Allograft Stem Cell Therapy/Allogenic Stem Cell Transplant
Allograft Stem Cell Therapy refers to the clinical use of stem cells that are collected from a donor and then transplanted into a matching recipient. Most often used to suppress disorders of a patient’s immune system, the goal of this therapy is to ultimately restore a recipient’s immune system to a disease-free state. In addition, stem cell therapy is now increasingly being investigated for its application in regenerative medicine, although this still remains primarily in the clinical testing phase. The biggest obstacle faced in allograft stem cell therapy—also known as allogenic stem cell transplant—is locating a suitable donor.
Sources of donor cells
Typically, donors come from the patient’s own family and cells are harvested through blood or bone marrow donation. Donors are evaluated through a process called tissue typing, which matches proteins known as human leukocyte antigens (HLAs) between the two. While an HLA-matched relative is the ideal donor candidate, other possibilities include an unrelated HLA-matched donor typically located through a donor registry, an HLA-mismatched relative, or umbilical cord blood.
Umbilical cord blood is another source for stem cells and offers a few advantages for transplant effectiveness. The stem cells found within cord blood have not yet matured, and thus are considered especially pluripotent. In other words, they have the ability to give rise to a variety of mature cell types. In addition, since these blood samples are immediately cryopreserved at the time of birth, their limited environmental exposure helps them to be more gently accepted by the recipient’s immune system.
Allogenic stem cell transplant—what the procedure entails
Prepping the recipient before, during, and after an allogenic stem cell transplant requires the a high degree of medical management and risk. Generally, to ready a patient for transplant, their immune system must be suppressed first. This down regulation can be intense and necessitates high-dose immunosuppressive drugs. There is great potential for side effects to occur at this time, and the patient must be quarantined to avoid infection exposure.
The allogenic transplant procedure itself is rather simple—the donor cells are prepared and delivered via IV over the course of an hour. The goal of treatment is for the donated stem cells to reach the recipient’s bone marrow and set up shop. Once there, engraftment of the new cells occurs as they begin to rebuild the recipient’s cache of healthy cells.
Patients are monitored closely over the course of a few months while their marrow rebuilds. Frequent blood counts are taken to monitor progress. Like any transplant of donor tissue, allogenic stem cell transplants pose a risk of graft-versus-host-disease (GVHD). In this complication, the donor cells fail to assimilate, and instead recipient attack tissues. The greater the match is between donor and recipient, the less likely this complication is to occur, but nonetheless, it can present a serious condition requiring its own management.
The stem cells found within cord blood have not yet matured, and thus are considered especially pluripotent.
Current and future applications for allogenic stem cell therapies
Allogenic stem cell therapy has a range of applications. Traditionally employed as a cancer-fighting treatment as described above, stem cells are now being utilized for a range of other degenerative ailments, too. For instance, bone-marrow derived stem cells have been successfully used to treat cardiac patients with ischemic heart failure. Patients with liver disease have also shown encouraging regenerative results following stem cell transplants.
The study and practical application of allografts have supported the use of mesenchymal stem cells (MSCs) in particular. These cells have shown the ability to circumvent negative reactions within a recipient’s immune system. This significantly decreases the amount of immunosuppression required across the entirety of the procedure. Recent studies have demonstrated that MSCs may also provide immunomodulatory benefits, and thus have potential to treat inflammation-related disorders in skeletal tissue.
In addition, donor cells that are harvested from healthy donors are shown to be more easily reproduced and stored in labs for future use. In comparison, autologous cells (those coming from the patient themselves) may be weaker and would require several weeks to expand, thereby delaying the transfusion in patients who are medically fragile and often can’t afford such a lengthy wait time.
Allogenic therapy in the scope of regenerative treatments
The future of regenerative medicine is bright. Ongoing investigative efforts are centered on the practicality of expanding cells in cultures, as these divisions tend to cause the cells to divide asymmetrically. The rapid expansion of cells in vitro has also been linked to genetic instability of the cells. One way around these unstable expansion challenges is to use therapeutic cloning. However, use of cloning in general is a controversial matter, and thus funding for these studies can be limited as a result.
The use of biological therapies present a compelling case overall. Stem cell therapy in particular certainly shows the potential for healing and regeneration of tissue and may be unmatched when compared to the limits of current pharmacological and surgical treatments.