ends of broken leg.
B. Develop a gel matrix disc containing genetically modified stem cells stem to secrete BMP4 and VEGF-A and implant it at the site of wound.
C. Make scaffold of material that resembles normal extracellular matrix that could be molded to form the shape of a bone needed and seed them with bone marrow stems cells
D. Develop a collagen gel containing plasmids carrying the human bone marrow cells and place them between ends of bones.
Which of the above methods would you employ to develop a new functional bone in patients with severely fractured bones?
(1) A and B (2) A, B and C
(3) A and C (4) C and DThe best methods are A, B and C, so the correct option is (2) A, B and C.
Understanding each method
A. Collagen gel with plasmids encoding human parathyroid hormone (PTH) – Useful
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PTH, in controlled intermittent or localized expression, can stimulate osteoblast activity and bone formation.
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Embedding PTH-expressing plasmids in a biodegradable collagen gel placed in the defect can act as a local gene-therapy depot, encouraging bone regeneration at the fracture site.
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Conceptually sound for promoting endochondral ossification.
B. Gel matrix with stem cells engineered to secrete BMP4 and VEGF-A – Very useful
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BMP4 (Bone Morphogenetic Protein 4) strongly induces osteogenesis and cartilage formation.
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VEGF-A promotes angiogenesis, providing blood supply crucial for survival and remodeling of new bone.
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A gel disc carrying genetically modified stem cells secreting these factors directly into the defect supports both bone formation and vascularization, a powerful regenerative approach.
C. ECM-like scaffold seeded with bone marrow stem cells – Useful
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A scaffold mimicking extracellular matrix provides 3D structural support and correct shape for the new bone.
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Seeding it with bone marrow–derived stem cells gives osteoprogenitors that can differentiate into osteoblasts and form functional bone tissue.
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This is a widely used tissue-engineering strategy for large bone defects.
D. Collagen gel containing plasmids “carrying the human bone marrow cells” – Conceptually flawed
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Plasmids are DNA molecules, not carriers of intact bone marrow cells.
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“Plasmids carrying the human bone marrow cells” is biologically incorrect; to add bone marrow cells one would directly seed them, not encode them in plasmids.
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Thus, D does not represent a valid or coherent therapeutic method.
Why option (2) is correct
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Methods A, B, and C all use rational combinations of gene delivery, growth factors, stem cells, and scaffolds that mirror natural endochondral ossification and fracture repair.
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Method D is not technically meaningful and would not be chosen.
Therefore, the best set of strategies to develop new functional bone in severe fractures is A, B and C (option 2).
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