“Bone is constantly renewing, living tissue”

The history of the group goes back to the early 80s, when doctors Jaume Aubia and Adolf Díez set up the bone metabolism research group. “At this time we had just started to use densiometers to measure bone density”, explains Xavier Nogués, coordinator of the current Genetics of Osteoporosis research group at the IMIM (Hospital del Mar Research Institute) and head of the internal medicine service at the Hospital del Mar. “It was after 1998 when the genetics side was developed more specifically, focusing on osteoporosis”, he says. That was when the collaboration with the Genetics Department of the University of Barcelona began, which is still going strong today.

The group is made up of doctors, biologists and biochemists, dedicated to the study of osteoporosis, the loss of bone mass due to imbalance between the formation and resorption (remodelling) of the bone. This condition is frequent in post-menopausal women because of decrease in oestrogen levels. “Bone is a constantly renewing, living tissue. Osteoblasts are cells which form bone, and osteoclasts destroy it. It is calculated that it takes 10 years to renew the whole skeleton, but there are always millions of units remodelling it”, explains the head of the group.

Looking for the genetic base 

There are many environmental factors affecting osteoporosis: tobacco, alcohol and certain medicines. But there is also an important genetic element, as osteoporosis has a heritability of 70-80%.Today, some 20 candidate genes are known which provoke susceptibility to osteoporosis, but none is particularly predominant.

One of the group’s projects deals specifically with these genes and involves a cohort of 1600 women. “Right now we’re working on two particular genes, OPG and RANKL, although we have worked on many others”, says Nogués. In addition, the group forms part of the multinational GEFOS consortium which brings together osteoporosis cohorts from various countries to enable a meta-analysis of up to 300,000 samples.

Osteoporosis and cancer 

The group has another project under way on osteoporosis and breast cancer, in collaboration with the team of Joan Albanell (IMIM). “One of the drugs taken by women with breast cancer, the aromatase inhibitor, may provoke osteoporosis. We are doing densiometry and clinical and genetic analysis on more than 450 patients to study a possible correlation”. To test the genetic findings from the patients, the group does in vitro gene expression studies on cultures of primary osteoblasts.

Microidentation, a new diagnostic method 

Approximately 35% of women over 50 suffer fractures because of osteoporosis, particularly around 60 years of age. “It is important to detect and treat the osteoporosis before a fracture, but densiometry is only done to women considered at risk, for example due to early menopause. There is still a long way to go”, explains Nogués. In fact, the group is heading up a project, in collaboration with the University of California, on a prototype portable device to determine the mechanical strength of the bone from a simple puncture which makes a microidentation in the tibia. “This system is painless and easily reproducible. Moreover it will be more economic, more accurate and more practical than densiometry”, comments Nogués.

According to the doctor, 90% of women with a fracture of the femur have never had densiometry or received treatment, even though efficient treatments exist which avoid the loss of bone mass. “A calcium rich diet (1000 mg/day) is also important, as is avoiding alcohol and tobacco, which increase bone resorption, whereas physical exercise stimulates bone formation”, advises Nogués.

This article was published in the El·lipse publication of the PRBB.

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