Current and Developing Pharmacologic Agents for Improving Skeletal Health in Adults with Osteogenesis Imperfecta.

Osteogenesis imperfecta (OI) is a genetic disorder characterized by increased bone fragility largely caused by defects in structure, synthesis, or post-translational processing of type I collagen. Drugs currently used to improve skeletal health in OI were initially developed to treat osteoporosis and clinical trials are ongoing to study their effectiveness in OI adults. Additionally, novel bone-protective agents are in preclinical studies and various phases of OI clinical trials. This review summarizes current knowledge on available pharmacologic agents and current drug trials involving OI participants. A PubMed online database search of all study types published in the English language using the terms "osteogenesis imperfecta," "OI," and "brittle bone disease" was performed in August 2022. Articles screened were restricted to adults. A ClinicalTrials.gov database search of all studies involving "osteogenesis imperfecta" was performed in August 2023. Although clinical trial data are limited, bisphosphonates and teriparatide may be useful in improving bone mineral density. As of yet, no clinical trials are available that adequately evaluate the usefulness of current therapies in reducing fracture risk. Several therapeutics, including teriparatide, setrusumab, anti-TGF-ß antibodies, and allogeneic stem cells, are being studied in clinical trials. Preclinical studies involving Dickkopf-1 antagonists present promising data in non-OI bone disease, and could be useful in OI. Research is ongoing to improve therapeutic options for adults with OI and clinical trials involving gene-editing may be possible in the coming decade.

Pre-op considerations in neuromuscular scoliosis deformity surgery: proceedings of the half day course at the 58th annual meeting of the Scoliosis Research Society.

Scoliosis is a common complication of neuromuscular disorders. These patients are frequently recalcitrant to nonoperative treatment. When treated surgically, they have the highest risk of complications of all forms of scoliosis. While recent studies have shown an improvement in the rate of complications, they still remain high ranging from 6.3 to 75% depending upon the underlying etiology and the treatment center (Mohamad et al. in J Pediatr Orthop 27:392-397, 2007; McElroy et al. in Spine, 2012; Toll et al. in J Neurosurg Pediatr 22:207-213, 2018; Cognetti et al. in Neurosurg Focus 43:E10, 2017). For those patients who are able to recover from the perioperative period without major complications, several recent studies have shown decreased long-term mortality and improved health-related quality of life in neuromuscular patients who have undergone spine fusion (Bohtz et al. in J Pediatr Orthop 31:668-673, 2011; Ahonen et al. in Neurology 101:e1787-e1792, 2023; Jain et al. in JBJS 98:1821-1828, 2016). It is critically important to optimize patients preoperatively to minimize the risk of post-operative complications and maximize long-term outcomes. In order to do so, one must familiarize themselves with the common complications and their treatment. The most common complications are pulmonary in nature. With reported rates as high as 23-29%, pre-operative optimization should be employed for these patients to minimize the risk of post-operative complications (Sharma et al. in Eur Spine J 22:1230-1249, 2013; Rumalla et al. in J Neurosurg Spine 25:500-508, 2016). The next most common cause of complications are implant related, with 13-23% of patients experiencing an implant-related complication that may require a second procedure (Toll et al. in J Neurosurg Pediatr 22:207-213, 2018; Sharma et al. in Eur Spine J 22:1230-1249, 2013) Therefore optimization of bone quality prior to surgical intervention is important to help minimize the risk of instrumentation failure. Optimization of muscle tone and spasticity may help to decrease the risk of instrumentation complications, but may also contribute to the progression of scoliosis. While only 3% of patients have neurologic complication, significant equipoise remains regarding whether or not patients should undergo prophylactic detethering procedures to minimize those risks (Sharma et al. in Eur Spine J 22:1230-1249, 2013). Although only 1.8% of complications are classified as cardiac related, they can be among the most devastating (Rumalla et al. in J Neurosurg Spine 25:500-508, 2016). Simply understanding the underlying etiology and the potential risks associated with each condition (i.e., conduction abnormalities in a patient with Rett syndrome or cardiomyopathies patients with muscular dystrophy) can be lifesaving. The following article is a summation of the half day course on neuromuscular scoliosis from the 58th annual SRS annual meeting, summarizing the recommendations from some of the world's experts on medical considerations in surgical treatment of neuromuscular scoliosis.

Approach to the Patient: Pharmacological Therapies for Fracture Risk Reduction in Adults With Osteogenesis Imperfecta.

CONTEXT: Osteogenesis imperfecta (OI) is a genetic disorder characterized by increased bone fragility largely caused by defects in structure, synthesis, or post-translational processing of type I collagen. The effectiveness of medications used for fracture reduction in adults with OI is understudied and practice recommendations are not well established. Drugs currently used to improve skeletal health in OI were initially developed to treat osteoporosis. Oral and intravenous bisphosphonates have been shown to improve bone mineral density (BMD) in adults with OI and are commonly used; however, conclusive data confirming fracture protection are lacking. Similarly, teriparatide appears to increase BMD, an effect that seems to be limited to individuals with type I OI. The role of denosumab, abaloparatide, romosozumab, and estradiol/testosterone in adult OI have not been systematically studied. Anti-sclerostin agents and transforming growth factor-beta antagonists are under investigation in clinical trials. OBJECTIVE: This review summarizes current knowledge on pharmacologic treatment options for reducing fracture risk in adults with OI. METHODS: A PubMed online database search of all study types published in the English language using the terms "osteogenesis imperfecta," "OI," and "brittle bone disease" was performed in June 2022. Articles screened were restricted to adults. Additional sources were identified through manual searches of reference lists. CONCLUSION: Fracture rates are elevated in adults with OI. Although clinical trial data are limited, bisphosphonates and teriparatide may be useful in improving BMD. Further research is needed to develop medications for adults with OI that will lead to definite fracture rate reduction.

An Unusual Presentation of Osteogenesis Imperfecta: A Case Report.

CASE: We report an 18-year-old patient with a clinical phenotype consistent with severe osteogenesis imperfecta (OI) with frequent fractures, short stature, shortening and bowing of extremities, and unusual radiographic features of severe fibrous dysplasia, including lytic lesions and a "ground-glass" appearance. Genetic testing for the patient was notable for a c.119C>T (p.Ser40Leu) variant in exon 1 of IFITM5 and a c.676C>A (Pro226Thr) variant in exon 5 of CREB3L1. CONCLUSION: This unusual skeletal presentation was in the setting of a rare IFITM5 mutation and represents a unique case of severe OI.

Widespread disturbance in extracellular matrix collagen biomarker responses to teriparatide therapy in osteogenesis imperfecta.

Osteogenesis imperfecta (OI), a heritable disorder caused by abnormalities in synthesis or processing of type I collagen, is characterized by skeletal fragility. Type I collagen interacts with multiple components of the extracellular matrix (ECM) including other collagens types. Thus, alterations in structure or quantity may broadly affect ECM homeostasis. In fact, while OI is clinically categorized by severity of bone disease, patients can also present with extra-skeletal manifestations, including the pulmonary, muscle and cardiovascular systems. Parathyroid hormone (PTH) is a regulator of skeletal homeostasis but the receptor for PTH/PTH1R is expressed in a variety of other tissues. Given interactions between type I collagen with other collagens in the ECM and the potential for PTH action on tissues beyond the skeleton, we explored whether serum levels of non-type I collagens are altered in response to teriparatide (human parathyroid hormone 1-34). We measured biomarkers of collagens II, III, IV, V, and VI in serum from individuals with type I and types III/IV OI in response to an 18 month course of teriparatide or placebo. These results were compared to similar biomarker measures in postmenopausal (PM) women without OI treated with teriparatide. In type I OI, teriparatide therapy increased concentrations of biomarkers of collagens II, III, IV, V, and VI. In individuals with types III/IV OI these biomarker changes in response to teriparatide were blunted, as we previously reported with collagen I biomarkers during teriparatide therapy. In contrast to OI, in PM women there were no effects of teriparatide on the collagen biomarkers we assessed (II, V, and VI). These findings suggest that in OI teriparatide therapy has abnormal effects on the homeostasis of many ECM collagens likely derived from skeletal as well as extra-skeletal tissues.

Prenatal Treatment of Thyroid Hormone Cell Membrane Transport Defect Caused by MCT8 Gene Mutation.

Background: Mutations of the thyroid hormone (TH)-specific cell membrane transporter, monocarboxylate transporter 8 (MCT8), produce an X-chromosome-linked syndrome of TH deficiency in the brain and excess in peripheral tissues. The clinical consequences include brain hypothyroidism causing severe psychoneuromotor abnormalities (no speech, truncal hypotonia, and spastic quadriplegia) and hypermetabolism (poor weight gain, tachycardia, and increased metabolism, associated with high serum levels of the active TH, T3). Treatment in infancy and childhood with TH analogues that reduce serum triiodothyronine (T3) corrects hypermetabolism, but has no effect on the psychoneuromotor deficits. Studies of brain from a 30-week-old MCT8-deficient embryo indicated that brain abnormalities were already present during fetal life. Methods: A carrier woman with an affected male child (MCT8 A252fs268*), pregnant with a second affected male embryo, elected to carry the pregnancy to term. We treated the fetus with weekly 500 µg intra-amniotic instillation of levothyroxine (LT4) from 18 weeks of gestation until birth at 35 weeks. Thyroxine (T4), T3, and thyrotropin (TSH) were measured in the amniotic fluid and maternal serum. Treatment after birth was continued with LT4 and propylthiouracil. Follow-up included brain magnetic resonance imaging (MRI) and neurodevelopmental evaluation, both compared with the untreated brother. Results: During intrauterine life, T4 and T3 in the amniotic fluid were maintained above threefold to twofold the baseline and TSH was suppressed by 80%, while maternal serum levels remained unchanged. At birth, the infant serum T4 was 14.5 µg/dL and TSH <0.01 mU/L compared with the average in untreated MCT8-deficient infants of 5.1 µg/ and >8 mU/L, respectively. MRI at six months of age showed near-normal brain myelination compared with much reduced in the untreated brother. Neurodevelopmental assessment showed developmental quotients in receptive language and problem-solving, and gross motor and fine motor function ranged from 12 to 25 at 31 months in the treated boy and from 1 to 7 at 58 months in the untreated brother. Conclusions: This is the first demonstration that prenatal treatment improved the neuromotor and neurocognitive function in MCT8 deficiency. Earlier treatment with TH analogues that concentrate in the fetus when given to the mother may further rescue the phenotype.

Alterations in non-type I collagen biomarkers in osteogenesis imperfecta.

Osteogenesis imperfecta [1] is a rare disorder of connective tissue caused by abnormalities in the synthesis or processing of type I collagen. Type I collagen is the most abundant type of collagen and is expressed in almost all connective tissues. Given that type I collagen interacts with other collagens based in the extracellular matrix (ECM), we hypothesized changes in type I collagen in OI would result in perturbations in the homeostasis of other collagen types. We measured serum biomarkers of several non-type I collagens in patients with mild (type I) and moderate-to-severe (type III/IV) OI. Compared to controls, those with moderate-to severe OI had a higher mean level of the synthesis markers of collagen III (ProC3) (P = 0.02), and levels of collagen V (ProC5) (P = 0.07) were slightly, but not significantly, higher. Degradation markers of collage type IV (C4M2) (P = 0.04) and type VI (C6M) (P = 0.003) were also higher. In each case, a test for trend suggested levels were higher in moderate-to-severe OI, intermediate in mild OI, and lowest in controls (P = 0.06-0.002). These changes supports the hypothesis that mutations in type I collagen induce a widespread alteration in the ECM, and that the diverse clinical manifestations of OI reflect an extensive disruption in ECM biology.

Serum Sclerostin Levels in Adults With Osteogenesis Imperfecta: Comparison With Normal Individuals and Response to Teriparatide Therapy.

Sclerostin (SOST), a glycoprotein primarily derived from osteocytes, is an important regulator of bone remodeling. Osteogenesis imperfecta (OI) is a heritable disorder of bone characterized by low bone mass, bone fragility, recurrent fractures, and bone deformities. Altered SOST-mediated signaling may have a role in pathogenesis of type I collagen-related OI; however, this has not been evaluated in humans. We measured serum SOST levels in adults with OI who were enrolled in a randomized, placebo-controlled clinical trial that evaluated the effects of osteoanabolic therapy with teriparatide. Compared with age- and sex-matched control participants, mean SOST levels were lower in those with type I or types III/VI OI (p < 0.0001). Receiver operating curve analysis revealed that sclerostin alone or sclerostin plus bone mineral content discriminated patients with OI from controls (area under the curve 0.80 and 0.87, respectively). SOST levels increased in the group of patients with type I OI during therapy with teriparatide (compared with placebo, p = 0.01). The increase was significant at 6, 12, and 24 months of therapy (p ≤ 0.02) and was apparent as early as 3 months (p = 0.06). The magnitude of increases in SOST levels during therapy was inversely correlated with increases in vertebral volumetric bone mineral density (vBMD). Overall, these results suggest that: 1) SOST regulation is fundamentally altered in osteogenesis imperfecta; 2) serum SOST levels could be a biomarker of OI in adults; and 3) alterations in SOST may help predict the response to anabolic therapies in OI. © 2017 American Society for Bone and Mineral Research.

Abnormal infant islet morphology precedes insulin resistance in PCOS-like monkeys.

Polycystic ovary syndrome (PCOS) is prevalent in reproductive-aged women and confounded by metabolic morbidities, including insulin resistance and type 2 diabetes. Although the etiology of PCOS is undefined, contribution of prenatal androgen (PA) exposure has been proposed in a rhesus monkey model as premenopausal PA female adults have PCOS-like phenotypes in addition to insulin resistance and decreased glucose tolerance. PA female infants exhibit relative hyperinsulinemia, suggesting prenatal sequelae of androgen excess on glucose metabolism and an antecedent to future metabolic disease. We assessed consequences of PA exposure on pancreatic islet morphology to identify evidence of programming on islet development. Islet counts and size were quantified and correlated with data from intravenous glucose tolerance tests (ivGTT) obtained from dams and their offspring. Average islet size was decreased in PA female infants along with corresponding increases in islet number, while islet fractional area was preserved. Infants also demonstrated an increase in both the proliferation marker Ki67 within islets and the beta to alpha cell ratio suggestive of enhanced beta cell expansion. PA adult females have reduced proportion of small islets without changes in proliferative or apoptotic markers, or in beta to alpha cell ratios. Together, these data suggest in utero androgen excess combined with mild maternal glucose intolerance alter infant and adult islet morphology, implicating deviant islet development. Marked infant, but subtle adult, morphological differences provide evidence of islet post-natal plasticity in adapting to changing physiologic demands: from insulin sensitivity and relative hypersecretion to insulin resistance and diminished insulin response to glucose in the mature PCOS-like phenotype.

Nonhuman primate models of polycystic ovary syndrome.

With close genomic and phenotypic similarity to humans, nonhuman primate models provide comprehensive epigenetic mimics of polycystic ovary syndrome (PCOS), suggesting early life targeting for prevention. Fetal exposure to testosterone (T), of all nonhuman primate emulations, provides the closest PCOS-like phenotypes, with early-to-mid gestation T-exposed female rhesus monkeys exhibiting adult reproductive, endocrinological and metabolic dysfunctional traits that are co-pathologies of PCOS. Late gestational T exposure, while inducing adult ovarian hyperandrogenism and menstrual abnormalities, has less dysfunctional metabolic accompaniment. Fetal exposures to dihydrotestosterone (DHT) or diethylstilbestrol (DES) suggest androgenic and estrogenic aspects of fetal programming. Neonatal exposure to T produces no PCOS-like outcome, while continuous T treatment of juvenile females causes precocious weight gain and early menarche (high T), or high LH and weight gain (moderate T). Acute T exposure of adult females generates polyfollicular ovaries, while chronic T exposure induces subtle menstrual irregularities without metabolic dysfunction.

Perinatal exposure to a high-fat diet is associated with reduced hepatic sympathetic innervation in one-year old male Japanese macaques.

Our group recently demonstrated that maternal high-fat diet (HFD) consumption is associated with non-alcoholic fatty liver disease, increased apoptosis, and changes in gluconeogenic gene expression and chromatin structure in fetal nonhuman primate (NHP) liver. However, little is known about the long-term effects that a HFD has on hepatic nervous system development in offspring, a system that plays an important role in regulating hepatic metabolism. Utilizing immunohistochemistry and Real-Time PCR, we quantified sympathetic nerve fiber density, apoptosis, inflammation, and other autonomic components in the livers of fetal and one-year old Japanese macaques chronically exposed to a HFD. We found that HFD exposure in-utero and throughout the postnatal period (HFD/HFD), when compared to animals receiving a CTR diet for the same developmental period (CTR/CTR), is associated with a 1.7 fold decrease in periportal sympathetic innervation, a 5 fold decrease in parenchymal sympathetic innervation, and a 2.5 fold increase in hepatic apoptosis in the livers of one-year old male animals. Additionally, we observed an increase in hepatic inflammation and a decrease in a key component of the cholinergic anti-inflammatory pathway in one-year old HFD/HFD offspring. Taken together, these findings reinforce the impact that continuous exposure to a HFD has in the development of long-term hepatic pathologies in offspring and highlights a potential neuroanatomical basis for hepatic metabolic dysfunction.