Sickle cell and implications of bone marrow transplant


Tolu Dehinde

I once attended a forum titled, ‘Amplify Sickle Cell Voices.’ The discussion centered on the aftermath of a bone marrow transplant. After the event, I asked friends from the Australian Sickle Cell Advocacy, who head ‘Amplify Sickle Cell Voices,’ to write something about the after-effects of having a bone marrow transplant. This was a collaborative work from Agnes N and Natalie K.

“I wonder what it will be…I would love it to be a girl. Imagine all the adorable outfits I will dress her in…Better start thinking of schools too… Should we go private or public? We just want the best for our precious baby…”

The joy and anticipation of an impending new life. Many parents’ lofty dreams are readjusted to include the grim confirmation of a sickle cell disease diagnosis as they traverse through the various stages of grief coursing from denial, anger, bargaining, depression to acceptance as we reluctantly resign or embrace ourselves to the unpredictable nature of this condition.

In acceptance, we also received a lifeline of hope of a cure through a bone marrow transplant. We embarked on finding out all we could about this silver bullet that will free our child from a life of pain, complications, and crippling stigma.

The silver bullet

So, what is this silver bullet? The bone marrow transplant procedure known as BMT is a medical procedure performed to replace bone marrow that has been damaged or destroyed by disease, infection, or chemotherapy.

This procedure involves transplanting blood stem cells from a healthy, often related donor to the affected recipient. These transplanted blood stem cells travel to the bone marrow where they will produce new blood cells and promote the growth of new marrow.

Most importantly BMT offers those living with sickle cell disease the opportunity to create healthy red blood cells that will carry oxygen and nutrients throughout the body. This will essentially shield the person affected and their loved ones from a life of pain and possible complications, and shield the latter ones from a life of witnessing this pain.

Free at last

If you can get over the hurdles of finding a suitable donor, a feat akin to finding a needle in a haystack; overcome the effects of the transplant treatment protocol which include chemotherapy and/or radiation which will annihilate any ability for the body to shield itself from vulnerabilities such as infections and the subsequent months of living in an eggshell, you will cross the finishing line, praising all who helped achieve this victory.

At this point, we will bid farewell to needles, pungent hospital smells and most importantly pain, and the anxiety of an impending crisis interfering with all our best plans. I bet the words inside a warrior going for BMT could be, “I would book a trip to snowy Aspen and challenge the weather honestly! Talk about living life on the edge and dangerously. I have been cured!”

Sickle cell free

While this cure offers a new lease on life to those who have experienced sickle cell disease, it unfortunately still does not preclude them from being completely free of it. What that means is that one is free from living with complications, however, that pesky sickle cell gene still exists and the risk of having offspring affected by the disease is still present if this person procreates with another individual affected by the disease or a carrier of the sickle cell trait.

Simply put, the HbSS gene is still present. This will not change through the bone marrow transplant procedure. There will be no change to an AS genotype and especially not the much-coveted AA genotype.

Perhaps, we need to revisit our understanding of the HbSS gene. So, what is it? HbSS is a form of sickle cell disorder where people inherited two sickle cell genes (“S”), one from each parent. This is commonly called sickle cell anaemia and it is the most severe form of the disease.

(1)Our body is made up of millions of cells, and in each cell, there are instructions, called genes, that make all the necessary structural components and chemicals for the body to function. These genes are packaged onto little, long strands known as chromosomes.

We all have 46 chromosomes arranged into 23 pairs. One copy of each pair is inherited from our mother and the other from our father. The first 22 chromosome pairs are numbered and are known as autosomal chromosomes. The 23rd pair is made up of the sex chromosomes called X and Y. Males have an X and a Y chromosome and females have two copies of the X chromosome.

Since all our chromosomes come in pairs, all our genes also come in pairs. Sometimes, a gene may have a variation in the instruction that causes the gene to no longer function. This variation is called a mutation or pathogenic variant, and means that the product produced by the gene, called a protein, is impaired or even absent.

Gene mutations may be inherited from a parent or occur for the first time in an individual. Once you have a gene mutation, however, it may be passed on to future generations. This is referred to as genetic inheritance.

While bone marrow has the potential to offer a cure, this is essentially a cure from the complications of the disease, offering the bone marrow of an affected person’s body to create healthy red blood cells necessary to transport oxygen throughout the body’s circulatory system estimated at approximately 60000 miles or 100000 kilometres without causing traffic jams.

We can distinctly see that BMT’s goal is a repair kit to the red blood cell-producing engine, and therefore will not repair the faulty genetic marker which essentially instructs the affected bone marrow to behave in a particular manner, resulting in the insufficient production of healthy red blood cells.

Fortunately, the advances of science and technology are bringing us closer to the reality of repairing a faulty genetic marker in the form of gene therapy such as CRISPR/Cas9 whose desired goal is to eventually repair the gene or even introduce a new gene; thus, ensuring that future generations are safe from sickle cell disease and its complications. The research is promising though its impact needs to still be thoroughly understood to ensure that adverse risks are not introduced either for the future generations that would be protected.

Reference: [1] https://www.genetics.edu.au/publications-and-resources/facts-sheets/fact-sheet-44-sickle-cell-disease

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