Delivery of autologous bone marrow precursor cells into the spinal cord via lumbar puncture technique in patients with spinal cord injury: A preliminary safety study

Abstract

Hematopoietic stem cells are adult precursor cells found mainly in the bone marrow and they provide the blood cells required for daily blood turnover and for fighting infections. Hematopoietic stem cell transplantation has been used for decades to treat blood cancers and other blood disorders. More recently, hematopoietic stem cell therapy has been shown to have considerable therapeutic potential for spinal cord injury (SCI); however, in most animal studies, stem cells have been directly injected into pathological central nervous system tissues and this model is very difficult to translate into clinical practice. Alternative and less invasive routes for delivering hematopoietic stem cells in animal models of SCI were described and the advantages of the percutaneous lumbar puncture (LP) technique have been recently demonstrated [1Bakshi A. Hunter C. Swanger S. et al.Minimally invasive delivery of stem cells for spinal cord injury: advantages of the lumbar puncture technique.J Neurosurg. 2004; 3: 330-337Google Scholar, 2Lepore A.C. Bakshi A. Swanger S. et al.Neural precursor cells can be delivered into the injured cervical spinal cord by intrathecal injection at the lumbar cord.Brain Res. 2005; (31);1405(1–2):206–216Google Scholar]. This proposition has not been described in humans. We therefore tested it by examining whether autologous bone marrow precursor cells can be delivered into the spinal cord via LP in patients with SCI. Ten patients with SCI (seven had paraplegia and three had quadriplegia) were enrolled. The median age was 24 years and the mean duration of injury was 3 years. Patients received daily doses of recombinat human granulocyte colony-stimulating factor (G-CSF; 10 μg/kg) for five consecutive days and 100 mL of bone marrow cells (BMC) were aspirated from the posterior iliac crest on day 6. All patients provided written informed consent. Mononuclear cells were separated by a Ficoll-Hypaque gradient, washed, and resuspended in phosphate-buffered saline. Flow cytometric enumeration of CD34+ cells was performed as previously described [3Gratama J.W. Sutherland D.R. Keeney M. Flow cytometric enumeration and immunophenotyping of hematopoietic stem and progenitor cells.Semin Hematol. 2001; 38: 139-147Abstract Full Text PDF PubMed Scopus (28) Google Scholar]. Cell viability was assessed with trypan blue viability test. Transplantation was performed 4 hours after bone marrow aspiration. The cerebrospinal fluid (CSF) samples were collected before and 7 days after the transplantation. Patients were followed every 1 week for 12 weeks. Safety was assessed throughout the study for all patients and a serious adverse event was defined as any event that resulted in death, was life-threatening, required hospitalization, resulted in persistent or substantial disability, or had important medical consequences. For each patient, 100 × 106 mononuclear cells were injected via LP; the median number of CD34+ cells was 1.0 × 106, ranging from 0.65 to 1.75 × 106. Trypan blue viability test performed before transplantation was superior to 90% in all samples. The patients were discharged after 1 day and have been seen as outpatients. CSF examination was normal at both times. The 12 weeks posttransplantation course was uneventful. Bone marrow precursor cells are clinically attractive because they can be obtained in patients at bedside, raising the possibility of an autologous model of cell therapy for SCI. However, the potential for hematopoietic stem cells to produce cell types other than blood cells has become the subject of intense scientific controversy, and it is still not clear whether they could be used on a clinical scale to restore tissues and organs other than blood and the immune system. In addition, the potential therapeutic effects of these cells for SCI are poorly understood. What is the optimal CD34+ cell dosage? Will multiple doses of CD34+ cells be more efficacious? Is CD34+ the most appropriate BMC subset? Will BMC subset combinations be more efficacious? The long-term follow-up of our patients will probably provide some information. The absence of cells in CSF samples obtained after 7 days is also intriguing. Although highly speculative, a possible explanation is that cells home toward the injured spinal cord [1Bakshi A. Hunter C. Swanger S. et al.Minimally invasive delivery of stem cells for spinal cord injury: advantages of the lumbar puncture technique.J Neurosurg. 2004; 3: 330-337Google Scholar]. All these issues need to be resolved in carefully designed experiments. Finally, our study demonstrated the possibility of delivering autologous bone marrow precursor cells via LP in patients with SCI. This procedure was feasible, safe, and well tolerated in this group of patients. The potential therapeutic effects of autologous bone marrow precursor cells for SCI remain to be elucidated.