Current Bottlenecks in MSC Research

Mesenchymal Stem Cells (MSCs) are widely studied in academic circles and an attractive cell source for clinical applications. MSCs not only possess the ability to self-renew and differentiate to a number of mesenchymal lineages in vitro and in vivo [1,2], but these cells also secrete a cadre of potent trophic factors that contribute to tissue remodeling and modulate the host immune response, making them an attractive cellular biopharmaceutical for the treatment of a number of degenerative diseases and traumatic injuries [3]). However, there is a significant need to improve current methods to efficiently expand standardized, well-characterized MSCs in vitro to the cell numbers needed for widespread, off-the-shelf clinical use. 

Despite their immense therapeutic potential, MSCs are very rare, comprising only 0.001%-0.01% of the mononuclear cells in the bone marrow [1]. Since a typical adult bone marrow aspirate yields very few MSCs (roughly 1 out of every 10,000 cells) [4] prolonged in vitro expansion is typically necessary before clinical use. However, MSCs will often senesce (i.e. stop growing) in culture before adequate cell numbers for transplantation (on the order of a billion cells) can be obtained. In addition, prolonged in vitro culture of MSCs has been shown to diminish their multilineage potential and impair their immunosuppressive activity [5-8]. The aforementioned challenges associated with MSC culture currently limit their therapeutic potential, and a significant need remains for methods to efficiently expand multipotent MSCs ex vivo.  Therefore, extensive effort has been put into developing methods to expand MSCs while maintaining their differentiation potential and paracrine activity. Cell plating density, culture surfaces, and the addition of growth factor supplements have all been investigated. Of these variables, the use of growth factor and cytokine supplements has proven to effectively modulate MSC growth and self-renewal [9] while maintaining desirable cell characteristics.   

There are three major challenges that cell and tissue engineering technology efforts face today. These challenges are:

1)   the cost of today’s primary cells is prohibitively high,

2)  primary cells are not readily available at volumes that support product development efforts.  Most cells are offered at less than one million cells per vial at an average cost of over $900 per million cells, and

3)  most product research is performed with cells produced using traditional small-scale processes that are not directly transferrable into a Good Manufacturing Practices (GMP) setting.  This results in great variability and hampered reproducibility, a tedious and tenuous FDA approval process, and slowed translation into First-in-Man studies and eventual commercialization.

Effectively expanding MSCs to commercially-relevant lot sizes of tens to hundreds of billions of cells/lot while maintaining cell phenotype and function requires new culture platforms and bioprocessing equipment. Importantly, this must be accomplished by producing cells with GMP-compatible raw materials and scalable manufacturing processes, with standardized procedures and under solid Quality Systems. Such improvements to current small scale MSC culture methods will drastically reduce total labor hours (a significant factor in final cost of goods) and reduce the total costs on a per cell basis[10]. However, with cost reduction and scale-up production comes greater need for thorough cell characterization[11]. This cost reduction is required as MSC technology graduates from the lab bench to the clinic, and then from the clinic to commercial products. 

At RoosterBio, we believe that as the cost of cells such as MSCs decreases and the availability increases, then the pace of new product development should accelerate, opening up cell- and tissue-based technology development to a much broader market.

What are your thoughts on how scale-up manufacturing technologies will impact MSC phenotype and function? What quality parameters do you think are most important to maintain? Please leave your comments below!

References

1.     Pittenger MF, et al. Science.  284:143-147; 1999.

2.     Pittenger MF, et al. Methods Mol Biol. 449:27-44; 2008.

3.     Baraniak PR and McDevitt TC. Regen Med. 5(1):121–143; 2010.

4.     Warnke PH, et al. J Craniomaxillofac Surg. 41:153-161; 2013.

5.     Li XY, et al.  Mol Med Rep. 6:1183-1189; 2012.

6.     Crisostomo PR, et al. Shock. 26:575-580; 2006.

7.     Wagner W, et al. PLoS One. 3:e2213; 2008.

8.     Binato R et al. Cell Prolif. 46(1):10-22; 2013.

9.     Gharibi B and Hughes FJ. Stem Cells Trans Med. 1:771-782; 2012.

10.   Deans, R Regen. Med. 7(6 Suppl.), 78–81; 2012.

11.   Carmen J, et al.  Regen Med. 7(1):85-100; 2012.