Title: Aggrecan heterogeneity in articular cartilage from patients with osteoarthritis

Transcription

1 Reviewer s report Title: Aggrecan heterogeneity in articular cartilage from patients with osteoarthritis Version: 0 Date: 21 Dec 2015 Reviewer: Debabrata Patra Reviewer s report: In this article the authors analyzed the heterogeneity of aggrecan degradation products from cartilage harvested from human patients suffering from OA and who also had total knee replacement. My major problem with this paper is the authors' conclusions and interpretation of their data. I see the same data and I interpret them differently based on what is shown. I have explained these differences below. Major issues: 1. Figure 2, page 11, line The authors claim that the two smallest fragment of 60 kda and 75 kda were generated by MMP (G1-MMP) or aggrecanase (G1-Agg) and that they confirmed this by neoepitope staining. (It would help to insert G1-MMP and G1-Agg as I have done in the sentence above to allow readers to understand their text and conclusions.) If these bands are generated by Aggrecanase and MMPs then this is an important conclusion and in addition to showing the G1 blot, the authors need to show the neoepitope blots to add to the gist of their data that these are generated by aggrecanase and/or MMPs, rather than "Data not shown". The generation of the smaller so called G1-MMP band could just be a degradation product of the larger G1-Agg band. Furthermore in line the authors claim that "in some individuals the aggrecanase G1 cleavage product predominates whereas in others the MMP product predominates. However in Table 2 when you study the figures generated from densitometric scanning of this same data only in 1 out of the 34 patients the value for G1-MMP is high. The majority of the patients, in about 22/34 it is the G1-Agg that is the predominant product and in the rest (9/34) they are similar. To me this means that in most patients it is the G1- Agg band that is primarily made and therefore activation of aggrecanase would be the predominant degradation mechanism in OA. I see later that the authors came to the same conclusion from Figure 7. Therefore all the more reason that they show the immunoblot where they confirm that the two bands are indeed G1-Agg and G1-MMP. 2. Figure 3. Page 12, line 18-20

2 Figure 5 Authors claim that the "fragment representing the free G1 region were much more abundant than in more remote areas indicating extensive degradation". In the panel immunoblotted with αg1, in Lane L1, degradation is extensive as the free G1 band is the predominant band, which is probably the only conclusion the authors can come to. The free G1 band is not necessarily more abundant than in lane M1 where the free G1 band (i.e.the upper band that may be the equivalent of the G1-Agg band when compared to Figure 2) is present in the same amount as the only G1 band in Lane L1. Furthermore, if you take into account the two free G1 bands in lane M1 (the 70 kd band plus the 55 kd band) then there is more free G1 not only in lane M1 but also in lane R1 when compared to lane L1. Strangely these lower bands do not have the same MWt as the G1-Agg and G1-MMP bands shown in Figure 2. Again in line 22-25, authors claim that by the use of diff antibodies (αg1, αg2, αcs1, and αg3), that this data in Figure 3 suggests that all fragments contain the G1. Overall the patterns of bands generated in αg2 and αcs1 blots are similar to that generated in the R1 and M1 lanes by αg1. However there are clearly additional bands in immunoblots with αg2 and αcs1 when compared to the αg1 blot, especially above the 220 kd mark, which is suggestive of bands that do not have G1. Which also means that in line their claim of "fragments that no longer possess a G1 domain are lost from the tissue" cannot be true. While the data about the peptide Antibody is interesting it does not add any value to the paper as it was not used in any analysis of the pathophysiology of the OA disease process (the allelic difference in the site was already known). In Discussion, Page 15, line As discussed above, they show that it is Aggrecanase primarily that comes into play in the pathophysiology of OA. Therefore they need to re-write this paragraph to reflect that. To say from their data that "cleavage attributable to MMPs or aggrecanases was also highly variable" is not in keeping with their data. Even though their data (Table 2 and Figure 7) suggests that most OA patients show the G1-Agg product as the predominant product which suggests at the very least a predominantly uniform end stage response to the disease resulting in aggrecan degradation by aggrecanases (rather than MMPs), they insist on claiming that "the proportion of aggrecan cleavage attributable to MMPs and aggrecanases was also highly variable" (line in page 15). Later they claim that "there is no unique mechanism responsible for cartilage destruction in OA" when almost all patients showed the generation of the G1-Agg product, showing that in all cases aggrecanases were involved. Their data on Link protein is not extensive and they do not report how many of these patients show this variation in Link protein degradation. However the variability of the link protein degradation is noted.

3 The article is full of grammatical errors and the authors would do well to edit the manuscript. Some minor issues: 1. In Figure 3, Molecular weight is written as MW x Why The R1 in the panel immunoblotted with anti-cs1 needs to be properly aligned. 3. Page 12, line 33-34, sentence should be "synovial fluid due to absence of interaction". 4. I noticed that the McGill University Review board provided the IRB for this work. Yet none of the authors have listed any association with McGill University in Author information. 5. On Page 4, line 50-52, IDG or IGD? 6. On Page 5, line 16-17, it should be "assumes uniform retention" and not "assumes uniform the retention" In Table 2, need to write that the ratio is G1-Agg/G1-MMP. 8. Page 7, line 18-19, please correct grammar-transfer or transferred? 9. On Page 7, line 4-5, Is 1 M Tris-HCl added for proteoglycan and 1 M Sodium Acetate added for protein recovery or a solution of 1 M Tris-HCl + 1 M Sodium Acetate added? 10. Page 13, line 36, change to "due to presence". 11. Please write Figure legends properly. There is information in the Figures that is not explained in legends. For example, in Figure 4 what is the lane marked as CS referring to. Undigested CS? What is the purpose of this lane, especially since this band does not comigrate with any other band in the figure? In Figure 2 legend one needs to explain what is G1-MMP or G1-Agg. 12. In Figure 1, what is the CS pointing to? Never explained in Figure legends or properly in the body of the manuscript. 13. In Table 1, page 26, the authors need to write "time in years between first report of disease symptoms and surgery (total knee replacement??) by each patients" as this is the sequence of events that happened, assuming that this is what the authors want to convey. Otherwise it seems like there were additional symptoms after the knee replacement. Are the methods appropriate and well described? If not, please specify what is required in your comments to the authors. Yes

4 Does the work include the necessary controls? If not, please specify which controls are required in your comments to the authors. Yes Are the conclusions drawn adequately supported by the data shown? If not, please explain in your comments to the authors. No Are you able to assess any statistics in the manuscript or would you recommend an additional statistical review? If an additional statistical review is recommended, please specify what aspects require further assessment in your comments to the editors. Not relevant to this manuscript Quality of written English Please indicate the quality of language in the manuscript: Needs some language corrections before being published Declaration of competing interests Please complete a declaration of competing interests, considering the following questions: 1. Have you in the past five years received reimbursements, fees, funding, or salary from an organisation that may in any way gain or lose financially from the publication of this manuscript, either now or in the future? 2. Do you hold any stocks or shares in an organisation that may in any way gain or lose financially from the publication of this manuscript, either now or in the future? 3. Do you hold or are you currently applying for any patents relating to the content of the manuscript? 4. Have you received reimbursements, fees, funding, or salary from an organization that holds or has applied for patents relating to the content of the manuscript? 5. Do you have any other financial competing interests? 6. Do you have any non-financial competing interests in relation to this paper? If you can answer no to all of the above, write 'I declare that I have no competing interests' below. If your reply is yes to any, please give details below.

5 I declare that I have no competing interests I agree to the open peer review policy of the journal. I understand that my name will be included on my report to the authors and, if the manuscript is accepted for publication, my named report including any attachments I upload will be posted on the website along with the authors' responses. I agree for my report to be made available under an Open Access Creative Commons CC-BY license ( I understand that any comments which I do not wish to be included in my named report can be included as confidential comments to the editors, which will not be published. I agree to the open peer review policy of the journal