Investigation of the presence of telocyte cells in the humaninfrapatellar fat pad using histological methods

Telocytes have been identified as a new cell type that can behave like mesenchymal stem cells and are closely related to previously identified progenitor cells, and even express similar cell surface markers. Although telocytes were previously known as interstitial Cajal-like cells (ICLC), they can now be distinguished from them by their moniliform appearance and long and thin telopodes. Telocytes are commonly found in bones, skeletal muscles, fascia, and joint synovium, and have also been identified in tissues and organs of many different species. These new cells are also found in the infrapatellar fat pad (IPF), but to date, there is no data in the literature explaining the presence, localization, roles, or morphological characterization of telocytes in the IPF. Telocytes have been shown to play important roles in the regulation of intercellular signaling, morphogenesis, and hemostasis, as well as in various pathologies. In general, CD34, vimentin, PDGRF-α and -β, c-kit and α-SMA have been accepted as reliable telocyte markers. In this study, tissue samples to be obtained from the human knee region were taken during the operation from 10 patients who underwent knee replacement surgery for various reasons such as trauma or osteoarthritis diagnosis. The IPFP tissues were labeled with immunohistochemical analyses and CD34/c-kit, CD34/PDGFR-α and CD34/PDGFR-ß dual staining methods. In this way, telocytes were separated from fibroblasts and pericytes and defined as completely different cells. Simultaneously, the ultrastructures of these cells were examined with transmission electron microscopy (TEM). In this thesis study, the first demonstration of the presence of telocyte cells in human IPFP also reveals that IPFP can be a good source of telocyte cells. Therefore, we believe that our study may be an important guide for further studies investigating telocyte cell isolation, characterization and therapeutic activities and may shed light on new cellular therapy-based approaches to various joint diseases.