Ketamine decreases cell viability of bone explants and impairs bone healing in rats.

BACKGROUND: Ketamine is a widely used anesthetic in experimental medicine. We have also used ketamine for surgical interventions and imaging in rats and found significantly impaired ossification between identically performed experiments, which only differed in the number of anesthetic events. In order to investigate this phenomenon, we estimated the absorbed ionizing radiation and also studied whether ketamine administration has disadvantageous effect on bone cell viability. METHODS: Spongious bone chips and parietal bone disks were harvested from rats. Explants were incubated in stem cell media containing 0.02, 0.2 and 2 mM ketamine. After 3 days of incubation, tetrazolium-based spectrophotometric assay was performed to measure cell viability. Size-specific dose estimation was used to calculate ionizing radiation of computed tomography imaging. RESULTS: We found that ketamine supplementation with 0.2 mM slightly decreased cell viability, while 2 mM caused significant reduction both in the spongious and cortical explants. The cumulative ionizing radiation was found to be negligible compared to irradiation dosages used to impair ossification. CONCLUSIONS: We conclude that multiple ketamine administration was responsible for the diminished regenerative potential of bone tissue in the present experimental setup. For this reason, we suggest that ketamine anesthesia should be avoided in studies investigating bone regeneration.

The Effects of Hyperacute Serum on the Elements of the Human Subchondral Bone Marrow Niche.

Mesenchymal stem cells (MSCs) are widely used in laboratory experiments as well as in human cell therapy. Their culture requires animal sera like fetal calf serum (FCS) as essential supplementation; however, animal sera pose a risk for clinical applications. Human blood derivatives, for example, platelet-rich plasma (PRP) releasates, are potential replacements of FCS; however, it is unclear which serum variant has the best effect on the given cell or tissue type. Additionally, blood derivatives are commonly used in musculoskeletal diseases like osteoarthritis (OA) or osteonecrosis as "proliferative agents" for the topical MSC pool. Hyperacute serum (HAS), a new serum derivative, has been designed to approximate the natural coagulation cascade with a single-step, additive-free preparation method. We investigated the effects of HAS on monolayer MSC cultures and in their natural niche, in 3D subchondral bone and marrow explants. Viability measurements, RT-qPCR evaluation for gene expression and flow cytometry for cell surface marker analysis were performed to compare the effects of FCS-, PRP-, or HAS-supplemented culture media. Monolayer MSCs showed significantly higher metabolic activity following 5 days' incubation in HAS, and osteoblast-specific mRNA expression was markedly increased, while cells also retained their MSC-specific cell surface markers. A similar effect was observed on bone and marrow explants, which was further confirmed with confocal microscopy analysis. Moreover, markedly higher bone marrow preservation was observed with histology in case of HAS supplementation compared to FCS. These findings indicate possible application of HAS in regenerative solutions of skeletal diseases like OA or osteonecrosis.