Review for 10.1186/s12876-023-03005-w (2023)

Title: PVA enema ameliorates DSS-induced acute colitis in mice
Version: 1 Date: 14 Aug 2023
Reviewer:  Maximilian Baumgartner
Reviewer's report:
In the manuscript entitled “PVA enema ameliorates DSS-induced acute colitis in mice” by
Zhiyong Zhan et al. the authors investigate the effect of polyvinyl alcohol enemas in a mouse
model of acute colitis. Overall the results are convincing and within the scope of the target
journal. However before publication several major and some minor issues need to be addressed:
Major comments:
In the method section the exact experimental conditions are not completely clear. When was
DSS given and when the enemas, at the same timepoint, was one started before the other ?
A graphical representation would aid in interpretation. If PVA and DSS was given together,
could there be a potential chemical effect of PVA diminishing the efficacy of DSS injuring the
mucosa? This needs to be discussed.
Another important point is, how was the histological scoring performed in detail: on the whole
slide, on random filed of views, how many field of views, where the persons scoring blinded
in terms of treatment? How many persons were scoring the sections, did different people assess
the same slide to prevent bias?
For immunohistochemistry the same applies as mentioned above, also when where cells
considered “positive”, for each antibody the specific location of the staining should be noted.
(i.e. cytoplasmic, in the nucleus ect.).
The statistical analysis of the paper is not completely clear to me, in each figure the exact
statistical test needs to be mentioned and if correction for multiple comparisons has been applied.
Where all groups compared to each other group or one reference group, if yes which was the
reference group? The comparisons and p-values in all figures of the manuscript are not clear
and need to be improved.
In terms of organoid data it was surprising to me that their number changes over time. Was the
size of organoids scored aswell? Why would the amount change if equal numbers were seeded
in all conditions. Where the organoids somehow disturbed ? How did their morphology change
in the different groups ?
Minor comments:
Abstract
In the method section of the abstract the number of mice in each group should be mentioned.
In the result section adjectives such as “dramatically” and “greatly” should be removed. I
would suggest comparing the mean values at a certain timepoint and also provide p-values. (For
example: at time point X there was a X-fold decrease in mean disease activity in the PVA group
ect.).
Introduction:
In the first sentence of the introduction “other reasons” should be removed and replaced by
for example “environmental factors”. The sentence about extraintestinal manifestations of UC
should be more specific, (i.e what symptoms). The last two sentence in the introduction should
be reworked:
The impact of PVA on what is not clear ? I would replace “the therapeutic effect of PVA on
UC” with “the therapeutic effect of PVA on a mouse model of UC” because the human disease
entity was not studied and DSS as a mouse model of acute colitis does not fully recapture UC
in humans.
Methods:
The instructions on fecal ocult blood testing and mouse sacrifice should be removed as this is
standard procedure (i.e. “Take an appropriate amount of mouse feces, apply it to the test card
A......” and “Press the mouse's head with the thumb and forefinger of left hand, pull the tail with
right hand, and pull back firmly. Dislocate the cervical vertebrae and die instantly. “)
Results:
In Figure 4 a zoom for each section should be included to appreciate the differences in IHC
staining.