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 l…