Scientists in Japan have reported the discovery of cells that behave like cardiac precursor cells and which are derived from human menstrual blood. The discovery corroborates similar reports made independently by researchers in the United States in November of 2007. In both cases, such a discovery identifies a new, non-invasive, inexpensive, universally available, easily obtainable and ethically non-controversial source of highly potent stem cells.

As described by the Japanese researchers, these MMCs (menstrual blood-derived mesenchymal cells) “began beating spontaneously after induction, exhibiting cardiomyocyte-specific potentials.” The researchers hypothesized that the majority of the cardiomyogenic cells found in the MMCs had originated from detached uterine endometrial glands, 76 to 97% of which were shown to transdifferentiate into cardiac cells in vitro. Additionally, the MMCs were found to proliferate an average of 28 generations, while the subpopulation of EMCs (endometrial gland-derived mesenchymal cells) were able to be engrafted onto a recipient’s heart via a 3-dimensional EMC cell sheet. When the MMCs were transplanted into rats who had suffered myocardial infarction, cardiac function was significantly restored.

The authors concluded that, “MMCs appear to be a potential novel, easily accessible source of material for cardiac stem cell-based therapy.”

The findings were reported by scientists at the Keijo University School of Medicine in Tokyo in collaboration with researchers at the National Research Institute for Child Health and Development in Tokyo, the National Cancer Center Research Institute in Tokyo, Kanazawa University School of Medicine, and Tokyo Women’s Medical University.

An advanced form of peripheral artery disease (PAD), critical limb ischemia is often associated with high levels of morbidity and mortality. Patients who suffer from this condition often experience acute pain in the affected limbs, even while at rest. In the past, amputation has often been the unfortunate result of this disease.

Now scientists in Italy have been able to utilize the body’s own supply of endogenous stem cells in the treatment of critical limb ischemia in a mouse model. Employing the standard paradigm of femoral artery ligation in the mice, the researchers stimulated the mobilization of endogenous stem cells with G-CSF (granulocyte colony stimulating factor) both exclusively and in combination with parathyroid hormone.

Improvement was seen in the mice, most dramatically with the G-CSF and parathyroid hormone combination which was found to induce angiogenesis in the ischemic muscles.

Although clinical trials have already been conducted in human patients in the U.S. in which mesenchymal stem cells have been used to treat peripheral artery disease, these results with G-CSF and parathyroid hormone indicate that additional combinations of pharmaceuticals may further optimize patient improvement.

In its second pre-clinical trial for the treatment of ischemic stroke, Pluristem Therapeutics Inc. has reported statistically significant results in both functional and anatomical improvement in an animal model after the use of one of its products which has been developed specifically for the treatment of stroke. Specializing in the commercialization of therapeutic products developed exclusively from adult mesenchymal stromal cells (MSCs) that are derived from the human placenta, Pluristem has developed a number of PLX (PLacental eXpanded) products, one of which, PLX-Stroke, is directly targeted for the treatment of ischemic stroke.

Using the widely accepted standard animal model for ischemic stroke, namely, hypertensive rats that had undergone middle cerebral arterial occlusion, the scientists systemically injected PLX-Stroke into some of the rats while other rats served as controls. In the rats that had received the PLX-Stroke, subsequent improvement was then observed both in functional paramaters such as the neurological severity scores and beam walking capability, as well as in anatomical parameters such as in the reduction of infarct size. The improvements were statistically significant when compared to the corresponding parameters in the control rats.

This pre-clinical study was conducted at the Fraunhofer Institute for Cell Therapy and Immunology in Leipzig, Germany, a branch of the Fraunhofer Society. According to Professor Frank Emmrich, who led the study, “PLX cells possibly show the potential to become a new treatment for the functional recovery from a stroke. The data show that a double injection of PLX cells at two different time points significantly improves the functional recovery and reduces the size of the lesion compared to the controls.” According to the President and CEO of Pluristem, Dr. Zami Aberman, “We are very excited about the results and believe that utilizing our PLX product may successfully treat millions of ischemic stroke patients and lead to a multi-billion dollar market. This independent study, together with the previously announced favorable pre-clinical results of PLX cells to treat limb ischemia and blood cancer, give us a robust pipeline for developing new therapeutic products.”

Approximately 90% of all strokes are ischemic, with the remaining 10% being hemorrhagic. Ischemic strokes are the result of an arterial occlusion in the brain, and it is estimated that approximately 2 million people per year throughout the world suffer ischemic strokes, many of whom either die or are rendered permanently disabled from the stroke. Now, adult stem cell studies such as these conducted by Pluristem offer a realistic and viable therapy which actually regenerates damaged neurological tissue.

Mesenchymal stem cells (MSCs) are recognized as one of the most important types of stem cells, with one of the longest and most clinically advanced histories. Although bone marrow is the usual source from which MSCs are derived, they are also known to exist in many other types of tissue such as umbilical cord and placental blood, menstrual blood, peripheral blood, muscle and teeth.

Now researchers in India have discovered MSCs in the limbus of the human eye. After examining the epithelial cells of limbal tissue from patient biopsy samples collected during eye surgery, the scientists identified cells with a spindle-like morphology. The cells were then characterized for a number of parameters including morphology and immunophenotyping, and upon expansion in the laboratory the cells were found to possess a phenotype similar to that of MSCs that are derived from bone marrow. Most significantly, the cells were found to be capable ot differentiating into adipocytes (fat tissue) and osteocytes (bone and cartilage tissue).

Why would stem cells which are capable of differentiating into cartilage and bone exist in the eye? The answer to questions such as this may shed light not only upon the role that these cells play in limbal stem cell transplants but also on the role of MSCs in wound healing and regeneration in general. Especially in ocular injuries and surgeries, the identification of various subsets of stem cells in the human limbus that are similar to bone marrow-derived MSCs is particularly relevant. Already by 1999, a publication in the New England Journal of Medicine (Tsubota et al.) had reported 70 corneal epithelial stem cell transplants in which a statistically significant improvement in vision had been observed.

The presence of MSCs in the eye represents what the discoverers refer to as cells that are “unique to the adult stem cell niche.” Scientists are now investigating further the precise properties of these unique cells, for additional clues into the nature of molecular and cellular regenerative mechanisms.

At the 2008 annual meeting of the Society for Gynecologic Investigation (SGI), held this month in San Diego, California, researchers from the Yale School of Medicine reported improvement in mice with Parkinson’s disease who were treated with uterine stem cells. A debilitating neurodegenerative disorder, Parkinson’s disease is characterized by insufficient dopamine action in the motor cortex and basal ganglia regions of the brain. In this study, stem cells that were derived from human endometrial stromal cells were successfully cultured to differentiate into neurons, complete with the characteristic axon-like projections and pyramidal cell bodies. When the differentiated cells were then transferred into the brains of the mice with Parkinson’s disease, the researchers observed not only the growth of new brain cells, but also an increase in dopamine levels in the brains of the mice.

According to Hugh Taylor, M.D., professor in the Department of Obstetrics, Gynecology and Reproductive Sciences, and chief of Reproductive Endocrinology and Infertility at the Yale School of Medicine, “Now we have found that we can turn uterine stem cells into neurons that can boost dopamine levels and partially correct the problem of Parkinson’s disease. The implications of our findings are that women have a ready supply of stem cells that are easily obtained, are differentiable into other cell types, and have great potential for other purposes.”

The scientists were awarded the SGI President’s Presenter Award for their publication.