TEK and osteoporosis: In a mouse study using a conditional knock out of STAT3 with the TIE2-Cre, in which the Cre recombinase is driven by the endothelial-specific promoter/enhancer and is thought to be expressed during an early stage of hematopoietic cell lineage, Zhang et al [24] reported that the loss of STAT3 resulted in mice with an increased osteoclast number and activity with a severe osteoporosis phenotype.