Cyanoacrylate in nerve repair: transient cytotoxic effect

Photomicrographs showing SH-SY5Y cell cultures 7 days (A and B), 14 days (C and D) and 28 days (E and F) after exposure to 0.1μl ECA. The width of the halo devoid of cells (1) between the adhesive (2) and the margin of the confluent cell layer (3) was measured at 24h and 7, 14, 21 and 28 days after exposure to the adhesive. Over time the halo became narrower and after 28 days (i.e. at the end of the measuring period) cells were growing at the margin of the adhesive (4). Arrows indicate unaffected cells in the intermediate area between confluent culture and the zone devoid of cells (B and D). Scale bars: A and C, 1000μm; B, D and E, 100μm; F, 50μm.

Exposure to ECA or BCA gave rise to a halo devoid of SH-SY5Y cells around the adhesive which grew significantly larger up to 7 days whereupon it decreased significantly in size to the end of the study period (P<0.001). Mean values with standard deviation of the measured halo width are given (n=8 cultures in each adhesive group for each time point). *P<0.05.

SH-SY5Y cells labelled with tubulin antibodies following exposure to ECA (A and B) or BCA (C and D) and controls (E and F). Immunofluorescence photomicrographs were taken immediately outside the cell-free halo (A and C) 24h or (B and D) 7 days after exposure to the adhesive and at random spots at corresponding time delays in controls. Note the loss of neurites, the change in cell shapes and cell sizes and texture degeneration 24h after incubation (A and C). At 7 days, exposed cells had regained their normal appearance (B and D), including neurites (arrows), and could not be distinguished from controls (F). Scale bar=20μm.

The sizes of SH-SY5Y cell bodies after exposure to ECA or BCA, as well as of time-matching controls (n=8), were measured at 24h and at 7 days after incubation. In the area close to the halo devoid of cells, 20 random SH-SY5Y cells in each culture were measured (total of 160 cells in each group for each time point). Values are means and standard deviation. **P<0.001.

Cell death caused by ECA or BCA assessed as the release of ⁵¹Cr. Cytotoxicity in both groups decreased rapidly between 24h and 14 days (*P<0.01, n=8 in each adhesive group for each time point). Values in the figure (means and standard deviation) were calculated by subtracting cell death values in controls from values in exposed cultures. No significant differences between groups were seen.