This is a double-blind, randomized, placebo-controlled, multicenter clinical trial in which 18 patients affected with chronic traumatic incomplete cervical spinal cord injury will be randomized to either the active treatment (2 doses of intrathecal WJ-MSC 3 months apart) or to placebo (2 intrathecal infusions, 3 months apart). Thereafter, patients will be followed-up for 12 months for safety and efficacy assessment.

Double-blind, randomized, placebo-controlled, multicenter clinical trial that will include 18 patients affected with chronic traumatic incomplete cervical spinal cord injury who will be randomized 1:1, stratified by center, to one of the 2 treatment arms of the study: WJ-MSC / WJ-MSC (at a dose of 1E6 ± 30% live cells / Kg of weight) or Placebo / placebo. Medication will be administered intrathecally at day 1 and at 3 months. The main objective of the trial is to assess safety at a 12-month follow-up. Secondary objectives include the evaluation of efficacy through clinical response, electrophysiological changes, questionnaires of functionality and quality of life, as well as the presence of anti-HLA antibodies and donor cellularity in the cerebrospinal fluid.

Inclusion Criteria:

1. Single spinal cord injury lesion caused by trauma
2. Affected cord segments between C1 and T1, confirmed by magnetic resonance
3. Incomplete lesion (ASIA B, C or D)
4. Chronic disease state (between 1 and 5 years after the injury)
5. Patients from 18 to 70 years of age, both sexes
6. Life expectancy > 2 years
7. Residence near the center during study participation and confidence that the patient will attend the follow-up visits
8. Given informed consent in writing
9. Patient is able to understand the study and its procedures

Exclusion Criteria:

1. Mechanic ventilation
2. Penetrating trauma affecting the spinal cord
3. Pregnant woman or without proper anticonceptive measures according to the investigator, or breath feeding
4. Planned spinal surgery within subsequent 12 month after entering the trial
5. Neurodegenerative diseases
6. Significant abnormal laboratory tests that contraindicates patient's participation in the study
7. Neoplasia within the previous 5 years, or without complete remission
8. Patient with communication difficulties
9. Simultaneous participation in another clinical trial or treated with an investigational medicinal product the previous 30 days, that could interfere in the results of the study
10. Previous treatment with and advanced Therapy Medicinal Product (cell therapy)
11. Contraindication for lumbar punction
12. Contraindication or inability to follow a rehabilitation program
13. Other pathologic conditions or circumstances that difficult participation in the study according to medical criteria
14. The patient does not accept to be followed-up for a period that could exceed the clinical trial length

Active treatment and placebo will be released using the same syringe and blinded in a way that it is no possible to distinguish one to the other.