Parkinson’s disease (PD) is a prevalent neurodegenerative disorder that affects 1% of the general population over the age of 60 years. It is a progressive condition characterized by loss of dopaminergic neurons in the region of the ventral midbrain, and nerves of the central and peripheral nervous systems. Therapeutic approaches to treatment of PD include medications, deep brain stimulation, and now, stem cell therapy.
Mesenchymal stem cells (MSCs) can be derived from the bone marrow, adipose (fat) tissue, umbilical cord blood, and amniotic fluid. These cells have the capacity to transform into osteocytes (bone cells), cardiomyocytes (heart muscle cells), chondrocytes (cartilage cells), and adipocytes (fat cells). In addition, MSCs have anti-inflammatory and immune system properties. There are two main categories of MSCs: naïve (directly isolated from mesenchymal tissues) and neurally-induced, which have much promise in the treatment of Parkinson’s disease.
Since the pathological hallmark of PD is loss of nigrostriatal dopamine neurons, current therapies target the dopamine receptors. Stem cell therapy clinical trials have shown much promise in the treatment of PD. Stem cells with the same properties of dopaminergic neurons could offer long-term improvement for many people.
In relation to stem cells for PD treatment, a research study in 2008 found reprogramming of mouse fibroblasts into stem cells through retroviral transduction of certain transcription factors. Afterwards, the neurons could integrate into the PD rat model. A follow-up study showed that the brain neurons of PD subjects yielded functional restoration in a preclinical model. In another study, transplantation of stem cells generated functional neurons in PD rat models, which improved motor deficits.
In one clinical study, scientists noted that infusion of growth factor (present from stem cells) into the parenchyma resulted in proliferation, migration, and differentiation of neural cells in rat models with PD. Other scientists found a turnover in dopaminergic neurons in certain brain sections of mouse models who received stem cell therapy. A recent study involving monkeys with Parkinson’s-like symptoms involved transplanting dopaminergic neurons from human stem cells into the animal’s brains. The monkeys were also treated with immunosuppressive drugs. Researchers followed the study subjects over two years, and found the neurons survived without any tumor growth. In addition, the transplant of cells improved the monkeys’ PD symptoms.
Umbilical cord blood has been used in some research regarding neurological conditions. This blood is rich in stem cells, and has been used safely for chronic spinal cord injury with no adverse reactions. Autologous MSCs have been isolated from the bone marrow, and then injected into the intrathecal space (around the spinal cord), allowing easy access to the spinal column and brain. Researchers have shown evidence of immunomodulatory effects within 24 hours after these injections, with good reports 6 months following therapy.
Several clinical studies have been conducted using human subjects with PD and stem cells. In a case study, the patient had noticeable symptom improvement at 12 months following treatment. Two other studies (combined 11 patients) were conducted. PET scan showed DA neuron survival on all subjects, and 7 had improvement of PD symptoms. In the larger studies, patients were observed for 3-4 years following treatment, and around 45% of the study subjects maintained symptom improvement at final report dates.
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Amniotic and Umbilical Cord Stem Cell Treatments
The most revolutionary regenerative medicine treatments now being offered include amniotic and umbilical stem cell treatments. These are FDA regulated and contain growth factors, hyaluronic acid, cytokines and stem cells.