Umbilical cord blood turns out to have a factor that can potentially fight inflammation, according to scientists at the University of Utah School of Medicine. This study was published online Sept. 6, 2016, in The Journal of Clinical Investigation.
“We found something we weren’t expecting, and it has taken us to new strategies for therapy that didn’t exist before,” says Guy Zimmerman, M.D., a professor of internal medicine at the University of Utah School of Medicine, who was also the senior author of this work. Dr. Zimmerman collaborated with associate professor of pediatrics, Christian Con Yost, M.D., and their colleagues for this work.
Inflammation is well-known to anyone who has whacked their leg, been stung by a bee or a wasp, or anyone who over-stressed their muscles. The redness, heat pain, and swelling are signs that the body is cleaning up damaged cells and their debris, fighting invading microorganisms, and beginning the healing process. However, under certain circumstances, inflammation can go overboard and turn against us and seriously and chronically damage healthy tissues. Out-of-control inflammation is probably the culprit behind several different conditions ranging from rheumatoid arthritis to sepsis. In fact, the inflammatory overreaction to infections is one of the most common causes of hospital deaths.
Dr. Yost and his coworkers successfully isolated a cord blood factor, called “neonatal NET inhibitory factor” or nNIF. This name comes from the ability of this factor to inhibit “NETs” or neutrophil extracellular traps. NETs or neutrophil extracellular traps are composed of processed chromatin bound to granular and selected cytoplasmic proteins that are released by white blood cells called neutrophils. NETs seem to be a kind of last resort that neutrophils turn to in order to control microbial infections. Even though NETs usually help our bodies ward off infectious bacteria and viruses, they can also damage blood vessels and organs during sepsis.
As physicians who have treated critically ill patients suffering from out-of-control inflammation, Drs. Zimmerman and Yost recognized the therapeutic potential of nNIF. “We knew we were onto something that could be very meaningful,” recalls Yost.
To test if this cord blood-based factor could control sepsis, Zimmerman and Yost and others treated groups of mice that suffered from laboratory-induced inflammatory disease. In the absence of treatment, only 20 percent of the mice survived longer than two to four days. However, 60% of those mice treated with nNIF survived after the same amount of time.
“Sepsis is a case where the body’s reaction to infection is lethal,” says Yost. “nNIF is offering insights into how to keep the inflammatory response within prescribed limits.” He adds that they will carry out additional studies to test the therapeutic properties of nNIF.
nNIF seems to be present for just a brief window of time at the beginning of life. It circulates in cord blood and persists in the baby’s own bloodstream for up to two weeks after birth. However, after two weeks, nNIF disappears and is not found in older babies and is completely absent from the blood of adults. Scientists in Yost’s laboratory also discovered that the placenta also contains a similar, albeit less potent, anti-inflammatory agent. The evanescent nature of these factors possibly indicates that inflammation is under tight control during this time, since the fragility of young babies might make extensive amounts of inflammation deleterious to their health.
“The beginning of life is a delicate balance,” says Yost. “Our work is showing that it is important to have the right defenses, but they have to be controlled.”
When pluripotent stem cells are differentiated into photoreceptor cells, and then implanted into the retina at the back of the eye of a laboratory animal, they do not always survive. However, pre-treatment of those cells with an antiaging glycoprotein (AAGP), made by ProtoKinetix, causes those transplanted cells to be 300 times more viable than cells not treated with this protein according to a study recently accepted for publication.
AAGP was invented by Dr. Geraldine-Castelot-Deliencourt and developed in partnership with the Institute for Scientific Application (INSA) of France. For her work in this area Dr. Castelot-Deliencourt was honored with France’s highest award for scientific accomplishment, the Francinov Award, in 2006.
AAGP significantly improves the viable yield of stem cells transplanted in retinal tissue, according to experiments conducted at the University of British Columbia in the laboratory of Dr. Kevin Gregory-Evans.
AAGP seems to protect cells from inflammation-induced cell death. This is based on experiments in which cultured cells that were treated with AAGP were significantly more resistant to hydrogen peroxide, ultraviolet A (wavelengths of 320-400 nanometers), and ultraviolet C (shorter than 290 nm). In addition, when exposed to an inflammatory mediator, interleukin β (ILβ), AAGP exposure reduced COX-2 expression three-fold. COX-2 is an enzyme that is induced by the various stimuli that stimulate Inflammation. It is, therefore, an excellent read-out of the degree to which inflammation has been induced. The fact that AAGP prevented the induction of COX-2 shows that this protein can inhibit the induction of inflammation. These data suggest that AAGP™ may not just be usable in cell and organ storage but also in pharmacological treatments.
Can what a mother eats affect her baby? Claudia Buss of the Charité – Universitätsmedizin Berlin and the University of California, Irvine and her colleagues conducted a longitudinal study of mothers and their newborn babies, and discovered that increased production of the cytokine interleukin-6 (IL-6) in mothers can lead to alterations in the brain connectivity of her offspring.
Buss and coworkers took blood samples of pregnant women and measured levels of the cytokine IL-6 early in pregnancy, during the middle of the pregnancy, and near the end of their pregnancy. Shortly after the birth of their babies, Buss and others conducted MRI scans of the newborns. “This is the only way that we will be able to understand prenatal influences that are not confounded by post-natal influences,” Buss said at a November 17th press conference at the Society for Neuroscience (SfN) annual meeting in Washington, DC. In particular, Buss and her team looked for patterns of synchronized activity in the default mode network (DMN). The DMN is a network of brain regions that are active when the individual is not focused on the outside world and the brain is awake, but at rest. During goal-oriented activity, the DMN is deactivated and another network called the task-positive network (TPN) is activated. The DMN may correspond to task-independent introspection, or self-referential thought, while the TPN corresponds to action. Dysfunction of the DMN has been linked to psychiatric disorders.
The group found that the infant DMN “doesn’t look like adult network, but it’s emerging,” Buss said. “It’s there in an immature state.” More importantly, higher maternal gestational IL-6 concentration predicted reduced DFM connectivity. The infant brain was “less strongly connected under conditions of high maternal IL-6 concentrations,” Buss said.
In another study by neuroscientists at Duke University showed that the maternal diet of mice can cause inflammatory and behavior changes in offspring. Staci Bilbo of Duke University and her team found that a high-fat diet in the mother can lead to inflammation in the body’s fat tissue as well as immune changes in brain that may be linked to psychiatric disorders like anxiety and depression. The researchers fed mice either a low-fat diet or a high-fat diet, either enriched or not enriched for branched chain amino acids (BCAAs). Bilbo’s group examined the mothers’ brains midway through pregnancy and found increased expression of inflammatory cytokines in the hypothalamuses of mice fed a high-fat diet. These changes were also accompanied by postpartum increases in depressive-like behaviors in mice fed a BCAA-enriched diet and an increase in anxiety-like behaviors in mice fed a high-fat diet.
According to Bilbro, the offspring of these mothers showed “striking” differences in the expression of inflammatory cell types and in the behavior of the newborn pups. Infants born to moms fed a high-fat diet showed decreased expression of microglia markers and increased anxiety-like behaviors. However, mice born to moms on a high-fat, high-BCAA diet showed increased expression of a marker for astrocytes.
“Maternal diet does matter,” said Bilbo. “We believe [these changes] may be contributing to both metabolic changes as well as mood changes” in the moms and their offspring.
Ischemia refers to the absence of oxygen in a tissue or organ. Ischemia can cause cells to die and organs to fail and protecting cells, tissues and organs from ischemia-based damaged is an important research topic.
Perfusion refers to the restoration of the blood flow to an organ or tissue that had experienced a cessation of blood flow for a period of time. Even though the restoration of circulation is far preferable to ischemia, perfusion has its own share of side effects. For example, perfusion heightens cells death and inflammation and this can greatly exacerbate the physical condition of the patient after a heart attack, traumatic limb injury, or organ donation.
“Think about trying to hold onto a nuclear power plant after you unplug the electricity and cannot pump water to cool it down,” said Jack Yu, Chief of Medical College of Georgia’s Section of Plastic and Reconstructive Surgery. “All kinds of bad things start happening,”
Earlier studies in the laboratory of Babak Baban have shown that stem cells can improve new blood vessel growth and turn down the severe inflammation after perfusion (see Baban, et al., Am J Physiol Regul Integr Comp Physiol. 2012 Dec;303(11):R1136-46 and Mozaffari MS, Am J Cardiovasc Dis. 2013 Nov 1;3(4):180-96). Baban is an immunologist in the Medical College of Georgia and College of Dental Medicine at Georgia Regents University.
The new study from the Baban laboratory shows that an enzyme called indolamine 2,3,-dioxygenase or IDO can regulate inflammation during perfusion. IDO is widely known to generate immune tolerance and dampen the immune response in the developing embryo and fetus, but it turns out that stem cells also make this enzyme.
In their study, Including IDO with bone marrow-derived stem cells increased the healing efficiency of injected stem cells.
Also indicators of inflammation, swelling, and cell death decreased in animals that received bone marrow-derived stem cell injections and had IDO. Baban’s group also showed that the injected stem cells increased endogenous expression of IDO in the perfused tissues.
Baban thinks that even though these experiments were performed in mice, because mice tend to be a rather good model system for limb perfusion/ischemia, these results might be applicable in the clinic. “We don’t want to turn off the immune system, we want to turn it back to normal,” said Baban
According to Baban’s collaborator, Jack Yu, even a short period of inadequate blood supply and nutrients results in the rapid accumulation of destructive acidic metabolites, reactive oxygen species (also known as free radicals), and cellular damage. The power plant of the cell, small structures called the mitochondria, tend to be one of the earliest casualties of ischemia/perfusion. Since mitochondria require oxygen to make a chemical called ATP, which is the energy currency in cells, a lack of oxygen makes the mitochondria leaky, swollen and dysfunctional.
“The mitochondria are very sick,” said Yu. ” When blood flow is restored, it can put huge additional stress on sick powerhouses. “They start to leak things that should not be outside the mitochondria.”
Without adequate energy production and a cellular power plant that leaks, the cells fill with toxic byproducts that cause the cells to commit a kind of cellular hari-kari. Inflammation is a response to dying cells, since the role of inflammation is to remove dead or dying cells, but inflammation can give the coup de grace to cells that are already on the edge. Therefore, inflammation can worsen the problem of cell death.
Even though these results were applied to limb ischemia perfusion, Baban and his colleagues think that their results are applicable to other types of ischemia perfusion events, such as heart attacks and deep burns. Yu, for example, has noticed that in the case of burn patients, the transplantation of new tissue into areas that have undergone ischemia perfusion can die off even while the patient is still in the operating room.
“It cuts across many individual disease conditions,” said Yu. Transplant centers already are experimenting with pulsing donor organs to prevent reperfusion trauma.
The next experiments will include determining if more is better. That is, if giving more stem cells will improve the condition of the injured animal. In these experiments, which were published in the journal PLoS One, only one stem cell dose was given. Also, IDO-enhancing drugs will be examined for their ability to prevent reperfusion damage.
Even though stem cells are not given to patients in hospitals after reperfusion, stem cell-based treatments are being tested for their ability to augment healing after reperfusion. Presently, physicians reestablish blood flow and then give broad-spectrum antibiotics. The results are inconsistent. Hopefully, this work by Baban and others will pave the road for future work that leads to human clinical trials.
Diabetes mellitus results from an insufficiency of insulin (Type 1 diabetes) or an inability to properly respond to insulin (Type 2 diabetes). Type 1 diabetes is caused by an attack by the patient’s own immune system on their pancreatic beta cells, which synthesize and secrete insulin. It is a disease characterized by inflammation in the pancreas. This suggests that abatement of inflammation in the pancreas might provide relief and delay the onset of diabetes.
Mesenchymal stem cells isolated from umbilical cord connective tissue, which is also known as Wharton’s jelly (WJ-MSCs), have the ability to reverse inflammatory destruction and might provide a way to delay or even reverse the onset of Type 1 diabetes.
To test this possibility, Jianxia Hu, Yangang Wang, and their colleagues took 60 non-obese diabetic mice and divided them into four groups: a normal control group, a normal diabetic group, a WJ-MSCs prevention group that was treated with WJ-MSCs before the onset of diabetes, and a WJ-MSCs treatment group that was treated with WJ-MSCs after the onset of diabetes.
After their respective treatments, the onset time of diabetes, levels of fasting plasma glucose (FPG), fed blood glucose levels and C-peptide (an indication of the amount of insulin synthesized), regulation of cytokines, and islet cells were examined and evaluated.
After WJ-MSCs infusion, fasting and fed blood glucose levels in WJ-MSCs treatment group decreased to normal levels in 6-8 days and were maintained for 6 weeks. The levels of fasting C-peptide of the WJ-MSC-treated mice was higher compared to diabetic control mice. In the WJ-MSCs prevention group, WJ-MSCs protected mice from the onset of diabetes for 8-weeks, and the fasting C-peptide in this group was higher compared to the other two diabetic groups.
Other comparisons between the WJ-MSC-treated group and the diabetic control group, showed that levels of regulatory T-cells (that down-regulate autoinflammation), were high and levels of pro-inflammatory molecules such as IL-2, IFN-γ, and TNF-α. The degree of inflammation in the pancreas was also examined, and pancreatic inflammation was depressed, especially in the WJ-MSCs prevention group.
These experiments show that infusions of WJ-MSCs can down-regulate autoimmunity and facilitate the recovery of islet β-cells whether given before or after onset of Type 1 Diabetes Mellitus. THis suggests that WJ-MSCs might be an effective treatment for Type 1 Diabetes Mellitus.
Italian researchers have derived stem cells from skin cells that can reduce the damage to the nervous system cause by a mouse version of multiple sclerosis. This experiment provides further evidence that stem cells from patients might be a feasible source of material to treat their own maladies.
The principal investigators in this work, Cecilia Laterza and Gianvito Martino, are from the San Raffaele Scientific Institute, Milan and the University of Milan, respectively.
Because multiple sclerosis results from the immune system attacking the myelin sheath that surrounds nerves, most treatments for this disease consist of agents that suppress the immune response against the patient’s own nerves. Unfortunately, these treatments have pronounced side effects, and are not effective in the progressive phases of the disease when damage to the myelin sheath might be widespread.
The symptoms of loss of the myelin sheath might one or more of the following: problems with touch or other such things, muscle cramping and muscle spasms, bladder, bowel, and sexual dysfunction, difficulty saying words because of problems with the muscles that help you talk (dysarthria), lack of voluntary coordination of muscle movements (ataxia), and shaking (tremors), facial weakness or irregular twitching of the facial muscles, double vision, heat intolerance, fatigue and dizziness; exertional exhaustion due to disability, pain, or poor attention span, concentration, memory, and judgment.
Clinically, multiple sclerosis is divided into the following categories on the basis of the frequency of clinical relapses, time to disease progression, and size of the lesions observed on MRI. These classifications are:
A) Relapsing-remitting MS (RRMS): Approximately 85% of cases and there are two types – Clinically isolated syndrome (CIS): A single episode of neurologic symptoms, and Benign MS or MS with almost complete remission between relapses and little if any accumulation of physical disability over time.
B) Secondary progressive MS (SPMS)
C) Primary progressive MS (PPMS)
D) Progressive-relapsing MS (PRMS)
The treatment of MS has 2 aspects: immunomodulatory therapy (IMT) for the underlying immune disorder and therapies to relieve or modify symptoms.
To treat acute relapses:
A) Methylprednisolone (Solu-Medrol) can hasten recovery from an acute exacerbation of MS.
B) Plasma exchange (plasmapheresis) for severe attacks if steroids are contraindicated or ineffective (short-term only).
C) Dexamethasone is commonly used for acute transverse myelitis and acute disseminated encephalitis.
For relapsing forms of MS, the US Food and Drug Administration (FDA) include the following:
A) Interferon beta-1a (Avonex, Rebif)
B) Interferon beta-1b (Betaseron, Extavia)
C) Glatiramer acetate (Copaxone)
D) Natalizumab (Tysabri)
F) Fingolimod (Gilenya)
G) Teriflunomide (Aubagio)
H) Dimethyl fumarate (Tecfidera)
For aggressive MS:
A) High-dose cyclophosphamide (Cytoxan).
In order to treat multiple sclerosis, restoring the damaged myelin sheath is essential for returning patients to their former wholeness.
In this study, this research team reprogrammed mouse skin cells into induced pluripotent skin cells (iPSCs), and then differentiated them into neural stem cells. Neural stem cells can differentiate into any cell type in the central nervous system.
Next, Laterza and her colleagues administered these neural stem/progenitor cells “intrathecally,” which simply means that they were injected into the spinal cord underneath the meninges that cover the brain and spinal cord to mice that had a rodent version of multiples sclerosis called EAE or experimental autoimmune encephalomyelitis.
EAE mice are made by injecting them with an extract of myelin sheath. The mouse immune system mounts and immune response against this injected material and attacks the myelin sheath that surrounds the nerves. EAE does not exactly mirror multiple sclerosis in humans, but it comes pretty close. While multiple sclerosis does not usually kill its patients, EAE either kills animals or leaves them with permanent disabilities. Animals with EAE also suffer severe nerve inflammation, which is distinct from multiple sclerosis in humans in which some nerves suffer inflammation and others do not. Finally, the time course of EAE is entirely different from multiple sclerosis. However, both conditions are caused by an immune response against the myelin sheath that strips the myelin sheath from the nerves.
The transplanted neural stem cells reduced the inflammation within the central nervous system. Also, they promoted healing and the production of new myelin. However, most of the new myelin was not made by the injected stem cells. Instead the injected stem cells secreted a compound called “leukemia inhibitory factor” that promotes the survival, differentiation and the remyelination capacity of both internal oligodendrocyte precursors and mature oligodendrocytes (these are the cells that make the myelin sheath). The early preservation of tissue integrity in the spinal cord limited the damage to the blood–brain barrier damage. Damage to the blood-brain barrier allows immune cells to infiltrate the central nervous system and destroy nerves. By preserving the integrity of the blood-brain barrier, the injected neural stem cells prevented infiltration of blood-borne of the white blood cells that are ultimately responsible for demyelination and axonal damage.
“Our discovery opens new therapeutic possibilities for multiple sclerosis patients because it might target the damage to myelin and nerves itself,” said Martino.
Timothy Coetzee, chief research officer of the National Multiple Sclerosis Society, said of this work: “This is an important step for stem cell therapeutics. The hope is that skin or other cells from individuals with MS could one day be used as a source for reparative stem cells, which could then be transplanted back into the patient without the complications of graft rejection.”
Obviously, more work is needed, but this type of research demonstrates the safety and feasibility of regenerative treatments that might help restore lost function.
Martino added, “There is still a long way to go before reaching clinical applications but we are getting there. We hope that our work will contribute to widen the therapeutic opportunities stem cells can offer to patients with multiple sclerosis.”
See Cecilia Laterza, et al. iPSC-derived neural precursors exert a neuroprotective role in immune-mediated demyelination via the secretion of LIF. NATURE COMMUNICATIONS 4, 2597: doi:10.1038/ncomms3597.
Wouldn’t it be nice to have cells that express the right molecules at the right place and the right time to augment or even initiate healing?
Researchers at the Brigham and Women’s Hospital and Harvard Stem Cell Institute have inserted modified messenger RNA to induce mesenchymal stem cells to produce adhesive proteins (PSGL-1)and secrete interleukin-10, a molecule that suppresses inflammation. When injected into the bloodstream of mice, these modified stem cells home to the right location, stick to that site, and secrete interleukin-10 (IL-10) to suppress inflammation.
Jeffrey Karp, Harvard Stem Cell Institute principal faculty member and leader of this research, said this about this work: “If you think of a cell as a drug factory, what we’re doing is targeting cell-based, drug factories to damaged tissues, where the cells can produce drugs at high enough levels to have a therapeutic effect.”
Karp’s paper reports a proof-of-principle study has piqued the interest of several biotechnology companies, since it has the potential to target biological drug to disease sites. While ranked as the top sellers in the drug industry, biological drugs are still challenging to use. Karp’s approach might improve the clinical applications of biological drugs and improve the somewhat mixed results of clinical trials with mesenchymal stem cells.
Mesenchymal stem cells (MSCs) have emerged as one of the favorite sources for stem cell therapies. The attractiveness of MSCs largely lies with their availability, since they are found in bone marrow, fat, liver, muscle, and many other places. Secondly, MSCs can be grown in culture for a limited period of time without a great deal of difficulty. Third, MSCs tend to be ignored by the immune system when injected. For these reasons, MSCs have been used in many clinical trials, and they appear to be quite safe to use.
To genetically modify MSCs, Karp and his co-workers made chemically modified messenger RNAs (mRNAs) whose bases differed slightly from natural mRNAs. These chemical modifications did not affect the recognition of the mRNA by the protein synthesis machinery of the MSCs, but did affect the recognition of these mRNAs by those enzymes that degrade mRNAs. Therefore, these synthetic mRNAs are very long-lived and the transfected cells end up making the proteins encoded by these mRNAs for a very long time. RNA transfection does not modify the genome of the host cells, and this makes it a very safe procedure, since the engineered cells will express the desired protein for some time, but not indefinitely.
The mRNAs introduced into the cultured MSCs included mRNAs that encode the IL-10 protein, which is cytokine that suppresses inflammation, the PSGL-1 protein, a cell-surface protein that sticks to the P-and E-selectin receptors, and the Fut7 gene product. FUT7 encodes an enzyme called fucosyltransferase 7, which adds a sugar called “fucose” to the PSGL-1 protein and without this sugar, PSGL-1 cannot bind to the selectins. Selectins are stored by cells and during inflammation, they are sent to the cell surface where they can bind cells and keep them there to mediate inflammation. By expressing PSGL-1 in the MSCs, Karp and his group hoped to that the engineered MSCs would bind to the surfaces of blood vessels and not be washed out.
Oren Levy, lead author of this paper, said, “This opens the door to thinking of messenger RNA transfection of cell populations as next generation therapeutics in the clinic, as they get around some of the delivery challenges that have been encountered with biological agents.”
A problem that constantly troubles clinical trials that use MSCs is that they are rapidly cleared from the bloodstream within a few hours or days after they are introduced. The Harvard team showed that rapid targeting of MSCs to inflamed tissue produced a therapeutic effect despite rapid clearance of the MSCs.
Karp and his colleagues would like to extend the lifespan of these cells in the bloodstream and they are presently experimenting with new synthetic mRNAs that encode pro-survival factors.
“We’ve interested to explore the platform nature of this approach and see what potential limitations it may have or how far we can actually push it. Potentially we can simultaneously deliver proteins that have synergistic therapeutic impacts,” said Weian Zhao, another author of this paper.
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?
Researchers at the University of Buffalo have discovered that stem cells are involved in the inflammation that promotes atherosclerosis.
Atherosclerosis or hardening of the arteries occurs when fat, cholesterol, and other substances build up in the walls of arteries and form hard structures called plaques. With the passage of time, these plaques can grow and block the arteries, depriving tissues of oxygen and nutrition.
High serum cholesterol levels have been unequivocally linked to an increased risk of arteriosclerosis. However, the deposition of cholesterol and other molecules underneath the inner layer (intima) of arteries requires a phenomenon known as inflammation. Inflammation occurs in response to tissue damage and it involves the dilation of blood vessels, increased blood flow the damaged area, the recruitment of white blood cells to the area, and increased heart, volume, and pain at the area in question. Increased inflammation within blood vessels damages the intimal layer and allows the deposition of cholesterol and other molecules underneath it to form an atheroma or a plaque.
The stem cell link to atherosclerosis is that the bone marrow-based stem cells that make our blood cells (hematopoietic stem/progenitor cells or HSPCs) ramp up their production of white blood cells in response to increased serum cholesterol levels.
Thomas Cimato, assistant professor in the Department of Medicine in the UB School of Medicine and Biomedical Sciences, said of his publication, “Our research opens up a potential new approach to preventing heart attack and stroke, by focusing on interactions between cholesterol and the HSPCs. Cimto also suggested that these findings could lead to the development of a useful therapy in combination with statins, or a treatment in place of statins for those who cannot tolerate statins.
In Cimato’s study, high cholesterol levels were shown to cause increases in the levels of interleukin -17 (IL-17). IL-17 is a cytokine that recruits monocytes and neutrophils to the site of inflammation. IL-17 boosts levels of granulocyte colony stimulating factor (GCSF), which is a factor that induces the release of HSPCs from the bone marrow to the peripheral circulation.
Cimato also found that statin drugs reduce the number of HSPCs in circulation, but not all patients responded similarly to statins. “We’ve extrapolated to humans what other scientists previously found in mice about the interactions between LDL, cholesterol, and these HSPCs,” said Cimato.
In order to transport cholesterol through the bloodstream, cells must construct a vehicle into which the cholesterol is packaged. Cholesterol does not readily dissolve in water. Therefore, packaging cholesterol into lipoprotein particles allows for its transport around the cell. Cell use cholesterol to vary the fluidity of their membranes, and to synthesize steroid hormones. Once cholesterol is absorbed from the diet, the cells of the small intestine package cholesterol and fat into a particle known as a chylomicron.
Chylomicrons are released by the small intestinal cells and they travel to the liver. In the liver, chylomicrons are disassembled and the cholesterol is packaged into a particle known as a very-low density lipoprotein particle (VLDL). After its release and sojourning through the bloodstream, the VLDL looses some surface proteins and is depleted of its fat and becomes known as a low-density lipoprotein or LDL particle. While these particles sojourn through the bloodstream, they release fat for tissues to use as an energy source.
LDL particles are gradually removed from circulation. If they build up to high concentrations, they can be taken up by a wandering white blood cell known as a macrophage. If these macrophages take up too much LDL, they can become a foam cell. Foams cells can become lodged underneath the intimal layer of blood vessels when inflammation occurs inside blood vessels, and this is the cause of atherosclerosis.
Increased LDL levels in mice have been shown to stimulate the release of HSPCs from bone marrow and accelerate the differentiation of these cells into white blood cells (neutrophils and monocytes) that participate in inflammation.
Mice do not regulate their cholesterol levels in the same way humans do. Cimato commented, “mice used for atherosclerosis studies have very low total cholesterol levels at baseline. We feed then very high fat diets in order to study high cholesterol but it isn’t easy to interpret what the levels in mice will mean in humans and you don’t know if extrapolating to humans will be valid.”
Therefore, in order to properly model cholesterol regulation in their human subjects, Cimato had them take statins for a two-week period followed by one-month intervals when they were off the drugs. “We modeled the mechanism of how LDL cholesterol affects stem cell mobilization in humans,” said Cimato.
The experiments showed that increased LDL levels tightly correlated with IL-17 levels.
Secondly, blood LDL levels also correlated with GCSF levels.
Finally, increasing GCSF levels led to higher levels of circulating HSPCs.
These circulating HSPCs increase the numbers of neutrophils, monocytes, and macrophages that are involved in the formation of plaque and atherosclerosis.
The next step is to determine if HSPCs, like LDL cholesterol levels are connected to stroke, cardiovascular disease and heart attacks.