*Article* **Devitalizing E** ff**ect of High Hydrostatic Pressure on Human Cells—Influence on Cell Death in Osteoblasts and Chondrocytes**

**Janine Waletzko 1,\*, Michael Dau 1, Anika Seyfarth 2, Armin Springer 3,4, Marcus Frank 3,4, Rainer Bader 2 and Anika Jonitz-Heincke 2**


Received: 12 May 2020; Accepted: 26 May 2020; Published: 28 May 2020

**Abstract:** Chemical and physical processing of allografts is associated with a significant reduction in biomechanics. Therefore, treatment of tissue with high hydrostatic pressure (HHP) o ffers the possibility to devitalize tissue gently without changing biomechanical properties. To obtain an initial assessment of the e ffectiveness of HHP treatment, human osteoblasts and chondrocytes were treated with di fferent HHPs (100–150 MPa, 250–300 MPa, 450–500 MPa). Devitalization e fficiency was determined by analyzing the metabolic activity via WST-1(water-soluble tetrazolium salt) assay. The type of cell death was detected with an apoptosis/necrosis ELISA (enzyme-linked immune sorbent assay) and flow cytometry. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) were carried out to detect the degree of cell destruction. After HHP treatment, the metabolic activities of both cell types decreased, whereas HHP of 250 MPa and higher resulted in metabolic inactivation. Further, the highest HHP range induced mostly necrosis while the lower HHP ranges induced apoptosis and necrosis equally. FESEM and TEM analyses of treated osteoblasts revealed pressure-dependent cell damage. In the present study, it could be proven that a pressure range of 250–300 MPa can be used for cell devitalization. However, in order to treat bone and cartilage tissue gently with HHP, the results of our cell experiments must be verified for tissue samples in future studies.

**Keywords:** high hydrostatic pressure; devitalization; decellularization; allografts; regenerative medicine; bone and cartilage regeneration
