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Growth Factors
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Growth Factors

Loss of cartilage usually occurs when the usual balance of building (synthesis) and breaking down (degradation) of tissue that helps to maintain a healthy joint becomes imbalanced. This leads to a steady decline in the quality and quantity of cartilage structure. These types of conditions are associated with significant disabilities and long-term (chronic) pain.

At a cellular level, these problems worsen because the cells that restore cartilage are incapable of secreting enough new material to combat the degradation or that there is simply not enough living cells to do the job. With this in mind, several avenues of research have been focused on method of stimulating the cellular regeneration of the damaged tissue.

Growth factors are really a broad range of diverse substances that are capable of activating and stimulating the growth and repair of damaged tissue as well as protect cells from death. They therefore offer a very promising avenue for both treatment and further study.

Cartilage degradation and subsequent osteoarthritis is more common in people aged over 50 years, but people of any age have a significantly increased risk of cartilage and joint damage that may lead to post-traumatic osteoarthritis after sports or other joint injuries.

Growth factor treatments offer potential benefits to prevent osteoarthritis (especially at its early stages) later in life, as well as being an immediate consideration after sports injury, when the prevention of further damage is a priority.

The information here offers an explanation of how growth factors work, the evidence for the specific types thought to be best for cartilage repair, the main advantages and risks and any common questions on the topic.

Intended audience

This article is intended for anyone suffering from damage to their articular cartilage and their families who would like to find out about growth factors, as well as anyone interested in cartilage problems.

What are growth factors?

Growth factors are a family of diverse substances found naturally in the body that promote and stimulate biological processes and growth. They are a crucial part of the self-regulation of the body (homeostasis), in which an internal balance occurs between mechanisms of growth (including repair and regeneration) and degradation, both of which are important in maintaining a healthy body (You might think about a home: to keep it “new”, it would be important to remove worn area (degradation) and then refurbish (repair and regeneration)).

Numerous growth factors are responsible for maintaining healthy cartilage in the joints, both promoting cartilage restoration and counterbalancing dedicated substances that break cartilage down.

For example, the bone morphogenetic proteins (BMP) are a family of restorative growth factors that were named years before their activity on cartilage was known. Subsequently, they have been studied for their therapeutic applicability in cartilage repair. Administration of extra BMP growth factors would, ideally, restore cartilage, and be effective regardless of the patient’s age, sex or the cause of cartilage damage.

Two of these proteins in particular, known as BMP-2 and BMP-7 (the latter also known as Osteogenic Protein-1, or OP-1) have been identified as powerful treatments for restoring damaged bone and cartilage. BMP-2 is approved in several countries for treating damaged spine and bone. However, it is only in the past decade that they have been examined more intently for cartilage repair.

In initial culture-dish experiments with engineered growth factors, BMP-7/OP-1 in particular produced the components of cartilage, as well as protected important cells from death and inhibited inflammation. In animal studies, it had a clear potential for halting the degradation of cartilage, as well promoting its repair. While complete restoration of cartilage has not yet been achieved, future studies will look at different formulations, delivery methods and other aspects that are hoped to improve outcomes significantly.

The delivery of these therapeutic agents is the focus of considerable study. Alongside simple injection, other approaches for delivery at the wound/damage site include scaffolds of bio-engineered structures that mimic the natural 3D environment of the body. This may help in the long-term delivery of growth factors over weeks or months, although it is still not clear what length of time of application would be enough.

Although less well-studied, two other agents are worth mentioning. Fibroblast growth factor 18 (FGF-18) stimulates connective tissue cells (fibroblasts) and platelet-rich plasma (PRP), which is a mixture of many proteins and growth factors, made by separating components of a patient’s own blood. PRP may have a role in wound-healing. Therapeutic injection of PRP into the joint may “rebalance” the pro-inflammatory and anti-inflammatory factors in the joint or, in some cases, it might reinvigorate tissue growth.

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