Though modern medicine has made remarkable strides in the past decades, there are still complications that can impede recovery after invasive treatments. Large injuries may necessitate surgical transplantation of multiple types of tissue, such as nerve, muscle, and bone, in a procedure known as Vascularized Composite Allotransplantation (VCA). Post-surgery, doctors must help manage the patient’s immune system to prevent it from mistaking the transplanted tissue for something dangerous. If the immune system perceives the tissue as a threat, it can attack the tissue and cause transplant rejection, which may harm or kill the patient. One factor that doctors must consider is that the tissues transplanted during VCAs have different immunological properties, and it is therefore difficult to manage them all using medication. Thus, scientists are trying to figure out a more reliable way of preventing transplant rejections in VCAs.
A potential treatment for VCA transplant rejection comes from a mechanism called regulatory T-cell (Treg) recruitment, which is one way that cancerous tumors fly under the radar of the immune system. Tregs are immune cells that detect markers on cell surfaces, allowing them to differentiate between cells that are part of the organism and foreign bodies. During Treg recruitment, the tumor secretes a substance called CCL22, which attracts Tregs and incorporates them into the tumor. This results in immune suppression because other immune cells do not perceive the tumor as a foreign body, preventing the immune system from attacking and destroying the tumor.
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Researchers found that microparticles that secrete CCL22 allowed transplanted tissue to survive longer in a rat’s body.
Image Source: fotografixx
A recent study looked to safely harness Treg recruitment to try and prevent transplant rejection. Researchers from the University of Pittsburgh created microparticles capable of being implanted in an organism and releasing CCL22. The microparticles were degradable, and the amount of CCL22 released was controlled in order to closely manage the size, location, and duration of immune suppression. The scientists injected either these microparticles or the standard medication into groups of rats that received hindlimb transplants. The rats who took the standard medication all rejected their transplants within two to three weeks, while the rats who received the microparticles had healthy transplants throughout the 200-day duration of this study. Comparing tissue samples from the two groups of rats also showed that the rats who received microparticles had many more Treg cells in their hindlimbs, suggesting that the microparticles were successful in performing Treg recruitment. This study provides evidence for a more effective method of immune suppression for VCAs. The results of this study may lead to better outcomes for transplant patients and help in developing treatments for other diseases where specific sites of immune suppression are needed as well.
Featured Image Source: Sasin Tipchai
