We searched for morphological evidence to support the hypothesis that stem cells are responsible for renal tubular cell proliferation. The rationale of the study was that if proliferation relies on progenitors, mitotically active cells should be less differentiated than their neighbors. As the retention of the @entity1014 analog @entity1603 has been the only approach employed to identify stem cells in the kidney up to now we additionally characterized @entity1603 -retaining cells. @entity35 kidneys were fixed by perfusion. Cycling cells identified by mitotic figures or the expression of the @entity1975 ( @entity1975 ) were examined by light microscopy and electron microscopy as well as immunofluorescence for four differentiation markers. Newborn @entity35 were injected with @entity1603 in order to detect label-retaining cells. After a period of 8, 14 and 35 weeks the kidneys were examined for @entity1603 by immunofluorescence and the four differentiation markers mentioned above. All cycling cells showed the same degree of differentiation compared to non-cycling cells. Most of the detected label-retaining cells were differentiated. We conclude that cycling cells in tubules of the healthy kidney are differentiated and that the retention of label is not a criterion to identify stem cells in renal tubules.

Tubular cell proliferation in the healthy XXXX kidney.

@entity35 :: ('10116', 'Species') :: ['Rat', 'rats'] @entity1603 :: ('MESH:D001973', 'Chemical') :: ['BrdU'] @entity1975 :: ('25737(Tax:10116)', 'Gene') :: ['PCNA', 'proliferating cell nuclear antigen'] @entity1014 :: ('MESH:D013936', 'Chemical') :: ['thymidine']
@entity35 :: (10116,Species) :: ['rat']
