Nerve regeneration changes with filters of different pore size.

An experimental reason for placing stumps of a transected nerve in an impermeable tube is that factors and soluble substances from the nerve stumps are pooled and separated from cells and soluble substances in the body in general. Previous work showed that certain parameters of regeneration were improved, however, when the impermeable tube was made completely permeable by cutting macroscopic holes in its side. To begin exploring the reasons for these improvements, we covered the holes in the permeable tubes with filters of two different pore sizes, and found that the improvements resulted when the pore size was large enough to allow both fluid and cells to exchange but not when the pore size allowed only fluid to exchange. These findings suggest that cells from the general connective tissue should be given consideration when designing experimental procedures to maximize the regeneration potential of regenerating axons.