Mammalian cells grown in culture excrete lactic acid and ammonium ions in quantities that may limit growth and reduce product synthesis. Frequent replenishment of the culture medium is often necessary to prevent waste product accumulation which could inhibit cell growth. Since increased medium replenishment results in increased usage of animal serum, the most expensive raw material, excessive production of waste products lowers the cell and product yield on serum, and hence increases production costs. Strategies for reducing the production of lactic acid and ammonium bymammalian cells via controlled addition of glucose and glutamine will be demonstrated. Mathematical relations coupling ammonium and glutamine kinetics will be described. Additionally, a method for automatic on-line estimation of the cell concentration was developed. This method involves calculating the ATP production rate from the oxygen uptake rate and the lactic acid production rate. Automatic online estimation of the cell concentration is critical if nutrient levels in large-scale mammaliancell cultures are to be accurately maintained via process control.

Umbilical cord blood-derived mononuclear cell (UCB-MNC) transplants improve recovery in animal spinal cord injury (SCI) models. We transplanted UCB-MNCs into 28 patients with chronic complete SCI in Hong Kong (HK) and Kunming (KM). Stemcyte Inc. donated UCB-MNCs isolated from human leukocyte antigen (HLA ≥4:6)-matched UCB units. In HK, four patients received four 4-μl injections (1.6 million cells) into dorsal entry zones above and below the injury site, and another four received 8-μl injections (3.2 million cells). The eight patients were an average of 13 years after C5-T10 SCI. Magnetic resonance diffusion tensor imaging of five patients showed white matter gaps at the injury site before treatment. Two patients had fiber bundles growing across the injury site by 12 months, and the rest had narrower white matter gaps. Motor, walking index of SCI (WISCI), and spinal cord independence measure (SCIM) scores did not change. In KM, five groups of four patients received four 4-μl (1.6 million cells), 8-μl (3.2 million cells), 16-μl injections (6.4 million cells), 6.4 million cells plus 30 mg/kg methylprednisolone (MP), or 6.4 million cells plus MP and a 6-week course of oral lithium carbonate (750 mg/day). KM patients averaged 7 years after C3-T11 SCI and received 3-6 months of intensive locomotor training. Before surgery, only two patients walked 10 m with assistance and did not need assistance for bladder or bowel management before surgery. The rest could not walk or do their bladder and bowel management without assistance. At about a year (41-87 weeks), WISCI and SCIM scores improved: 15/20 patients walked 10 m ( p = 0.001) and 12/20 did not need assistance for bladder management ( p = 0.001) or bowel management ( p = 0.002). Five patients converted from complete to incomplete (two sensory, three motor; p = 0.038) SCI. We conclude that UCB-MNC transplants and locomotor training improved WISCI and SCIM scores. We propose further clinical trials.

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Mammalian cell products have great medical and clinical importance, but to date, production methods employed to manufacture these products on a large scale are not as cost efficient as they could be. The implementation of process control would greatly improve the productivity of these products. Recently developed methods to produce cells on a large scale, such as microcarriers, artificial capillaries, tubular spiral film, and microencapsulation must be optimized, and the problem of oxygen transfer limitation must be solved. The accumulation of potentially toxic waste products can inhibit growth and reduce productivity. This effect can be reduced by either adjusting the environmental parameters of a fed-batch culture, so that the cell's metabolism is shifted away from producing these compounds, or by continually perfusing medium through the culture. If these technical barriers can be overcome, the cost of producing products derived from mammalian cells can be greatly reduced.