The Foundation of Bone Strength: Osteoblasts and Bone Remodelling

Alex Auld


May 2, 2023

As we age, our bodies undergo many changes, one of which is a natural decline in bone mineral density. While this is a normal part of the ageing process, it can lead to serious health issues like osteoporosis: the weakening of bones that can make them more fragile and susceptible to fracture.  

In this blog, we'll delve into the fascinating role of osteoblasts in maintaining bone health and explore how these cells help preserve bone strength. 

The Mighty Osteoblasts

Osteoblasts are specialised bone-building cells that play a crucial role in maintaining your bone health. These cells are responsible for producing the extracellular matrix and laying down new bone mineral, which is essential for strong, healthy bones. 

Osteoblasts originate from bone marrow stem cells and are constantly working in harmony with other bone cells, like osteoclasts, to maintain a balanced process known as bone remodelling.

Bone Remodelling: A Delicate Balance

During bone remodelling, old bone is broken down by osteoclasts, and new bone is formed by osteoblasts. This process is essential for maintaining bone strength and repairing micro-damage. 

The bone remodelling process occurs in a well-regulated sequence of events:

1. Resting

The bone remodeling process begins with a resting phase. During this period, bone-lining cells, which cover the bone surface, are in a domant state. These cells help to maintain the structural integrity of the bone and protect the underlying bone tissue from damage.

2. Resorption

The next phase in the bone remodeling process is resorption. In this stage, osteoclasts – the bone-resorbing cells – are activated and attach to the bone surface. They secrete enzymes and acids that break down the mineralised bone matrix, releasing calcium and other minerals into the bloodstream. This process of bone resorption creates small cavities in the bone tissue.

3. Reversal

Following resorption, the bone remodeling process enters the reversal phase. During this transitional period, bone-lining cells release growth factors and proteins that attract osteoblast precursors to the resorption site. This sets the stage for the formation of new bone tissue.

4. Formation

In the formation phase, osteoblasts synthesise and secrete the collagen-rich organic matrix known as osteoid. These cells also produce specific proteins that help in the formation of the new bone tissue. The osteoid forms the framework for the new bone and is gradually deposited in the small cavities created during the resorption phase.

5. Mineralisation

The final step in the bone remodeling process is mineralisation. During this phase, the newly formed osteoid undergoes mineralisation through the deposition of calcium and phosphate ions. This process transforms the soft osteoid into a hard, mineralised bone matrix, which restores the structural integrity and strength of the bone.

When osteoblasts and osteoclasts work together efficiently, your bones remain strong and healthy. However, as we age, the balance of these two cell types can shift. As the rate of resorption begins to outweigh the rate of bone formation and mineralisation, this causes a decrease in bone mineral density and increases the risk of fractures.

Factors Influencing Osteoblast Function

Several factors can influence the function of osteoblasts and, consequently, bone health:


Sex hormones like oestrogen and testosterone play a crucial role in maintaining bone health. A decline in sex hormone levels, such as the fall in oestrogen production during menopause, can lead to a decrease in osteoblast activity and an increase in bone loss.


Adequate intake of nutrients like calcium, vitamin D, and protein is essential for optimal osteoblast function. Insufficient nutrient intake can impair osteoblast activity and contribute to poor bone health.

Physical activity 

Weight-bearing exercises, such as walking, jogging, or strength training, can stimulate osteoblast activity and promote the formation of new bone.


Certain genetic factors have been found to influence the function of osteoblasts and the bone remodelling process. For example, our WNT16 & Age-Related Bone Mineral Density report explores how variants of the WNT16 gene, which encodes a signalling molecule involved in the activity of osteoblasts, can accelerate bone loss. 

Research has shown that the ‘C’ variant (rs2707466) is linked to lower bone mineral density and a greater risk of bone fracture, with one study finding that people with osteoporotic forearm fractures were 1.44 times more likely to carry the CC genotype compared to other possible genotypes (CT or TT).

Understand Your Personal Bone Health Risk

Curious to know if you carry the WNT16 gene variant associated with lower bone density and increased risk of fracture? Discover your personal result, along with personalised preventative recommendations, with a FitnessGenes DNA analysis test

In addition to WNT16 & Age-Related Bone Mineral Density, you’ll also receive access to 145+ genetic reports, all delivered with personalised recommendations, to help you maintain the health of your bones, brain, heart, hormones, and more.

Alex Auld

One of FitnessGenes' first full-time employees, Alex re-joined the company in 2021 after completing his MA in Global Communications at the University of London. He now oversees all customer communications, helping to ensure that our members get the most from their results. An amateur triathlete, you can expect to find him in the pool, on the bike, or running laps of his local park most weekends.

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