Our phase 1/2 pilot clinical trial using combined intrathecal and intravenous injection of bone marrow–derived autologous MSCs in 34 patients with MS and ALS was aimed at exploring the feasibility and safety of this type of cell therapy. The 6 to 25 months of follow-up did not reveal any significant immediate or late adverse effects and indicated clinical stabilization or improvement in some patients. Magnetic resonance imaging indicated possible dissemination of the MSCs from the lumbar site of inoculation to the occipital horns, meninges, spinal roots, and spinal cord parenchyma ( and ). Immunological analysis of lymphocyte subsets and cytokine production, performed in 12 patients, demonstrated the immediate in vivo immunomodulating effects of MSCs, starting as early as 4 hours after MSC transplantation and including an increase in CD4+ CD25+ regulatory cells and a reduction in the proportion of activated dendritic cells and lymphocytes and of lymphocyte proliferation ().
One of the possible approaches to enhancing neuroprotective mechanisms and inducing neuroregeneration in progressive MS and ALS may involve the use of adult or nonembryonic stem cells, which are more differentiated than embryonic stem cells and can be harvested from various tissues. Bone marrow MSCs mainly support the processes of hematopoiesis and hematopoietic stem cell engraftment but can also give rise to cells of mesodermal origin such as osteoblasts, adipocytes, and chondrocytes. Recent studies have described the following additional properties of MSCs: (1) a debatable ability to transdifferentiate into cells of endodermal and ectodermal origin,6,47,48
including possible neural transdifferentiation,15,17,19
and (2) systemic (peripheral) and local (in the CNS) immunomodulatory effects.8,9,49–51
The use of bone marrow–derived stem cells offers several practical advantages: (1) MSCs can be obtained readily and safely from adult bone marrow, even from patients with advanced disease; (2) MSCs, which are normally present in small concentrations in the bone marrow compartment, can be enriched and greatly expanded by in vitro culturing; (3) autologous MSCs can be administered safely without the need for immunosuppressive treatment to prevent rejection; and (4) adult MSCs were shown to be less prone to genetic abnormalities and malignant transformation during multiple passages in vitro, thus implying a low risk for induction of treatment-related malignant neoplasms.52–55
The preclinical studies,28–39
together with the cumulative data from ongoing clinical trials with MSCs in various clinical conditions (reviewed by Giordano et al27
), provided the scientific basis for our trial. The only available data on the use of MSCs in neurological conditions include a small study56
in 7 patients with ALS and a trial from Iran57
that did not report any significant adverse events. Two additional, recently published studies, a phase 1 trial in patients with ALS (with intraspinal injection of MSCs)58
and a small pilot study with 3 patients with MS that used intravenous administration of adipose tissue MSCs,59
also support the safety of the use of MSCs.
Our main finding was the feasibility and acceptable safety profile of transplantation of autologous stem cells from the bone marrow in patients with MS and ALS. None of our patients experienced significant adverse effects during the 6- to 25-month observation. In 20 patients, follow-up MRI 1 year after transplantation did not reveal any unexpected pathology or significant new activity of the disease.
Several clinical trials in nonneurological diseases28–39
have indicated that intravenous administration of MSCs is a safe procedure. Our study additionally shows an acceptable short-term safety profile of the intrathecal route of administration of stem cells at doses of up to 70 million cells per injection per patient. The intrathecal approach for cell-based therapies in neurological diseases such as MS and ALS, in which the areas of tissue damage are widespread throughout the neuroaxis, may increase the possibility of migration of the injected cells to the proximity of the CNS lesions. The injected cells may circulate with the flow of the cerebrospinal fluid and have a better chance of reaching the affected CNS areas. Our animal studies showed that this route of administration could induce superior neurotrophic and neuroprotective effects.25
However, the optimal route of stem cell administration in general—and particularly MSC administration—in patients with neurological diseases remains debatable. Other investigators have claimed that intravenous injection may be sufficient and equally effective (at least in the case of MS) because MSCs exert peripheral immunomodulating effects and may also migrate through the blood to the damaged areas of the CNS after receiving inflammatory signals.23–25
A possible drawback of the intravenous administration of MSCs is that most of the cells injected into the blood will home to the lungs, lymph nodes, and other tissues, greatly reducing the number of cells available to migrate to the CNS. Moreover, intrathecal delivery of cells may focus their possible immunomodulatory and trophic effects directly on the CNS, without producing systemic adverse effects.
The initial findings of our trial support the possibility of migration of MSCs from their site of injection (lumbar area of the cerebrospinal fluid) to the brain ventricles and spinal cord parenchyma. Despite the absence of definite proof, the hypointense signals in the meninges and the spinal cord parenchyma, shown in our MRI studies (), may indicate the presence of supra-paramagnetic particles (ferumoxides-labeled MSCs) in these CNS areas. However, the hypointense areas could also be related to the presence of macrophages that phagocytized the iron oxide magnetic resonance contrast agent and migrated to the inflammatory MS lesions.
Our data also demonstrate and confirm, to our knowledge for the first time in human neurological diseases, the in vivo systemic immunomodulatory effects of MSCs previously described in animal studies.25
The finding of early clinical stabilization or improvement in some of the patients could be related to these immunomodulating effects. The possibility of neuroprotection and neuroregeneration through transdifferentiation of MSCs into cells of the neuronal or glial lineage, although theoretically viable, has yet to be proved by neuroimaging studies. Further controlled trials are warranted to evaluate the long-term safety and the potential clinical efficacy of MSC transplantation. According to recent consensus papers,60,61
intravenous injection of MSCs (at a suggested dose of 106
/kg, which has been shown to be optimal for effective immunomodulation) seems to be the most feasible approach in designing future efficacy trials in patients with active MS.