Ligament cells, isolated using the explant method, have been established as playing a pivotal role in ligament ossification, a finding confirmed in prior studies.7,10 In another transcriptomic study (GSE69787) focusing on ligament cells isolated from OPLL and non-OPLL patients, we observed upregulation of LOXL2 in OPLL-derived ligament cells (Fig. S4c). The gene discussed is LOXL2; the disease is ossification of the posterior longitudinal ligament of the spine.