COL1A1 and hematocrit: Interestingly, we found most of the CCL21+ cells were distributed in TC zones of TLOs in thyroid tissues of HT patients (Fig. 5d), in which CCL21 was co-expressed with COL1A1 (Fig. 5e) but not with ACTA2 (Fig. 4f); thus, the CCL21+ cells were defined as CCL21+ fibroblasts.