Spinal cord injury research triggering an immune system response. Animal studies with injection of bone marrow stem cells have shown improvement in motor function; however not so in a human trial a year post-injury. More trials are underway. Adipose and umbilical tissue stem cells need further study before human trials can be performed, but two Korean studies were begun to investigate adipose cells in SCI patients. Transplantation of tissues such as olfactory ensheathing cells from the olfactory bulbs has been shown to produce beneficial effects in spinal cord injured rats. Trials have also begun to show success when olfactory ensheathing cells are transplanted into
Dorsal nerve cord tubes. The process by which this is performed is called invagination. The cells essentially convolute into the body cavity, arranging themselves on the dorsal plane above the notochord, as mentioned above. The evolutionary explanation to this adaptation from a solid cord to hollow tube is unknown. In vertebrates, the dorsal nerve cord is modified into the central nervous system, which comprises the brain and spinal cord. Dorsal means the "back" side, as opposed to ventral which is the "belly" side of an organism. In bipedal organisms dorsal is the back and ventral is the front. In organisms which walk on