Diffusion Chambers

Abstract

Diffusion chambers include a diversity of planar and tubular configurations, including flat sheets, disks, hollow fibers and wide-bore tubes.^1–5 Although various device designs have been studied for nearly half a century, these experiments have been performed mainly in rodents, and only recently has any progress with the diffusion chamber technique been reported in large animals.⁶ In the late 1940s/early 1950s, Algire and coworkers^7–9 first transplanted cells enclosed in Millipore diffusion chambers into mice, in order to study the mechanisms of cellular immune rejection. The viability of the implanted tissue was severely compromised by fibrous overgrowth of the extracapillary-situated chambers. Subsequent studies with islet allografts and xenografts in rodents were equally discouraging ^10–17 Although partial or transient normoglycemia was achieved in some studies, the outer membrane surface was rapidly covered by fibrosis, and islet survival was not observed after a few weeks of transplantation. Furthermore, Theodorou and Howell¹⁸ investigated the in vitro glucoseinsulin transfer kinetics of this kind of macroencapsulation device and found that the transit half-time of insulin (almost an hour) was less than optimal for physiologic regulation of blood glucose concentrations.