Efficacy of Intradiscal Injection of BM-MSC in Subjects With Chronic Low Back Pain (LBP) Due to Lumbar Degenerative Disc Disease (DDD) Unresponsive

Inclusion Criteria: * Age between 18 and 60 years. * Symptomatic chronic low back pain unresponsive to conservative therapy (including physical therapy performed during at least 1 month before inclusion and pain medication with level 2 analgesics in failure or intolerant to level during at least 1 month) for at least 3 months. * DDD assessed by (Pfirrmann's score modified Griffith et al) grade 4 to 7 at one level. If second level, it should be adjacent (Pfirrmann's score 1-4 maximum) * Low back Pain baseline \> 40 mm on VAS (0-100). * NSAID washout of at least 2 days before screening * Painkillers washout of at least 24 hours before screening Exclusion Criteria: * Congenital or acquired diseases leading to spine deformations that may upset cell application (hyperlordosis, scoliosis, isthmus lesion, sacralization and hemisacralization). * Symptomatic posterior lumbo-articular osteoarthritis or predominant facet syndrome on Xray or MRI (osteophyte and facet hypertrophy). * Prior to the screening visit, has received: * Oral corticosteroid therapy within the previous 3 months, OR * Intramuscular, intravenous or epidural corticosteroid therapy within the previous 3 months * Spinal segmental instability (defined by lumbar dynamic X-Ray in extension/flexion with antero-post translation \> 3 mm and/or angular mobility \> 15°). * Spinal canal stenosis (Schizas score \> B). * History of spinal infection. * Lumbar disc herniation with non truncated sciatica or cruralgia, as well as lumbar cysts and radiculopathy * Previous discal puncture or previous spine surgery. * DDD on 3 levels, or DDD on 2 levels but not adjacent, or DDD with modic 2 or 3 phases * Patients not eligible to the intravertebral disc surgery * Patients who have the risk to undergo a surgery in the next 6 months * Obesity with body mass index (BMI in Kg/size in m2) greater than 35 (obesity grade II). * Participation in another clinical trial or treatment with another investigational product within 30 days prior to inclusion in the study. * Abnormal blood tests: hepatic (alanine aminotransferase (ALT) and/or aspartate aminotransferase (AST) \>1.5 × upper limit of normal (ULN)), renal, pancreatic or biliary disease, blood coagulation disorders, anemia or platelet count of \<100 × 109/ * Significant medical problems, such as uncontrolled hypertension, symptomatic heart failure; or any other clinically relevant condition or current medication that in the opinion of the investigator contra-indicates the u…