PHYSICAL AND HISTOLOGICAL BEHAVIOR OF A NEW INJECTABLE COLLAGEN (GAX-65) IMPLANTED INTO THE SUBMUCOSAL SPACE OF THE MINIPIG BLADDER

The aim of our study was to analyze the physical and histological beha vior of a second generation collagen (GAX 65) in the mini-pig bladder, comparing it to the commonly used substance for injection (GAX 35). G AX 65 is a glutaraldehyde cross-linked bovine collagen with a collagen concentration of 65 mg./ml. This much higher collagen concentration c ould be achieved due to sophisticated manufacturing technology. In 18 mini-pigs 2 to 4, 1 ml. deposits of GAX 65 and 35, respectively, were implanted into the submucosal space of the surgically opened bladder. The animals were sacrificed at months 1, 2, 4 and 6. The elevation (he ight equals protrusion of the implant into the bladder) and volume of the implants were measured and calculated immediately after injection and at necropsy. Histology was performed. The GAX 65 implants had a le sser decrease of elevation and volume during the 6-month observation p eriod. Histology showed that the invasion of endogenous fibroblasts in to the GAX 35 and 65 implants, and the formation of porcine collagen t ypes I and III were almost identical. Clinically GAX 65 has better ele vation properties than GAX 35 although statistical analysis did not sh ow any significant difference (p = 0.07 to 0.25). However, preservatio n of the volume of the GAX 65 implant was significantly superior (p le ss than or equal to 0.05) compared to that of GAX 35. Therefore, GAX 6 5 will most probably prove to be an excellent substance for the endosc opic treatment of vesicoureteral reflux and incontinence in children.