no. 971 for the year 2005 which includes the following:

Is bone marrow transplantation permissible in Islamic law? Please bear in mind that bone marrow is not an organ but a [substance] which the body produces and replenishes after donation.

There is no legal objection to bone marrow transplantation based on the analogy to the permissibility of blood donation. This is because both are replenished by the donor's body after donation. Blood transfusions are permissible if they save a life or help an organ to heal. According to Hanafi scholars, transplants are also permissible if they speed recovery.

The above answers the question and Allah Almighty knows best.