Technique for bilateral intracranial implantation of cells in monkeys using an automated delivery system

Intracerebral grafting combined with gene transfer may provide a powerful t echnique for local delivery of therapeutic agents into the CNS. The present study was undertaken to: (i) develop a reliable and reproducible automated cell implantation system, (ii) determine optimal implantation parameters o f cells into the striatum, (iii) determine upper safe limits of cellular im plantation into the neostriatum of monkeys. Autologous fibroblasts were inf used into six sites of the striatum in nonhuman primates (Macaca mulatta, n = 11). Twenty-six-gauge cannulae were inserted vertically through cortical entry sites into the striatum (two sites in the caudate nucleus and four s ites in the putamen) at predefined coordinates based on magnetic resonance imaging (MRI). The cannulae were guided by an electronically operated, hydr aulic micropositioner and withdrawn at controlled rates, while cells (5, 10 , 20, 40, or 80 mul/site) were infused simultaneously. Varying infusion rat es and cell concentrations were also evaluated. Visualization and evaluatio n of graft placement were performed using contrast MRI at 3-5 days postsurg ery. Animals were monitored for signs of clinical complications and sacrifi ced 2 weeks following surgery. Postimplantation MRI revealed a tissue mass effect of the implant with shifting of midline, edema, and infiltration of the white tracts at 40 and 80 mul/site. In addition, these animals develope d transient hemiparesis contralateral to the implant site. MRI of animals g rafted with 20 mul/site exhibited columnar-shaped implants and evidence of infiltration into white matter tracts possibly due to a volume effect. No c linical side effects were seen in this group. At 14 days post surgery, MRI scans showed consistent columnar grafts (measuring approximately 5 mm in he ight) throughout the striatum in animals implanted with 5 or 10 mul/site. N o signs of clinical side effects were associated with these volumes and pos tmortem histological examination confirmed MRI observations. Optimal surgic al parameters for delivery of cells into the striatum consist of a graft vo lume of 10 mul/site, an infusion rate of 1.6 mul/min, a cell concentration of 2.0 x 10(5) cells/mul. and a cannula withdrawal rate of 0.75 mm/min. The se results show that infusion of cells into the striatum can be done in a s afe and routine manner.