Cultivating human Schwann cells for tissue engineering of peripheral nerves

Abstract

Cultivation of human cells is well established. The cultivation of human Schwann cells may offer a new therapeutic approach for treatment of degenerative and traumatic lesions of the peripheral nervous system. Currently, Schwann cells in combination with other biological matrices are used as tissue-engineered biological nerve grafts in animal models. Cultivation of human Schwann cells, however, is more difficult than cultivation of rodent cells. A high cell yield is only achieved by pharmacological stimulation, which should not be used in clinical therapy. Thus, we aimed to establish an easy method of cultivating human Schwann cells from peripheral nerve neuromas that have developed after a complete nerve lesion. As these neuromas have to be resected in any case to allow proper nerve reconstruction, their removal does not lead to additional neurological defects. Schwann cells were cultivated from the neuromas of eleven patients, aged 5 to 75 years. All patients suffered from a complete median nerve lesion at the level of the distal forearm, which could not be treated primarily. Two weeks after trauma, the patients underwent secondary reconstruction by autologous sural nerve grafts. During this operation, the neuromas were resected. Control cultures were established from remaining parts of the sural nerve. Cell yield was determined on the first, third and seventh day in vitro. Schwann cells were stained for S100. Viability was assessed with fluoresceine-fluorescence. The cell count was assessed with regard to the donor age. The growth rate of Schwann cells was found to be donor-age dependent. The highest cell yield was obtained from adult neuromas. By the third day in vitro, they showed a 1.5 fold increased cell count compared with juvenile nerves and neuromas. By the seventh day in vitro, Schwann cells from adult neuromas were increased 2.5 times compared with cells from juvenile nerves and 7 times compared to cells from adult sural nerves. Cultivation of Schwann cells taken from sural nerves of patients older than 65 years was not possible. The utilization of neuromas as a source for human Schwann cells allows an age-independent cultivation within a short time period without any pharmacological treatment. These neuromas are virtually predegenerated and show an activation of Schwann cells implying good adherence and high mitotic activity in culture. Normal nerve tissue as a source for Schwann cells for tissue-engineered nerves is only sufficient in young patients due to its greater proliferative potential. The age-dependent proliferation underlines the need for alternative sources for Schwann cells.