We report on the structure and transport properties of nanocrystalline manganite La0.7Sr0.3MnO3 (LSMO) synthesized on nanowires-engineered MgO substrates by pulsed laser deposition, which is compared with reference samples deposited directly on flat MgO substrates. Such LSMO/MgO nanocomposites show enhanced low field magnetoresistance, especially at low temperature, due to the dominant spin-polarized intergrain tunneling. This work suggests that growing on nanoengineered substrates is a viable route to achieve nanostructured materials with desired crystalline structure and physical properties.