Long term use of interleukin-1 inhibitors reduce flare activity in patients with fibrodysplasia ossificans progressiva.

OBJECTIVES: Fibrodysplasia ossificans progressiva (FOP) is one of the most catastrophic forms of genetic heterotopic ossification (HO). FOP is characterized by severe, progressive inflammatory flare-ups, that often lead to HO. The flare-ups are associated with increased inflammatory cytokine production, suggesting auto-inflammatory features driven by interleukin-1ß (IL-1ß). This study describes the short- and long-term responses of FOP patients to anti-IL-1 therapy. METHODS: Previously, we reported that a patient with FOP treated with anti-IL-1 agents showed dramatically lower rates of flare-ups, improved flare-up symptoms, decreased use of glucocorticoids, and apparently decreased size of residual lesions. Plasma analyses also showed marked elevation in IL-1ß levels during a FOP flare, further supporting a role of IL-1ß in the pathogenesis of FOP flares. Here, we report results from long-term therapy with IL-1 inhibitors in that patient, and describe 3 additional patients, from two medical centers. RESULTS: All 4 patients showed persistent improvement in flare activity during treatment with IL-1 inhibitors, with minimal formation of new HO sites. Two patients who stopped therapy experienced resurgence of flare activity that was re-suppressed upon re-initiation. These patients had IL-1ß levels comparable to those in IL-1ß-driven diseases. Child Health Assessment Questionnaires confirmed extensive subjective improvements in the pain and general health visual analogue scales. CONCLUSION: This case series demonstrates significant benefits from IL-1 inhibitors for reducing flare activity and improving the general health of patients with FOP. These data provide strong support for additional studies to better understand the function of IL-1 inhibition, primarily in reducing formation new HO. FUNDING: RH received support from the International FOP Association ACT grant; ECH received support from NIH/NIAMS R01AR073015 and the UCSF Robert Kroc Chair in Connective Tissue and Rheumatic Diseases III.

Human iPSC-Derived Proinflammatory Macrophages cause Insulin Resistance in an Isogenic White Adipose Tissue Microphysiological System.

Chronic white adipose tissue (WAT) inflammation has been recognized as a critical early event in the pathogenesis of obesity-related disorders. This process is characterized by the increased residency of proinflammatory M1 macrophages in WAT. However, the lack of an isogenic human macrophage-adipocyte model has limited biological studies and drug discovery efforts, highlighting the need for human stem cell-based approaches. Here, human induced pluripotent stem cell (iPSC) derived macrophages (iMACs) and adipocytes (iADIPOs) are cocultured in a microphysiological system (MPS). iMACs migrate toward and infiltrate into the 3D iADIPOs cluster to form crown-like structures (CLSs)-like morphology around damaged iADIPOs, recreating classic histological features of WAT inflammation seen in obesity. Significantly more CLS-like morphologies formed in aged and palmitic acid-treated iMAC-iADIPO-MPS, showing the ability to mimic inflammatory severity. Importantly, M1 (proinflammatory) but not M2 (tissue repair) iMACs induced insulin resistance and dysregulated lipolysis in iADIPOs. Both RNAseq and cytokines analyses revealed a reciprocal proinflammatory loop in the interactions of M1 iMACs and iADIPOs. This iMAC-iADIPO-MPS thus successfully recreates pathological conditions of chronically inflamed human WAT, opening a door to study the dynamic inflammatory progression and identify clinically relevant therapies.

Improving care pathways for people living with rare bone diseases (RBDs): outcomes from the first RBD Summit.

INTRODUCTION: Rare bone diseases (RBDs) are a heterogenous group of disorders that are poorly understood and challenging to treat. This creates a plethora of unmet needs for people with RBDs as well as their families and care providers, including diagnostic delays, limited access to expert care, and a lack of specialized treatments. The RBD Summit, which took place across 2 days in November 2021, was a virtual meeting of 65 RBD experts from clinical, academic, and patient communities as well as the pharmaceutical industry. The first meeting of its kind, the RBD Summit aimed to facilitate dialog and information exchange between delegates to advance knowledge and awareness of RBDs and improve patient outcomes. METHODS: Key challenges were discussed, and actions for overcoming them were proposed, including how obstacles to diagnosis can be overcome by (a) improving awareness of RBDs, (b) the implementation of a person-centered care pathway, and (c) how to narrow the communication gap between patients and healthcare professionals. RESULTS: Agreed actions were categorized as short term and long term, and priorities determined. CONCLUSION: In this position paper, we provide an overview of key discussions from the RBD Summit, summarize the subsequent action plan, and discuss the next steps in this continued collaboration.

A Case of Hypercalcemia from PTHrP-Producing Fibromyxoid Sarcoma Responsive to Glucocorticoid Therapy.

The treatment of parathyroid hormone-related protein (PTHrP)-mediated hypercalcemia of malignancy includes treating the malignancy, intravenous fluids, and anti-resorptive therapies such as zoledronic acid or denosumab. PTHrP-mediated hypercalcemia has been reported in benign conditions such as systemic lupus erythematous (SLE) and sarcoidosis and appears to be responsive to glucocorticoids. We report a case of PTHrP-induced hypercalcemia due to a malignancy-low grade fibromyxoid sarcoma-that responded to glucocorticoid treatment. This is the first report of glucocorticoids controlling PTHrP-mediated hypercalcemia of malignancy. Immunohistochemistry of the surgical pathology localized PTHrP staining to the vascular endothelial cells within the tumor. Further studies are needed to elucidate the mechanism of glucocorticoid action in the treatment of PTHrP-mediated hypercalcemia of malignancy.

Study methodology and insights from the palovarotene clinical development program in fibrodysplasia ossificans progressiva.

BACKGROUND: The design of clinical trials in rare diseases is often complicated by a lack of real-world translational knowledge. Fibrodysplasia ossificans progressiva (FOP) is an ultra-rare genetic disorder characterized by skeletal malformations and progressive heterotopic ossification (HO). Palovarotene is a selective retinoic acid receptor gamma agonist. Here, we describe the methodology of three studies in the palovarotene clinical development program in FOP and discuss insights that could inform future research, including endpoint suitability and the impact of trial design. METHODS: PVO-1A-001 (NCT02322255) was a prospective, protocol-specified, longitudinal FOP natural history study (NHS). PVO-1A-201 (NCT02190747) was a randomized, double-blind, placebo-controlled phase II trial; PVO-1A-202 (NCT02279095) was its open-label extension. Trial designs, including treatment regimens and imaging assessments, were refined between PVO-1A-201 and PVO-|1A-202, and within PVO-1A-202, based on emerging data as the studies progressed. Palovarotene doses were administered using a flare-up treatment regimen (higher dose for 2/4 weeks, followed by lower dose for 4/≥8 weeks; from flare-up onset), with or without accompanying chronic (daily) treatment. Flare-up and disease progression outcomes were assessed, including incidence and volume of new HO during flare-ups and/or annually, as well as other clinical, patient-reported, and exploratory outcomes. Safety was monitored throughout all studies. RESULTS: Overall, 114 and 58 individuals with FOP were enrolled in the NHS and phase II trials, respectively. Results of the NHS and PVO-1A-201 were published in 2022; complete results of PVO-1A-202 will be publicly available in due course. Together the studies yielded important information on endpoint suitability, including that low-dose whole-body computed tomography was the optimum imaging modality for assessing HO progression annually and that long study durations are needed to detect substantial changes in functional and patient-reported outcomes. CONCLUSIONS: A flexible clinical development program is necessary for underexplored rare diseases to overcome the many challenges faced. Here, the NHS provided a longitudinal evaluation of FOP progression and interventional trials were based on emerging data. The studies described informed the design and endpoints implemented in the phase III MOVE trial (NCT03312634) and provide a foundation for future clinical trial development. TRIAL REGISTRATION: NCT02322255 (registered 23/12/2014); NCT02190747 (registered 15/07/2014); NCT02279095 (registered 30/10/2014).

EML4::ALK fusions in complex lymphatic malformations.

Gorham-Stout disease (GSD) and generalized lymphatic anomaly (GLA) are subtypes of complex lymphatic malformations (CLMs) with osseous involvement that cause significant complications, including pain and pathologic fractures. As with other vascular anomalies, somatic mosaic mutations in oncogenes are often present, and the mTOR inhibitor sirolimus alleviates symptoms in some, but not all, patients. We describe two patients, one with GSD and one with GLA, found to have EML4::ALK fusions. This report of a targetable, oncogenic fusion in vascular malformations expands our understanding of the genetic basis for CLMs and suggests additional targeted therapies could be effective.

Most Fractures Treated Nonoperatively in Individuals With Fibrodysplasia Ossificans Progressiva Heal With a Paucity of Flareups, Heterotopic Ossification, and Loss of Mobility.

BACKGROUND: Fibrodysplasia ossificans progressiva (FOP) is an ultrarare genetic disorder with episodic and progressive heterotopic ossification. Tissue trauma is a major risk factor for flareups, heterotopic ossification (HO), and loss of mobility in patients with FOP. The International Clinical Council on FOP generally recommends avoiding surgery in patients with FOP unless the situation is life-threatening, because soft tissue injury can trigger an FOP flareup. Surprisingly little is known about flareups, HO formation, and loss of mobility after fractures of the normotopic (occurring in the normal place, distinct from heterotopic) skeleton when treated nonoperatively in patients with FOP. QUESTIONS/PURPOSES: (1) What proportion of fractures had radiographic evidence of union (defined as radiographic evidence of healing at 6 weeks) or nonunion (defined as the radiographic absence of a bridging callus at 3 years after the fracture)? (2) What proportion of patients had clinical symptoms of an FOP flareup because of the fracture (defined by increased pain or swelling at the fracture site within several days after closed immobilization)? (3) What proportion of patients with fractures had radiographic evidence of HO? (4) What proportion of patients lost movement after a fracture? METHODS: We retrospectively identified 36 patients with FOP from five continents who sustained 48 fractures of the normotopic skeleton from January 2001 to February 2021, who were treated nonoperatively, and who were followed for a minimum of 18 months after the fracture and for as long as 20 years, depending on when they sustained their fracture during the study period. Five patients (seven fractures) were excluded from the analysis to minimize cotreatment bias because these patients were enrolled in palovarotene clinical trials (NCT02190747 and NCT03312634) at the time of their fractures. Thus, we analyzed 31 patients (13 male, 18 female, median age 22 years, range 5 to 57 years) who sustained 41 fractures of the normotopic skeleton that were treated nonoperatively. Patients were analyzed at a median follow-up of 6 years (range 18 months to 20 years), and none was lost to follow-up. Clinical records for each patient were reviewed by the referring physician-author and the following data for each fracture were recorded: biological sex, ACVR1 gene pathogenic variant, age at the time of fracture, fracture mechanism, fracture location, initial treatment modality, prednisone use at the time of the fracture as indicated in the FOP Treatment Guidelines for flare prevention (2 mg/kg once daily for 4 days), patient-reported flareups (episodic inflammatory lesions of muscle and deep soft connective tissue characterized variably by swelling, escalating pain, stiffness, and immobility) after the fracture, follow-up radiographs of the fracture if available, HO formation (yes or no) as a result of the fracture determined at a minimum of 6 weeks after the fracture, and patient-reported loss of motion at least 6 months after and as long as 20 years after the fracture. Postfracture radiographs were available in 76% (31 of 41) of fractures in 25 patients and were independently reviewed by the referring physician-author and senior author for radiographic criteria of fracture healing and HO. RESULTS: Radiographic healing was noted in 97% (30 of 31) of fractures at 6 weeks after the incident fracture. Painless nonunion was noted in one patient who sustained a displaced patellar fracture and HO. In seven percent (three of 41) of fractures, patients reported increased pain or swelling at or near the fracture site within several days after fracture immobilization that likely indicated a site-specific FOP flareup. The same three patients reported a residual loss of motion 1 year after the fracture compared with their prefracture status. HO developed in 10% (three of 31) of the fractures for which follow-up radiographs were available. Patient-reported loss of motion occurred in 10% (four of 41) of fractures. Two of the four patients reported noticeable loss of motion and the other two patients reported that the joint was completely immobile (ankylosis). CONCLUSION: Most fractures treated nonoperatively in individuals with FOP healed with few flareups, little or no HO, and preservation of mobility, suggesting an uncoupling of fracture repair and HO, which are two inflammation-induced processes of endochondral ossification. These findings underscore the importance of considering nonoperative treatment for fractures in individuals with FOP. Physicians who treat fractures in patients with FOP should consult with a member of the International Clinical Council listed in the FOP Treatment Guidelines ( https://www.iccfop.org ). LEVEL OF EVIDENCE: Level IV, therapeutic study.

The natural history of fibrodysplasia ossificans progressiva: A prospective, global 36-month study.

PURPOSE: We report the first prospective, international, natural history study of the ultra-rare genetic disorder fibrodysplasia ossificans progressiva (FOP). FOP is characterized by painful, recurrent flare-ups, and disabling, cumulative heterotopic ossification (HO) in soft tissues. METHODS: Individuals aged ≤65 years with classical FOP (ACVR1R206H variant) were assessed at baseline and over 36 months. RESULTS: In total, 114 individuals participated; 33 completed the study (mean follow up: 26.8 months). Median age was 15.0 (range: 4-56) years; 54.4% were male. During the study, 82 (71.9%) individuals reported 229 flare-ups (upper back: 17.9%, hip: 14.8%, shoulder: 10.9%). After 84 days, 14 of 52 (26.9%) imaged flare-ups had new HO at the flare-up site (mean new HO volume: 28.8 × 103 mm3). Mean baseline low-dose whole-body computed tomography (excluding head) HO volume was 314.4 × 103 mm3; lowest at 2 to <8 years (68.8 × 103 mm3) and increasing by age (25-65 years: 575.2 × 103 mm3). The mean annualized volume of new HO was 23.6 × 103 mm3/year; highest at 8 to <15 and 15 to <25 years (21.9 × 103 and 41.5 × 103 mm3/year, respectively) and lowest at 25 to 65 years (4.6 × 103 mm3/year). CONCLUSION: Results from individuals receiving standard care for up to 3 years in this natural history study show the debilitating effect and progressive nature of FOP cross-sectionally and longitudinally, with greatest progression during childhood and early adulthood.

Whole-body Computed Tomography Versus Dual Energy X­ray Absorptiometry for Assessing Heterotopic Ossification in Fibrodysplasia Ossificans Progressiva.

Fibrodysplasia ossificans progressiva (FOP) is an ultra-rare genetic disorder that leads to heterotopic ossification (HO), resulting in progressive restriction of physical function. In this study, low-dose, whole-body computed tomography (WBCT) and dual energy X-ray absorptiometry (DXA) were evaluated to determine the preferred method for assessing total body burden of HO in patients with FOP. This was a non-interventional, two-part natural history study in patients with FOP (NCT02322255; date of registration: December 2014). In Part A (described here), WBCT and DXA scans were individually assessed for HO presence and severity across 15 anatomical regions. All images were independently reviewed by an expert imaging panel. Ten adult patients were enrolled across four sites. The sensitivity to HO presence and severity varied considerably between the two imaging modalities, with WBCT demonstrating HO in more body regions than DXA (76/138 [55%] versus 47/113 [42%]) evaluable regions). Inability to evaluate HO presence, due to overlapping body regions (positional ambiguity), occurred less frequently by WBCT than by DXA (mean number of non-evaluable regions per scan 1.2 [standard deviation: 1.5] versus 2.4 [1.4]). Based on the increased sensitivity and decreased positional ambiguity of low-dose WBCT versus DXA in measuring HO in patients with FOP, low-dose WBCT was chosen as the preferred imaging for measuring HO. Therefore, low-dose WBCT was carried forward to Part B of the natural history study, which evaluated disease progression over 36 months in a larger population of patients with FOP.

Cell-autonomous correction of ring chromosomes in human induced pluripotent stem cells.

Ring chromosomes are structural aberrations commonly associated with birth defects, mental disabilities and growth retardation. Rings form after fusion of the long and short arms of a chromosome, and are sometimes associated with large terminal deletions. Owing to the severity of these large aberrations that can affect multiple contiguous genes, no possible therapeutic strategies for ring chromosome disorders have been proposed. During cell division, ring chromosomes can exhibit unstable behaviour leading to continuous production of aneuploid progeny with low viability and high cellular death rate. The overall consequences of this chromosomal instability have been largely unexplored in experimental model systems. Here we generated human induced pluripotent stem cells (iPSCs) from patient fibroblasts containing ring chromosomes with large deletions and found that reprogrammed cells lost the abnormal chromosome and duplicated the wild-type homologue through the compensatory uniparental disomy (UPD) mechanism. The karyotypically normal iPSCs with isodisomy for the corrected chromosome outgrew co-existing aneuploid populations, enabling rapid and efficient isolation of patient-derived iPSCs devoid of the original chromosomal aberration. Our results suggest a fundamentally different function for cellular reprogramming as a means of 'chromosome therapy' to reverse combined loss-of-function across many genes in cells with large-scale aberrations involving ring structures. In addition, our work provides an experimentally tractable human cellular system for studying mechanisms of chromosomal number control, which is of critical relevance to human development and disease.

Surgical management of bilateral hip fractures in a patient with fibrodysplasia ossificans progressiva treated with the RAR-γ agonist palovarotene: a case report.

BACKGROUND: Fibrodysplasia ossificans progressiva (FOP) is an ultra-rare disorder marked by painful, recurrent flare-ups and heterotopic ossification (HO) in soft and connective tissues, which can be idiopathic or provoked by trauma, illness, inflammation, or surgery. There are currently no effective treatments for FOP, or for patients with FOP who must undergo surgery. Palovarotene, an investigational retinoic acid receptor-γ agonist, offers a potential avenue to prevent HO formation. CASE PRESENTATION: The patient is a 32 year-old male, who at age 29 enrolled in a study evaluating palovarotene to prevent HO formation in FOP. One year after starting palovarotene, he fell resulting in a left intertrochanteric fracture. He underwent intramedullary nailing of the femur shaft with screw placement at the distal femur. After surgery, he received palovarotene at 20 mg/day for 4 weeks, then 10 mg/day for 8 weeks. Imaging 12 weeks after surgery showed new bridging HO at the site of intramedullary rod insertion and distal screw. Nine months after the left hip fracture, the patient had a second fall resulting in a subdural hematoma, left parietal bone fracture, and right intertrochanteric fracture. He underwent intramedullary nailing of the right hip, in a modified procedure which did not require distal screw placement. Palovarotene 20 mg/day was started at fracture occurrence and continued for 4 weeks, then reduced to 10 mg/day for 8 weeks. HO also formed near the insertion site of the intramedullary rod. No HO developed at the right distal intramedullary rod. After each fracture, the patient had prolonged recurrent flare-ups around the hips. CONCLUSION: Surgery is only rarely considered in FOP due to the high risks of procedural complications and potential for inducing HO. This case emphasizes the risks of increased flare activity and HO formation from injury and surgery in patients with FOP. The efficacy of HO prevention by palovarotene could not be assessed; however, our observation that palovarotene can be administered in an individual with FOP following surgery with no negative impact on clinical fracture healing, osteointegration, or skin healing will help facilitate future trials testing the role of palovarotene as a therapy for HO.

Therapeutic advances for blocking heterotopic ossification in fibrodysplasia ossificans progressiva.

Fibrodysplasia ossificans progressiva (FOP) is a rare genetic disease in which heterotopic bone forms in muscle and soft tissue, leading to joint dysfunction and significant disability. FOP is progressive and many patients are wheelchair-bound by the 3rd decade of life. FOP is caused by an activating mutation in the ACVR1 gene, which encodes the activin A Type 1 receptor. Aberrant signalling through this receptor leads to abnormal activation of the pSMAD 1/5/8 pathway and triggers the formation of bone outside of the skeleton. There is no curative therapy for FOP; however, exciting advances in novel therapies have developed recently. Here, we review the clinical and translational pharmacology of three drugs that are currently in clinical trials (palovarotene, REGN 2477 and rapamycin) as well as other emerging treatment strategies for FOP.

Special considerations for clinical trials in fibrodysplasia ossificans progressiva (FOP).

Clinical trials for orphan diseases are critical for developing effective therapies. One such condition, fibrodysplasia ossificans progressiva (FOP; MIM#135100), is characterized by progressive heterotopic ossification (HO) that leads to severe disability. Individuals with FOP are extremely sensitive to even minor traumatic events. There has been substantial recent interest in clinical trials for novel and urgently-needed treatments for FOP. The International Clinical Council on FOP (ICC) was established in 2016 to provide consolidated and coordinated advice on the best practices for clinical care and clinical research for individuals who suffer from FOP. The Clinical Trials Committee of the ICC developed a focused list of key considerations that encompass the specific and unique needs of the FOP community - considerations that are endorsed by the entire ICC. These considerations complement established protocols for developing and executing robust clinical trials by providing a foundation for helping to ensure the safety of subjects with FOP in clinical research trials.

Inflammation in Fibrodysplasia Ossificans Progressiva and Other Forms of Heterotopic Ossification.

PURPOSE OF REVIEW: Heterotopic ossification (HO) is associated with inflammation. The goal of this review is to examine recent findings on the roles of inflammation and the immune system in HO. We examine how inflammation changes in fibrodysplasia ossificans progressiva, in traumatic HO, and in other clinical conditions of HO. We also discuss how inflammation may be a target for treating HO. RECENT FINDINGS: Both genetic and acquired forms of HO show similarities in their inflammatory cell types and signaling pathways. These include macrophages, mast cells, and adaptive immune cells, along with hypoxia signaling pathways, mesenchymal stem cell differentiation signaling pathways, vascular signaling pathways, and inflammatory cytokines. Because there are common inflammatory mediators across various types of HO, these mediators may serve as common targets for blocking HO. Future research may focus on identifying new inflammatory targets and testing combinatorial therapies based on these results.

BMP-SMAD-ID promotes reprogramming to pluripotency by inhibiting p16/INK4A-dependent senescence.

Fibrodysplasia ossificans progressiva (FOP) patients carry a missense mutation in ACVR1 [617G > A (R206H)] that leads to hyperactivation of BMP-SMAD signaling. Contrary to a previous study, here we show that FOP fibroblasts showed an increased efficiency of induced pluripotent stem cell (iPSC) generation. This positive effect was attenuated by inhibitors of BMP-SMAD signaling (Dorsomorphin or LDN1931890) or transducing inhibitory SMADs (SMAD6 or SMAD7). In normal fibroblasts, the efficiency of iPSC generation was enhanced by transducing mutant ACVR1 (617G > A) or SMAD1 or adding BMP4 protein at early times during the reprogramming. In contrast, adding BMP4 at later times decreased iPSC generation. ID genes, transcriptional targets of BMP-SMAD signaling, were critical for iPSC generation. The BMP-SMAD-ID signaling axis suppressed p16/INK4A-mediated cell senescence, a major barrier to reprogramming. These results using patient cells carrying the ACVR1 R206H mutation reveal how cellular signaling and gene expression change during the reprogramming processes.

Fibrodysplasia ossificans progressiva: a current review of imaging findings.

OBJECTIVE: Fibrodysplasia ossificans progressiva is a rare genetic disorder characterized by congenital skeletal deformities and soft tissue masses that progress to heterotopic ossification. Deformities of the great toes are distinctive, and heterotopic ossification in the soft tissues follows an expected anatomic and temporal pattern. In addition to heterotopic ossification, osteochondromata, middle ear ossification, demyelination, lymphedema, and venous thrombosis are characteristic. Awareness of this constellation of findings is important to early diagnosis and surveillance. CONCLUSIONS: Recognition of the imaging manifestations of fibrodysplasia ossificans progressiva is imperative to early diagnosis in order to appropriately direct patient care and preclude unnecessary biopsies or surgical procedures.

Assessing the osteoblast transcriptome in a model of enhanced bone formation due to constitutive Gs-G protein signaling in osteoblasts.

G protein-coupled receptor (GPCR) signaling in osteoblasts (OBs) is an important regulator of bone formation. We previously described a mouse model expressing Rs1, an engineered constitutively active Gs-coupled GPCR, under the control of the 2.3 kb Col I promoter. These mice showed a dramatic age-dependent increase in trabecular bone of femurs. Here, we further evaluated the effects of enhanced Gs signaling in OBs on intramembranous bone formation by examining calvariae of 1- and 9-week-old Col1(2.3)/Rs1 mice and characterized the in vivo gene expression specifically occurring in osteoblasts with activated Gs G protein-coupled receptor signaling, at the cellular level rather than in a whole bone. Rs1 calvariae displayed a dramatic increase in bone volume with partial loss of cortical structure. By immunohistochemistry, Osterix was detected in cells throughout the inter-trabecular space while Osteocalcin was expressed predominantly in cells along bone surfaces, suggesting the role of paracrine mediators secreted from OBs driven by 2.3 kb Col I promoter could influence early OB commitment, differentiation, and/or proliferation. Gene expression analysis of calvarial OBs revealed that genes affected by Rs1 signaling include those encoding proteins important for cell differentiation, cytokines and growth factors, angiogenesis, coagulation, and energy metabolism. The set of Gs-GPCRs and other GPCRs that may contribute to the observed skeletal phenotype and candidate paracrine mediators of the effect of Gs signaling in OBs were also determined. Our results identify novel detailed in vivo cellular changes of the anabolic response of the skeleton to Gs signaling in mature OBs.

A Case of Hypercalcemia and Overexpression of CYP27B1 in Skeletal Muscle Lesions in a Patient with HIV Infection After Cosmetic Injections with Polymethylmethacrylate (PMMA) for Wasting.

Foreign body-induced granuloma is an uncommon yet clinically significant cause of hypercalcemia. The molecular mechanisms are uncertain, although extrarenal calcitriol production has been proposed. We describe severe hypercalcemia associated with increased levels of plasma calcitriol in a patient with HIV and local granulomatous reaction 5 years after injection of polymethylmethacrylate (PMMA) as dermal filler for cosmetic body sculpting. Extensive evaluation revealed no identifiable cause of increased calcitriol levels. Nuclear imaging was remarkable for diffuse uptake in the subcutaneous tissues of the buttocks. Subsequent muscle biopsy and immunohistochemical staining showed strong local expression of CYP27B1 within histiocytes surrounding globules of PMMA. This case highlights an unfortunate complication of dermal fillers and shows that inflammatory cells can express high levels of CYP27B1 even without frank granulomas. The growing trend of body contour enhancement using injectable fillers should raise suspicion for this cause of hypercalcemia in clinical practice. Patients with HIV who receive this treatment for lipodystrophy or other cosmetic purposes may have increased susceptibility to hypercalcemia in the setting of underlying chronic inflammation. This may be a concern when changing anti-retroviral therapy, since alterations in levels of HIV viremia may initiate or contribute to worsening hypercalcemia.

Chronic recurrent multifocal osteomyelitis with an atypical presentation in an adult man.

We present the case of a 33-year-old man with no significant medical history who developed right scapular pain, left-sided sacroiliac joint pain, and lower back pain, and was eventually diagnosed with chronic recurrent multifocal osteomyelitis (CRMO). Imaging demonstrated multiple scattered T2-hyperintense lesions on MRI at the spine and the left SI joint, some of which progressed and one regressed in size on follow-up. Histopathology demonstrated only non-specific chronic inflammation compatible with CRMO. No evidence of infectious organisms or neoplastic processes was found. The pain was relapsing and remitting in nature. Laboratory investigations were notable for no evidence of hematologic malignancy or infection, but only a mild increase in alkaline phosphatase. This case highlights that CRMO, despite being thought of as a childhood-onset disease, can present in adults as well, and also provides illustrative examples of imaging and histological findings.

Activated Gs signaling in osteoblastic cells alters the hematopoietic stem cell niche in mice.

Adult hematopoiesis occurs primarily in the BM space where hematopoietic cells interact with stromal niche cells. Despite this close association, little is known about the specific roles of osteoblastic lineage cells (OBCs) in maintaining hematopoietic stem cells (HSCs), and how conditions affecting bone formation influence HSC function. Here we use a transgenic mouse model with the ColI(2.3) promoter driving a ligand-independent, constitutively active 5HT4 serotonin receptor (Rs1) to address how the massive increase in trabecular bone formation resulting from increased G(s) signaling in OBCs impacts HSC function and blood production. Rs1 mice display fibrous dysplasia, BM aplasia, progressive loss of HSC numbers, and impaired megakaryocyte/erythrocyte development with defective recovery after hematopoietic injury. These hematopoietic defects develop without compensatory extramedullary hematopoiesis, and the loss of HSCs occurs despite a paradoxical expansion of stromal niche cells with putative HSC-supportive activity (ie, endothelial, mesenchymal, and osteoblastic cells). However, Rs1-expressing OBCs show decreased expression of key HSC-supportive factors and impaired ability to maintain HSCs. Our findings indicate that long-term activation of G(s) signaling in OBCs leads to contextual changes in the BM niche that adversely affect HSC maintenance and blood homeostasis.