On 2015 Nov 05, David Attwell commented:

Contractile pericytes should not be confused with smooth muscle cells. David Attwell, University College London, E-mail D.Attwell@ucl.ac.uk

The original definition of pericytes by Zimmermann (1923) (translated into English here) included in this cell class the contractile cells on capillaries which Hill et al. (2015) re-name in their paper to be smooth muscle cells (despite their clear morphological difference from classical arteriolar smooth muscle cells). Unfortunately, because Hill et al. re-named pericytes in this way, the title and text of their paper are misleading. Zimmermann (1923), and most workers since in the field of vascular biology, would define as pericytes the spatially-isolated contractile cells on capillaries that Hill et al. (2015) observe to control capillary blood flow in health and disease, confirming previous papers showing that pericytes have this role (Hall et al., 2014; Yemisci et al., 2009). Further discussion can be found in: Attwell, Mishra, Hall, O’Farrell & Dalkara (2015) What is a pericyte? J Cereb Blood Flow & Metab. advance online publication.

On 2015 Nov 05, David Attwell commented:

Contractile pericytes should not be confused with smooth muscle cells. David Attwell, University College London, E-mail D.Attwell@ucl.ac.uk

The original definition of pericytes by Zimmermann (1923) (translated into English here) included in this cell class the contractile cells on capillaries which Hill et al. (2015) re-name in their paper to be smooth muscle cells (despite their clear morphological difference from classical arteriolar smooth muscle cells). Unfortunately, because Hill et al. re-named pericytes in this way, the title and text of their paper are misleading. Zimmermann (1923), and most workers since in the field of vascular biology, would define as pericytes the spatially-isolated contractile cells on capillaries that Hill et al. (2015) observe to control capillary blood flow in health and disease, confirming previous papers showing that pericytes have this role (Hall et al., 2014; Yemisci et al., 2009). Further discussion can be found in: Attwell, Mishra, Hall, O’Farrell & Dalkara (2015) What is a pericyte? J Cereb Blood Flow & Metab. advance online publication.