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Bioreactors with a controlled physiological environment are being developed to study various cell processes. The influences of mechanostimulation on bone cell cultures can be investigated using a compression bioreactor. The developed bioreactor system applies a cyclic compression force to the specimen via an eccentrically mounted push rod. The compression force is monitored by a force sensor to detect changes in the material properties of the specimen. Depending on the piston setting, a stroke of 0.28 - 2.50 mm can be applied to the specimen. The bioreactor system was tested with a trial run of 18 days. A sample was continuously stimulated with a loading frequency of 2 Hz and a stroke of 1.50 mm. The sterility in the cell chamber as well as the functionality of the realised bioreactor stimulation system could be successfully confirmed

Background: Bone defects due to malignant tumor often lead to repeated surgery or amputation. Thus, a major objective in orthopedic surgery is the extracorporeal devitalization of tumor-bearing bone segments following reimplantation. Extracorporeal irradiation or autoclaving are possible methods even though they may cause severe loss of biomechanical and biological properties. Yet previous studies have shown that high hydrostatic pressure (HHP) allows for complete devitalization of tumor-afflicted bone segments, while the biomechanical and biological properties of bone tissue remained unchanged. The subject of the present study is revitalization of human bone segments after HHP treatment to acquire knowledge about the ingrowth and regeneration of osteoblast-like cells after such treatment., Materials and Methods: Bone pieces of 5 mm(3) were obtained from cancellous bone, taken from human femoral heads of 6 patients undergoing surgery for total hip arthroplasty, and exposed to hydrostatic pressure levels of 0, 300, and 600 MPa for 10 min at 37°C. Following the HHP treatment, bone segments were coated with primary human bone cells (10,000 cells/segment), cultured for 42 days and cell viability and proliferation quantified at different time points., Results: An adhesion rate of 73.8% on day 1 and an increase in proliferation between day 14 and 42 were determined. Pretreatment of bone segments with 300 and 600 MPa did not affect cell adhesion or proliferation. Histology showed intact cells and new bone formation on the bone specimens; elevated expression of alkaline phosphatase, osteocalcin, and collagen type I was seen by immunohistochemistry., Conclusion: The present study demonstrates, for the first time, the successful revitalization of HHP-treated bone segments. Concerning proliferation and osteogenic differentiation, the findings are a promising demonstration of sufficient osseointegration. Along with previous results, we anticipate that a pressure of a maximum 350 MPa does induce devitalization of malignant bone tumor segments, while HHP treatment of bone matrix up to 600 MPa does not affect osteoconductivity and osteoinductivity.

At present, in orthopedic surgery, the reconstruction of bone defects following resection of malignant tumors is effected by several methods. The irradiation and autoclaving of bone segments are the 2 methods of choice to extracorporeally devitalize the resected tumor-bearing bone segments. An alternative, gentle method of devitalizing bone-associated cells by exposing normal and tumor cells to extracorporeal high hydrostatic pressure (HHP) has been introduced. The aim of this study was to examine the ex vivo effect of HHP on the cell growth of normal and tumor-afflicted freshly-resected small human bone segments. For this, tumor-afflicted human bone segments of 5 x 5 x 5 mm in size, obtained during surgery from 14 patients suffering from chondrosarcoma or osteosarcoma, in comparison to bone segments obtained from 36 patients with normal bone, disease were exposed to HHP levels of 0, 150 and 300 MPa for 10 min at 37 degrees C. Following HHP-treatment, the specimens were placed into cell culture and observed for cell outgrowth up to 50 days. In control samples (0 MPa), rapid outgrowth of cells was observed. HHP-treatment of 150 MPa however, resulted in reduced outgrowth of cells from these bone specimens; at 300 MPa, no outgrowth of cells was detected. Light microscopy and standard histological examination showed morphological changes between control samples (0 MPa) and 150 MPa. Our results suggest that the treatment of tumor-afflicted bone and the associated cartilage by HHP leads to the devitalization of bone cells concomitant with complete impairment of cellular outgrowth, a precondition for re-implantation of the HHP-treated bone.