Transition from static culture to stirred tank bioreactor for the allogeneic production of therapeutic discogenic cell spheres.

BACKGROUND: Culturing cells as cell spheres results in a tissue-like environment that drives unique cell phenotypes, making it useful for generating cell populations intended for therapeutic use. Unfortunately, common methods that utilize static suspension culture have limited scalability, making commercialization of such cell therapies challenging. Our team is developing an allogeneic cell therapy for the treatment of lumbar disc degeneration comprised of discogenic cells, which are progenitor cells expanded from human nucleus pulposus cells that are grown in a sphere configuration. METHODS: We evaluate sphere production in Erlenmeyer, horizontal axis wheel, stirred tank bioreactor, and rocking bag format. We then explore the use of ramped agitation profiles and computational fluid dynamics to overcome obstacles related to cell settling and the undesired impact of mechanical forces on cell characteristics. Finally, we grow discogenic cells in stirred tank reactors (STRs) and test outcomes in vitro (potency via aggrecan production and identity) and in vivo (rabbit model of disc degeneration). RESULTS: Computation fluid dynamics were used to model hydrodynamic conditions in STR systems and develop statistically significant correlations to cell attributes including potency (measured by aggrecan production), cell doublings, cell settling, and sphere size. Subsequent model-based optimization and testing resulted in growth of cells with comparable attributes to the original static process, as measured using both in vitro and in vivo models. Maximum shear rate (1/s) was maintained between scales to demonstrate feasibility in a 50 L STR (200-fold scale-up). CONCLUSIONS: Transition of discogenic cell production from static culture to a stirred-tank bioreactor enables cell sphere production in a scalable format. This work shows significant progress towards establishing a large-scale bioprocess methodology for this novel cell therapy that can be used for other, similar cell therapies.

Design of experiment (DOE) applied to artificial neural network architecture enables rapid bioprocess improvement.

Modern bioprocess development employs statistically optimized design of experiments (DOE) and regression modeling to find optimal bioprocess set points. Using modeling software, such as JMP Pro, it is possible to leverage artificial neural networks (ANNs) to improve model accuracy beyond the capabilities of regression models. Herein, we bridge the gap between a DOE skill set and a machine learning skill set by demonstrating a novel use of DOE to systematically create and evaluate ANN architecture using JMP Pro software. Additionally, we run a mammalian cell culture process at historical, one factor at a time, standard least squares regression, and ANN-derived set points. This case study demonstrates the significant differences between one factor at a time bioprocess development, DOE bioprocess development and the relative power of linear regression versus an ANN-DOE hybrid modeling approach.

In vitro and in vivo evaluation of discogenic cells, an investigational cell therapy for disc degeneration.

BACKGROUND/CONTEXT: Disc degeneration (DD) is a significant driver of low back pain and few treatments exist to treat the pain and disability associated with the disease. PURPOSE: Our group has developed a method to generate therapeutic discogenic cells as a potential treatment for symptomatic DD. These cells are derived and modified from adult nucleus pulposus cells. In this study, we evaluated the characteristics, mode of action, and in vivo efficacy and safety of these cells prior to human clinical testing. STUDY DESIGN: Privately funded in vitro studies and in vivo preclinical models were used in this study. METHODS: Discogenic cells generated from different adult human donors were evaluated for surface marker expression profile, matrix deposition and tumorigenic potential. Discogenic cells were then injected subcutaneously into nude mice to assess cell survival and possible extracellular matrix production in vivo. Finally, a rabbit model of DD was used to evaluate the therapeutic potential of discogenic cells after disc injury. RESULTS: We found that discogenic cells have a consistent surface marker profile, are multipotent for mesenchymal lineages, and produce extracellular matrix consisting of aggrecan, collagen 1 and collagen 2. Cells did not show abnormal karyotype after culturing and did not form tumor-like aggregates in soft agar. After subcutaneous implantation in a nude mouse model, the human discogenic cells were found to have generated regions rich with extracellular matrix over the course of 4 months, with no signs of tumorigenicity. Intradiscal injection of human discogenic cells in a rabbit model of DD caused an increase in disc height and improvement of tissue architecture relative to control discs or injection of vehicle alone (no cells) with no signs of toxicity. CONCLUSIONS: This study demonstrates that intradiscal injection of discogenic cells may be a viable treatment for human degenerative disc disease. The cells produce extracellular matrix that may rebuild the depleting tissue within degenerating discs. Also, the cells do not pose any significant safety concerns. CLINICAL SIGNIFICANCE: Human clinical testing of discogenic cells combined with a sodium hyaluronate carrier is ongoing in multiple randomized, controlled, double-blinded studies in the United States (clinicaltrials.gov identifier NCT03347708) and Japan (clinicaltrials.gov identifier NCT03955315).