Owing to the importance of stem cell culture systems in clinical applications, researchers have extensively studied them to optimize the culture conditions and increase efficiency of cell culture. A spheroid culture system provides a similar physicochemical environment in vivo by facilitating cell–cell and cell–matrix interaction to overcome the limitations of traditional monolayer cell culture. In suspension culture, aggregates of adjacent cells form a spheroid shape having wide utility in tumor and cancer research, therapeutic transplantation, drug screening, and clinical study, as well as organic culture. There are various spheroid culture methods such as hanging drop, gel embedding, magnetic levitation, and spinner culture. Lately, efforts are being made to apply the spheroid culture system to the study of drug delivery platforms and co-cultures, and to regulate differentiation and pluripotency. To study spheroid cell culture, various kinds of biomaterials are used as building forms of hydrogel, film, particle, and bead, depending upon the requirement. However, spheroid cell culture system has limitations such as hypoxia and necrosis in the spheroid core. In addition, studies should focus on methods to dissociate cells from spheroid into single cells.

Adipose tissue-derived mesenchymal stem cells (AT-MSCs) offer potential as a therapeutic option for chronic discogenic low back pain (LBP) because of their immunomodulatory functions and capacity for cartilage differentiation. The goal of this study was to assess the safety and tolerability of a single intradiscal implantation of combined AT-MSCs and hyaluronic acid (HA) derivative in patients with chronic discogenic LBP. We performed a single-arm phase I clinical trial with a 12-month follow-up and enrolled 10 eligible chronic LBP patients. Chronic LBP had lasted for more than 3 months with a minimum intensity of 4/10 on a visual analogue scale (VAS) and disability level ≥ 30% on the Oswestry Disability Index (ODI). The 10 patients underwent a single intradiscal injection of combined HA derivative and AT-MSCs at a dose of 2 × 107 cells/disc (n = 5) or 4 × 107 cells/disc (n = 5). Safety and treatment outcomes were evaluated by assessing VAS, ODI, Short Form-36 (SF-36), and imaging (lumbar spine X-ray imaging and MRI) at regular intervals over 1 year. No patients were lost at any point during the 1-year clinical study. We observed no procedure or stem cell-related adverse events or serious adverse events during the 1-year follow-up period. VAS, ODI, and SF-36 scores significantly improved in both groups receiving both low (cases 2, 4, and 5) and high (cases 7, 8, and 9) cell doses, and did not differ significantly between the two groups. Among six patients who achieved significant improvement in VAS, ODI, and SF-36, three patients (cases 4, 8, and 9) were determined to have increased water content based on an increased apparent diffusion coefficient on diffusion MRI. Combined implantation of AT-MSCs and HA derivative in chronic discogenic LBP is safe and tolerable. However, the efficacy of combined AT-MSCs and HA should be investigated in a randomized controlled trial in a larger population. ClinicalTrials.gov NCT02338271 . Registered 7 January 2015.