Chronic kidney disease (CKD) is a complicated systemic disease displaying various pathophysiological symptoms including mineral bone disorder (CKD-MBD). Ideally, early intervention for CKD-MBD would be desirable, however, there is not enough evidence regarding treatment of CKD-MBD, especially in its early stages, due to its multifactorial pathophysiology and the difficulty in generating adequate animal models. In this study, we evaluated the efficacy of a tissue nonspecific alkaline phosphatase (TNAP) inhibitor, SBI-425 in a CKD-MBD animal model, produced by a combination of nephrectomy and high inorganic phosphate (Pi) diet. This combination induced renal damage, and significantly elevated blood urea nitrogen (BUN). Plasma levels of fibroblast growing factor 23 (FGF-23), parathyroid hormone (PTH) and phosphate were also elevated, leading to ectopic calcification in the kidneys, particularly in the renal tubules. We orally administered SBI-425 twice daily for 12 weeks at doses of 1 and 10 mg/kg, and this treatment significantly inhibited the progression of calcium deposition in the renal tubules. Furthermore, SBI-425 effectively prevented the deterioration of plasma parameters, BUN, FGF-23, PTH, and phosphate. In conclusion, our findings suggest that TNAP inhibition can effectively slow the progression of CKD-MBD by inhibiting the calcification in the renal tubules. These results may have implications for better clinical care of patients with CKD.

Pathological ectopic calcification of soft tissues can arise from reduced or absent levels of inorganic pyrophosphate (PPi), a key inhibitor of calcium hydroxyapatite deposition in soft connective tissues. The role of PPi in regulating mineralization has been recognized for decades, thanks to the pivotal work of Herbert Fleisch and colleagues; and its clinical relevance has been underscored by the identification of hereditary metabolic disorders, collectively termed PPi deficiency syndromes. These are caused by pathogenic variants in the essential genes for maintaining PPi homeostasis: ATP-binding cassette subfamily C member 6 (ABCC6), ectonucleotide pyrophosphate phosphodiesterase 1 (ENPP1), progressive ankylosis protein (ANK), tissue-nonspecific alkaline phosphatase (ALPL), CD73, and CD39. In recent years, abnormalities in lipid metabolism have been reported in these monogenic conditions. However, a common understanding of these alterations has yet to be established. This review provides an overview of the pathophysiology of PPi deficiency syndromes-pseudoxanthoma elasticum, generalized arterial calcification of infancy, arterial calcification due to CD73 deficiency, ankylosis, and Hutchinson-Gilford progeria syndrome-highlighting the lipid metabolism alterations in cells, animal models, and patients. We explore the evidence for a potential role of PPi-regulating proteins in lipid metabolic pathways to demonstrate that lipid alterations are not coincidental but entail opportunities for future research and for potential therapeutic interventions.

Pyrophosphate dysregulation and impaired FGF23/FGFR signaling contributes to impaired matrix mineralization in bone marrow stromal cultures from sickle cell disease mice.

N-linked glycosylation plays an essential role in the stability and function of tissue-nonspecific alkaline phosphatase.

Hypophosphatasia (HPP) is an exceptional genetic bone disorder of metabolic character caused by a deficit of the tissue-nonspecific alkaline phosphatase isoenzyme (TNSALP). This protein is encoded by the ALPL (alkaline phosphatase liver/bone/kidney) gene. In the medical literature, HPP is also known as Rathbun's syndrome, named after the Canadian physician who first identified this disorder. Patients exhibit persistently low serum alkaline phosphatase (ALP) levels. In fact, ALP renders this measure a reliable indicator of the condition. Adult HPP is varied, with some patients exhibiting only moderate, non-pathognomonic symptoms. They include arthropathy, arthrodynia, chondrocalcinosis, osteopenia, osteomalacia, and generic musculoskeletal discomfort. Healthcare may require coordinating several services to manage a patient with HPP. This comprehensive review will highlight the genetic knowledge, pathology data, and patient management approaches, including Medicare's coverage. In addition, this paper aims to address specific themes related to HPP, including its significance, current challenges, and controversies.

The BMP2/7 heterodimer is known as a stronger inducer of osteogenic differentiation than BMP2 or BMP7 homodimers. Our aim was to establish BMP2/7-expressing human dental pulp stem cells (DPSCs) to evaluate tReceived: 23 October 2025; Revised: 29 November 2025; Accepted: 3 December 2025; Published: 3 December 2025 he osteogenic potential of the genetically modified cells. Lentiviral transduction was used to introduce the Tet-ON-regulated transgene-containing vector to the cells. Endogenous heterodimers were detected at the mRNA and protein levels using RNA-seq, qPCR, and Western blot, while secreted heterodimers were detected using ELISA assays. Osteogenic differentiation was monitored by measuring alkaline phosphatase (ALP) activity, mineralization, and the expression levels of RUNX2 and ALPL genes. Our results showed that ALP activity did not change in the transduced DPSCs; however, increased mineralization was detected, which correlates with the results obtained by RNA sequencing. Based on our results, BMP2/7-expressing DPSCs could be used in the treatment of bone defects, where heterodimers may have not only autocrine but also paracrine effects.

Here we report a Chinese infant with hypophosphatasia (HPP) carrying alkaline phosphatase (ALPL) gene mutations. Genetic analysis of the patient’s ALPL gene revealed a maternally inherited canonical splice-site variant (c.997+1G>T; pathogenic; PVS1 + PM2 + PP4) and a paternally inherited missense variant (c.1405C>T, p.His469Tyr; reclassified as pathogenic; PP4 + PM2 + PP3). Both variants have previously been reported in gnomAD with very low frequency in Chinese infants.

Adult hypophosphatasia (HPP) is caused by genetic variations in the ALPL gene causing a loss-of-function, leading to disruptions in normal skeletal mineralization processes. However, the impact of adult HPP extends beyond the skeletal system, as the ubiquitous expression and involvement of the affected enzyme in the body’s metabolic processes result in a broad spectrum of symptoms. Consequently, individuals with HPP mostly experience a diminished quality of life (QoL). The severity and presentation of the disease are highly heterogeneous. Despite this variability, the underlying reasons and contributing factors remain poorly understood. This study aims to get a better understanding of HPP patients QoL and identify parameters that correlate with their QoL. To address this, our study retrospectively analyzed 146 adult patients diagnosed with HPP. Health-related quality of life was assessed using the Short Form Health Survey version 1.0 (SF-36 v1), and pain levels were assessed using the brief pain inventory. Our findings indicate that HPP compromises not only physical health but also significantly impacts mental well-being, with a Physical Component Summary of 39.9 and a Mental Component Summary of 39.3. Moreover, we observed that patients’ QoL was inversely associated with factors such as obesity, lower concentrations of alkaline phosphatase (ALP) and bone-specific alkaline phosphatase (BAP). Additionally, indicators of physical status demonstrated a strong correlation with QoL. These results underscore the need for a systematic approach to monitoring both somatic parameters and mental health in adult HPP patients to help evaluate disease progression, treatment effects, and overall patient condition. Clinicians can utilize objective criteria, namely physical status indicators, ALP and BAP concentrations, and BW as additional tools in assessing patients’ conditions, as these factors are linked to QoL in HPP. This may help clinicians estimate patients disease status and may help to assess and monitor the impact of therapy on QoL.

Background: Knockout of 2′,3′-cyclic-nucleotide 3′-phosphodiesterse (an enzyme that converts 2′,3′-cAMP to 2′-AMP) reduces 2′-AMP production and improves renal perfusion in renal ischemia-reperfusion injury (R-IRI). These findings motivated our hypothesis, herein tested, that 2′-AMP causes renal vasoconstriction. Methods: The effect of 2′-AMP on renal vascular resistance (RVR) was investigated in rat kidneys, both in vitro and in vivo. 2′-AMP interactions with P2X1 receptors (P2X1Rs) were investigated in membrane preparations and HEK cells. Urinary 2′-AMP levels were assessed in cardiac surgery/cardiopulmonary bypass (CS-CPB) patients using mass spectrometry. Results: In vitro , intra-renal-artery-infused 2′-AMP was rapidly metabolized to adenosine and did not increase RVR. Co-administration of a tissue non-specific alkaline phosphatase (TNAP) inhibitor (TNAPI) reduced 2′-AMP metabolism, thus enabling 2′-AMP to trigger renal vasoconstriction. In vivo , kidneys rapidly metabolized intra-renal-artery-infused 2′-AMP to adenosine; this was blocked with a TNAPI. In vivo , intra-renal-artery-infused 2′-AMP decreased RVR, as did adenosine. By contrast, when co-administered with a TNAPI, 2′-AMP increased RVR, and this response was inhibited by NF449 (P2X1R antagonist). In membranes, 2′-AMP enhanced 3 H-αβ-methylene-ATP (P2X1R agonist) binding to P2X1Rs, and in HEK cells 2′-AMP doubled αβ-methylene-ATP-induced (and P2X1R-mediated) calcium influx. In TNAPI+2′-AMP-pretreated, but not naïve, rats, βγ-methylene-ATP (P2X1R agonist) caused renal vasoconstriction. In rats, R-IRI reduced renal TNAP activity, and TNAP inhibition worsened R-IRI. In CS-CPB patients, urinary 2′-AMP levels were elevated 169% during CS-CPB and were associated with a 45% increase in peak 24-hour post-procedure serum creatinine. Conclusions: 2′-AMP is a renal vasoconstrictor; however, TNAP, by metabolizing 2′-AMP to adenosine, protects against 2′-AMP-induced renal vasoconstriction. This protection is lost when TNAP activity is reduced. 2′-AMP-induced renal vasoconstriction involves positive allosteric modulation of P2X1Rs that enhances ATP-induced opening of P2X1R channels. R-IRI reduces renal TNAP activity, and TNAP inhibition worsens R-IRI outcomes.

Fibroblast growth factor 2 promotes matrix vesicle-mediated mineralization of human umbilical cord perivascular cells by regulating phosphate metabolism.

Involvement of impaired phosphate production and aberrant extracellular ATP signaling in the pathogenesis of hypophosphatasia: Analysis of ALPL-Knockout human iPS cell models.

A fully automated immunoassay for quantifying tissue-nonspecific alkaline phosphatase activity on calcified extracellular vesicles for cardiovascular risk assessment.

Hypophosphatasia (HPP) is a heritable multisystem disorder caused by pathogenic variants in the tissue non-specific alkaline phosphatase (ALP)-coding gene ALPL. The genotype-phenotype correlation in heterozygous adults with HPP remains incompletely understood. In this genotype-based study, we aimed to measure the prevalence of pathogenic or likely-pathogenic ALPL variants and test the hypothesis that HPP penetrance is low in adult carriers. A total of 37,147 genomes from unselected individuals visiting a tertiary care, academic medical center were investigated. Variants classified as pathogenic or likely-pathogenic were observed with a prevalence of 0.3% (n=109) or 1/341. Variant c.571G>A was most frequent (67.9%). A subset of 70 individuals had linked electronic health records (EHRs) and were termed ALPL+. All 70 ALPL+ individuals showed mild, mainly neurological, symptoms often reported in adults with HPP. However, low serum ALP, a hallmark of HPP, was found in only 65.7% (38/70) of ALPL+ individuals, and 12.9% (9/70) met the diagnostic criteria for HPP based on consensus guidelines, thus complete penetrance was low. Compared to controls lacking pathogenic or likely-pathogenic variants (ALPL-), the ALPL+ individuals had a higher probability of progression for mobility issues (median age 73 years ALPL+ vs. 82 years ALPL-, p=0.03), as well as a similar probability of progression for fatigue, arthritis or dental problems. Unexpectedly, 3.4% (5/148) of individuals in the ALPL- group met the diagnostic criteria for HPP, possibly due to unidentified variants or non-ALPL genetic factors. Overall, the data support our hypothesis and aids the management of carries of pathogenic ALPL variants.

Hypophosphatasia is a rare hereditary disease caused by a deficiency of tissue-nonspecific alkaline phosphatase, leading to impaired mineralization of bones and teeth. The article presents a clinical case of a child with an infantile form of hypophosphatasia, manifested by delayed motor development, deformation of the lower extremities and premature loss of teeth. The diagnosis was confirmed by a molecular genetic study that revealed compound heterozygous mutations in the ALPL gene. Enzyme replacement therapy with asfotase alpha was prescribed, against the background of which positive dynamics were noted.

HighlightsWhat are the main findings?First bullet: functional characterization of 21 ALPL genetic variants identified in well clinical ascertained HPP patients that provided novel insights about the protein stability and residual enzymatic activity of the mutants.Second bullet: a multifaceted comparison among functional, genotypic, clinical/biochemical and in silico data that might represent a higher and more accurate level of a basic genotype-phenotype correlation.What are the implications of the main findings?First bullet: a greater comprehension of the presumed effect of an ALPL genetic variant on the whole TNAP protein function.Second bullet: the multi-data comparison might represent for the clinician an innovative tool for the follow up and management of a HPP patient.Background. Hypophosphatasia (HPP) is a rare genetic disorder caused by impaired tissue non-specific alkaline phosphatase (ALPL/TNSALP) activity that impacts the musculoskeletal and neurological systems. It is extremely variable, with up to six forms of increasing severity. The large phenotypic variability and the still remaining high number of variants of uncertain significance (VUS) in the ALPL gene represent a conundrum for clinicians dealing with people suspected to be suffering from HPP. Methods. We applied a multi-faceted bench-based and high-throughput bioinformatics analysis to investigate the effect of 21 ALPL variants (18 deleterious—pathogenic or likely pathogenic—and 3 VUS) on the structure and function of the mutated encoded protein. The results were compared with available clinical and biochemical data. Results. Most variants were downregulated or not expressed by Western blot analysis. Impairment of the enzymatic activity was confirmed in vitro for all variants by a specific colorimetric enzymatic assay. In silico prediction was in line with functional data and allowed for preliminary categorization of variants based on their impact on both the overall stability of the protein complex and local structural alterations. Coherence among bioinformatics, experimental and clinical data was documented for more than 70% of the variants. Conclusions. Functional and in silico characterizations of ALPL variants in people with a suspicion of HPP offer integrative strategies to genotyping in assisting clinicians for diagnosis confirmation in doubtful cases.

Background Hypophosphatasia (HPP) is a rare inherited metabolic disorder of low prevalence, characterized by low activity of tissue-nonspecific alkaline phosphatase (TNSALP), causing defective mineralization of teeth and bone. Odontohypophosphatasia (odonto-HPP) is the mildest form of hypophosphatasia, with manifestations limited to dental features, such as premature loss of primary teeth. Case Report This case report presents a 3-year-old female patient who was diagnosed with odonto-HPP. There was a history of premature exfoliation of the lower primary central incisors shortly after eruption, without any accompaniment of pain or bleeding. She was referred at the hospital on a clinical suspicion of hypophosphatasia for further evaluation. The diagnosis of odonto-HPP was confirmed following bone densitometry and genetic analysis, which revealed a subtle mutation of the ALPL gene. Clinical assessment revealed normal body growth without systemic defects. Mandibular anterior region showed bone resorption and gingival recession, whereas the overall eruption pattern of teeth was normal. Treatment included vitamin D supplementation and dietary counseling. The patient is currently receiving follow-up every two years. Conclusion The case, as the second reported case of HPP on Lesvos Island, highlights the importance of recognizing early dental manifestations of the condition and the critical role of the dentist in the recognition and referral of such cases. Early diagnosis promotes effective surveillance and avoids unwarranted intervention.

Background: Tissue-nonspecific alkaline phosphatase (TNAP) has emerged as a key contributor to vascular calcification. Prior studies have linked elevated plasma TNAP levels to increased coronary artery calcium scores. Our group demonstrated that TNAP overexpression in endothelial cells promotes calcification and accelerates coronary atherosclerosis. In the current study, we hypothesize that plasma TNAP can directly contribute to vascular calcification. We generated a transgenic mouse model with hepatocyte-targeted TNAP overexpression (hTNAPOE) on a low-density lipoprotein receptor mutant background. Methods: hTNAPOE male and female mice and littermate controls (n=10-12 per group) were fed a western diet to induce atherosclerosis. Cardiac function parameters, along with ascending aortic velocity, were assessed using electrocardiograms. At the terminal time point (42 weeks), the mice were fasted for 5 hours, and plasma was collected by cardiac puncture. Livers and hearts were dissected for histological evaluation. ALP activity was assessed in liver sections to confirm hTNAP overexpression. Plasma alkaline phosphatase (ALP), cholesterol, and triglycerides were measured. Micro-computed tomography (μCT) was employed to detect vascular calcification. Data were analyzed using a two-way ANOVA, accounting for sex and genotype. Results: Our results demonstrated a 10-fold increase in circulating ALP in the plasma of hTNAPOE female mice and a 100-fold increase in male mice compared to control mice (p<0.0001). There was no significant difference in triglycerides; cholesterol levels were mildly elevated in hTNAPOE mice (36% in males and 14% in females, p<0.05). hTNAPOE mice exhibited significantly greater calcification in whole-heart preparations, confirming our hypothesis (p<0.01). Surprisingly, we didn’t see increased aortic root calcification in hTNAPOE mice; however, coronary artery calcification was significantly increased (p<0.05). hTNAPOE mice presented with increased left ventricular mass normalized to body weight, implying the pathophysiologic significance of calcification. While hTNAPOE mice showed higher calcification, ascending aortic velocity, an indicator of stenosis, did not differ between the groups. Conclusion: Overexpression of hTNAP in mice resulted in a significant increase in circulating ALP in plasma and increased coronary calcification.

Tissue-nonspecific alkaline phosphatase (TNAP) is primarily known for its role in skeletal mineralization, through the hydrolysis of inorganic pyrophosphate (PPi). Here we demonstrate that TNAP-knockout mice exhibit liver steatosis and reduced serum triglyceride levels, mirroring the effects of choline deficiency, which impairs phosphatidylcholine synthesis, an essential component of VLDL. In fasting WT mice, TNAP inhibition via SBI-425 administration decreases choline levels in blood and liver. Incubating mouse or human serum with SBI-425 inhibits the dephosphorylation of phosphocholine and phosphoethanolamine, an alternative substrate for hepatic phosphatidylcholine synthesis. In hepatocytes, TNAP inhibition impedes proliferation when the medium is supplemented with phosphocholine instead of choline. Recombinant TNAP hydrolyzes phosphocholine and phosphoethanolamine with similar efficiency than PPi. X-ray diffraction and cryo-EM identified the residues in TNAP’s active site interacting with phosphocholine, PPi and the TNAP inhibitor. In summary, TNAP is the phosphatase enabling cellular choline uptake during fasting, participating in hepatic lipid metabolism.

Disclosure: P. Pierog: None. M. Brophy: None. W. Wong: None. X. Zhang: None. L. Li: None. J. Hickey: None. A. Lundberg: None. W. Bainter: None. C. Bullock: None. S. Keegan: None. S. Bedard-Shurtleff: None. T. Mullen: None. J. Edelstein: None. S. Bhawsar: None. G. Adekanye: None. E. Liberzon: None. S. Singh: None. M. Musial-Siwek: None. A. Hohmann: None. S. Arlauckas: None. A. Lazorchak: None. H. Liu: None. R. Morgan: None.Hypophosphatasia (HPP) is a rare metabolic disorder that causes skeletal abnormalities, chronic pain, and systemic complications. The condition arises from loss-of-function mutations in the ALPL gene that encodes the tissue-nonspecific alkaline phosphatase (TNSALP) enzyme. Deficient TNSALP activity leads to the accumulation of inorganic pyrophosphate (PPi), an inhibitor of bone mineralization, and pyridoxal 5’-phosphate responsible for disease manifestation. To address limitations of current therapies, we have developed a B cell-based cell therapy, termed BE-102. BE-102 is manufactured from primary human B cells by isolating, activating, and precision engineering with CRISPR/Cas9 followed by AAV and homology directed repair mediated insertion of human ALPL gene into CCR5 locus. Engineered TNSALP-producing cells, have properties of long-lived plasma cells and are expected to reduce elevated levels of substrates PPi and PLP, that accumulate in patients with HPP. BE-102 cells were manufactured from six healthy donors and were characterized for viability (84.9 ± 3.5%), CD38+ expression (93.3 ± 4.3%), ALPL transgene integration (45.1 ± 7.2%) and TNSALP secretion rate (9.5 ± 10.2 ng/mL/hour). In vitro pharmacology results demonstrate that BE-102 secretes active TNSALP (409.7 ± 10.2 µUnits/mL), which is capable of rescuing calcium deposition inhibited by PPi in a cell-based in vitro test system. Having demonstrated the in vitro function of BE-102, in vivo studies (N=3) were conducted in immune-deficient NOG-hIL6 mice. The animals received a single intravenous (IV) injection of 2 x107 viable cells. Human TNSALP was detected in serum at every time point starting at Day 1 and up to 6 months following a single dose of BE-102 using a human specific immunocapture assay. Consistent with BE-102 pharmacology, serum ALP activity showed statistically significant increase in BE-102 treated animals as compared to vehicle-treated animals. The in vivo data confirm long-term engraftment and continuous production of active TNSALP. Consistent with the expected pharmacology of BE-102 and construct design of ALPL transgene, human TNSALP activity was detected at day 90 in the bones of animals treated with BE-102 surrogate construct secreting TNSALP. These data confirm the delivery of functional TNSALP secreted by the surrogate construct to the bone, one of the main HPP disease target organs. Finally, clinical chemistry and hematology results from the end of the studies were all within acceptable ranges. Safety data together with the absence of adverse clinical observations and no unscheduled animal deaths support that BE-102 was well-tolerated in vivo. In summary, pharmacology and safety data establish non-clinical proof of concept that BE-102, has the potential to be a disease-modifying therapy by providing sustained level of active TNSALP following a single IV infusion for patients with HPP.Presentation: Monday, July 14, 2025

X-linked hypophosphatemia (XLH) is caused by mutations in the PHEX gene, which leads to increased levels of fibroblast growth factor 23 and hypophosphatemia, contributing to rickets, osteomalacia, and dentoalveolar defects, including severe dentin hypomineralization, thin cementum, and alveolar bone osteomalacia. Current XLH treatment options appear to have limited efficacy on dentoalveolar tissues, suggesting underlying disease mechanisms that remain unchecked. Increased production of inorganic pyrophosphate (PPi) and osteopontin (OPN), both mineralization inhibitors, has been posited to contribute to mineralization defects in XLH. The enzyme, tissue-nonspecific alkaline phosphatase (TNAP) reduces PPi levels via hydrolysis and inactivates OPN by dephosphorylation. Our previous study showed improved alveolar bone socket healing in Hyp mice administered mineralized tissue-targeted TNAP (TNAP-Fc-D10). We hypothesized that increased TNAP would partially ameliorate developmental mineralization defects in XLH by dually reducing PPi levels and dephosphorylating and inactivating OPN. In a proof-of-principle study to investigate pathological mechanisms, we delivered systemic (subcutaneous injection) and local (submucosal injection to mandibles) TNAP-Fc-D10 injections to the Hyp mutant mouse model of XLH from 7 to 60 d postnatal (dpn). While systemic delivery was ineffective at improving dentin or bone properties, micro-CT and histology analyses demonstrated that local delivery of TNAP-Fc-D10 increased dentin thickness, root length, alveolar bone volume, alveolar bone proper (ABP) volume and density, PDL attachment, and acellular cementum thickness, compared to control Hyp mice receiving a sham injection. Dynamic mechanical testing confirmed partially improved mechanical properties in locally treated vs untreated Hyp mice, suggesting incompletely improved periodontal function. Quantitative PCR revealed increased Dspp expression in molars of treated Hyp mice. In conclusion, we found TNAP administration reduced dentoalveolar defects in Hyp mice when delivered locally into dentoalveolar structures, proof-of-principle pointing to a pathological contribution by PPi and/or OPN and highlighting a promising adjunctive approach considering limitations of current treatment modalities.