Inactivation of the Progesterone Receptor in Mx1+ Cells Potentiates Osteogenesis in Calvaria but Not in Long Bone

Targeting PRMT9-mediated arginine methylation suppresses cancer stem cell maintenance and elicits cGAS-mediated anticancer immunity

Current anticancer therapies cannot eliminate all cancer cells, which hijack normal arginine methylation as a means to promote their maintenance via unknown mechanisms. Here we show that targeting protein arginine N-methyltransferase 9 (PRMT9), whose activities are elevated in blasts and leukemia stem cells (LSCs) from patients with acute myeloid leukemia (AML), eliminates disease via cancer-intrinsic mechanisms and cancer-extrinsic type I interferon (IFN)-associated immunity. PRMT9 ablation in AML cells decreased the arginine methylation of regulators of RNA translation and the DNA damage response, suppressing cell survival. Notably, PRMT9 inhibition promoted DNA damage and activated cyclic GMP-AMP synthase, which underlies the type I IFN response. Genetically activating cyclic GMP-AMP synthase in AML cells blocked leukemogenesis. We also report synergy of a PRMT9 inhibitor with anti-programmed cell death protein 1 in eradicating AML. Overall, we conclude that PRMT9 functions in survival and immune evasion of both LSCs and non-LSCs; targeting PRMT9 may represent a potential anticancer strategy.

Sites of Cre-recombinase activity in mouse lines targeting skeletal cells

The Cre/Lox system is a powerful tool in the biologist's toolbox, allowing loss-of-function and gain-of-function studies, as well as lineage tracing, through gene recombination in a tissue-specific and inducible manner. Evidence indicates, however, that Cre transgenic lines have a far more nuanced and broader pattern of Cre activity than initially thought, exhibiting "off-target" activity in tissues/cells other than the ones they were originally designed to target. With the goal of facilitating the comparison and selection of optimal Cre lines to be used for the study of gene function, we have summarized in a single manuscript the major sites and timing of Cre activity of the main Cre lines available to target bone mesenchymal stem cells, chondrocytes, osteoblasts, osteocytes, tenocytes, and osteoclasts, along with their reported sites of "off-target" Cre activity. We also discuss characteristics, advantages, and limitations of these Cre lines for users to avoid common risks related to overinterpretation or misinterpretation based on the assumption of strict cell-type specificity or unaccounted effect of the Cre transgene or Cre inducers. © 2021 American Society for Bone and Mineral Research (ASBMR).

Aldo-keto reductase family 1 member C1 regulates the osteogenic differentiation of human ASCs by targeting the progesterone receptor

BACKGROUND

As a promising way to repair bone defect, bone tissue engineering has attracted a lot of attentions from researchers in recent years. Searching for new molecular target to modify the seed cells and enhance their osteogenesis capacity is one of the hot topics in this field. As a member of aldo-keto reductase family, aldo-keto reductase family 1 member C1 (AKR1C1) is reported to associate with various tumors. However, whether AKR1C1 takes part in regulating differentiation of adipose-derived mesenchymal stromal/stem cells (ASCs) and its relationship with progesterone receptor (PGR) remain unclear.

METHODS

Lost-and-gain-of-function experiments were performed using knockdown and overexpression of AKR1C1 to identify its role in regulating osteogenic and adipogenic differentiation of hASCs in vitro. Heterotypic bone and adipose tissue formation assay in nude mice were used to conduct the in vivo experiment. Plasmid and siRNA of PGR, as well as western blot, were used to clarify the mechanism AKR1C1 regulating osteogenesis.

RESULTS

Our results demonstrated that AKR1C1 acted as a negative regulator of osteogenesis and a positive regulator of adipogenesis of hASCs via its enzyme activity both in vitro and in vivo. Mechanistically, PGR mediated the regulation of AKR1C1 on osteogenesis.

CONCLUSIONS

Collectively, our study suggested that AKR1C1 could serve as a regulator of osteogenic differentiation via targeting PGR and be used as a new molecular target for ASCs modification in bone tissue engineering.

High susceptibility to collagen-induced arthritis in mice with progesterone receptors selectively inhibited in osteoprogenitor cells

Background

Progesterone receptor (PR) affects immunomodulation, and lack of PR in osteoprogenitor cells primarily affects pathways associated with immunomodulation, especially in males. In this study, we selectively deleted PR from osteoprogenitor cells using Prx1-Cre to evaluate the tissue-specific effects of PR on the pathegenesis of inflammatary arthritis (IA).

Methods

Collagen-induced arthritis (CIA) was used as an IA animal model. Both male and female PR^ΔPrx1 mice and their wild-type (WT) littermates were immunized with collagen II (CII) emulsified complete Freund’s adjuvant (CFA). Joint erosion, inflammation, and cartilage damage were assessed using a semiquantitative histologic scoring system. Bone volume and erosions in knee and ankle joints were quantitated using microCT and histology.

Results

Bone erosions developed in both paw joints in 37.5% and 41.7% of the WT and PR^ΔPrx1 female mice and in 45.4 and 83.3% of the WT and PR^ΔPrx1 male mice, respectively. Also, both joint damage and subchondral bone erosions were significantly more severe in male PRcKO-CIA mice than in male WT-CIA mice. Female PR^ΔPrx1 mice also developed higher bone loss in the knee joints than the KO-normal or WT-CIA females although with less severity compared to the male mice.

Conclusions

The presence of PR in osteoprogenitor cells decreased the development of collagen-induced arthritis and might help to explain the sex differences observed in human inflammatory arthritis.

A comparative study of hBM-MSCs' differentiation toward osteogenic lineage in the presence of progesterone and estrogen hormones separately and concurrently in vitro

Promising cell sources for tissue engineering comprise bone marrow derived-mesenchymal stem cells (BM-MSCs) that have multiple differentiation potentials. Also, sex hormones act as important elements in bone development and maintenance, and the roles of two female sex steroid hormones known as estrogen (17-β estradiol) and progesterone in osteogenic differentiation of human BM-MSCs (hBM-MSCs) are studied. For this purpose, hBM-MSCs were treated with a 1 × 10^-6  M concentration of 17-β estradiol and progesterone separately and simultaneously while the optimum concentrations were obtained by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Osteogenic differentiation tests including measurement of alkaline phosphatase (ALP) enzyme activity, the content of total mineral calcium, mineralized matrix staining by Alizarin Red and Von Kossa solutions, real-time reverse transcription polymerase chain reaction (RT-PCR), and immunofluorescence staining were carried out on Days 7 and 14 of differentiation. To exhibit the morphology of the cells, the BM-MSCs were stained with acridine orange (AO) solution. In this study, the results of ALP activity assay, calcium content and real-time RT-PCR assay and also all tests of differentiation staining have shown that 17-β estradiol has been recognized as an enhancing factor of osteogenic differentiation. Furthermore, MTT assay and AO staining revealed progesterone as a factor that seriously improved the proliferation of hBM-MSCs. Generally, the 17-β estradiol individually or in the presence of progesterone has more effects on BM-MSCs' osteogenic differentiation compared to progesterone alone. In this study, it is indicated that the effect of the 17-β estradiol and progesterone concurrently was the same as individual 17-β estradiol on the differentiation of hBM-MSCs.

Inhibition of mesenchymal stromal cells' chemotactic effect to ameliorate paraquat-induced pulmonary fibrosis

BACKGROUND

Paraquat (PQ) poisoning is one of the leading causes of suicide attempts in China signature by acute onset of respiratory distress with massive matrix production resulting in progressive pulmonary fibrosis. There is no specific antidote and mortality remains high without effective treatment available. The cellular mechanisms underlying PQ-induced pulmonary fibrosis remain largely unknown.

OBJECTIVES

To determine the origin of mesenchymal stem cells (MSCs) migrated to the lung after PQ exposure and their roles in PQ-induced pulmonary fibrosis, to further explore the possible mechanisms involved in these processes, and to help finding novel therapies.

METHODS

We used a combination of lineage tracking techniques to investigate the contributions of several cells of MSCs, marked by Nestin or CXCL12, and traced their co-expression of α-smooth muscle actin (α-SMA), a marker for fibrosis, or their co-location with matrix production, marked by collagen-1 production (Col1-GFP) following PQ exposure. Then, we used a CXCL12flox/flox; Prx1-Cre mice and a pharmacologic agent AMD3100 to selectively deplete chemotactic mechanism of the MSCs, and tested pro-fibrotic pathways, fibrotic processes and survival of mice after PQ exposure.

RESULTS

Our results showed that after paraquat exposure, the residential Nestin + MSCs were quickly expanded and contributed to extracellular matrix production. Moreover, when we used a CXCL12flox/flox; Prx1-Cre mice to selectively deplete chemotactic mechanism of the MSC, we found that PQ exposure in these mice failed to activate pro-fibrotic pathways including TGF-β, Wnt and EGFR signaling. Furthermore, when the chemotactic effect of MSCs via CXCL12 was blocked by a pharmacologic agent, AMD3100, it alleviated the development of the fibrotic process and improved survival rate in mice exposed to PQ.

CONCLUSION

Collectively, our data suggest paraquat intoxication rapidly activated Nestin + MSCs and that blocking chemotactic effects of MSCs by perivascular CXCL12 inhibition may effectively protect pulmonary injury following paraquat exposure. Our results revealed a novel mechanism for post-PQ lung injury and indicated a novel therapeutic option to attenuate fibrosis induced by paraquat.

Tyrosine kinase inhibitors and mesenchymal stromal cells: effects on self-renewal, commitment and functions

The hope of selectively targeting cancer cells by therapy and eradicating definitively malignancies is based on the identification of pathways or metabolisms that clearly distinguish “normal” from “transformed” phenotypes. Some tyrosine kinase activities, specifically unregulated and potently activated in malignant cells, might represent important targets of therapy. Consequently, tyrosine kinase inhibitors (TKIs) might be thought as the “vanguard” of molecularly targeted therapy for human neoplasias. Imatinib and the successive generations of inhibitors of Bcr-Abl1 kinase, represent the major successful examples of TKI use in cancer treatment. Other tyrosine kinases have been selected as targets of therapy, but the efficacy of their inhibition, although evident, is less definite. Two major negative effects exist in this therapeutic strategy and are linked to the specificity of the drugs and to the role of the targeted kinase in non-malignant cells. In this review, we will discuss the data available on the TKIs effects on the metabolism and functions of mesenchymal stromal cells (MSCs). MSCs are widely distributed in human tissues and play key physiological roles; nevertheless, they might be responsible for important pathologies. At present, bone marrow (BM) MSCs have been studied in greater detail, for both embryological origins and functions. The available data are evocative of an unexpected degree of complexity and heterogeneity of BM-MSCs. It is conceivable that this grade of intricacy occurs also in MSCs of other organs. Therefore, in perspective, the negative effects of TKIs on MSCs might represent a critical problem in long-term cancer therapies based on such inhibitors.

Sex dimorphic regulation of osteoprogenitor progesterone in bone stromal cells

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.

The Effect of Estradiol on the Growth Plate Chondrocytes of Limb and Spine from Postnatal Mice in vitro: The Role of Estrogen-Receptor and Estradiol Concentration

Objectives: Skeletal development is a complex process. Little is known about the different response of limb or spine growth plate chondrocytes (LGP or SGP) to the estrogen level and the role of estrogen receptor (ER) during postnatal stage.

Methods: LGP and SGP chondrocytes were isolated from 50 one-week mice and treated with different concentrations of 17β-estradiol. Cell viability was measured by cell counting kit-8 (CCK-8). The expression of collagen II and X were evaluated by real-time PCR and Western blotting. Then, the response of LGP or SGP chondrocyte after with or without estradiol and specific ER antagonists to block the effect of ERs were also measured by Western blotting and immunofluorescence.

Results: Estradiol promoted the chondrogensis of the chondrocytes in vitro and achieved the maximal expression of type II collagen at the dose of 10^-7 M. Additionally, the regulatory effect of estradiol on the chondrogenesis can be mainly relied on ERα. The LGP chondrocytes were more sensitive to the estradiol treatment than SGP in the expression of type II collagen.

Conclusions: Estrogen at a pharmacological concentration (10^-7 M) could stimulate the maximal production of type II collagen in the growth plate chondrocytes in vitro, which exerts its activity mainly through ERα in the chondrogenesis. Furthermore, the LGP chondrocytes were more sensitive to the estradiol treatment than SGP in the chondrogenesis.

Changes of serum sclerostin and Dickkopf-1 levels during the menstrual cycle. A pilot study

Studies in postmenopausal women have identified sclerostin as a strong candidate for mediating estrogen effects on the skeleton. The effects of estradiol on sclerostin and Dickkopf-1 in younger women remain unclear. The main purpose of this study is to investigate the impact of estradiol and gonadotrophins fluctuations during the menstrual cycle on circulating sclerostin and Dickkopf-1 levels and the possible relationship of sclerostin and Dickkopf-1 with changes in N-terminal propeptide of type 1 collagen and C-telopeptide of collagen cross-links. Fourteen healthy premenopausal Caucasian women, with regular menses, aged 33.6 ± 4.5 years participated. After the first day of menstruation and every-other-day up to the next menses, fasting serum estradiol, luteinizing hormone, follicle-stimulating hormone, sclerostin, Dickkopf-1, N-terminal propeptide of type 1 collagen, and C-telopeptide of collagen cross-links levels were measured in peripheral blood. Participants completed dietary questionnaires and the International physical activity questionnaire during the cycle. Neither sclerostin nor Dickkopf-1 levels changed significantly across the menstrual cycle (p = 0.18 and p = 0.39, respectively), while N-terminal propeptide of type 1 collagen and C-telopeptide of collagen cross-links levels presented cyclic variation (p < 0.001 and p = 0.004, respectively). Baseline sclerostin (29.23 ± 10.62 pmol/L) positively correlated with N-terminal propeptide of type 1 collagen (r = 0.71, p < 0.01) and C-telopeptide of collagen cross-links (r = 0.63, p < 0.05), while Dickkopf-1 (4.82 ± 2.23 pmol/L) correlated positively with N-terminal propeptide of type 1 collagen (r = 0.56, p < 0.05). Mid-cycle E2 levels presented significant negative association with the percent decrease of C-telopeptide of collagen cross-links at all-time points during the luteal period (r = -0.60 to -0.68, p < 0.05-0.01). Circulating sclerostin and Dickkopf-1 levels do not change across the menstrual cycle and do not demonstrate any relationship with estradiol in premenopausal women. Further investigation is needed concerning the role of sclerostin and Dickkopf-1 on bone turnover in young estrogen-sufficient women.