Defects in the Cell Cycle of Fibroblasts Obtained from Patients With Cystic Fibrosis

Abstract

Some years ago, Danes and Beam (1) discovered that the fibroblasts obtained from the cutaneous biopsy of patients diagnosed as cystic fibrotic were more metachromatic than similar cells derived from patients with conditions other than cystic fibrosis. In our studies of the population doubling times of diploid human fibroblasts in culture (2), we reported that the fibroblasts derived from cutaneous biopsies of three different patients with cystic fibrosis had significantly longer population doubling times than did either normal diploid human fibroblasts or cells derived from patients with acid mucopolysac-charidoses (Hunter's and Hurler's disease). Further, we have reported (3) that cystic fibrosis-derived cutaneous fibroblasts do not make normal amounts of collagen hydroxypro-line when exposed in vitro to ascorbic acid and radioactive proline.

The findings, then, of metachromasia, prolonged population doubling time and failureof collagen synthesis on the part of fibroblasts derived from the skin of patients with cystic fibrosis suggest in general that these cells are not normal in their in vitro behavior. We have pointed out that there is no evidence in vivo to support the proposition that the fibroblasts of patients with cystic fibrosis are in any way inadequate or different from normal (4). We presume, then, that the autosomal recessive defect in these patients manifests itself in their cutaneous fibroblasts because of the inadequate in vitro medium in which they are normally cultivated. Therefore, it might appear that cells from cystic fibrosis patients are sufficiently “sick” in vitro so as to have lost both their ability to make collagen or divide at the proper rate and hence accumulate supernormal amounts of metachromatic granules.

This paper analyzes the cell cycle of cystic fibrosis-derived fibroblasts and statistically demonstrates their failure to support a normal population doubling time in vitro and indicates that this is due largely to a failure of the cystic fibrosis-derived cells to enter the cell cycle in normal numbers.