Sex dimorphic regulation of osteoprogenitor progesterone in bone stromal cells

Abstract

Increasing peak bone mass is a promising strategy to prevent osteoporosis. A mouse model of global progesterone receptor (PR) ablation showed increased bone mass through a sex-dependent mechanism. Cre-Lox recombination was used to generate a mouse model of osteoprogenitor-specific PR inactivation, which recapitulated the high bone mass phenotype seen in the PR global knockout mouse mode. In this work, we employed RNA sequencing analysis to evaluate sex-independent and sex-dependent differences in gene transcription of osteoprogenitors of wild-type and PR conditional knockout mice. PR deletion caused marked sex hormone-dependent changes in gene transcription in male mice as compared to wild-type controls. These transcriptional differences revealed dysregulation in pathways involving immunomodulation, osteoclasts, bone anabolism, extracellular matrix interaction and matrix interaction. These results identified many potential mechanisms that may explain our observed high bone mass phenotype with sex differences when PR was selectively deleted in the MSCs.

Keywords: RNA-seq; bone; osteoprogenitor; progesterone receptor; signaling pathways.

Figure 1

Prx1; PRcKO mice and their littermates had similar changes in bone turnover following gonadal deficiency in both sexes. Mice were ovariectomized (OVX) or orchiectomized (ORX) at two-months of age and sacrificed one month post-surgery. Mice were given two fluorescents labeling at −7 and −1 day(s) before sacrifice. (A). Dynamic bone histomorphometry was performed at the distal femurs from wild type and Prx1; PRcKO mice of both sexes at 3 months of age. (B). Representative distal femurs from 2-month-old female and male Prx1; PRcKO mice were OVX or ORX.

Figure 2

KEGG pathway analysis on DEGs identified in males. (A) Bar plot ranking selected pathways by –log₁₀(FDR) values for enrichment of DEGs up-regulated in PRcKO. (B) Bar plot ranking selected pathways by –log₁₀(FDR) values for enrichment of DEGs down-regulated in PRcKO.

Figure 3

Validation of select gene expressions by qRT-PCR. (A) qPCR vs RNA-seq for selected genes. log₂ (fold change) values plotted and used to assess correlation. (B) Whole bone RT-PCR for selected genes (n=4–6/group). Mean +/− SEM (* p < 0.05; Mann-Whitney test vs. WT).