Conclusion
sFLT1-positive histiocytes are generally part of the inflammatory infiltrates noted in CKD and are particularly abundant in forms of interstitial nephritis. Their presence promotes an anti-angiogenic state locally in the tubulointerstitium that could inhibit capillary repair, contribute to peritubular capillary loss, and enhance fibrosis in CKD.
Methods
Fifty-two renal biopsies were studied for sFLT1 expression using immunohistochemistry and evaluated on a 0-4 grading scale of positive cells within inflammatory infiltrates. These included drug-induced interstitial nephritis (6); allografts (12), with polyomavirus nephritis (3); diabetes mellitus (10); lupus glomerulonephritis (6); pauci-immune vasculitis (7); IgA nephropathy (6); and miscellaneous CKD (5).
Results
Forty-seven biopsies had inflammatory infiltrates of which 37 had sFLT1-positive cells: of these biopsies, 3 were grade 4, i.e., had cells that constituted more than 50% of the inflammatory infiltrate, 9 were grade 3 (25%-50%), 5 were grade 2 (10%-25%), 3 were grade 1 (10%), and 17 were grade 0.5 (<10%). There was a robust correlation (r2 = 0.89) between degree of inflammation and sFLT1-positive cells. CD68/sFLT1 co-immunostaining studies indicated that sFLT1-positive cells were histiocytes. The surrounding capillary network was reduced.