A new proof-of-concept study has found a combination of two drugs, already approved by the FDA for other uses, may boost the release of stem cells from bone marrow and accelerate the healing of broken bones. Only demonstrated in animals at this stage, the researchers suggest clinical trials could progress rapidly considering the drugs have already been demonstrated as safe in humans.

"The body repairs itself all the time, says corresponding author on the study Sara Rankin. We know that when bones break they will heal, and this requires the activation of stem cells in the bone. However, when the damage is severe, there are limits to what the body can do of its own accord.

A great deal of current research is focusing on mesenchymal stem cell (MSC) therapies. MSCs are a type of adult stem cell that can grow into a variety of different cell types including muscle, fat or bone. Many current MSC treatments in development involve extracting a small number from a patient, growing them in laboratory conditions, then injecting them back into the patient.

The new research set out to investigate whether any currently approved drugs can function to mobilize the bodys natural ability in releasing MSCs, with a view on speeding up healing of bone fractures. A study published in the journal npj Regenerative Medicine, describes the testing of two already approved drugs in a rodent spinal injury model.

The two drugs tested were an immunostimulant called Plerixafor, used to stimulate the release of stem cells from bone marrow in cancer patients, and a beta-3 adrenergic agonist developed to help bladder control.

The results suggest the duo of drugs mobilize MSCs into the bloodstream and speed up the process of bone formation and healing by enhancing the binding of calcium to the injury site. Tariq Fellous, first author on the new study, suggests the next step is to investigate whether this drug combination enhances blood MSC levels in human subjects.

We first need to see if these medications release the stem cells in healthy volunteers, before we can then test them in patients with fractures, says Fellous. We have the drugs and know they are safe to use in humans - we just need the funding for the human trials.

The researchers say prior studies have identified circulating MSCs increase in volume following injuries such as burns, bone fractures, and even heart attack. The hypothesis is that the release of MSCs is a physiological process aiding general regeneration following injury, and if circulating numbers of MSCs could be pharmacologically enhanced then a variety of types of tissue regeneration could be accelerated.

It is important to note the current study only examined increases in circulating MSCs and the rate of spine injury healing compared to no drug treatment. The current research offers no indication whether the drug duo influences nerve healing or restores movement.

So, more work is certainly necessary to understand how clinically useful these results actually are. However, as the studys co-first author Andia Redpath notes, this re-purposing of existing medicines to boost stem cell activity is an easier, cheaper, and more efficient way to enhance healing compared to other, more complex and time-consuming, stem cell treatments in development.

Rather than devising new stem cell treatments from scratch that involve lengthy and expensive trials, our approach harnesses the power of the bodys own stem cells, using existing drugs, says Redpath. We already know the treatments in our study are safe, its now just a matter of exploring further if they help our bodies heal.

The new study was published in the journal npj Regenerative Medicine.

Source: Imperial College London

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