en Cellular & Molecular Research Cellular & Molecular Research Original Research Original Research <span style="font-size:13pt"><span style="text-justify:kashida"><span style="text-kashida:0%"><span style="text-autospace:none"><span style="font-family:&quot;Times New Roman&quot;,serif"><span style="font-style:italic"><b><span style="font-size:9.0pt"><span style="font-style:normal">Background: </span></span></b><span style="font-size:9.0pt"><span style="font-style:normal">Many elder people have knee osteoarthritis (OA). The patients are faced with pain and disability in movement. Given the challenging lifestyle of the patients, finding an efficient therapy approach is necessary. Since low-level laser therapy applies to the treatment of many diseases, it seems it can be a suitable option for the treatment of knee OA. The present study aimed to evaluate the molecular mechanism of laser therapy on knee OA via a protein expression change study. </span></span></span></span></span></span></span></span><br> <span style="font-size:13pt"><span style="text-justify:kashida"><span style="text-kashida:0%"><span style="text-autospace:none"><span style="font-family:&quot;Times New Roman&quot;,serif"><span style="font-style:italic"><span style="font-size:9.0pt"><span style="font-style:normal">&nbsp;&nbsp; <b>Methods:</b> The present study examines the gene expression profile of patients with OA in the knee using bioinformatics. The protein expression change profile of synovial fluid of knee OA patients is extracted from the literature and is analyzed based on the rate of expression and interactions between the differentially expressed proteins (DEPs). The results are compared with the DEPs of similar tissue of the treated knee OA patients (from published documents) after laser therapy.</span></span></span></span></span></span></span></span><br> <span style="font-size:13pt"><span style="text-justify:kashida"><span style="text-kashida:0%"><span style="text-autospace:none"><span style="font-family:&quot;Times New Roman&quot;,serif"><span style="font-style:italic"><span style="font-size:9.0pt"><span style="font-style:normal">&nbsp;&nbsp; <b>Results:</b> Apolipoprotein B (APOB) and matrix metallopeptidase 2 (MMP2) were determined as the hub bottlenecks of the protein-protein interaction (PPI) network of synovial fluid of knee OA patients. MMP2, complement 5, transthyretin, and apolipoprotein A-1 from laser-treated patients were related to the PPI network of knee OA patients. The reduction of Interleukin-6 activity was highlighted as a critical event as a function of laser on the human body. </span></span></span></span></span></span></span></span><br> <span style="font-size:13pt"><span style="text-justify:kashida"><span style="text-kashida:0%"><span style="text-autospace:none"><span style="font-family:&quot;Times New Roman&quot;,serif"><span style="font-style:italic"><span style="font-size:9.0pt"><span style="font-style:normal">&nbsp;&nbsp; <b>Conclusion:</b> In conclusion, it was noted that the main phenomenon associated with laser therapy-induced improvement in the condition of knee OA patients is the downregulation of MMP2.&nbsp; </span></span></span></span></span></span></span></span><br> <span style="font-size:13pt"><span style="text-justify:kashida"><span style="text-kashida:0%"><span style="text-autospace:none"><span style="font-family:&quot;Times New Roman&quot;,serif"><span style="font-style:italic"><span style="font-size:9.0pt"><span style="font-style:normal"></span></span></span></span></span></span></span></span><br> &nbsp; Low-Level Laser Therapy, Knee Osteoarthritis, Proteomics, MMP2, Network Analysis 1014 1018 http://mjiri.iums.ac.ir/browse.php?a_code=A-10-8378-1&slc_lang=en&sid=1 Reza M Robati rmrobati@gmail.com 200319475328460080976 200319475328460080976 No Skin Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran Zahra Razzaghi z.razzaghi@sbmu.ac.ir 200319475328460080977 200319475328460080977 Yes Laser Application in Medical Sciences Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran Babak Arjmand mgrc.tums@gmail.com 200319475328460080978 200319475328460080978 No Cell Therapy and Regenerative Medicine Research Center, Endocrinology and Metabolism Molecular-Cellular Sciences Institute, Tehran University of Medical Sciences, & Iranian Cancer Control Center, Tehran, Iran Mostafa Rezaei Tavirani tavirani@yahoo.com 200319475328460080979 200319475328460080979 No Proteomics Research Center, Faculty of Paramedical Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran Fatemeh Sheibani fatemehsheibani.md@gmail.com 200319475328460080980 200319475328460080980 No Laser Application in Medical Sciences Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran