Background and Aim: Chronic low back pain is one of the most commoncauses of disability in all societies. Even after invasive treatments, about70% to 80% of patients will have recurrent pain. Disc degenerationcommonly occurs due to changes in disc morphology compositionof the extracellular matrix as well as loss of disc cells, therefore,a potential therapeutic strategy would be the augmentation of thedisc cell population to restore normal biologic function and matrixinsufficiencies. Mesenchymal stromal cells (MSCs) are a source of suchcells for regeneration of disc. Our goal in this phase 1 clinical trial wasto evaluate the safety of post-endoscopic surgery implantation of nucleuspulposus derived chondrocytes.Methods: Patients with chronic low back pain who did not respond toconservative treatments for at least 6 months of treatment and who werecandidates for endoscopic disc enucleation, were enrolled in this clinicaltrial. Patients underwent endoscopic disc enucleation surgery. During theoperation, the protruded part of the nucleus pulposus, was removed andthis sample of nucleus pulposus was sent to the Royan Institute cleanroom for culturing chondrocytes. One month later, and upon arrivalthe number of chondrocytes reached a limit of 20 million chronocitiesper disc, these cells were reimplanted. Patients were evaluated for sideeffects according to the Common Terminology Criteria for Adverse Events(CTCAE) version 4.0. They were followed up 3, 6, 12 and 24 months afterimplantation of chondrocytes.Results: Five patients were included in this clinical trial, including1 female and 4 men. The mean age and average BMI were 40.3-yearand 25.5 kg/m2, respectively. Meantime when patients had low backpain was: 14 ± 1 months. They were followed up for two years afterchondrocytes implantation. No side effects were seen at this periodof time. Baseline visual analogue scale (VAS) and Oswestry low back pain questionnaire (ODI) values and follow up data are shown in theTable. The pain of all the patien ts was reduced according to VAS andODI questionnaire 6 months after i mplantation of chondrocytes, andthis decrease remained two years a fter implantation. According to theresults of MRIs, the amount of disk protrusion decreased compared topre-implantation and remained the same for two years after implantationConclusion: In this clinical trial, we investigated the safety of intradiscalimplantation of autologous nucleu s pulposus derived chondrocytesfor the patients suffering from c h ronic uncontrolled low back pain.According to the results of this t reatment, it can be concluded thattreatment of chronic low back pain using of chondrocytes derived fromthe autologous intervertebral dis c , is safe, which has had very goodeffects on our patient’s outcomes. To further investigations for evaluatingthis implantation efficacies, this treatment should be taken on a largernumber of patients and with longer time for follow-up.