Saturday, August 14, 2010

Increase your Bone Length with Bone Autographs?

Bone Autographs were developed as a potential way to aid amputees regrow lost limbs.  A bone autograph is a a scaffold that is injected between a gap in the bone and the bone the naturally grows back in that area.  A bone autograph refers to using an individuals own bone to build the scaffold for new bone to grow around it.  The first usage that comes to mind for a bone a autograph is for limb lengthening surgery, you could cut the bone in two and grow a lot faster than 1 mm a day(still problems with soft tissue though).  Now this bone doesn't grow out of nowhere, when the bone is separated the periosteum and trabecular bone are separated too given the body complete access to the periosteal progenitor cells and trabecular bone stem cells.  Now I think a bone graft is too cumbersome but it can be used to exemplify the bones ability(specifically MSCs and progenitor cells) to grow bone out of nowhere.  And we can study if the scaffold(the bone graft) has properties similar to the hyaline cartilage growth plate line.

Here's a full study by Paul Wooley, the Kansas bone grafting scientist who's received a lot of attention lately.

Biocompatibility of Poly-ε-caprolactone-hydroxyapatite composite on mouse bone marrow-derived osteoblasts and endothelial cells

"Tissue-engineered bone may be developed by seeding the cells capable of both osteogenesis and vascularization on biocompatible composite scaffolds. The current study investigated the performance of mice bone marrow-derived osteogenic cells and endothelial cells as seeded on hydroxyapatite (HA) and poly-ε-caprolactone (PCL) composite scaffolds."

"Mononuclear cells were induced to osteoblasts and endothelial cells respectively(no cartilage so no endochondral ossification), which were defined by the expression of osteocalcin, alkaline phosphatase (ALP), and deposits of calcium-containing crystal for osteoblasts, or by the expression of vascular endothelial growth factor receptor-2 (VEGFR-2) and von Willebrand factor (vWF), and the formation of a capillary network in Matrigel™ for endothelial cells. Both types of cell were seeded respectively on PCL-HA scaffolds at HA to PCL weight ratio of 1:1, 1:4, or 0:1 and were evaluated using scanning electron microscopy, ALP activity (of osteoblasts) and nitric oxide production (of endothelial cells) plus the assessment of cell viability."

"The results indicated that HA led to a positive stimulation of osteoblasts viability and ALP activity, while HA showed less influence on endothelial cells viability. An elevated nitric oxide production of endothelial cells was observed in HA-containing group."

The HA graft was successful in stimulating bone growth around the graft.  What the scientists did to counteract this lack of endothelial cell viability(blood vessal viability) was to place endothelial cells directly onto the bone graft.

"Hydroxyapatite (HA) is the inorganic part of the naturally occurring bone, and is known to be both biocompatible and osteoconductive."

In conclusion, I think Hydroxyapatite grafting will be the future of limb lengthening surgery.  It doesn't appear to have any applications to trying to induce growth in the hyaline cartilage growth plate line(LSJL).  It's something to watch in the future definitely.

Here's a grant that wants to develop a tissue engineering approach to growth plate regeneration using stem cells by Chelsea Shields Bahney.

"I have characterized hypertrophic maturation of MSCs in tissue-engineered scaffolds and developed a MMP-7 bioresponsive system tuned to chondrogenesis. "<-We have to study MMP-7.


  1. You've probably read this, but:

    Dunno, might be helpful to look at this :)

  2. So LSJL don't work? Are you sure?