Roles of the kidney in the formation, remodeling and repair of bone

p38 Signaling Mediates Naringin-Induced Osteogenic Differentiation of Porcine Metanephric Mesenchymal Cells

OBJECTIVE

To explore the potential of metanephric mesenchymal cells (MMCs) for osteogenesis and naringin's ability to enhance this process and its molecular mechanism.

METHODS

Porcine MMCs at 70 days of gestation were used as tool cells, cultured in osteogenic induction medium, identified by immunocytochemistry staining. Osteogenic potential of porcine MMCs and naringin's ability to enhance this process was tested by detecting changes in cell viability, alkaline phosphatase (ALP) activity, the expression of runt-related transcription factor 2 (Runx2), osteopontin (OPN) and osteocalcin (OCN), and the formation of mineralized nodules, and the application of the p38 signaling pathway inhibitor SB203580 vitiated the osteogenesis-promoting effect of naringin.

RESULTS

Immunocytochemical staining showed that the cells were Vimentin and Six2(+), E-cadherin and CK-18(-). Naringin can activate the p38 signaling pathway to enhance the osteogenesis of porcine MMCs by increasing cell viability, ALP activity, the expressions of Runx2, OPN and OCN, and the formation of mineralized nodules (P<0.05). The application of p38 signaling pathway inhibitor SB203580 vitiated the osteogenesis-promoting effect of naringin, manifested by decreased ALP activity, the expressions of Runx2, OPN and OCN, and the formation of mineralized nodules (P<0.05).

CONCLUSION

Naringin, the active ingredient of Chinese herbal medicine Rhizoma Drynariae for nourishing Shen (Kidney) and strengthening bone, enhances the osteogenic differentiation of renal MMCs through the p38 signaling pathway.

Chronic heat stress induces renal fibrosis and mitochondrial dysfunction in laying hens

BACKGROUND

Heat stress in laying hens negatively affects egg production and shell quality by disrupting the homeostasis of plasma calcium and phosphorus levels. Although the kidney plays an important role in calcium and phosphorus homeostasis, evidence regarding the effect of heat stress on renal injury in laying hens is yet to be elucidated. Therefore, the aim of this study was to evaluate the effects of chronic heat stress on renal damage in hens during laying periods.

METHODS

A total of 16 white-leghorn laying hens (32 weeks old) were randomly assigned to two groups (n = 8). One group was exposed to chronic heat stress (33 °C for 4 weeks), whereas the other group was maintained at 24 °C.

RESULTS

Chronic heat exposure significantly increased plasma creatinine and decreased plasma albumin levels (P < 0.05). Heat exposure also increased renal fibrosis and the transcription levels of fibrosis-related genes (COLA1A1, αSMA, and TGF-β) in the kidney. These results suggest that renal failure and fibrosis were induced by chronic heat exposure in laying hens. In addition, chronic heat exposure decreased ATP levels and mitochondrial DNA copy number (mtDNA-CN) in renal tissue, suggesting that renal mitochondrial dysfunction occurs under conditions of heat stress. Damaged mitochondria leak mtDNAs into the cytosol and mtDNA leakage may activate the cyclic GMP-AMP synthase (cGAS) stimulator of interferon genes (STING) signaling pathway. Our results showed that chronic heat exposure activated the cGAS-STING pathway as indicated by increased expression of MDA5, STING, IRF7, MAVS, and NF-κB levels. Furthermore, the expression of pro-inflammatory cytokines (IL-12) and chemokines (CCL4 and CCL20) was upregulated in heat-stressed hens.

CONCLUSIONS

These results suggest that chronic heat exposure induces renal fibrosis and mitochondrial damage in laying hens. Mitochondrial damage by heat stress may activate the mtDNA-cGAS-STING signaling and cause subsequent inflammation, which contributes to the progression of renal fibrosis and dysfunction.

Impact of Adipose Tissue Depot Harvesting Site on the Multilineage Induction Capacity of Male Rat Adipose-Derived Mesenchymal Stem Cells: An In Vitro Study

Recently, substantial attention has been paid toward adipose-derived mesenchymal stem cells (AdMSCs) as a potential therapy in tissue engineering and regenerative medicine applications. Rat AdMSCs (r-AdMSCs) are frequently utilized. However, the influence of the adipose depot site on the multilineage differentiation potential of the r-AdMSCs is still ambiguous. Hence, the main objective of this study was to explore the influence of the adipose tissue harvesting location on the ability of r-AdMSCs to express the stem-cell-related markers and pluripotency genes, as well as their differentiation capacity, for the first time. Herein, we have isolated r-AdMSCs from the inguinal, epididymal, peri-renal, and back subcutaneous fats. Cells were compared in terms of their phenotype, immunophenotype, and expression of pluripotency genes using RT-PCR. Additionally, we investigated their potential for multilineage (adipogenic, osteogenic, and chondrogenic) induction using special stains confirmed by the expression of the related genes using RT-qPCR. All cells could positively express stem cell marker CD 90 and CD 105 with no significant in-between differences. However, they did not express the hematopoietic markers as CD 34 and CD 45. All cells could be induced successfully. However, epididymal and inguinal cells presented the highest capacity for adipogenic and osteogenic differentiation (21.36-fold and 11.63-fold for OPN, 29.69-fold and 26.68-fold for BMP2, and 37.67-fold and 22.35-fold for BSP, respectively, in epididymal and inguinal cells (p < 0.0001)). On the contrary, the subcutaneous cells exhibited a superior potential for chondrogenesis over the other sites (8.9-fold for CHM1 and 5.93-fold for ACAN, (p < 0.0001)). In conclusion, the adipose tissue harvesting site could influence the differentiation capacity of the isolated AdMSCs. To enhance the results of their employment in various regenerative cell-based therapies, it is thus vital to take the collection site selection into consideration.

Long-Term Cola Intake Does Not Cause Evident Pathological Alterations in the Femoral Bone Microstructure: An Animal Study in Adult Mice

Short-term animal experiments and association studies in humans have shown that cola intake may have a detrimental impact on bone mineral density (BMD); however, other bone parameters have not been investigated. This study examined the effects of long-term cola consumption on the femoral bone microstructure using adult mice (n = 32) as an animal model, which were divided into water and cola groups depending on whether they received water or cola along with a standard rodent diet for 6 months. Micro-computed tomography revealed that cola intake did not significantly affect all measured parameters characterizing trabecular bone mass and microarchitecture, as well as cortical microarchitecture and geometry in both sexes, although a slight deterioration of these parameters was noted. Cola consumption also resulted in a slightly, statistically insignificant worsening of bone mechanical properties. In contrast to female mice, males receiving cola had a lower area of primary osteons' vascular canals. Nevertheless, long-term cola intake did not cause evident pathological alterations in the femur of adult mice, possibly due to a balanced diet and no restriction of physical activity. Therefore, the adverse effects of cola consumption on BMD, the only bone parameter studied so far, may be caused by other risk and lifestyle factors.

Diabetic Kidney Disease Is Associated With Increased Complications Following Operative Management of Ankle Fractures

Background:

Diabetes mellitus and peripheral neuropathy are established risk factors for complications in operatively treated ankle fractures. Generally, the presence of peripheral neuropathy and diabetic nephropathy have been used as independent variables in studies of diabetic ankle fracture cohorts but are typically treated as binary risk factors. Our purpose was to quantify the effects of risk factors on complication rate specific to diabetic patients undergoing ankle fracture fixation.

Methods:

We identified 617 rotational ankle fractures treated operatively at a single academic medical center from 2010 to 2019, of which 160 were identified as diabetic. Of these, 91 ankle fractures in 90 diabetic patients met criteria for retrospective review of clinical and radiographic data. Criteria included perioperative laboratory studies, including glycated hemoglobin (HbA1c) and estimated glomerular filtration rate (eGFR), as well as follow-up radiographs in the electronic record. We defined complications in this surgical cohort as deep surgical site infection, unplanned return to the operating room, and failure of fixation. Logistic regression was performed and odds ratios (ORs) calculated.

Results:

The overall complication rate was 28.6% (26/91) in this cohort. Median follow-up was 29 weeks (range: 5-520 weeks). Mean perioperative HbA1c in patients who experienced postoperative complications was 7.6% (range: 5.1%-14.2%) compared with 7.8% (range: 5.6%-13.5%) who did not ( P = .69). Diabetic patients with chronic kidney disease (eGFR <60 mL/min per body surface area) (OR 5.29, P = .006) and peripheral neuropathy (OR 4.61, P = .003) were at significantly higher risk of all complications compared with diabetic patients without these comorbidities. Of note, we did not find an association between perioperative HbA1c or body mass index and complication rate.

Conclusion:

Patients with diabetes complicated by chronic kidney disease are at significantly higher risk of complications following operative management of ankle fractures. Our study also corroborated previous reports that within this high-risk cohort, the presence of peripheral neuropathy is a significant risk factor for complications. These sequalae of diabetic disease are manifestations of microvascular disease, glycosylation of soft tissues, and impaired metabolic pathways. Identifying these risk factors in diabetic patients allows for patient-specific risk stratification, education, and management decisions of ankle fractures.

Level of Evidence:

Level III, retrospective cohort study.

Overview of Traditional and Environmental Factors Related to Bone Health

Bone mass in adulthood depends on growth and mineralization acquired during childhood and adolescence. It is well known that these stages of life are crucial for bone development, where genetic, nutritional, hormonal, and lifestyle factors play a significant role. Bone loss is normally a natural and slow process that begins years later after the peak bone mass is achieved and continues throughout the lifespan. Lifestyle choices in childhood and adolescence such as minimal physical activity, excessive caffeine or carbonated beverages intake, malnutrition, cigarette use, or high alcohol consumption and other factors like environmental pollutants can also negatively affect bone health and accelerate the bone loss process. The aim of this work is an overview of risk factors associated with inadequate bone health in early life.

Klotho and Mesenchymal Stem Cells: A Review on Cell and Gene Therapy for Chronic Kidney Disease and Acute Kidney Disease

Chronic kidney disease (CKD) and acute kidney injury (AKI) are public health problems, and their prevalence rates have increased with the aging of the population. They are associated with the presence of comorbidities, in particular diabetes mellitus and hypertension, resulting in a high financial burden for the health system. Studies have indicated Klotho as a promising therapeutic approach for these conditions. Klotho reduces inflammation, oxidative stress and fibrosis and counter-regulates the renin-angiotensin-aldosterone system. In CKD and AKI, Klotho expression is downregulated from early stages and correlates with disease progression. Therefore, the restoration of its levels, through exogenous or endogenous pathways, has renoprotective effects. An important strategy for administering Klotho is through mesenchymal stem cells (MSCs). In summary, this review comprises in vitro and in vivo studies on the therapeutic potential of Klotho for the treatment of CKD and AKI through the administration of MSCs.

High sodium chloride affects BMP-7 and 1α-hydroxylase levels through NCC and CLC-5 in NRK-52E cells

A diet high in sodium chloride (NaCl) can affect renal function damage and increase urinary calcium excretion, leading to bone loss. in renal tubules, Na-Cl co-transporter (NCC) and chloride channel 5 (CLC-5) are involved in regulating urinary calcium excretion. In addition, some cytokines, such as Bone morphogenetic protein 7 (BMP-7) and 1α-hydroxylase, are synthesized by renal tubules, which target on bone and play important roles on bone metabolism. However, the specific mechanisms between NaCl and these ion channels or cytokines still need investigations from many aspects. This study, in culture normal rat renal tubular epithelial NRK-52E cells, showed that high concentrations of NaCl significantly inhibited the cell viability and increased the cell apoptosis. High concentration of NaCl reduce bone mineral density (BMD), as demonstrated by the significantly increased mRNA and protein levels of NCC and osteopontin (OPN), but decreased the levels of CLC-5, BMP-7, and 1α-hydroxylase. In addition, we found that ovariectomized (OVX) rats on a high-salt diet for 12 weeks had altered levels of these indices in the renal cortices. Moreover, the BMD in fourth and fifth lumbar vertebra (LV4 and 5) and femurs were significantly decreased and bone microstructure was destroyed of these rats. We also demonstrated that high concentration of NaCl enhanced the inhibition of these cytokines which is beneficial to increase BMD, induced by modulating ion channels NCC and CLC-5. In conclusion, our results indicate that high concentration of NaCl reduce BMD by regulating ion channels NCC and CLC-5.

Age-associated changes in microRNAs affect the differentiation potential of human mesenchymal stem cells: Novel role of miR-29b-1-5p expression

Age-associated osteoporosis is widely accepted as involving the disruption of osteogenic stem cell populations and their functioning. Maintenance of the local bone marrow (BM) microenvironment is critical for regulating proliferation and differentiation of the multipotent BM mesenchymal stromal/stem cell (BMSC) population with age. The potential role of microRNAs (miRNAs) in modulating BMSCs and the BM microenvironment has recently gained attention. However, miRNAs expressed in rapidly isolated BMSCs that are naïve to the non-physiologic standard tissue culture conditions and reflect a more accurate in vivo profile have not yet been reported. Here we directly isolated CD271 positive (+) BMSCs within hours from human surgical BM aspirates without culturing and performed microarray analysis to identify the age-associated changes in BMSC miRNA expression. One hundred and two miRNAs showed differential expression with aging. Target prediction and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses revealed that the up-regulated miRNAs targeting genes in bone development pathways were considerably enriched. Among the differentially up-regulated miRNAs the novel passenger strand miR-29b-1-5p was abundantly expressed as a mature functional miRNA with aging. This suggests a critical arm-switching mechanism regulates the expression of the miR-29b-1-5p/3p pair shifting the normally degraded arm, miR-29b-1-5p, to be the dominantly expressed miRNA of the pair in aging. The normal guide strand miR-29b-1-3p is known to act as a pro-osteogenic miRNA. On the other hand, overexpression of the passenger strand miR-29b-1-5p in culture-expanded CD271+ BMSCs significantly down-regulated the expression of stromal cell-derived factor 1 (CXCL12)/ C-X-C chemokine receptor type 4 (SDF-1(CXCL12)/CXCR4) axis and other osteogenic genes including bone morphogenetic protein-2 (BMP-2) and runt-related transcription factor 2 (RUNX2). In contrast, blocking of miR-29b-1-5p function using an antagomir inhibitor up-regulated expression of BMP-2 and RUNX2 genes. Functional assays confirmed that miR-29b-1-5p negatively regulates BMSC osteogenesis in vitro. These novel findings provide evidence of a pathogenic anti-osteogenic role for miR-29b-1-5p and other miRNAs in age-related defects in osteogenesis and bone regeneration.

A Comparative Study of the Effect of Anatomical Site on Multiple Differentiation of Adipose-Derived Stem Cells in Rats

Mesenchymal stem cells (MSCs) derived from adipose tissue are evolved into various cell-based regenerative approaches. Adipose-derived stem cells (ASCs) isolated from rats are commonly used in tissue engineering studies. Still, there is a gap in knowledge about how the harvest locations influence and guide cell differentiation. This study aims to investigate how the harvesting site affects stem-cell-specific surface markers expression, pluripotency, and differentiation potential of ASCs in female Sprague Dawley rats. ASCs were extracted from the adipose tissue of the peri-ovarian, peri-renal, and mesenteric depots and were compared in terms of cell morphology. MSCs phenotype was validated by cell surfaces markers using flow cytometry. Moreover, pluripotent gene expression of Oct4, Nanog, Sox2, Rex-1, and Tert was evaluated by reverse transcriptase-polymerase chain reaction (RT-PCR). ASCs multipotency was evaluated by specific histological stains, and the results were confirmed by quantitative polymerase chain reaction (RT-qPCR) expression analysis of specific genes. There was a non-significant difference detected in the cell morphology and immunophenotype between different harvesting sites. ASCs from multiple locations were significantly varied in their capacity to differentiate into adipocytes, osteoblastic cells, and chondrocytes. To conclude, depot selection is a critical element that should be considered when using ASCs in tissue-specific cell-based regenerative therapies research.

Novel Dent disease 1 cellular models reveal biological processes underlying ClC-5 loss-of-function

Dent disease 1 (DD1) is a rare X-linked renal proximal tubulopathy characterized by low molecular weight proteinuria and variable degree of hypercalciuria, nephrocalcinosis and/or nephrolithiasis, progressing to chronic kidney disease. Although mutations in the electrogenic Cl-/H+ antiporter ClC-5, which impair endocytic uptake in proximal tubule cells, cause the disease, there is poor genotype-phenotype correlation and their contribution to proximal tubule dysfunction remains unclear. To further discover the mechanisms linking ClC-5 loss-of-function to proximal tubule dysfunction, we have generated novel DD1 cellular models depleted of ClC-5 and carrying ClC-5 mutants p.(Val523del), p.(Glu527Asp) and p.(Ile524Lys) using the human proximal tubule-derived RPTEC/TERT1 cell line. Our DD1 cellular models exhibit impaired albumin endocytosis, increased substrate adhesion and decreased collective migration, correlating with a less differentiated epithelial phenotype. Despite sharing functional features, these DD1 cell models exhibit different gene expression profiles, being p.(Val523del) ClC-5 the mutation showing the largest differences. Gene set enrichment analysis pointed to kidney development, anion homeostasis, organic acid transport, extracellular matrix organization and cell-migration biological processes as the most likely involved in DD1 pathophysiology. In conclusion, our results revealed the pathways linking ClC-5 mutations with tubular dysfunction and, importantly, provide new cellular models to further study DD1 pathophysiology.

The spanning plate as an internal fixator in complex distal radius fractures: a prospective cohort study

OBJECTIVE

Minimal invasive temporary spanning plate (SP) fixation of the wrist has been described as an alternative treatment method in complex distal radius fractures (DRFs). The purpose of this study is to conduct an outcome analysis of all consecutive DRFs treated by SP fixation representing the so far largest published patient cohort outside the United States.

METHODS

Indication for SP fixation include DRFs with severe metaphyseal comminution, radiocarpal fracture dislocations with concomitant ligamentous injuries and very distal intra-articular fractures lacking the possibility of adequate plate anchoring. All consecutive patients undergoing SP fixation of DRFs were prospectively included in a single level I trauma centre between 01/01/2018 and 31/12/2020. For functional and patient-rated outcome analysis only patients who completed the 12 month follow-up were included.

RESULTS

In the mentioned timeframe, a total of 562 DRFs were treated operatively of which 28 underwent SP fixation. Average age was 58.1 years (range 22-95 years). The fracture type ranged from AO/OTA type B1.1 to C3.3 and included 8 fracture dislocations. SP removal was performed on average 3.7 months after the initial operation (range 1.4-6.5 months). Twenty-five patients completed the 12 month follow-up (mean 14.5 months, range 12-24). Radiological evidence of fracture healing appeared on average 9.9 weeks (range 5-28 weeks) after the initial operation. One patient experienced asymptomatic non-union. Mean radial inclination, volar tilt and ulnar variance at 1 year were all within the acceptable limit predictive of symptomatic malunion. Complications included two patients with tendon rupture and one patient with extensor tendon adhesions needing tenolysis at the time of plate removal leaving an overall complication rate of 12%. There was no implant failure and no infection. Mean satisfaction score was 8.3 (range 4-10) and mean visual analogue scale for resting pain was 0.8 (range 0-5). The mean PRWE score was 17.9 (range 0-59.5) and the mean DASH score was 16.6 (range 0-60.8). Grip strength averaged 23 kg (range 4-74 kg) amounting to 68% of the opposite side. Range of motion regarding the extension/flexion, radial/ulnar abduction and pronation/supination arc reached 72%, 77% and 95% compared to the unaffected side, respectively.

CONCLUSIONS

The radiological, functional and patient-rated outcomes in this study are remarkably good considering the complexity of the included fractures. Therefore, this method represents a valuable alternative for the treatment of complex DRFs in selected patients.

Immunopathophysiology of trauma-related acute kidney injury

Physical trauma can affect any individual and is globally accountable for more than one in every ten deaths. Although direct severe kidney trauma is relatively infrequent, extrarenal tissue trauma frequently results in the development of acute kidney injury (AKI). Various causes, including haemorrhagic shock, rhabdomyolysis, use of nephrotoxic drugs and infectious complications, can trigger and exacerbate trauma-related AKI (TRAKI), particularly in the presence of pre-existing or trauma-specific risk factors. Injured, hypoxic and ischaemic tissues expose the organism to damage-associated and pathogen-associated molecular patterns, and oxidative stress, all of which initiate a complex immunopathophysiological response that results in macrocirculatory and microcirculatory disturbances in the kidney, and functional impairment. The simultaneous activation of components of innate immunity, including leukocytes, coagulation factors and complement proteins, drives kidney inflammation, glomerular and tubular damage, and breakdown of the blood-urine barrier. This immune response is also an integral part of the intense post-trauma crosstalk between the kidneys, the nervous system and other organs, which aggravates multi-organ dysfunction. Necessary lifesaving procedures used in trauma management might have ambivalent effects as they stabilize injured tissue and organs while simultaneously exacerbating kidney injury. Consequently, only a small number of pathophysiological and immunomodulatory therapeutic targets for TRAKI prevention have been proposed and evaluated.

Preclinical safety and efficacy of 24R,25-dihydroxyvitamin D3 or lactosylceramide treatment to enhance fracture repair

Background/Objective

Cyp24a1-null mice deficient in 24,25(OH)₂D₃ display impaired callus formation during the endochondral phase of bone fracture repair. The 24,25(OH)₂D₃ metabolite acted by binding to the TLC domain containing 3B isoform 2 (TLCD3B2, previously named FAM57B2) effector protein, which then synthesizes lactosylceramide (LacCer). Treatment with 24,25(OH)₂D₃ or LacCer restored callus size and mechanical properties in Cyp24a1-null mice.

Methods

To assess the safety of these molecules and test their efficacy for bone healing in wild-type, non-genetically modified mice, we treated 12-week-old, osteotomized C57BL/6 female mice with each compound for up to 21 days post-osteotomy. Control cohorts were injected with vehicle.

Results

Neither compound was found to exhibit any nephro- nor hepato-toxicity. Calcemia remained stable throughout the experiment and was unaffected by either treatment. Supplementation with 24,25(OH)₂D₃ increased circulating levels of this metabolite about 8-fold, decreased 1,25(OH)₂D₃ levels, and significantly increased circulating 1,24,25(OH)₃D₃ levels, suggesting 1?-hydroxylation of 24,25(OH)₂D₃. TLCD3B2 was found to be expressed in fracture callus at the surface of unmineralized or pre-mineralized cartilage on day 10 and day 12 post-osteotomy and to progressively recede to become undetectable by day 18. Treatment with 24,25(OH)₂D₃ or LacCer reduced the number of TLCD3B2-positive cells. Both treatments also significantly increased stiffness and elastic modulus of the healing bone callus.

Conclusion

Exogenous administration of 24,25(OH)₂D₃ or LacCer improved the biomechanical properties of repaired bones in wild-type animals without affecting circulating calcium levels or other blood parameters, demonstrating preclinical safety and efficacy.

Translational potential

Our data suggest the use of 24R,25-dihydroxyvitamin D₃ or lactosylceramide for ameliorating fracture healing in clinical practice.

Fibroblast growth factor 23 counters vitamin D metabolism and action in human mesenchymal stem cells

Chronic kidney disease (CKD) is associated with elevated circulating fibroblast growth factor 23 (FGF23), impaired renal biosynthesis of 1α,25-dihydroxyvitamin D (1α,25(OH)₂D), low bone mass, and increased fracture risk. Our previous data with human mesenchymal stem cells (hMSCs) indicated that vitamin D metabolism in hMSCs is regulated as it is in the kidney and promotes osteoblastogenesis in an autocrine/paracrine manner. In this study, we tested the hypothesis that FGF23 inhibits vitamin D metabolism and action in hMSCs. hMSCs were isolated from discarded marrow during hip arthroplasty, including two subjects receiving hemodialysis and a series of 20 subjects (aged 49-83 years) with estimated glomerular filtration rate (eGFR) data. The direct in vitro effects of rhFGF23 on hMSCs were analyzed by RT-PCR, Western immunoblot, and biochemical assays. Ex vivo analyses showed positive correlations for both secreted and membrane-bound αKlotho gene expression in hMSCs with eGFR of the subjects from whom hMSCs were isolated. There was downregulated constitutive expression of αKlotho, but not FGFR1 in hMSCs obtained from two hemodialysis subjects. In vitro, rhFGF23 countered vitamin D-stimulated osteoblast differentiation of hMSCs by reducing the vitamin D receptor, CYP27B1/1α-hydroxylase, biosynthesis of 1α,25(OH)₂D₃, and signaling through BMP-7. These data demonstrate that dysregulated vitamin D metabolism in hMSCs may contribute to impaired osteoblastogenesis and altered bone and mineral metabolism in CKD subjects due to elevated FGF23. This supports the importance of intracellular vitamin D metabolism in autocrine/paracrine regulation of osteoblast differentiation in hMSCs.

GDF11 promotes osteogenesis as opposed to MSTN, and follistatin, a MSTN/GDF11 inhibitor, increases muscle mass but weakens bone

MSTN, a member of the TGF-β family, has been widely shown to suppress muscle growth, leading to an intense effort being directed at targeting MSTN to treat patients with muscle loss. GDF11 is another TGF-β family member closely related to MSTN, but its postnatal function is less clear. Using conditional knockout techniques, we show that GDF11 enhances bone mass in contrast to MSTN, emphasizing that MSTN/GDF11 inhibitors, such as FST, can induce adverse effects on bone through GDF11 inhibition. Because most MSTN inhibitors also inhibit GDF11 due to the high sequence similarity between MSTN and GDF11, our findings suggest that their opposing roles must be carefully considered when developing MSTN inhibitors for clinical applications.

Growth and differentiation factor 11 (GDF11) and myostatin (MSTN) are closely related transforming growth factor β (TGF-β) family members, but their biological functions are quite distinct. While MSTN has been widely shown to inhibit muscle growth, GDF11 regulates skeletal patterning and organ development during embryogenesis. Postnatal functions of GDF11, however, remain less clear and controversial. Due to the perinatal lethality of Gdf11 null mice, previous studies used recombinant GDF11 protein to prove its postnatal function. However, recombinant GDF11 and MSTN proteins share nearly identical biochemical properties, and most GDF11-binding molecules have also been shown to bind MSTN, generating the possibility that the effects mediated by recombinant GDF11 protein actually reproduce the endogenous functions of MSTN. To clarify the endogenous functions of GDF11, here, we focus on genetic studies and show that Gdf11 null mice, despite significantly down-regulating Mstn expression, exhibit reduced bone mass through impaired osteoblast (OB) and chondrocyte (CH) maturations and increased osteoclastogenesis, while the opposite is observed in Mstn null mice that display enhanced bone mass. Mechanistically, Mstn deletion up-regulates Gdf11 expression, which activates bone morphogenetic protein (BMP) signaling pathway to enhance osteogenesis. Also, mice overexpressing follistatin (FST), a MSTN/GDF11 inhibitor, exhibit increased muscle mass accompanied by bone fractures, unlike Mstn null mice that display increased muscle mass without fractures, indicating that inhibition of GDF11 impairs bone strength. Together, our findings suggest that GDF11 promotes osteogenesis in contrast to MSTN, and these opposing roles of GDF11 and MSTN must be considered to avoid the detrimental effect of GDF11 inhibition when developing MSTN/GDF11 inhibitors for therapeutic purposes.

Plasma Klotho concentration is associated with the presence, burden and progression of cerebral small vessel disease in patients with acute ischaemic stroke

Klotho is a soluble or membrane-bound anti-aging protein, whose protective actions are important for a prudential function of many organs. Because Klotho and cerebral small vessel disease (SVD) are associated with ageing process and endothelial dysfunction, it is possible that Klotho has an association with cerebral SVD. We aimed to investigate the association of plasma Klotho concentration with the presence, burden and progression of cerebral SVD. We prospectively enrolled 262 patients with first-ever acute cerebral infarction, performed brain MRI and collected their blood samples within 24 hours of admission. An enzyme-linked immunosorbent assay was used for evaluating plasma Klotho concentration. We estimated the total SVD score of each patient after determining the presence and burden of high-grade white matter hyperintensities (HWMHs), cerebral microbleeds (CMBs), high-grade perivascular spaces (HPVSs) and asymptomatic lacunar infarctions (ALIs). Univariate and multivariate analyses were conducted to investigate association of Klotho with cerebral SVD and the total SVD score. Of the 262 patients, 152 (58.0%) were men. The mean age of these patients was 64.7 years. The mean ± standard deviation of plasma Klotho concentration was 329.8 ± 194.1 pg/mL. In multivariate analysis, plasma Klotho concentration was negatively associated with the presence of HWMHs [Odds ratio (OR): 0.13, p = 0.047], HPVSs (OR: 0.22, p = 0.024) and ALIs (OR: 0.53, p = 0.021) but not associated with the presence of CMBs (OR: 0.39, p = 0.404). Plasma Klotho concentration was also negatively related to the total SVD score (unstandardized coefficients beta: −0.895, standard error = 0.317, p = 0.005, R² = 0.239). Furthermore, plasma Klotho concentration was negatively related to the presence (OR: 0.75, 95% CI: 0.59–0.96, p = 0.025) and severity of cerebral SVD progression (OR: 0.72, 95% CI: 0.56–0.92, p = 0.009). In conclusion, plasma Klotho concentration was negatively associated with the presence, burden and progression of cerebral SVD.

A Wearable Iron-Based Implant as an Intramedullary Nail in Tibial Shaft Fracture of Sheep

A stable repaired fracture is the key factor responsible for the recovery of a damaged bone. The iron-based implant is one of the biodegradable metals that have been proven safe as a fracture fixation device. The objective of our experimental approach was to examine the potential of the iron-based implant as a biodegradable metal in tibia shaft fracture in sheep chronically. The samples used for this experiment were iron-based and stainless steel implants. Each had a diameter of 5 mm. These samples were analyzed through 3 phases which are material characterization, in vitro and in vivo examination. The samples were examined using a scanning electron microscope with energy dispersive spectrometer and X-ray diffraction. Based on the analysis carried out, the samples contained 90,02% and 60,81% Fe for iron-based implant and stainless implant, respectively. Both implants maintained high viability when being in contact with calf pulmonary artery endothelial cells, indicating that both implants had a minimum response to the cell in a hemocytometer and methyl tetrazolium (MTT) assay. The systemic effect of the implants was observed using hematology and blood chemistry examination. Data collection also shows that both implants also had a minimum response to the erythrocytes, leucocytes, blood chemistry, and blood mineral during the period of observation. Therefore, it could be concluded that the iron-based implant is tolerable for a period of 9 months. It also has the potential to be used as a biodegradable orthopedic implant.

Natural Products as Potential Bone Therapies

Demands for natural products, in the form of botanicals, dietary supplements, and herbal medicine, for management of chronic diseases are increasing globally. Natural products might be an alternative for the management of bone health to meet the demands of a growing aging population. Different types of natural products, including Chinese herbal medicine decoctions, herbs, and isolated phytochemicals, have been demonstrated to exert bone protective effects. The most common types of bone protective bioactives are flavonoids, stilbene, triterpenoids, coumestans, lignans, and phenolic acid. The actions of natural products can be mediated by acting systemically on the hormonal axis or locally via their direct or indirect effects on osteogenesis, osteoclastogenesis, as well as adipogenesis. Furthermore, with the use of metabolomic and microbiome approaches to understand the actions of natural products, novel mechanisms that involve gut-brain-bone axis are also revealed. These studies provide evidence to support the use of natural products as bone therapeutics as well as identify new biological targets for novel drug development.

The Effects of a High-Protein Diet on Bone Mineral Density in Exercise-Trained Women: A 1-Year Investigation

The effects of long-term high-protein consumption (i.e., >2.2 g/kg/day) are unclear as it relates to bone mineral content. Thus, the primary endpoint of this investigation was to determine if consuming a high-protein diet for one year affected various parameters of body composition in exercise-trained women. This investigation is a follow-up to a prior 6-month study. Subjects were instructed to consume a high-protein diet (>2.2 g/kg/day) for one year. Body composition was assessed via dual-energy X-ray absorptiometry (DXA). Subjects were instructed to keep a food diary (i.e., log their food ~three days per week for a year) via the mobile app MyFitnessPal^®. Furthermore, a subset of subjects had their blood analyzed (i.e., basic metabolic panel). Subjects consumed a high-protein diet for one year (mean ± SD: 2.3 ± 1.1 grams per kilogram body weight daily [g/kg/day]). There were no significant changes for any measure of body composition over the course of the year (i.e., body weight, fat mass, lean body mass, percent fat, whole body bone mineral content, whole body T-score, whole body bone mineral density, lumbar bone mineral content, lumbar bone mineral density and lumbar T-score). In addition, we found no adverse effects on kidney function. Based on this 1-year within-subjects investigation, it is evident that a diet high in protein has no adverse effects on bone mineral density or kidney function.

FGF23-klotho axis, bone fractures, and arterial stiffness in dialysis: a case-control study

We performed a case-control study on 130 age- and sex-matched hemodialysis patients. In multivariate analysis, we observed that FGF23 levels were associated with fracture incidence and that soluble α-klotho levels were associated with the aortic-brachial arterial stiffness ratio.

INTRODUCTION

New bone markers such as sclerostin, Dickkopf-related protein 1 (DKK1), fibroblast growth factor-23 (FGF23), and α-klotho have been identified as potential key players in bone and vascular abnormalities of chronic kidney disease. Therefore, we aimed to assess whether these markers are associated with fractures, bone metabolism, and vascular stiffness in dialysis patients.

METHODS

In a prospective hemodialysis cohort, where plasma samples and vascular assessment were performed at baseline, we matched patients who experienced a fracture during follow-up with sex- and age-matched non-fractured patients on a 1:4 ratio. Sclerostin, DKK1, α-klotho, FGF23, and markers of bone formation (alkaline phosphatase and procollagen type 1-N terminal propeptide [P1NP]) and bone resorption (tartrate-resistant acid phosphatase 5b [TRAP5b]) were measured in baseline plasma samples. Aortic-brachial pulse wave velocity ratio, a blood pressure independent measure of arterial stiffness, was used to assess vascular stiffness at baseline.

RESULTS

We included 130 hemodialysis patients (26 fractured, 104 non-fractured) with a median follow-up of 42 months and a median age of 72 years. In multivariate Cox regression models, high FGF23 levels were associated with increased fracture incidence (adjusted HR = 2.97; 95% CI 1.18, 7.43). α-Klotho levels were associated with bone formation but not resorption markers. In both univariate and multivariable adjusted models, α-klotho levels were inversely associated with the aortic-brachial pulse wave velocity ratio (β = - 0.070; 95% CI - 0.133, - 0.006).

CONCLUSIONS

These results suggest a role for FGF23/klotho axis on bone and vascular metabolism in dialysis populations.

Bone regeneration strategies: Engineered scaffolds, bioactive molecules and stem cells current stage and future perspectives

Bone fractures are the most common traumatic injuries in humans. The repair of bone fractures is a regenerative process that recapitulates many of the biological events of embryonic skeletal development. Most of the time it leads to successful healing and the recovery of the damaged bone. Unfortunately, about 5-10% of fractures will lead to delayed healing or non-union, more so in the case of co-morbidities such as diabetes. In this article, we review the different strategies to heal bone defects using synthetic bone graft substitutes, biologically active substances and stem cells. The majority of currently available reviews focus on strategies that are still at the early stages of development and use mostly in vitro experiments with cell lines or stem cells. Here, we focus on what is already implemented in the clinics, what is currently in clinical trials, and what has been tested in animal models. Treatment approaches can be classified in three major categories: i) synthetic bone graft substitutes (BGS) whose architecture and surface can be optimized; ii) BGS combined with bioactive molecules such as growth factors, peptides or small molecules targeting bone precursor cells, bone formation and metabolism; iii) cell-based strategies with progenitor cells combined or not with active molecules that can be injected or seeded on BGS for improved delivery. We review the major types of adult stromal cells (bone marrow, adipose and periosteum derived) that have been used and compare their properties. Finally, we discuss the remaining challenges that need to be addressed to significantly improve the healing of bone defects.

Disease and Symptom Care: A Focus on Specific Needs of Patients With Multiple Myeloma

Patients with multiple myeloma (MM) often deal with short- and long-term side effects of the treatment and disease sequelae. Reasons for inadequately managed symptoms are multifactorial (e.g., the patient may fear treatment interruption, the clinician does not assess or address the symptoms) and can affect patients' ability to remain on the recommended treatment. This article provides background surrounding this supplement's development and describes the importance of symptom assessment and management.
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Calcium Bioavailability from Mineral Waters with Different Mineralization in Comparison to Milk and a Supplement

OBJECTIVE

The aim of the present study was to compare the bioavailability of calcium from 3 mineral waters with different concentrations of minerals with that of milk and a calcium supplement.

METHODS

A single-center, randomized controlled trial with a crossover design with 21 healthy men and women was conducted at the Institute of Food Science and Human Nutrition, Leibniz University Hannover. The participants consumed the 5 test products providing 300 mg of calcium each on 5 examination days with 1-week wash-out phases in between. Primary outcome variables were the area under the curve of serum calcium levels for 10-hour (AUC_0-10h) and 24-hour urinary calcium excretion.

RESULTS

In all groups, no significant differences in the AUC_0-10h of serum calcium levels as well as in the 24-hour urinary calcium excretion were observed. Likewise, mean changes in serum phosphate and urinary phosphate, as well as serum parathormone, showed no differences between the groups.

CONCLUSION

Given an equivalent bioavailability of calcium in all test products, neither a high concentration of SO₄^2- or of HCO₃ influenced the bioavailability of calcium. Accordingly, the use of mineral water with high concentrations of calcium constitutes a calorie-free calcium source that can improve calcium supply.

Klotho preservation via histone deacetylase inhibition attenuates chronic kidney disease-associated bone injury in mice

Bone loss and increased fracture are the devastating outcomes of chronic kidney disease-mineral and bone disorder (CKD-MBD) resulting from Klotho deficit-related mineral disturbance and hyperparathyroidism. Because Klotho down-regulation after renal injury is presumably affected by aberrant histone deacetylase (HDAC) activities, here we assess whether HDAC inhibition prevents Klotho loss and attenuates the CKD-associated bone complication in a mouse model of CKD-MBD. Mice fed adenine-containing diet developed the expected renal damage, a substantial Klotho loss and the deregulated key factors causally affecting bone remodeling, which were accompanied by a marked reduction of bone mineral density. Intriguingly, administration of a potent HDAC inhibitor trichostatin A (TSA) impressively alleviated the Klotho deficit and the observed alterations of serum, kidney and bone. TSA prevented Klotho loss by increasing the promoter-associated histone acetylation, therefore increasing Klotho transcription. More importantly the mice lacking Klotho by siRNA interference largely abolished the TSA protections against the serum and renal abnormalities, and the deranged bone micro-architectures. Thus, our study identified Klotho loss as a key event linking HDAC deregulation to the renal and bone injuries in CKD-MBD mice and demonstrated the therapeutic potentials of endogenous Klotho restoration by HDAC inhibition in treating CKD and the associated extrarenal complications.

Respiratory alkalosis may impair the production of vitamin D and lead to significant morbidity, including the fibromyalgia syndrome

Hyperventilation caused by physical and/or psychological stress may lead to significant respiratory alkalosis and an elevated systemic pH. The alkalotic pH may in turn suppress the normal renal release of phosphate into the urine, thereby interrupting the endogenous production of 1,25-dihydroxyvitamin D (calcitriol). This could cause a shortfall in its normal production, leading to a variety of adverse consequences. It might partially explain the pathogenesis of acute mountain sickness, a treatable disease characterized by severe hyperventilation secondary to the hypoxia of high altitude exposure. Milder degrees of hyperventilation due to different forms of stress may produce other conditions which share characteristics with acute mountain sickness. One of these may be the fibromyalgia syndrome, a chronic painful disorder for which no satisfactory treatment exists. Should fibromyalgia and acute mountain sickness have a common etiology, may they also share a common form of treatment? Evidence is presented to support this hypothesis.

Comparative bone regeneration study of hardystonite and hydroxyapatite as filler in critical-sized defect of rat calvaria

Bone grafts made from nanofibrous polycaprolactone loaded with bone-mimicking ceramic hydroxyapatite or hardystonite showed efficient bone healing in an in vivo rat skull defect model.

Nephrotoxicity of Kalach 360 SL: biochemical and histopathological findings

Kalach 360 SL (KL) is a commercial herbicide which contains 360 g/l of glyphosate used in both agricultural and urban areas throughout the world including Tunisia. We aimed to evaluate the effects of KL on rats' renal system. Female Wistar rats were divided into three groups: group 1 (n = 6) received a standard diet and served as control, groups 2 and 3 (n = 12 each) received 0.07 ml (D1: 126 mg/kg), and 0.175 ml (D2: 315 mg/kg) of KL, respectively, for 60 d. The chronic exposure to KL induced a significant increase in plasma creatinine, urea, and uric acid levels. Creatinine clearance decreased in KL-treated groups, compared with controls. Several urine parameters, such as urine-specific gravity and urine osmolality, significantly decreased, while dieresis and urinary Na/K + ratio increased in KL-treated groups. These findings suggested a distal tubular damage caused by tubular necrosis. Moreover, the chronic exposure to KL induced an increase in lipid peroxidation (LPO) and a decrease in antioxidant status, enzymatic activities (superoxide dismutase and catalase) and non-enzymatic levels (vitamin C), which led to an oxidative stress. Histopathological studies showed a peritubular inflammatory reaction, nephrose, fragmented glomeruli, necrotic epithelial cells, and tubular dilatation. These results could have significant health implications for animal and human populations. Further data are necessary to investigate the potential consequences of chronic dose exposure during life.