Ten women with severe osteoporosis broke far fewer bones in the years after they received a single drip of their own bone marrow cells, modified so they might find their way back to bone. The results of this first test in people were published in the journal Cell on September 11, 20261. Across the group, fractures from fragile bones fell from 8 a year to 0.5 a year in the first two years, a 94% drop2. But the trial had no comparison group, and most of the women were also taking standard osteoporosis drugs, so it cannot say how much of that drop came from the cells2.
What happened
The study was led by José Moraleda of the University of Murcia in Spain and Robert Sackstein of the Miami Veterans Affairs Healthcare System in the United States3. It was a Phase 1 trial, the first and smallest stage of testing in people, designed mainly to check safety and whether the treatment could be made and given at all1.
The 10 women were 51 to 72 years old and had already had fractures caused by osteoporosis2. Before the trial, they had been breaking bones in the spine, hip, arm and other places roughly once every one to two years on average3.
Doctors drew about 60 milliliters of marrow, roughly four tablespoons, from each woman’s hip2. In the lab they grew a type of marrow cell called mesenchymal stromal cells, or MSCs, which can turn into osteoblasts, the cells that build bone2. They then changed the cells’ surface and gave each woman one intravenous dose of her own cells2.
Giving the cells an address
The idea behind the trial is a delivery problem. When MSCs are grown in a lab and put into a vein, they do not easily reach bone3. The team tried to fix that by changing the sugary coating on the outside of the cells2.
They added a sugar called fucose to a surface molecule called CD442. To do this, the cells were bathed in a liquid with an enzyme and a sugar donor molecule called GDP-fucose4. The result is a structure called HCELL, which can grab onto molecules lining blood vessels in bone marrow1. The tag lasts about 48 hours, which appears to be long enough to help circulating cells slow down along marrow blood vessels and move into the tissue2. It does not permanently change the cells’ DNA2.
The approach goes back to a 2008 study in mice, published in Nature Medicine, in which Sackstein and colleagues showed the same sugar engineering could steer human MSCs into bone marrow2. When the team gave these modified cells to mice, skeletal tissue formed3. The human trial began in 20153.
The evidence so far
Beyond the 94% drop in the first two years, fractures stayed less frequent over the full follow-up of about six years, going from 0.54 to 0.11 per patient-year4. Put another way, fractures went from about once every one to two years to about once every 10 years3.
The team also looked inside the bones:
- Bone samples (biopsies) taken four months after treatment showed that the average bone tissue area nearly doubled4.
- A CT-based measure of the quality of the spongy bone inside the skeleton had improved by two years2.
- Blood markers linked to bone building rose and stayed higher for more than six months after the single drip4.
- The standard bone density scan used in clinics, called DXA, did not show significant improvement across the group2.
The women also reported changes. By 24 months, bone pain was down about 34% and physical disability scores had improved by about 30%1.
On safety, the researchers followed the women for a median of about six years and reported no serious side effects attributable to the cell drip2. There was no observed rise in cancer3.
What it does not show yet
Ten people are far too few to establish that the therapy prevents fractures2. Several features of the trial make the result hard to read:
- No comparison group. No women got a dummy treatment or no treatment, so the researchers could not tell how much the cells contributed to the drop in fractures2.
- Other drugs. Most women were on standard osteoporosis medicines before and during the trial3, and medication changes were allowed afterward when medically needed1.
- Cells not tracked. The researchers could not follow the cells inside the body to show how many actually reached bone3.
- Small numbers. A dramatic percentage drop can look especially large when it comes from very few patients1.
Outside experts also urged caution about the blood markers. Richard Eastell, a professor of bone metabolism at the University of Sheffield who was not involved, told the journal Nature that rises in these proteins can also happen when bone is being broken down3:
increases in these proteins can also occur during bone resorption.
Reactions from other scientists not involved ranged from enthusiastic to measured. Ajit Varki of the University of California, San Diego, told Nature that the trial “showed an almost 100% efficacy sustained for several years—and no side effects”2. Jasmin Merzaban of King Abdullah University of Science and Technology said the fracture drop six years on “means that something is happening,” but added that “to answer questions about treatment efficacy, we need larger randomized clinical trials”3.
Who is behind it
Robert Sackstein, one of the study’s authors and a developer of the cell-coating method, holds intellectual-property rights related to the technology under US National Institutes of Health policies2. That is relevant as the method moves toward larger trials and possible commercial use2. The sources reviewed did not describe who funded the trial.
How it fits the field
Osteoporosis makes bones thin and fragile, and it is especially common after menopause3. About 200 million women worldwide are estimated to have it3, and 1 in 3 women over 50 is at risk of an osteoporosis-related fracture4.
Current medicines either slow bone loss or encourage new bone, and larger studies have shown they reduce fracture risk1. They require long-term use and can cause side effects such as heartburn and nausea, and about 30% to 35% of patients stop taking them4. The cell approach is not an approved replacement for these drugs1.
The trial also touches a wider question. Some researchers worry that cells from older or sicker people may be too worn out for repair treatments; the reports say this small study hints that such cells may still be useful when steered to the right place1. Some coverage frames the result as early evidence that therapeutic cells can be sent to a chosen tissue without permanently changing their DNA2. Both ideas still need larger studies.
What to watch next
The team is preparing a follow-up trial of about 100 osteoporosis patients who are already on standard drug treatment3. They plan three groups: one gets tagged cells from their own marrow, one gets tagged cells from healthy donors, and one gets no cell therapy3. A comparison like this is what the first trial lacked, and it is the step that could show whether the cells themselves change fracture rates.
