Synthetic Matrices that Induce Stem Cell-Mediated Bone Formation

Biomimetic matrices resemble living structures even though they are made from synthetic materials. Researchers in the laboratory of Shyni Varghese at the UC San Diego Jacobs School of Engineering have used calcium phosphate to direct mesenchymal stem cells to form bone. In doing so, Varghese and his colleagues have identified a surprising pathway from biomaterials to bone.

Varghese and his colleagues think that their work may point out new targets for treating bone defects, such as major fractures, and bone metabolic disorders such as osteoporosis.

The first goal of this research was to use materials to build something that looked like bone. This way, stem cells harvested from bone marrow (the squishy stuff inside our bones) could sense the presence of bone and differentiate into osteoblasts, the cells in our bodies that build bone.

“We knew for years that calcium phosphate-based materials promote osteogenic differentiation of stem cells, but none of use knew why.” said Varghese. “As engineers, we want to build something that is reproducible and consistent, so we need to know how building factors contribute to this end.”

Varghese and co-workers discovered that phosphate ions dissolved from calcium phosphate-based materials and these stray phosphate ions are taken up by the stem cells and used for the production of adenosine triphosphate or ATP. ATP is the energy currency of the cell, and it is the way cells store energy in a form that is readily usable for powering other reactions.

In stem cells, the generation of ATP eventually increases the intracellular concentration of the ATP breakdown product adenosine, and adenosine signals to stem cells to differentiate into osteoblasts and make bone.

Varghese said that she was surprised that “the biomaterials were connected to metabolic pathways. And we didn’t know how these metabolic pathways could influence stem cells,” and their commitment to bone formation.

These results also explain another clinical observation. Plastic surgeons have been using fat-based stem cells for eyelid lifts, breast augmentation, and other types of reconstructive surgeries. In once case, a plastic surgeon injected a dermal filler that contained calcium hydroxyapatite with the fat-based stem cells into a woman’s eyelid to provide an eye lift. However, the stem cells formed bone, and the poor lady’s lid painfully clicked every time she blinked and she had to have surgery to remove the ectopic bone. These results from Varghese’s laboratory explains why these fat-based stem cells formed bone in this case, and great care should be taken to never use such fillers in fat-based transplantation procedures.

Artificial Bones From Umbilical Cord Stem Cells

I am back from vacation. We visited some colleges in Indiana for my daughter who will be a senior this year. She really liked Taylor University and Anderson University. We’ll see if the tuition exchange works out.

Now to blogging.

Scientists from Granada, Spain have patented a hew biomaterial that consists of activated carbon cloth that just happens to be able to support the growth of cells that have the ability to regenerate bone. These results came from experiments that were conducted outside any living animals, but they hope to confirm these results in a living animal in the near future.

This new biomaterial facilitates the growth of bone-making cells derived from umbilical cord stem cells. This activated carbon cloth acts as a scaffold for cells that differentiate into “osteoblasts,” which are bone-building cells. This activated carbon cloth gives the osteoblasts a proper surface upon which to promote the growth of new bone.

Bone loss as a result of cancer, trauma, or degenerative bone diseases requires replacement bone to heal to damaged bone. Making new bone in the laboratory that can be transplanted is an optimal strategy for treating these patients.

Even though this laboratory-made bone was not used in living laboratory animals to date, the laboratory results look quite impressive. In the future, such techniques could help manufacture medicines or other sources of material to repair bone or lost cartilage. Once such artificial bone has been made in the laboratory, the Spanish team hopes to transplant it into rats or rabbits to determine if it can regenerate bone in such creatures.

Presently, no materials exist to replace lost bone. The method used to make bone by the research team from Granada uses a three-dimensional support that facilitates the production of those cell types that regenerate bone without the need for additional growth factors.

The growth of these umbilical cord stem cells on activated carbon cloth produced a product that could produce organic bone, but also mineralize the organic bone matrix. This patent could have numerous clinical applications in regenerative medicine and the Granada group hopes to obtain funding to continue this work and achieve their ultimate objective: to regenerate bones by implanting biomaterial in patients with bone diseases.