The effect of storage medium tonicity on osteochondral autograft plug diameter

Antiseptic solutions modulate the paracrine-like activity of bone chips: differential impact of chlorhexidine and sodium hypochlorite

AIM

Chemical decontamination increases the availability of bone grafts; however, it remains unclear whether antiseptic processing changes the biological activity of bone.

MATERIALS AND METHODS

Bone chips were incubated with four different antiseptic solutions including (1) povidone-iodine (0.5%), (2) chlorhexidine diguluconate (0.2%), (3) hydrogen peroxide (1%) and (4) sodium hypochlorite (0.25%). After 10 min. of incubation, changes in the capacity of the bone-conditioned medium (BCM) to modulate gene expression of gingival fibroblasts was investigated.

RESULTS

Conditioned medium obtained from freshly prepared bone chips increased the expression of TGF-β target genes interleukin 11 (IL11), proteoglycan4 (PRG4), NADPH oxidase 4 (NOX4), and decreased the expression of adrenomedullin (ADM), and pentraxin 3 (PTX3) in gingival fibroblasts. Incubation of bone chips with 0.2% chlorhexidine, followed by vigorously washing resulted in a BCM with even higher expression of IL11, PRG4 and NOX4. These findings were also detected with a decrease in cell viability and an activation of apoptosis signalling. Chlorhexidine alone, at low concentrations, increased IL11, PRG4 and NOX4 expression, independent of the TGF-β receptor I kinase activity. In contrast, 0.25% sodium hypochlorite almost entirely abolished the activity of BCM, whereas the other two antiseptic solutions, 1% hydrogen peroxide and 0.5% povidone-iodine, had relatively no impact respectively.

CONCLUSION

These in vitro findings demonstrate that incubation of bone chips with chlorhexidine differentially affects the activity of the respective BCM compared to the other antiseptic solutions. The data further suggest that the main effects are caused by chlorhexidine remaining in the BCM after repeated washing of the bone chips.

Approaches to preserve human osteochondral allografts

Osteochondral defects may progress to osteoarthritis. Many attempts have been developed to overcome this issue, including osteochondral autografts and allografts. The goal of this study was to develop a new protocol for storage of human osteochondral allografts. Osteochondral plugs were randomly allocated in the following groups: control, immediate freezing up to -70 °C, cooling at 4 °C, and storage at 37 °C. Samples from the cooling at 4 °C and storage at 37 °C groups were stored in tubes containing medium plus human albumin and analyzed after 1, 3, and 14 days. The frozen groups' samples were cryopreserved for 1 year in cryotubes containing medium only (FM), medium plus human albumin (FA), and medium plus human albumin and glucose (FG) and were then analyzed. Analysis involved histological study with hematoxylin-eosin and Safranin O and a modified Live/Dead assay. In samples stored both at 37 and 4 °C, analysis showed statistically significant higher cellular mortality at 14 days compared to 1 and 3 days, but mortality in the 4 °C group was lower. In the freezing protocols, the FA group showed less cellular mortality than the FM and FG groups. Cooling at 4 °C offers better preservation capacity than storage at 37 °C, but both offer the capacity for preservation for 14 days. Adding human albumin to the storage medium is useful in reducing cellular mortality in samples frozen for 1 year.