Currently, we do not yet know if the trigger for arthrosis is due to the alteration of cartilage or other processes. On the other hand, the results of these phenomena are well-known: the cartilage of the joints concerned become rough and thin. The bones become worn; they become damaged and tend to change shape, creating bone spurs, called osteophytes. For the people affected, arthrosis does not take any prisoners: among the most common symptoms are creaking of the joints when they are used, stiffness and pain.  Eventually, arthrosis really handicaps the lives of patients. It leads to social isolation because moving has become so painful for them.

Limited help

Up to the present, the main treatments offered to patients consisted of trying to ease their symptoms. Weight loss, physiotherapy and the practice of certain exercises helped them to an extent, to ease their pain. When this doesn’t work, the medication route is chosen, from paracetemol to non-steroidal anti-inflammatories to cortisone derivatives, glucosamines or, among others, injections of hyaluronic acid. These different products generally help to reduce symptoms. Yet the therapeutic arsenal is poor and is, in any case, insufficient to counter the progression of the disease. In a certain number of cases, pain and deterioration of the joint leads to the operating table where a surgeon replaces the joint with a prosthetic.

Already considered to be a veritable public health problem, according to the experts, during the coming years arthrosis will affect an even greater number of people. In this context, the study of a molecule capable of halting the progression of the disease represents a very attractive prospect.

One drug can be hidden by another  

Question: how can a treatment aimed at post-menopausal osteoporosis also be used in treating arthrosis? These two complaints have causes and consequences that are totally different.  Osteoporosis is defined as a disease characterized by a reduction in bone mass. It leads to bone fragility and an increase in the risk of fractures, in particular of vertebrae, wrists and the neck of the femur. (Read : The silent enemy)
 
“Strontium Ranelate is actually a medicine developed in the precise area of treatment for post-menopausal osteoporosis; it has been registered and marketed in Europe, Latin America, the Middle East and in Asia. It is characterized by a unique mode of action. In effect, it combines an inhibition of resorption due to osteoclasts and stimulation of the formation of osteoblasts. This treatment, which acts on the structure of the bone has shown its efficiency among a very large group of menopausal women, ranging from those showing osteoporosis at the start of the menopause to those aged up to 80, and more recently, among men with the disease. Therefore, it succeeds in reducing fractures of the backbone, the appendicular skeleton and the hip in persons under risk. Its ease of use (unlike other treatments, it does not require the patient to remain upright for half an hour after taking the medication, nor to drink large quantities of water to avoid contact with the esophageal mucosa) contributes to its popularity with the patients”, confirms Professor Reginster. Launched onto the market in 2006 in Belgium under the name of Protelos, it is reimbursable since 2007 and is widely prescribed. But why think of this as a new therapeutic tool?

In fact, different factors progressively caused the “penny to drop” for the specialists and led them to ask whether this molecule could not also have an effect on arthrosis. Pre-clinical studies had shown that strontium ranelate added to cultures of human chondrocytes (the cells which form cartilage) helped to stimulate the production of collagen II and high-density proteoglycans, that is to say, components of the cartilaginous matrix. This means that the molecule succeeds in restoring a balance between the formation and deterioration of cartilage. Another clue: “In the subchondral bone of dogs that had torn their anterior cruciate ligament, we noticed a drop in sclerosis after taking strontium ranelate, which represented a beneficial and preventative effect on arthrosis”, adds Professor Reginster. Due to these different positive signs it was decided to move on to humans by means of in-depth studies.