Pretreatment of Mesenchymal Stem Cells with Melatonin Improves Their Healing Properties in Animals with Strokes

The transplantation of mesenchymal stem cells or MSCs as they as affectionately known, does indeed benefit patients who have had a stroke. Unfortunately, the benefits of MSC transplantation if is limited by inability of these cells to survive after they are implanted into a low-oxygen environment. When a person suffers from a stroke, a blood vessel that feeds the brain has been blocked, and this blockage results in the death of particular cells in the brain. The affected areas of the brain, however, have been deprived of oxygen, and the transplantation of new cells into these areas can result in the prompt death of the implanted cells.

Fortunately, previous studies have revealed that pretreatment of the implanted cells with the hormone melatonin can increase the survival of MSCs that were implanted into kidneys that suffered oxygen deprivation. Therefore, could melatonin pretreatment also improve MSC survival in the case of strokes?

A new study by Guo-Yuan Yang and his colleagues at the Med-X Research Institute in Shanghai, China has examined the effects of melatonin pretreatment on the survival of MSCs that were implanted into the brains of laboratory animals that suffered a stroke.

In a nutshell, Yang and his colleagues showed that melatonin pretreatment greatly increased survival of cultured MSCs when these cells were subjected to low-oxygen conditions. Then when they went whole hog and transplanted their melatonin-pretreated MSCs into the brains of animals that had suffered a stroke, they once again observed that these cells survived at a substantially higher rate than their untreated counterparts. Melatonin-pretreated MSCs also further reduced bleeds into the brain (infarction) and improved the behavioral outcomes of the laboratory animals.

When Yang’s group examined the molecules secreted by the melatonin-treated MSCs, they discovered that the melatonin-pretreated MSCs made a lot more blood-vessel-promoting proteins (such as vascular endothelial growth factor or VEGF), and nerve cell-promoting molecules. Not surprisingly, the rats implanted with melatonin-pretreated MSCs shows significantly more new blood vessels formed, new neurons formed, and better looking brains in general.

Melatonin treatment increased the levels of two signaling molecules, p-ERK1/2, in MSCs. These particular signaling molecules are linked to higher survival rates. When Yang and his crew blocked melatonin signaling by treating cells with as drug called luzindole, these positive effects were reversed and when another drug called U0126, which prevents ERK from becoming phosphorylated was also applied to the cells, it completely reversed the protective effects of melatonin.

These results show that melatonin improves MSC survival and function. Furthermore, melatonin does this by activating the ERK1/2 signaling pathway. Therefore, mesenchymal cells pretreated by melatonin may represent a viable approach to enhance the beneficial effects of stem cell therapy for strokes, and maybe other conditions too? Well shall see. Stay tuned…..

Primed Fat-Based Stem Cells Enhance Heart Muscle Proliferation

A Dutch group from the University of Groningen has shown that fat-based stem cells can enhance the proliferation of cultured heart muscle cells. The stem cells used in these experiments were preconditioned and this pretreatment greatly enhanced their ability to activate heart muscle cells.

This paper, by Ewa Przybyt, Guido Krenning, Marja Brinker, and Martin Harmsen was published in the Journal of Translational Medicine. To begin, Przybyt and others extracted human adipose derived stromal cells (ADSC) from fat tissue extracted from human liposuction surgeries. To do this, they digested the fat with enzymes, centrifuged and washed it, and then grew the remaining cells in culture.

Then they used rat neonatal heart muscle cells and infected them with viruses that causes them to glow when certain types of light was shined on them. Then Przybyt and others co-cultured these rat heart cells with human ADSCs.

In the first experiment, the ADSCs were treated with drugs to prevent them from dividing and then they were cultured with rat heart cells in a one-to-one ratio. The heart muscle cells grew faster with the ADSCs than they did without them. To determine if cell-cell contact was required for this stimulation, they used the culture medium from ADSCs and grew the heart cell on this culture medium. Once again, the heart cells grew faster with the ADSC culture medium than without it. These results suggest that the ADSCs stimulate heart cell proliferation by secreting factors that activate heart cell division.

Another experiment subjected the cultured heart cells to the types of conditions they might experience inside the heart after a heart attack. For example, heart cells were subjected to low oxygen tensions (2% oxygen), and inflammation – two conditions found within the heart after a heart attack. These treatments slowed heart cell growth, but this heart cell growth was restored by adding the growth medium of ADSCs. Even more remarkably, when ADSCs were grown in low-oxygen conditions or treated with inflammatory molecules (tumor necrosis factor-alpha or interleukin-1beta), the culture medium increased the fractions of cells that grew. Therefore, ADSCs secrete molecules that increase heart muscle cell proliferation, and increase proliferation even more after the ADSCs are preconditioned by either low oxygen tensions or inflammation.

In the next experiment, Przybyt and others examined the molecules secreted by ADSCs under normal or low-oxygen tensions to ascertain what secreted molecules stimulated heart cell growth. It was clear that the production of a small protein called interleukin-6 was greatly upregulated.

Could interleukin-6 account for the increased proliferation of heart cells? Another experiment showed that the answer was yes. Cultured heart cells treated with interleukin-6 showed increased proliferation, and when antibodies against interleukin-6 were used to prevent interleukin-6 from binding to the heart cells, these antibodies abrogated the effects of interleukin-6.

Przybyt and others then took these results one step further. Since the signaling pathways used by interleukin-6 are well-known, they examined these pathways. Now interleukin-6 signals through pathways, once of which enhances cell survival, and another pathway that stimulated cell proliferation. The cell proliferation pathway uses a protein called “STAT3” and the survival function uses a protein called “Akt.” Both pathways were activated by interleukin-6. Also, the culture medium of ADSCs that were treated with interleukin-6 induced the interleukin-6 receptor proteins (gp80 and gp130) in cultured heart muscle cells. This gives heart muscle cells a greater capacity to respond secreted interleukin-6.

This paper shows that stromal stem cells from fat has the capacity, in culture, to activate the growth of cultured heart muscle cells. Also, if these cells were preconditioned with low oxygen tensions or pro-inflammatory molecules, those fat-based stem cells secreted interleukin-6, which enhanced heart muscle cell survival, and proliferation, even if those heart muscle cells are exposed to low-oxygen tensions or inflammatory molecules.

This suggests that preconditioned stem cells from fat might be able to protect heart muscle cells and augment heart healing after a heart attack. Alternatively, cardiac administration of interleukin-6 after a heart attack might prove even more effective to protect heart muscle cells and stimulate heart muscle cell proliferation. Human trials anyone?