Myofibroblast involvement in chronic transplant rejection.

BACKGROUND

Chronic rejection remains the major cause of late graft failure. We studied the renal tissue of 10 renal transplant patients with chronic rejection in whom biopsies had been performed at various time points over a 15-year posttransplant period to ascertain whether myofibroblasts (MF) have a role in this process.

METHODS

Biopsies were grouped into five categories with respect to time after vascular anastomosis: 0 (n=10); 1 day to 3 months (n=7); 6-24 months (n=5); 36-72 months (n=7); and >72 months (n=5). A control group consisted of patients who had undergone routine biopsies at 0 (n=10), 3 (n=10), 12 (n=6), 60 (n=5), and >60 months (n=6) with no rejection. MF were identified by morphology and alpha-smooth muscle actin immunostaining. T cells and macrophages (MF) were identified using an antisera to CD3 and CD68, respectively. Collagen III deposition was similarly quantified by immunohistochemistry. Interstitial fractional area was measured by point counting.

RESULTS

At all time points studied beyond time 0, there were significant increases in interstitial fractional area, collagen III staining, MF, and T-cell staining in patients with chronic rejection compared with the controls. Staining for alpha-smooth muscle actin increased with time in conjunction with worsening fibrosis and collagen deposition.

CONCLUSIONS

In this study, MF were a major component of the interstitial infiltrate of the 10 patients with chronic transplant rejection. Abnormal persistence of these cells in the interstitium is one of the events that contributes to pathologic scarring of the kidney.