Chronic Kidney Disease (CKD) is one of the most common illnesses of geriatric cats. It is estimated that 35 percent of cats over the age of 13 suffer from CKD, and the incidence appears to be increasing. Unless the underlying cause of the initial kidney injury is discovered and treated, CKD invariably progresses.
Unfortunately, an underlying cause is rarely identified. In some instances — even after identifying the initial cause of the kidney injury — a threshold or “trigger-point” has already been reached, and the self-perpetuating mechanisms of kidney destruction are activated.
Currently, CKD is incurable. It is possible to delay the inevitable progression of the disease, improve the cat’s quality of life and extend the cat’s survival time through a variety of dietary and drug interventions. The treatments tend to focus on management of the symptoms. Sadly, with the exception of a kidney transplant, it hasn’t been possible to improve the function of the diseased kidneys. Until now.
Stem cell therapy is a rapidly evolving field in veterinary medicine. Stem cells are cells that have the potential to develop into any type of cell in the body. They have the ability to multiply, and yet still retain the potential to develop into other types of cells. There are two main types of stem cells: embryonic (derived from fetal tissues) and somatic (derived from adult tissues).
The main sources of stem cells in the adult are the bone marrow and adipose (fat) tissue. In veterinary medicine, the studies involving stem cells employ adult stem cells, often from the animal’s own body. The most common therapeutic use of stem cells in veterinary medicine has been for the treatment of musculoskeletal injuries in horses and dogs, however, a recent study in the Journal of Feline Medicine and Surgery reveals the potential for stem cell therapy to help cats with chronic kidney disease.
Six cats were used in the study. Two were healthy and served as controls, while four cats had CKD. The cats were sedated, and bone marrow and adipose tissue was collected from each cat. Stem cells were harvested from these tissues.
Using ultrasound guidance, stem cells were injected into the kidney, at three different sites, in each of the cats. Seven days after injection, and then again 30 days after injection, the injected kidneys were evaluated using a technique called nuclear scintigraphy, which calculates the ability of the kidneys to filter toxins from the bloodstream. The blood levels of the kidney toxins were also measured.
Research shows promise
The results were encouraging. Two cats with less severe CKD showed mild improvement in filtering ability, and a modestly lowered blood level of creatinine, one of the principal kidney toxins. The authors of the study noted that although the levels were lower, they were not statistically significant (however, this was attributed, in part, to the small number of cats enrolled in the study). Two cats with more severe CKD did not show improvement in kidney function and both cats were eventually euthanized due to progression of their kidney disease.
The authors concluded that injection of stem cells directly into the kidneys is feasible in cats with CKD. Two of the four cats in the study showed modest improvement in kidney function, although clearly the number of cats in the study was too few to draw any meaningful conclusions. Unfortunately, the large number of sedations and the relatively complex procedure of injecting the cells into the kidney using ultrasound guidance make widespread clinical use unlikely.
Interestingly, more recent studies in which the stem cells were injected into the blood stream — rather than directly into the kidney — suggest that stem cells do not have be injected directly into the site of interest, making future treatments potentially less difficult and expensive.
Questions to answer
Although the initial studies are promising, three fundamental questions need to be answered: What is the optimal tissue source for the stem cells — bone marrow or adipose tissue? How many stem cells need to be injected in order to see a positive response? What is the best route of administration —directly into the damaged organ, or intravenously?
Many more studies will need to be performed to properly address these questions. Stem cell therapy is already being employed in the treatment of muscular and skeletal disorders, and it holds the potential to treat a wide range of clinical disorders, including chronic kidney disease. — Arnold Plotnick, DVM