Peripheral nerve regeneration and electrophysiological recovery with CIP-treated allogeneic acellular nerves.

Acellular nerve grafts are a desirable alternative to autografts, both because the source of acellular nerves is potentially unlimited and because they have the same matrix structure as natural nerves, which would facilitate axon growth from the defective nerve stump. Although some acellular nerves have been developed, most of them were studied in isogenic transplantation models and evaluated only by histological observation. In the present study, novel allogeneic acellular nerves prepared using the cold isostatic pressuring (CIP) method were developed and assessed as a potential substitute for autografts. The host immune response to acellular nerves and fresh nerves was analyzed using Lewis rats as donors and SD rats as recipients, which is the allogeneic transplantation model, by subcutaneous implantation for one month. In addition, sciatic nerve transplantation into a 10-mm nerve gap was carried out using the same model, and the axonal growth in acellular nerve transplantation was evaluated histologically and electrophysiologically, and compared with that of axons in the autograft transplant area. The subcutaneously implanted acellular nerves contained more macrophages and less vasculature than the allogeneic fresh nerves. In spite of these results of the subcutaneous implantation, Schwann cell infiltration in the graft transplanted into the sciatic nerve gap was observed after the short-term transplantation. The myogenic potential, which was measured as an index of electrophysiological function in acellular nerve transplantation, was also recovered in the long-term transplantation. Our results indicate that the acellular nerves developed herein have the potential to support nerve regeneration and might be useful as an alternative to autografts.

Long-term culture of fetal liver cells using a three-dimensional porous polymer substrate.

To develop a bioartificial liver, long-term culture of fetal liver cells over a month's time was performed under three different culture conditions, i.e., stationary cultures and shaken-flask cultures, both by using a substratum made of porous polyvinyl formal (PVF) resin and conventional monolayer dish cultures as controls. Time course changes in cell numbers and albumin secretion were evaluated in cultures using Williams' E medium (WE) or minimum essential medium alpha (aMEM) supplemented with serum and hormones. In the WE medium, the numbers of fetal liver cells in all culture conditions gradually decreased with time, and albumin secretion rates rapidly decreased. In the stationary cultures using PVF, however, a significant increase in albumin secretion was observed after two weeks of culture. When cells were cultured in aMEM, the fetal liver cells exhibited sufficient proliferation in stationary and monolayer cultures, although albumin secretion rates per single cell were lower than those in WE. On the basis of these results, another series of culture experiments were performed, in which aMEM was used for the first 10 days to encourage cell proliferation, and the medium was changed to WE afterward. In these cultures, albumin secretion rates in the stationary cultures dramatically increased after the medium exchanges and were maintained at these high levels throughout the remaining culture period.