Glucocorticoids Decrease Longitudinal Bone Growth in Pediatric Kidney Transplant Recipients by Stimulating the FGF23/FGFR3 Signaling Pathway

Novel evidence in vivo: Berberine ameliorated glucocorticoid-induced post-natal growth retardation by regulating the GH/IGF-1 axis through KMT1A downregulation

BACKGROUND

Glucocorticoids (GCs) are widely used anti-inflammatory agents that inhibit growth in children. However, their mechanisms and effect on the growth hormone (GH)/insulin-like growth factor (IGF)-1 axis remain unclear.

PURPOSE

This study, we aimed to establish a mouse model of GC-induced growth retardation during the critical growth period and explore the underlying mechanisms. Additionally, we aimed to identify novel biomarkers and potential therapeutic agents for GC-induced growth impairment.

METHODS

Four-week-old mice were treated with GCs for two weeks and subsequently assessed for body length, weight, and body composition. Immunohistochemical analysis of the growth plate in the proximal tibia and biochemical assays of blood were performed to evaluate changes in growth plate length and GH/IGF-1 axis. KMT1A expression and its effects on Ghr expression were examined, and the impact of berberine on GC-induced growth retardation was assessed.

RESULTS

GCs significantly reduced growth by impairing growth plate expansion, disrupting the GH/IGF-1 axis, and downregulation of the GH receptor (Ghr) and Igf-1 levels in the liver. These changes were attributed to the upregulation of the H3K9 trimethyltransferase KMT1A, which decreased Ghr transcription in the liver. In vitro screening of natural compounds revealed that berberine chloride hydrate decreased the KMT1A levels and increased GHR levels. Berberine chloride hydrate also effectively ameliorated GC-induced growth retardation by restoring Ghr expression via KMT1A inhibition, thereby enhancing the circulating IGF-1 levels.

CONCLUSION

Overall, our findings highlight the potential of targeting KMT1A using berberine chloride hydrate as an epigenetic modifier to treat GC-induced growth impairment.

Chronic Kidney Disease-Mineral Bone Disorder (CKD-MBD) in Pediatric Kidney Transplant Recipients

Kidney transplantation remains the gold standard treatment for end-stage kidney disease (ESKD), effectively alleviating numerous comorbidities and offering a substantial survival advantage over long-term dialysis. Despite advancements in immunosuppressive regimens and improvements in graft and patient survival rates, extended patient longevity brings an accumulating burden and complexity of bone disease in this population, which often goes underrecognized. The present study reviews the pathophysiology of CKD-MBD in pediatric KTR, focusing on the progression of bone disease before and after transplantation. We aim to enhance understanding of available screening options, highlighting their advantages and limitations, to support more informed decision-making in CKD-MBD management.

Cushing's disease and bone

Bone impairment associated with Cushing's disease (CD) is a complex disorder, mainly involving deterioration of bone quality and resulting in an increased fracture rate, often despite normal bone mineral density. Bone complications are common in patients with CD at the time of diagnosis but may persist even after successful treatment. There is currently no agreement on the optimal diagnostic methods, thresholds for anti-osteoporotic therapy and its timing in CD. In this review, we summarize the current data on the pathophysiology, diagnostic approach and management of bone complications in CD.

Fibroblast growth factor 23 inhibition attenuates steroid-induced osteonecrosis of the femoral head through pyroptosis

Steroid-induced osteonecrosis of the femoral head (SONFH) is the predominant cause of non-traumatic osteonecrosis of the femoral head (ONFH). Impaired blood supply and reduced osteogenic activity of the femoral head are the key pathogenic mechanisms of SONFH. Fibroblast growth factor 23 (FGF23) levels are not only a biomarker for early vascular lesions caused by abnormal mineral metabolism, but can also act directly on the peripheral vascular system, leading to vascular pathology. The aim of this study was to observe the role of FGF23 on bone microarchitecture and vascular endothelium, and to investigate activation of pyroptosis in SONFH. Lipopolysaccharide (LPS) combined with methylprednisolone (MPS) was applied for SONFH mouse models, and adenovirus was used to increase or decrease the level of FGF23. Micro-CT and histopathological staining were used to observe the structure of the femoral head, and immunohistochemical staining was used to observe the vascular density. The cells were further cultured in vitro and placed in a hypoxic environment for 12 h to simulate the microenvironment of vascular injury during SONFH. The effect of FGF23 on osteogenic differentiation was evaluated using alkaline phosphatase staining, alizarin red S staining and expression of bone formation-related proteins. Matrigel tube formation assay in vitro and immunofluorescence were used to detect the ability of FGF23 to affect endothelial cell angiogenesis. Steroids activated the pyroptosis signaling pathway, promoted the secretion of inflammatory factors in SONFH models, led to vascular endothelial dysfunction and damaged the femoral head structure. In addition, FGF23 inhibited the HUVECs angiogenesis and BMSCs osteogenic differentiation. FGF23 silencing attenuated steroid-induced osteonecrosis of the femoral head by inhibiting the pyroptosis signaling pathway, and promoting osteogenic differentiation of BMSCs and angiogenesis of HUVECs in vitro.

[Clinical study on growth impairment induced by oral glucocorticoids based on FGF23/Klotho homeostasis observations]

OBJECTIVES

To observe the correlation between growth impairment induced by long-term oral glucocorticoids (GC) therapy and the ratio of FGF23/Klotho in children with primary nephrotic syndrome (PNS).

METHODS

A prospective study was conducted on 56 children with GC-sensitive PNS who had discontinued GC therapy for more than 3 months and revisited the Department of Pediatrics of the First Affiliated Hospital of Henan University of Traditional Chinese Medicine between June 2022 and December 2022. After monitoring qualitative and quantitative urine protein levels upon admission, the children with proteinuria relapse were treated with GC (GC group; n=29), while those without relapse did not receive GC treatment (non-GC group; n=27). In addition, 29 healthy children aged 3 to prepuberty were selected as the control group. Height, bone age, growth rate, and the FGF23/Klotho ratio were compared among the groups. The correlations of the FGF23/Klotho ratio with height, bone age, and growth rate were analyzed.

RESULTS

The FGF23/Klotho ratio in the GC group was significantly higher than that in the non-GC group after 1 month of GC therapy (P<0.05), and the height and bone age growth rates within 6 months were lower than those in the non-GC group (P<0.05). Correlation analysis showed significant negative correlations between the FGF23/Klotho ratio after 1 month of treatment and the growth rates of height and bone age within 6 months in children with PNS (r=-0.356 and -0.436, respectively; P<0.05).

CONCLUSIONS

The disturbance in FGF23/Klotho homeostasis is one of the mechanisms underlying the growth impairment caused by long-term oral GC therapy.

Glucocorticoid induced bone disorders in children: Research progress in treatment mechanisms

Long-term or supra-physiological dose of glucocorticoid (GC) application in clinic can lead to impaired bone growth and osteoporosis. The side effects of GC on the skeletal system are particularly serious in growing children, potentially causing growth retardation or even osteoporotic fractures. Children's bone growth is dependent on endochondral ossification of growth plate chondrocytes, and excessive GC can hinder the development of growth plate and longitudinal bone growth. Despite the availability of drugs for treating osteoporosis, they have failed to effectively prevent or treat longitudinal bone growth and development disorders caused by GCs. As of now, there is no specific drug to mitigate these severe side effects. Traditional Chinese Medicine shows potential as an alternative to the current treatments by eliminating the side effects of GC. In summary, this article comprehensively reviews the research frontiers concerning growth and development disorders resulting from supra-physiological levels of GC and discusses the future research and treatment directions for optimizing steroid therapy. This article may also provide theoretical and experimental insight into the research and development of novel drugs to prevent GC-related side effects.

Exogenous growth hormone functionally alleviates glucocorticoid-induced longitudinal bone growth retardation in male rats by activating the Ihh/PTHrP signaling pathway

Glucocorticoid (GC)-induced longitudinal bone growth retardation is a common and severe adverse effect in pediatric patients receiving GC immunosuppressive therapy. Molecular mechanisms underlying GC-induced growth inhibition are unclear. GC withdrawal following short-term high-dose use is common, including in the immediate post-transplant period. However, whether skeleton growth recovery is sufficient or whether growth-promoting therapy is required following GC withdrawal is unknown. The aim of this study was to investigate the effect of exogenous growth hormone (GH) on growth plate impairment in GC-induced longitudinal bone growth retardation. Here, apoptotic chondrocytes in the hypertrophic layer of growth plates increased whereas Indian Hedgehog (Ihh) and Parathyroid Hormone Related Peptide (PTHrP) protein levels in the growth plate decreased following GC exposure. The hypertrophic zone of the growth plate expanded following GC withdrawal. Subcutaneously injected GH penetrated the growth plate and modified its organization in rats following GC withdrawal. Ihh and PTHrP expression in GC-induced apoptotic chondrocytes decreased in vitro. GH promoted chondrocyte proliferation by activating Ihh/PTHrP signaling. Downregulating Ihh using specific siRNAs increased chondrocyte apoptosis and inhibited PTHrP, Sox9, and type II collagen (Col2a1) protein expression. GH inhibited apoptosis of Ihh-deficient growth plate chondrocytes by upregulating PTHrP, Sox9, and Col2a1 expression. Thus, reversal of the effect of GC on growth plate impairment following its withdrawal is insufficient, and exogenous GH provides growth plate chondral protection and improved longitudinal growth following GC withdrawal by acting on the Ihh/PTHrP pathway.

Current status of glucocorticoid usage in solid organ transplantation

Glucocorticoids (GCs) have been the mainstay of immunosuppressive therapy in solid organ transplantation (SOT) for decades, due to their potent effects on innate immunity and tissue protective effects. However, some SOT centers are reluctant to administer GCs long-term because of the various related side effects. This review summarizes the advantages and disadvantages of GCs in SOT. PubMed and Scopus databases were searched from 2011 to April 2021 using search syntaxes covering “transplantation” and “glucocorticoids”. GCs are used in transplant recipients, transplant donors, and organ perfusate solution to improve transplant outcomes. In SOT recipients, GCs are administered as induction and maintenance immunosuppressive therapy. GCs are also the cornerstone to treat acute antibody- and T-cell-mediated rejections. Addition of GCs to organ perfusate solution and pretreatment of transplant donors with GCs are recommended by some guidelines and protocols, to reduce ischemia-reperfusion injury peri-transplant. GCs with low bioavailability and high potency for GC receptors, such as budesonide, nanoparticle-mediated targeted delivery of GCs to specific organs, and combination use of dexamethasone with inducers of immune-regulatory cells, are new methods of GC application in SOT patients to reduce side effects or induce immune-tolerance instead of immunosuppression. Various side effects involving different non-targeted organs/tissues, such as bone, cardiovascular, neuromuscular, skin and gastrointestinal tract, have been noted for GCs. There are also potential drug-drug interactions for GCs in SOT patients.

Practice patterns and influence of allograft nephrectomy in pediatric kidney re-transplantation: A pediatric nephrology research consortium study

INTRODUCTION

There are no guidelines regarding management of failed pediatric renal transplants.

MATERIALS & METHODS

We performed a first of its kind multicenter study assessing prevalence of transplant nephrectomy, patient characteristics, and outcomes in pediatric renal transplant recipients with graft failure from January 1, 2006, to December 31, 2016.

RESULTS

Fourteen centers contributed data on 186 pediatric recipients with failed transplants. The 76 recipients that underwent transplant nephrectomy were not significantly different from the 110 without nephrectomy in donor or recipient demographics. Fifty-three percent of graft nephrectomies were within a year of transplant. Graft tenderness prompted transplant nephrectomy in 91% (P < .001). Patients that underwent nephrectomy were more likely to have a prior diagnosis of rejection within 3 months (43% vs 29%; P = .04). Nephrectomy of allografts did not affect time to re-listing, donor source at re-transplant but significantly decreased time to (P = .009) and incidence (P = .0002) of complete cessation of immunosuppression post-graft failure. Following transplant nephrectomy, recipients were significantly more likely to have rejection after re-transplant (18% vs 7%; P = .03) and multiple rejections in first year after re-transplant (7% vs 1%; P = .03).

CONCLUSIONS

Practices pertaining to failed renal allografts are inconsistent-40% of failed pediatric renal allografts underwent nephrectomy. Graft tenderness frequently prompted transplant nephrectomy. There is no apparent benefit to graft nephrectomy related to sensitization; but timing / frequency of immunosuppression withdrawal is significantly different with slightly increased risk for rejection following re-transplant.

Growth in children on kidney replacement therapy: a review of data from patient registries

Growth retardation is a major complication in children with chronic kidney disease (CKD) and on kidney replacement therapy (KRT). Conversely, better growth in childhood CKD is associated with an improvement in several hard morbidity-mortality endpoints. Data from pediatric international registries has demonstrated that improvements in the overall conservative management of CKD, the search for optimal dialysis, and advances in immunosuppression and kidney transplant techniques have led to a significant improvement of final height over time. Infancy still remains a critical period for adequate linear growth, and the loss of stature during the first years of life influences final height. Preliminary new original data from the European Society for Paediatric Nephrology/European Renal Association-European Dialysis and Transplant Association (ESPN/ERA-EDTA) Registry confirm an association between the final height and the height attained at 2 years in children on KRT.

Hydrogen sulfide inhibits calcium and phosphorus loss after fracture by negatively regulating glucocorticoid/glucocorticoid receptor α

AIMS

Post-fracture calcium and phosphorus excretion is greater than influx, which might be caused by stress. Glucocorticoid is known to enhance calcium and phosphorous excretion, and hydrogen sulfide (H₂S) has been shown to exert inhibitory effects on glucocorticoid. Therefore, this study explored whether H₂S could inhibit calcium and phosphorus loss after fracture by regulating glucocorticoid and/or its receptor.

MAIN METHODS

The following properties were analyzed in rats with femur fractures: serum and urinary calcium and phosphorus (by colorimetry); bone turnover markers alkaline phosphatase, serum type 1 collagen amino terminal peptide, type 1 procollagen carboxy terminal peptide, and anti-tartaric acid phosphatase (by ELISA); factors related to calcium-phosphorus metabolism including glucocorticoid, parathyroid hormone, calcitonin, fibroblast growth factor 23, and 1,25(OH)₂D₃ (by ELISA); and sulfhydration of glucocorticoid receptor α in the kidney (by immunoprecipitation linked biotin-switch assay), after supplementing with mifepristone, the H₂S donor GYY4137 or H₂S generating enzyme inhibitors aminooxyacetic acid and propargylglycine.

KEY FINDINGS

Serum H₂S decreased and glucocorticoid secretion increased in rats post-fracture. The glucocorticoid receptor inhibitor mifepristone partly blunted calcium and phosphorus loss. Furthermore, supplementation with GYY4137 reduced glucocorticoid secretion; inhibited glucocorticoid receptor α activity by sulfhydration; downregulated vitamin D 1α-hydroxylase expression; and upregulated 24-hydroxylase, calbindin-D28k, and sodium phosphate cotransporter 2a expression in the kidney; thereby inhibiting calcium and phosphorus loss induced by fracture. Moreover, inhibiting endogenous H₂S generation showed opposite effects.

SIGNIFICANCE

Our findings suggest that H₂S antagonized calcium and phosphorus loss after fracture by reducing glucocorticoid secretion and inhibiting glucocorticoid receptor α activity by sulfhydration.

Glucocorticoids dexamethasone and prednisolone suppress fibroblast growth factor 23 (FGF23)

Fibroblast growth factor 23 (FGF23) is a hormone mainly secreted by bone cells. Its most prominent effects are the regulation of renal phosphate reabsorption and calcitriol (active vitamin D, 1,25(OH)₂D₃) formation, effects dependent on its co-receptor αKlotho. Besides these actions, further paracrine and endocrine effects exist. The production of FGF23 is regulated by 1,25(OH)₂D₃, parathyroid hormone, dietary phosphate intake, iron status, as well as inflammation. Glucocorticoids are hormones with anti-inflammatory properties and are, therefore, widely used for acute and chronic inflammatory diseases, autoimmune disorders, and malignancies. The present study explored whether glucocorticoids influence the production of FGF23 in vitro as well as in mice. Fgf23 transcription was analyzed by semi-quantitative real-time PCR. Serum concentrations of FGF23 and 1,25(OH)₂D₃ were measured by ELISA. Urinary phosphate and Ca²⁺ excretion were determined in metabolic cages. As a result, in UMR106 rat osteoblast-like cells and in MC3T3-E1 cells, both, dexamethasone and prednisolone, downregulated Fgf23 transcription and FGF23 protein synthesis. Dexamethasone increased Dmp1 and Phex (encoding FGF23-regulating genes) as well as Nfkbia (encoding NFκB inhibitor IκBα) transcription in UMR106 cells. In mice, a single injection of dexamethasone or prednisolone was followed by a significant decrease of serum C-terminal and intact FGF23 concentration and bone Fgf23 mRNA expression within 12 h. These effects were paralleled by increased renal phosphate excretion and enhanced 1,25(OH)₂D₃ formation. We conclude that a single glucocorticoid treatment strongly downregulates the FGF23 plasma concentration. KEY MESSAGES: Glucocorticoids dexamethasone and prednisolone suppress the formation of bone-derived hormone fibroblast growth factor 23 (FGF23) in vitro. The effect is accompanied by an upregulation of Dmp1, Phex, and IκBα, negative regulators of FGF23, in UMR106 osteoblast-like cells. Glucocorticoid receptor antagonist RU-486 attenuates the effect of dexamethasone on FGF23, Dmp1, and Phex. In mice, a single glucocorticoid dose suppresses FGF23 and enhances 1,25(OH)₂D₃ (active vitamin D).

Cortisol and Phosphate Homeostasis: Cushing's Syndrome Is Associated With Reversible Hypophosphatemia

OBJECTIVES

The influence of hypercortisolism on phosphate homeostasis is relatively unknown. A few previous studies have reported on patients with Cushing's syndrome (CS) with hypophosphatemia in whom serum phosphate normalized after initiation of treatment for CS. We aimed to investigate the prevalence of hypophosphatemia in CS, the association between the degree of hypercortisolism and serum phosphate and the change in serum phosphate after remission of CS. We compared the prevalence of hypophosphatemia in CS with the prevalence in the population-based Rotterdam Study (RS).

METHODS

Patients diagnosed with CS and treated at the Department of Endocrinology of Erasmus MC in the period of 2002-2020 were included and data was collected on age at diagnosis, sex, serum phosphate, calcium and potassium levels, kidney function and BMI. Using multivariate linear regression, we analyzed the association between 24h urinary free cortisol excretion (UFC) and serum phosphate. Changes in serum phosphate and covariates were tested with a repeated measurement ANOVA, using mean levels of laboratory values for the periods before remission, and 0-14 days and 15-180 days after remission.

RESULTS

Hypophosphatemia before treatment was present in 16% of the 99 CS patients with data on serum phosphate, 24h UFC and covariates. In comparison, the prevalence of hypophosphatemia in RS was 2.0-4.2%. Linear regression showed a negative association between the level of UFC and serum phosphate at diagnosis, which remained significant after adjusting for covariates [β -0.002 (95%CI -0.004; -0.0004), p=0.021]. A subset of 24 patients had additional phosphate measurements at 0-14 days and 15-180 days after remission. In this subgroup, serum phosphate significantly increased from 1.03 ± 0.17 mmol/L prior to remission to 1.22 ± 0.25 mmol/L 15-180 days after remission (p = 0.008). BMI decreased after remission [-1.1 kg/m², (95%CI -2.09 to -0.07), p=0.037]. Other covariates did not show an equivalent change over time.

CONCLUSION

In this retrospective study, we found that 16% of patients with CS had hypophosphatemia. Moreover, serum phosphate was related to the level of cortisoluria and increased after remission of CS. Potential underlying mechanisms related to urinary phosphate excretion and possibly involving FGF23, BMI and parathyroid hormone levels should be further explored.

CKD-MBD post kidney transplantation

Complications of chronic kidney disease-associated mineral and bone disorders (CKD-MBD) are frequently observed in pediatric kidney transplant recipients and are associated with high morbidity, including growth failure, leg deformities, bone pain, fractures, osteonecrosis, and vascular calcification. Post-transplant CKD-MBD is mainly due to preexisting renal osteodystrophy and cardiovascular changes at the time of transplantation, glucocorticoid treatment, and reduced graft function. In addition, persistent elevated levels of parathyroid hormone (PTH) and fibroblast growth factor 23 may cause hypophosphatemia, resulting in impaired bone mineralization. Patient monitoring should include assessment of growth, leg deformities, and serum levels of calcium, phosphate, magnesium, alkaline phosphatase, 25-hydroxyvitamin D, and PTH. Therapy should primarily focus on regular physical activity, preservation of transplant function, and steroid-sparing immunosuppressive protocols. In addition, adequate monitoring and treatment of vitamin D and mineral metabolism including vitamin D supplementation, oral phosphate, and/or magnesium supplementation, in case of persistent hypophosphatemia/hypomagnesemia, and treatment with active vitamin D in cases of persistent secondary hyperparathyroidism. The latter should be done using the minimum PTH-suppressive dosages aiming at the recommended CKD stage-dependent PTH target range. Finally, treatment with recombinant human growth hormone should be considered in patients lacking catch-up growth within the first year after transplantation.

Mechanisms Underlying Bone Loss Associated with Gut Inflammation

Patients with gastrointestinal diseases frequently suffer from skeletal abnormality, characterized by reduced bone mineral density, increased fracture risk, and/or joint inflammation. This pathological process is characterized by altered immune cell activity and elevated inflammatory cytokines in the bone marrow microenvironment due to disrupted gut immune response. Gastrointestinal disease is recognized as an immune malfunction driven by multiple factors, including cytokines and signaling molecules. However, the mechanism by which intestinal inflammation magnified by gut-residing actors stimulates bone loss remains to be elucidated. In this article, we discuss the main risk factors potentially contributing to intestinal disease-associated bone loss, and summarize current animal models, illustrating gut-bone axis to bridge the gap between intestinal inflammation and skeletal disease.

Bone biomarkers in de novo renal transplant recipients

Successful kidney transplantation (partly) corrects the physiologic and metabolic abnormalities driving chronic kidney disease - mineral and bone disorders. At the same time, renal transplant recipients are exposed to immunosuppressive agents that may affect bone metabolism. Bone biomarkers have been suggested as surrogates of or adjuncts to bone biopsy and imaging techniques to assess bone health and to classify risk of bone loss and fractures. Bone biomarkers may be classified as circulating factors that affect bone metabolism (commonly referred to as bone metabolism markers) or that reflect bone cell number and/or activity (commonly referred to as bone turnover markers). A growing body of evidence shows that successful renal transplantation has a major impact on both bone metabolism and bone turnover. Analytical issues, including the cross-reactivity with fragments, complicate the interpretation of bone biomarkers, especially in the setting of a rapid changing kidney function, as is the case after successful renal transplantation. Overall, bone turnover seems to decline following renal transplantation, but inter-individual variability is substantial. Preliminary evidence indicates that bone biomarkers may be useful in guiding mineral and bone therapy in renal transplant recipients.