Celltherapy for pain with the transplantation of encapsulated xenogeneic cells secreting opiate

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Recently the technique of transplantation of encapsulated cells has progressed. Semipermeable membranes used for capsules allow transport of low molecular weight substances, but prevent the inward diffusion of both the humoral and the cellular elements of the immune system. The proopiomelanocortin gene transfected Neuro2A which secrete beta-endorphin, were enclosed in polymer capsules at a density of 5*10^6/ml, and transplanted into the spinal CSF space from the occipto-atlantal junction of male Sprague-Dawley rats. Three analgesiometric tests-the tail pinch test, the hot plate test, and electrical stimulation test-showed that the rats with encapsulated Neuro2A were significantly less sensitive to pain after transplantation than control animals. Morphological study revealed that the encapsulated cells survived for a month after transplantation into the CSF space. However, the encapsulated Neuro2A in the CSF space of Japanese monkeys showed much worse viability than that of rats. We speculated that complement or natural antibody may penetrate the capsules and attack the xenogeneic cells. Therefore, encapsulated sensitised sheep red blood cells were incubated in 10% human serum medium. To assess the degree of the hemolysis, absorbance at the wavelength (541nm) of medium was measured. The result suggested that double membrane consisted of PM30 (Amicon Co. ; MW cut off of 30kD) and K6305 (Kuraray Co. ; MW cut off of 13kD) could prohibit the penetration of complement. Next we will try the transplantation of double membrane capsules containing Neuro2A in the CSF space of Japanese monkey.In our cell therapy, it has been a little difficult to control the amount of secreted opiate. However, recently, the transcriptional activation system by tetracyclin has been developed, and this system may help the control of opiate secretion.We are constructing the cDNA including this system for making a new cell line.