Effect of Cryopreservation on Cell Proliferation and Immunogenicity of Transplanted Human Heart Cells

Effect of Cryopreservation on Cell Proliferation and Immunogenicity of Transplanted Human Heart Cells

Hiroki Yokomuro, MD, PhD,1 Noritsugu Shiono, MD, PhD,1 Tsukasa Ozawa, MD, PhD,1

Takeshiro Fujii, MD, PhD,1 Yoshinori Watanabe, MD, PhD,1 Nobuya Koyama, MD, PhD,1 and

Mitsumasa Okada, PhD2

http://www.atcs.jp/pdf/2010_16_2/105.pdf

Critique

Introduction:

This paper has an excellent introduction to the reason why it is studying the effects of cryopreservation: the necessity of having cardiac cells on standby for unexpected treatment and also the need to be able to effectively transport these kinds of cells and still be viable for treatment. The research was specifically on the effects of cryopreservation on cardiac cells and their viability, cellular proliferation and immunogenicity after being cultured for 15 days. They clearly declare all logistical aspects of patient consent and proper handling of cardiac tissue.

Procedure and materials:

The paper goes on to describe its procedures and generate a couple of figures as well as a small analysis and a concise conclusion regarding the entire experiment. The protocols were excellently done with specific, yet concise, details about each step without bogging down the reader. A nice flowchart of each experiment and control also allows someone to quickly understand the general process of this experiment.

They tested a control group of cells harvested from tissue and cultured directly after, and two experimental groups: one involving a cell harvest from tissue, cryopreservation and then culture; the other taking tissue, cryopreserving it, and then harvesting cells to culture with. To sum up the results, the paper found that cryopreservation is a useful method for preserving and transporting cells because it increases cell proliferation and decreases their immunogenicity. However, a closer inspection of the paper reveals many problems with making these conclusions.

Results and Discussion

In this section they reported a slew of numbers and provided many line graphs to illustrate the change in levels of certain cell contents and growth factors related to cryopreservation. The largest concern I had with their data was in their harvested cell count, their variation between samples was way too big. For example, I quote (.29 +/- .15) * 10^6 as their cell survival rate from their noncryopreserved cultures. That’s a huge range, why is this so variable? They don’t even address this wide variation beyond statistical figures. They do attribute a dip in cell proliferation between weeks 1 and 3 as transfer loss of cells as they were replated, but that still doesn’t explain the variations between samples. It seems like they had to pick and choose particular data points in order to come to the conclusion that overall cellular proliferation was better in cryopreserved settings. Otherwise the data they collected varies too much and doesn’t really give a great picture of what’s really going on with cellular proliferation. With this in mind, it’s hard to take their quantitative analysis of the cells seriously because it is unknown which of these samples were used and which of the better variations were presented.

Another problem was with their presentation of data. The paper has a tendency to throw all these numbers concerning variations in growth factors and other measurements into a paragraph when they created figures depicting the same information. It was unnecessary for them to fill in 3-4 paragraphs just listing these numbers.

Example Quotation:

"The ratios of heart cells at G2 + M and S phases were 6.23 ± 1.05% (n = 5) and 4.95 ± 0.86% (n = 6) in the control group, 8.67 ± 1.14% and 8.06 ± 0.99% in the cryopreserved cells group (n = 8), and 11.2 ± 4.15% and 11.1 ± 1.77% in the cryopreserved tissues (n = 3 group)."

This kind of information would be better suited listed below its respective plot rather than explained like this. Some of the figures they used, like Figures 5 and 7, really should have been bar graphs because the line-connected data points aren’t depicting a trend but instead just a flat difference before and after cryopreservation.

Conclusion

Overall their conceptual and procedural details of their experiment were effective, but their data and analysis presentation could have been better. The wide variation in collected cells can completely skew the range of results from their appended tests and creates some suspicion as to what was actually presented and analyzed.