Autologous bone marrow mononuclear cell therapy of ischemic stroke in sheep
Autologous bone marrow mononuclear cell (BMMNC) therapy was proven to be effective in rodent stroke models, and the first phase I/II clinical investigations are under way to assess their therapeutic potential in patients. However, our knowledge on therapeutic mechanisms, proof-of-concept efficacy in gyrencephalic brains, as well as long-term impact on neurofunctional parameters and lesion size development is still fragmentary. Here 32 adult Merino rams were subjected to permanent middle cerebral artery occlusion after an initial health check and prestudy surveillance. Following baseline neurofunctional assessment, animals were subjected to control or autologous BMMNC IV administration (>4.0 × 106 BMMNCs per kg body weight) 24 h after stroke (n = 16 each). Animals were monitored for 42 days by behavioral phenotyping, magnetic resonance imaging (MRI), [15O]- H2O-, and [18F]-fluorodeoxyglucose positron emission tomography (PET) before postmortem histological assessment. All experiments were conducted randomized and blinded, and strict exclusion/inclusion criteria were applied. The therapeutic approach was safe, but eight animals (3× control; 5× BMMNC treated) had to be removed from the trial due to violation of preset inclusion criteria including insufficient BMMNC numbers per kg bodyweight. BMMNC therapy was associated with amelioration of functional deficits from day 7 (p < 0.01) and reduction of MRI lesion size at day 42 (p < 0.01) after stroke. Treatment also improved cerebral blood flow (p < 0.05) and glucose metabolism (p < 0.01) at day 42 as shown by PET. Moreover, there was an increase in cerebral capillary density and a reduction of glial reactivity in white matter areas (p < 0.05), potentially indicating a more suitable environment for endogenous functional regeneration/brain plasticity. The therapeutic effect was preserved when controlling for animal age and weight at trial induction, initial lesion size, and poststroke functional deficits. Therapeutic effects were confirmed after controlling for confounding factors including animal age, weight, and initial functional impairment. The approach seems promising, but current findings of reduced efficacy in aged and hypertensive subjects may call for a more detailed investigation of optimal therapeutic circumstances before moving ahead to large-scale clinical trials.