**5. Conclusions**

In conclusion, we confirmed that OA IFP is more inflamed and vascularized compared to ACL IFP, both at the histological and molecular levels. Moreover, we found that OA IFP adipocytes are larger and numerically lower than ACL IFP adipocytes. ECM collagen types distribution in the OA IFP group is different compared to controls, possibly explaining the biomechanical characteristics changes of OA IFP tissue. This study supports the hypothesis that IFP is involved in OA pathology. The clinical relevance of this work is that inflammation and fibrosis of IFP could represent possible

therapeutic targets to counteract OA pathology. In this regard, future studies targeting inflammation and/or fibrosis of OA IFP are needed.

**Supplementary Materials:** Supplementary materials can be found at http://www.mdpi.com/1422-0067/21/17/ 6016/s1.

**Author Contributions:** Conceptualization, E.B., V.M., M.R., and M.F.; formal analysis, E.B. and M.S.; investigation, E.B., C.G.F., E.L.C., M.G., G.S., and A.P. (Assunta Pozzuoli); resources, E.B., A.P. (Assunta Pozzuoli), E.O., G.F., A.B., and P.R.; data curation, E.B., V.M., and M.F.; writing—original draft preparation, E.B. and M.F.; writing—review and editing, E.B., V.M., C.G.F., M.S., M.R., E.O., G.F., and M.F.; supervision, V.M., M.R., R.R., R.V., P.R., and M.F.; funding acquisition, M.R., V.M., A.P. (Andrea Porzionato), and R.D.C. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the L.i.f.e.L.a.b. Program of the 'Consorzio per la Ricerca Sanitaria' (CORIS) of the Veneto Region, Italy, grant number DGR1017, 17 July 2018.

**Acknowledgments:** Part of these data were first presented as a poster at the 2019 Congress of the Italian Society of Anatomy and Histology (SIAI) (Naples, 22–24 September). The authors are grateful to Diego Guidolin for the collagen analysis.

**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study, in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.
