Developing a cell-microcarrier tissue engineered product for muscle repair using a bioreactor system.

Fecal incontinence, although not life-threatening, has a high impact in the economy and in patient quality of life. So far, available treatments are based on both surgical and non-surgical approaches. These can range from changes in diet, to bowel training, or sacral nerve stimulation, but none of which provide a long-term solution. New regenerative medicine-based therapies are emerging, which aim at regenerating the sphincter muscle and restore continence. Usually, these consist of the administration of a suspension of expanded skeletal-derived muscle cells (SkMDCs) to the damaged site. However, this strategy often results in a reduced cell viability due to the need for cell harvesting from the expansion platform, as well as the non-native use of a cell suspension to deliver the anchorage-dependent cells. Here, we propose the proof-of-concept for the bioprocessing of a new cell delivery method for the treatment of fecal incontinence, obtained by a scalable two-step process. Firstly, patient isolated SkMDCs were expanded using planar static culture systems. Secondly, by using a single-use PBS-mini Vertical-Wheel®bioreactor, the expanded SkMDCs were combined with biocompatible and biodegradable (i.e., directly implantable) poly(lactic-co-glycolic acid) (PLGA) microcarriers, previously prepared by thermally induced phase separation (TIPS). This process allowed for up to 80% efficiency of the SkMDCs to attach to the microcarriers. Importantly, SkMDCs were viable during all the process and maintained their myogenic features (e.g., expression of the CD56 marker) after adhesion and culture on the microcarriers. When SKMDCs-containing microcarriers were placed on a culture dish, cells were able to migrate from the microcarriers onto the culture surface and differentiate into multinucleated myotubes, which highlights their potential to regenerate the damaged sphincter muscle after administration into the patient. Overall, this study proposes an innovative method to attach SkMDCs to biodegradable microcarriers, which can provide a new treatment for fecal incontinence.