Background:The hypoxic cartilaginous growth plate is rich in extracellular matrix (ECM). Results: Expression of the key enzymes in ECM synthesis, the collagen prolyl 4-hydroxylases (C-P4Hs), is induced specifically by hypoxia-inducible factor 1. Conclusion: Hypoxia inducibility of C-P4Hs ensures sufficient C-P4H activity in hypoxic chondrocytes. Significance: Quantitative regulation of C-P4H may be a key modality by which hypoxia influences early chondrocyte survival and differentiation.

An endoplasmic reticulum transmembrane prolyl 4-hydroxylase (P4H-TM) is able to hydroxylate the ␣ subunit of the hypoxia-inducible factor (HIF) in vitro and in cultured cells, but nothing is known about its roles in mammalian erythropoiesis. We studied such roles here by administering a HIF-P4H inhibitor, FG-4497, to P4h-tm Ϫ/Ϫ mice. This caused larger increases in serum Epo concentration and kidney but not liver Hif-1␣ and Hif-2␣ protein and Epo mRNA levels than in wild-type mice, while the liver Hepcidin mRNA level was lower in the P4h-tm Ϫ/Ϫ mice than in the wild-type. Similar, but not identical, differences were also seen between FG-4497-treated Hif-p4h-2 hypomorphic (Hif-p4h-2 gt/gt ) and Hif-p4h-3 Ϫ/Ϫ mice versus wild-type mice. FG-4497 administration increased hemoglobin and hematocrit values similarly in the P4h-tm Ϫ/Ϫ and wild-type mice, but caused higher increases in both values in the Hif-p4h-2 gt/gt mice and in hematocrit value in the Hif-p4h-3 Ϫ/Ϫ mice than in the wild-type. Hif-p4h-2 gt/gt /P4h-tm Ϫ/Ϫ double genemodified mice nevertheless had increased hemoglobin and hematocrit values without any FG-4497 administration, although no such abnormalities were seen in the Hif-p4h-2 gt/gt or P4h-tm Ϫ/Ϫ mice. Our data thus indicate that P4H-TM plays a role in the regulation of EPO production, hepcidin expression, and erythropoiesis. (Blood. 2012;120(16): 3336-3344) IntroductionErythropoiesis is a tightly controlled process, its key regulator being erythropoietin (EPO). During embryonic development most of the EPO production occurs in the liver, whereas the major EPO source in adults is the kidney, although the liver maintains a capacity for its expression. 1,2 Hypoxia-inducible transcription factor (HIF) plays a pivotal role in the regulation of the transcription of the EPO gene and numerous other hypoxia-regulated genes, including many additional genes influencing erythropoiesis. [1][2][3][4] The HIF-␣ subunit isoforms HIF-1␣ and HIF-2␣ are synthesized constitutively, and hydroxylation of 2 critical prolines generates 4-hydroxyproline residues that target HIF-␣ for rapid degradation in normoxia. [5][6][7] In hypoxia, this hydroxylation is inhibited, so that HIF-␣ escapes degradation, translocates into the nucleus, and dimerizes with HIF-␤. 5-7 HIF-1␣ is expressed in all nucleated cells, whereas HIF-2␣ expression is restricted to specific cell types, including renal interstitial cells and hepatocytes. 1,2 Renal and hepatic EPO production in adults is primarily regulated by HIF-2␣, but HIF-1␣ also plays a role in several situations. 1,2 Erythropoiesis requires iron. Hepcidin, a 25-amino-acid peptide secreted predominantly from hepatocytes, is the central regulator of iron metabolism. It down-regulates ferroportin and thus inhibits the absorption of dietary iron and the release of iron form erythrocytes and macrophages. 8,9 Hepcidin expression is lowered by hypoxia and agents that stabilize HIF-2␣ leading to increased serum EPO concentration and erythropoiesis, its regulation also involving the hemojuvelin/...

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WHAT THIS PAPER ADDS Patient selection should be a key component of carotid surgery reports. A calculator was created where the presence and recentness of symptoms, sex, increasing stenosis severity, and complication rates could all be combined into a single figure. The calculator was tested on real life material and some theoretical inclusion scenarios. Single hospital treatment development over time and benchmarking between hospitals can be monitored when registered data includes these parameters, ultimately leading to improved patient selection.Objective: Considering carotid endarterectomy (CEA), reporting treatment delay, symptom status, and surgical complication rates separately gives an incomplete picture of efficacy; therefore, the aim was to combine these factors and develop a reporting standard that better describes the number of potentially prevented strokes. With a real life cohort and theoretical inclusion scenarios, the aim was to explore the stroke prevention potential of different carotid practices. Methods: Landmark studies for symptomatic and asymptomatic patients were revisited. By using published estimates of treatment effect, a simplified calculator was designed to assess the five year stroke prevention rate per 1000 CEAs (stroke prevention potential [SPP], range 0e478), including the presence and recentness of symptoms, sex, increasing stenosis severity, and complication rates. Patients operated on for carotid stenosis at Helsinki University Hospital (HUH) between 2008 and 2016 were collected from a vascular registry (HUSVASC) and categorised according to the model. The local annual complication rate was re-evaluated and added to the model. The HUH patient cohort was incorporated into the SPP model, and changes over time analysed. Finally, theoretical changes in patient selection were compared in order to explore the theoretical impact of patient selection and shortening of the delay. Results: Fifteen hundred and five symptomatic and 356 asymptomatic carotid stenoses were operated on with stroke plus death rates of 3.6% and 0.3%, respectively. The proportion of CEAs performed within two weeks of the index event increased over the follow up period, being 77% in 2016. The SPP increased from 123 in 2008 to 229 in 2016. Theoretically, 350 ischaemic strokes were prevented in the period 2008e16, with 1861 CEAs. Conclusions: National and international comparison of different CEA series is irrelevant if the inclusion criteria are not considered. A calculator that is easy to apply to large scale high quality registered data was developed and tested. SPP was found to increase over time, which is a probable sign of improved patient selection and an increased number of strokes prevented by the CEAs performed.

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Proper deposition of the extracellular matrix and its major components, the collagens, is essential for endochondral ossification and bone mass accrual. Collagen prolyl 4‐hydroxylases (C‐P4Hs) hydroxylate proline residues in the ‐X‐Pro‐Gly‐ repeats of all known collagen types. Their product, 4‐hydroxyproline, is essential for correct folding and thermal stability of the triple‐helical collagen molecules in physiological body temperatures. We have previously shown that inactivation of the mouse P4ha1 gene, which codes for the catalytic α subunit of the major C‐P4H isoform, is embryonic lethal, whereas inactivation of the P4ha2 gene produced only a minor phenotype. Instead, mice with a haploinsufficiency of the P4ha1 gene combined with a homozygous deletion of the P4ha2 gene present with a moderate chondrodysplasia due to transient cell death of the growth plate chondrocytes. Here, to further characterize the bone phenotype of the P4ha1+/−; P4ha2−/− mice, we have carried out gene expression analyses at whole‐tissue and single‐cell levels, biochemical analyses, microcomputed tomography, histomorphometric analyses, and second harmonic generation microscopy to show that C‐P4H α subunit expression peaks early and that the C‐P4H deficiency leads to reduced collagen amount, a reduced rate of bone formation, and a loss of trabecular and cortical bone volume in the long bones. The total osteoblast number in the proximal P4ha1+/−; P4ha2−/− tibia and the C‐P4H activity in primary P4ha1+/−; P4ha2−/− osteoblasts were reduced, whereas the population of osteoprogenitor colony‐forming unit fibroblasts was increased in the P4ha1+/−; P4ha2−/− marrow. Thus, the P4ha1+/−; P4ha2−/− mouse model recapitulates key aspects of a recently recognized congenital connective tissue disorder with short stature and bone dysplasia caused by biallelic variants of the human P4HA1 gene. Altogether, the data demonstrate the allele dose‐dependent importance of the C‐P4Hs to the developing organism and a threshold effect of C‐P4H activity in the proper production of bone matrix. © 2022 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Background and Purpose- Carotid endarterectomy (CEA) is recommended within 14 days after carotid artery stroke to prevent recurrence. However, the optimal timing of CEA after intravenous thrombolysis (IVT) remains unclear. We studied the safety of CEA after IVT while taking into account both stroke recurrence and CEA-related complications. Methods- Patients who underwent IVT followed by CEA in Helsinki University Hospital 2005 to 2016 were withdrawn from prospectively collected registers. The incidence of stroke recurrence during the time between IVT and CEA, peri/postoperative stroke, hyperperfusion syndrome or drug-resistant high blood pressure, and 3-month outcome measured by modified Rankin Scale was recorded. Stroke patients treated with CEA without preceding IVT were used as controls. Results- Altogether 128 CEAs with preceding IVT and 777 CEAs for stroke without IVT were identified. The median time from IVT to CEA was 9 days (range, 0-349 days; interquartile range, 16). Seven patients (5.5%) underwent CEA within 24 hours, 20 (15.6%) within 48 hours and 87 (68.0%) within 2 weeks from IVT. Stroke recurrence in IVT-CEA patients was 5.5% at median 4 days after IVT (range, 0-8 days). Outcome from CEAs performed within 48 hours from IVT did not differ from CEAs performed later with respect to peri/postoperative ischemic strokes (5.0% and 3.7%), hemorrhagic strokes (5.0% and 1.9%), neck hematomas (5.0% and 8.3%), myocardial infarctions (0.0% and 0.9%), or 3-month modified Rankin Scale. There was a tendency toward higher incidence of hyperperfusion syndrome in the patients operated within 48 hours from IVT (20.0% versus 6.5%; P=0.070). The CEA-related stroke rate was similar to that of the operation without thrombolysis. Only smoking was significantly associated with peri/postoperative stroke (odds ratio, 21.82; 95% confidence interval, 1.08-439.58). Conclusions- Time between IVT and CEA was not associated with CEA-related complications. The high rate of stroke recurrence during the waiting time for CEA underscores the importance of shortening surgery delays.