Phd2

Inhibiting Phd2 may be a potential drug target to help people grow taller.

Conditional Deletion of Prolyl Hydroxylase Domain-containing Protein 2 (Phd2) Gene Reveals its Essential Role in Chondrocyte Function and Endochondral Bone Formation.

“The hypoxic growth plate cartilage requires hypoxia-inducible factors (HIFs)-mediated pathways to maintain chondrocyte survival and differentiation. HIF proteins are tightly regulated by prolyl hydroxylase domain-containing protein 2 (Phd2) mediated proteosomal degradation. We conditionally disrupted the Phd2 gene in chondrocytes by crossing Phd2 floxed mice with Col2α1-Cre transgenic mice, and found massive increases (>50%) in the trabecular bone mass of long bones and lumbar vertebra of the Phd2 conditional knockout (cKO) mice caused by significant increases in trabecular number and thickness and reductions in trabecular separation. Cortical thickness and tissue mineral density at the femoral mid-diaphysis of the cKO mice were also significantly increased. Dynamic histomorphometric analyses revealed increased longitudinal length and osteoid surface per bone surface (OS/BS) in the primary spongiosa of the cKO mice, suggesting elevated conversion rate from hypertrophic chondrocytes to mineralized bone matrix as well as increased bone formation in the primary spongiosa. In the secondary spongiosa, bone formation measured by MS/BS and MAR were not changed but resorption was slightly reduced. Increases in the mRNA levels of Sox9, Osterix (Osx), Col2, Aggrecan, ALP, Bsp, VEGF, Epo, and glycolytic enzymes in the growth plate of cKO mice were detected by quantitative RT-PCR. Immunohistochemistry revealed an increased HIF-1α protein level in the hypertrophic chondrocytes of cKO mice. Infection of chondrocytes isolated from Phd2 floxed mice with adenoviral Cre resulted in similar gene expression patterns as observed in the cKO growth plate chondrocytes. Our findings indicate that Phd2 suppresses endochondral bone formation, in part, via HIF-dependent mechanisms in mice.”

“hypertrophic chondrocytes can transdifferentiate into osteoblasts and contribute to trabecular, endosteal, and cortical bone formation”

“In chondrocytes, HIF-1 increases the expression of VEGF and promotes angiogenesis in the
surrounding perichondrium ”

Only deletion of Phd2 in chondrocytes seems to increase height.  Deletion of Phd2 in say osteoblasts seems to decrease height.  Also Phd2 cKo seems to result in shorter overall body length. It’s just the primary spongosia that’s increased in length.

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