Grafting of neural tissue in chronically injured spinal cord: influence of the donor tissue on regenerative activity

The potential role of regenerative medicine in the man-agement of traumatic patients

Traumatic injury represents the most common cause of death in ages 1 to 44 years and a significant proportion of patients treated in hospital emergency wards each year. Unfortunately, for patients who survive their injuries, survival is not equal to complete recovery. Many traumatic injuries are difficult to treat with conventional therapy and result in permanent disability. In such situations, regenerative medicine has the potential to play an important role in recovery of function. Regenerative medicine is a field that seeks to maintain or restore function with the development of biological substitutes for diseased or damaged tissues. Several regenerative approaches are currently under investigation, with a few achieving clinical application. For example, engineered skin has gained FDA approval, and more than 20 tissue engineered skin substitutes are now commercially available. Other organ systems with promising animal models and small human series include the central and peripheral nervous systems, the musculoskeletal system, the respiratory and genitourinary tracts, and others. This paper will be a clinically oriented review of the regenerative approaches currently under investigation of special interest to those caring for traumatic patients.

Bone marrow stromal cells can achieve cure of chronic paraplegic rats: Functional and morphological outcome one year after transplantation

Chronic paraplegia resulting from severe spinal cord injury (SCI) is considered to be an irreversible condition. Nevertheless, recent studies utilizing adult stem cells appear to offer promise in the treatment of this and other neurological diseases. Here, we show that progressive functional motor recovery is achieved over the course of the year following the administration of bone marrow stromal cells (BMSC) in traumatic central spinal cord cavities of adult rats with chronic paraplegia. At this time, functional recovery is almost complete and associated with evident nervous tissue regeneration in the previously injured spinal cord.

Cell therapy using bone marrow stromal cells in chronic paraplegic rats: Systemic or local administration?

Recent studies showed the therapeutic effect of bone marrow stromal cells (BMSC) after spinal cord injury (SCI). In the present study, we compared the effect of systemic and local administration of BMSC in adult Wistar rats suffering chronic paraplegia as consequence of severe SCI. Adult Wistar rats were subjected to a weight-drop impact causing complete paraplegia, and 3 months later, all the animals remained without signs of functional recovery. At this moment, 3 x 10(6) BMSC were injected intravenously (n: 20) or into traumatic spinal cord cavity (n: 20). Outcome was evaluated until sacrifice of the animals, 6 months later, using the Basso-Beattie-Bresnehan (BBB) score, the cold spray test, and measuring the thigh perimeter. After sacrifice, samples of spinal cord tissue were studied histologically. The results showed that intravenous administration of BMSC achieves some degree of functional recovery when compared to controls. Nevertheless, administration of BMSC into postraumatic spinal cord cavity promotes a clear and progressive functional recovery, significantly superior to the recovery obtained by means of the intravenous administration. This effect is associated to long-term presence of BMSC in the injured spinal cord tissue, with images suggesting neuronal differentiation and spinal cord reconstruction.

Schwann cells induce neuronal differentiation of bone marrow stromal cells

Bone marrow stromal cells are multipotent stem cells that have the potential to differentiate into bone, cartilage, fat and muscle. Recently, bone marrow stromal cells have been shown to have the capacity to differentiate into neurons under specific experimental conditions, using chemical factors. We now describe how bone marrow stromal cells can be induced to differentiate into neuron-like cells when they are co-cultured with Schwann cells. When compared with chemical differentiation, expression of neuronal differentiation markers begins later, but one week after beginning co-culture, most bone marrow stromal cells showed a typical neuronal morphology. Our present findings support the transdifferentiation of bone marrow stromal cells, and the potential utility of these cells for the treatment of degenerative and acquired disorders of the nervous system.

Functional recovery in chronic paraplegia after bone marrow stromal cells transplantation

Previous reports showed the therapeutic effect of transplants of bone marrow stromal cells (BMSC) after incomplete traumatic spinal cord lesions. We studied the effect of this form of therapy in chronically paraplegic Wistar rats due to severe spinal cord injury (SCI). Rats were subjected to weight-drop impact causing paraplegia, and BMSC or phosphate buffered saline (PBS) was injected into spinal cord 3 months after injury. Functional outcome was measured using the Basso-Beattie-Bresnehan score until sacrifice of the animals, 4 weeks after transplantation. At this time, samples of spinal cord tissue were studied histologically. The results showed a clear and progressive functional recovery of the animals treated with BMSC transplantation, compared to controls. Grafted BMSC survived into spinal cord tissue, forming cell bridges within the traumatic centromedullary cavity. In this tissue, cells expressing neuronal and astroglial markers can be seen, together with a marked ependymal proliferation, showing nestin-positivity. These findings suggest the utility of BMSC transplantation in chronically established paraplegia.

Functional recovery in chronic paraplegic rats after co-grafts of fetal brain and adult peripheral nerve tissue

BACKGROUND

In recent years, experimental studies have sought some type of functional improvement in traumatic paraplegia by transplanting neural tissue into the injured spinal cord. The aim of this work is to study the possibility of functional recovery in chronic paraplegic rats after co-transplantation of fetal cerebral tissue and adult peripheral nerve tissue.

METHODS

Seventy adult female Wistar rats were subjected to spinal cord injury at the T6-T8 level, causing complete paraplegia. Three months later, in 50 rats (grafted group) the injured spinal cord tissue received a graft of fetal brain cortex associated with crushed adult peripheral nerve. All the animals (grafted and control groups) were subjected to daily rehabilitation procedures from the first week after the injury, and evaluated weekly for motor and sensory recovery. Statistical analysis of different behavioral data between control and grafted animals was performed using the Kruskal-Wallis ANOVA and the nonparametric Wilcoxon test.

RESULTS

Between 8 and 12 months after transplantation, progressive signs of functional recovery were observed in the grafted animals, associated with an increase in muscle mass in the lower extremities, findings that were significantly different from those in nongrafted animals (p < 0.05). At this time, donor cerebral tissue is integrated into previously injured spinal cord and results in formation of bundles of nerve fibers that emerge from the area of the transplant and surround the spinal cord beneath the lesion.

CONCLUSIONS

Delayed co-transplantation of fetal cerebral tissue and peripheral nerve tissue can be used to achieve anatomical remodeling and long-term functional recovery in rats rendered paraplegic as result of severe spinal cord injury. These findings support the possibility of functional recovery after chronic traumatic paraplegia.