gms | German Medical Science

Objectives: Non or delayed bone healing remains an unsolved challenge in orthopaedic and trauma surgery. Since the resources of autologous bone grafting are limited and harvesting procedure is associated with relevant co-morbidity alternative techniques supporting bone regeneration are required. One example is the application of mesenchymal stroma cells (MSCs), bone marrow aspiration concentrate (BMAC) or platelet rich plasma (PRP) and its derivates. During the last years, extracellular vesicles (EVs) derived from MSCs have come into the focus of research (biological nano particles). EC can be filtrated sterile, show no self-renewal potential and some data indicate also osteopromotive properties. In this study we present and characterize different subtypes of MSC-EVs.

Methods: Characteristic cell-tissue-composits (CTC) of 30 probands were harvested under vacuum and sterile conditions during total hip or knee replacement using the internal filter of a surgical suction handle. Afterwards mononuclear cells (MNC) were isolated from the autologous tissue using standardized protocols followed by in vitro cultivated. According to the criteria of the International Society of Cellular Therapy (ISCT), MSCs were identified. MSC-EV were isolated from culture supernatants of osteogenic stimulated MSCs cultures, filtrated and characterized by imaging flow cytometry. Unstimulated MSC cultures served as controls. Here, to exclude individual variance, the specimens were used as a case-control-study. We hypothesize that there were different MSC-EV subtypes showing characteristic kinetics of surface marker expression.

Results and conclusion: The characterization of MSC-EVs by 18 different surface markers showed significant differences to unstimulated control groups.

Here, we could demonstrate for the first time the osteogenic in vitro potential of different subtypes of MSC-EVs derived from surgical site tissue. The distribution of subtypes corresponds to immunomodulation according to potential increased bone regeneration. Especially the kinetics of surface marker expression documents a high dynamic showing relevant differences even after one week in culture.

Due to its easy availability our data indicate that cell-free MSC-EVs could be a comprehensive and standardized therapeutic alternative tool to stimulate bone healing. However, further studies are required showing the safety and clinical relevance of this cell-free therapeutic agent.