Italian scientists from Milan have used skin-derived stem cells in combination with a previously developed collagen tube to successfully bridge the gaps in injured nerves in a rat model, On the strength of that animal model system, the Italian group successfully used this procedure to heal the damaged peripheral nerves in the upper arms of a patient whose only other option was limb amputation.
“Peripheral nerve repair with satisfactory functional remains a great surgical challenge, especially for severe nerve injuries resulting in extended nerve defects,” said the corresponding author of this study Dr, Yvan Torrente of the Department of Pathophysiology and Transplantation at the University of Milan. “However, we hypothesized that the combination of autologous (self donated) stem cells placed in collagen tubes to bridge gaps in the damaged nerves would restore the continuity of injured nerves and save from amputation the upper arms of a patient with poly-injury to motor and sensory nerves.”
Although autologous nerve grafting has been the “gold standard” for reconstructive surgeries, these researchers recognized the disadvantages of such a procedure. Graft availability is the first drawback of autologous nerve grafting. Secondly, the condition of the donor site or “donor site morbidity.” If the donor site is in bad shape, taking a nerve from that site will probably make the donor site worse and provide a nerve that does not work as well. Finally, neuropathic pain is also an issue.
Autologous skin-derived stem cells have several advantages over autologous nerve grafts. First, the skin provides an accessible source of stem cells that are rapidly expandable in culture. Secondly, these skin-derived cells are capable of survival and integration within host tissues.
The NeuraGen nerve guide is a tiny collagen tube that connects the two damaged ends of a nerve together to mediate and expedite nerve healing. NeuraGen tubes guide the transplanted stem cells to the gaps in the damaged nerves. Torrente and his co-workers developed and tested the NeuraGen tubes in rats, and the US Food and Drug Administration (FDA) has approved NeuraGen for use in human patients. See this figure from the NeuraGen web site:
Torrente and others successfully used skin-derived stem cells and NeuraGen tubes to heal the severed sciatic nerves in rats. Therefore, once the FDA approved NeuraGen tubes, Torrente tried NeuraGen tubes in human patients with severe peripheral nerve damage.
A three-year follow-up on one particular patient showed that injured median and ulnar nerves showed extensive healing as ascertained by magnetic resonance imaging. Functional tests, such as pinch gauge tests, static two-point discrimination and monofilament touch tests established the functional recovery of these peripheral nerves in the patient.
“Our three-year follow-up has witnesses nerve regeneration with suitable functional recovery in the patient and the salvage of upper arms from amputation,” said researchers from Torrente’s group. “This finding opens an alternative avenue for patients who are at-risk of amputation after the injury to important nerves.”
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.