Paradoxical effects of statins on aortic valve myofibroblasts and osteoblasts: implications for end-stage valvular heart disease

OBJECTIVES

We evaluated the effects of statins on aortic valve myofibroblasts (AVMFs) and osteoblast calcification in vitro.

METHODS AND RESULTS

Cultured porcine AVMFs and M2-10B4 cells were treated with simvastatin and pravastatin. Mevalonate, a 3-hydroxy-3-methylglutaryl (HMG)-coenzyme A (CoA) reductase metabolite, was added in parallel experiments. Manumycin A, which inhibits protein prenylation, was added to cultures in the absence of statins. Calcification was assessed by counting the number of calcific nodules formed and measuring alkaline phosphatase activity (APA). Statins inhibited calcific nodule formation (P<0.01) and APA (P<0.01) in AVMFs. Mevalonate reversed the statin effect on nodule formation (P<0.05) and APA (P<0.01). Manumycin A had no effect on either parameter. M2-10B4 cells treated with simvastatin formed more calcific nodules compared with controls (P<0.01), although pravastatin had no effect. Both statins, however, resulted in increased APA in M2-10B4 cells (P<0.01). Mevalonate had no impact on nodule numbers or APA in M2-10B4 cells.

CONCLUSIONS

Statins inhibit calcification in AVMFs by inhibiting the cholesterol biosynthetic pathway, independent of protein prenylation, but paradoxically stimulate bone cell calcification. Because 15% of patients with end-stage valvular heart disease exhibit mature bone in their aortic valves, statins may differentially regulate calcification within a valve, limiting dystrophic calcification but promoting ossification of formed bone.

Influenza-like viral illnesses and flare-ups of fibrodysplasia ossificans progressiva

Flare-ups of fibrodysplasia ossificans progressiva are most commonly triggered by soft tissue trauma. After observing severe flare-ups of fibrodysplasia ossificans progressiva in two half-sisters with culture-confirmed influenza B infections, we hypothesized that influenza-like viral illnesses also can trigger fibrodysplasia ossificans progressiva flare-ups. To address this hypothesis, we designed a questionnaire to assess whether patients with fibrodysplasia ossificans progressiva experienced influenza symptoms during the 2000 to 2001 influenza season, and whether these symptoms were correlated with flare-ups of the condition. The questionnaire was sent to patients with fibrodysplasia ossificans progressiva worldwide. Of the 264 patients surveyed, 123 (47%) responded. The survey revealed that the risk of a disease flare-up of fibrodysplasia ossificans progressiva during an influenza-like viral illness was increased at least threefold and possibly much more. The survey data strongly supported the hypothesis that influenza-like viral illnesses are associated with disease flare-ups in patients who have fibrodysplasia ossificans progressiva. Influenza-like viral illnesses may be a source of previously unrecognized muscle injury leading to heterotopic ossification and permanent loss of mobility in these patients. These findings have important implications for understanding and preventing environmental triggers of disease activity in this population of patients genetically susceptible to progressive heterotopic ossification.

Heterotopic ossification

Heterotopic ossification, the formation of bone in soft tissue, requires inductive signaling pathways, inducible osteoprogenitor cells, and a heterotopic environment conducive to osteogenesis. Little is known about the molecular pathogenesis of this condition. Research into two rare heritable and developmental forms, fibrodysplasia ossificans progressiva and progressive osseous heteroplasia, has provided clinical, pathologic, and genetic insights. In fibrodysplasia ossificans progressiva, overexpression of bone morphogenetic protein 4 and underexpression of multiple antagonists of this protein highlight the potential role of a potent morphogenetic gradient. Research on fibrodysplasia ossificans progressiva also has led to the identification of the genetic cause of progressive osseous heteroplasia: inactivating mutations in the alpha subunit of the gene coding for the stimulatory G protein of adenylyl cyclase. Better understanding of the complex developmental and molecular pathology of these disorders may lead to more effective strategies to prevent and treat other, more common forms of heterotopic ossification.

In vivo somatic cell gene transfer of an engineered Noggin mutein prevents BMP4-induced heterotopic ossification

BACKGROUND

The formation of the skeleton requires inductive signals that are balanced with their antagonists in a highly regulated negative feedback system. Inappropriate or excessive expression of BMPs (bone morphogenetic proteins) or their antagonists results in genetic disorders affecting the skeleton, such as fibrodysplasia ossificans progressiva. BMP signaling mediated through binding to its receptors is a critical step in the induction of abnormal ossification. Therefore, we hypothesized that engineering more effective inhibitors of this BMP-signaling process may lead to the development of therapies for such conditions.

METHODS

BMP4-induced heterotopic ossification was used as a model for testing the ability of the BMP antagonist Noggin to block de novo bone formation, either by local or systemic delivery. Since Noggin naturally acts locally, a Noggin mutein, hNOGDeltaB2, was engineered and was shown to circulate systemically, and its ability to block heterotopic ossification was tested in a mouse model with use of adenovirus-mediated somatic cell gene transfer.

RESULTS

A mouse model of BMP4-induced heterotopic ossification was developed. Local delivery of wild-type NOG inhibited heterotopic ossification, but systemic administration was ineffective. In contrast, systemic delivery of the adenovirus encoding hNOGDeltaB2 resulted in systemic levels that persisted for more than two weeks and were sufficient to block BMP4-induced heterotopic ossification.

CONCLUSIONS

BMP4-induced heterotopic ossification can be prevented in vivo either by local delivery of wild-type Noggin or after somatic cell gene transfer of a Noggin mutein, hNOGDeltaB2. Furthermore, the data in the present study provide proof of concept that a naturally occurring factor can be engineered for systemic delivery toward a desirable pharmacological outcome.

CLINICAL RELEVANCE

Blocking bone formation is clinically relevant to disorders of heterotopic ossification in humans, such as fibrodysplasia ossificans progressiva. Furthermore, development of BMP antagonists as therapeutic agents may provide modalities for the treatment of other pathologic conditions that arise from aberrant expression of BMPs and/or from a lack of their antagonists.

Stromal cells of fibrodysplasia ossificans progressiva lesions express smooth muscle lineage markers and the osteogenic transcription factor Runx2/Cbfa-1: clues to a vascular origin of heterotopic ossification?

Fibrodysplasia ossificans progressiva (FOP) is a rare heritable genetic disorder, which is characterized pathologically by sporadic episodes of explosive growth of mesenchymal cells in skeletal muscle followed by cellular differentiation to heterotopic bone through an endochondral process. This study examined the histological origin and differentiation state of stromal cells in early FOP lesions and investigated the association between the phenotype of these FOP cells and bone formation. Interestingly, FOP lesional stromal cells were found to display characteristics of the smooth muscle (SM) cell lineage and are therefore potentially of vascular origin. These cells co-express multiple SM lineage markers along with multiple proteins associated with bone formation including the obligate osteogenic transcription factor Runx2/Cbfa-1. It is hypothesized that the stromal cells of early FOP lesions may be locally recruited vascular cells or cells of the bone marrow stroma and that these cells maintain the potential (given the correct environmental stimuli) to differentiate along an endochondral ossification pathway.

Progressive osseous heteroplasia in the face of a child

We describe a rare case of progressive osseous heteroplasia of the face in a child. Biopsy showed osteoma cutis superficially with ectopic bone formation in the deeper tissues including skeletal muscle. Analysis of DNA from peripheral blood leukocytes showed mutations in the gene encoding the alpha subunit of the stimulatory G protein of adenylyl cyclase (GNAS1), confirming the diagnosis of progressive osseous heteroplasia.

Paresis of a bone morphogenetic protein-antagonist response in a genetic disorder of heterotopic skeletogenesis

BACKGROUND

Fibrodysplasia ossificans progressiva is a rare genetic disorder characterized by congenital malformations of the great toes and by progressive heterotopic bone formation. Bone morphogenetic protein-4 (BMP-4) messenger ribonucleic acid (mRNA) and protein are uniquely overexpressed in lymphocytes and lesional cells from patients who have fibrodysplasia ossificans progressiva. However, the BMP-4 gene is not mutated in fibrodysplasia ossificans progressiva. The activities of BMPs are specified in part by the formation of morphogen gradients that are further regulated by an array of secreted antagonists. Recent studies have indicated that BMP-4 upregulates the expression of the BMP antagonists noggin, gremlin, and follistatin, thereby establishing an autoregulatory feedback loop. Therefore, a defect in the feedback pathway between BMP-4 and one or more of its extracellular antagonists could contribute to the elevated BMP-4 activity characteristic of fibrodysplasia ossificans progressiva.

METHODS

Basal and BMP-4-induced expression of noggin, gremlin, follistatin, and chordin mRNA were investigated in control and fibrodysplasia ossificans progressiva lymphoblastoid cell lines with use of reverse transcriptase-polymerase chain reaction and Northern analysis.

RESULTS

In the absence of exogenous BMP-4 stimulation (basal state), steady-state levels of all of the BMP antagonists that were investigated were similar in fibrodysplasia ossificans progressiva and control cell lines. Upon stimulation with recombinant human BMP-4, control lymphoblastoid cell lines exhibited a marked increase in expression of noggin and gremlin mRNA. Fibrodysplasia ossificans progressiva cells, however, showed a dramatically attenuated response to BMP-4 stimulation compared with that of controls.

CONCLUSIONS

These data indicate a paresis of a BMP-antagonist response, suggesting the loss of a negative feedback mechanism by which cells normally regulate the magnitude and boundaries of ambient morphogenetic signals. This paresis may account in part for the increased BMP-4 activity in fibrodysplasia ossificans progressiva.

Bone morphogenetic protein-4 regulation in fibrodysplasia ossificans progressiva

Fibrodysplasia ossificans progressiva is a rare genetic disorder in which connective tissues are replaced with heterotopic bone through an endochondral process. Bone morphogenetic protein-4 messenger ribonucleic acid and protein levels are elevated in the cells of patients with fibrodysplasia ossificans progressiva, but the molecular mechanism of this steady-state elevation is unknown. Nuclear run-on assays and messenger ribonucleic acid stability assays were done to examine the molecular mechanisms of increased bone morphogenetic protein-4 messenger ribonucleic acid. The bone morphogenetic protein-4 transcription rate in patient cells was found to be enhanced fivefold to sevenfold over normal control cells, suggesting that elevated steady-state levels of this transcript were attributable at least in part to an enhancement in transcription initiation. The stability of bone morphogenetic protein-4 messenger ribonucleic acid was found to be similar for patient and control cells and to have an extremely brief half-life, with bone morphogenetic protein-4 messenger ribonucleic acid almost completely decayed (75%) by 40 minutes. This unusually brief half-life suggests that a high fidelity control over temporal expression of the bone morphogenetic protein 4-message can be maintained. The data document that enhanced transcription rather than increased messenger ribonucleic acid stability is responsible for the elevation in steady-state levels of bone morphogenetic protein-4 messenger ribonucleic acid, and suggest that an inappropriate enhancement of the rate of bone morphogenetic protein-4 transcription plays a critical role in the molecular pathophysiology of fibrodysplasia ossificans progressiva.

Exoneration of NF-kappaB dysregulation in fibrodysplasia ossificans progressiva

Fibrodysplasia ossificans progressiva is a disabling genetic disorder characterized by congenital skeletal malformations and progressive heterotopic ossification. New episodes of ossification are heralded by preosseous inflammatory lesions replete with B and T lymphocytes that overexpress bone morphogenetic protein-4. NF-kappaB is an inflammatory mediator that plays a critical role in developmental skeletogenesis and in suppression of bone morphogenetic protein-4 expression. Because of its multiple roles in inflammation, skeletogenesis, and bone morphogenetic protein-4 regulation, NF-kappaB may play an important functional role in the pathogenesis of fibrodysplasia ossificans progressiva. To clarify the potential role of NF-kappaB in the pathophysiologic features of fibrodysplasia ossificans progressiva, the role of NF-kappaB in regulating bone morphogenetic protein-4 signaling in patient-derived lymphoblastoid cell lines was examined. General NF-kappaB activity and specific NF-kappaB suppression of bone morphogenetic protein-4 expression were not altered in fibrodysplasia ossificans progressiva. In addition, despite the proximity of the gene for the p50 subunit of NF-kappaB (NFKB1 on long arm of chromosome 4) to the recently mapped locus for fibrodysplasia ossificans progressiva, a detailed linkage exclusion analysis in four multigenerational families with the disorder excluded NFKB1 as the causative gene for fibrodysplasia ossificans progressiva. These data exonerate NF-kappaB as the critical molecular and genetic pathogenic mediator in fibrodysplasia ossificans progressiva and, therefore, implicate a defect in another regulatory pathway as the cause for bone morphogenetic protein-4 overexpression in the disease.

Paternally inherited inactivating mutations of the GNAS1 gene in progressive osseous heteroplasia

BACKGROUND

Progressive osseous heteroplasia (POH), an autosomal dominant disorder, is characterized by extensive dermal ossification during childhood, followed by disabling and widespread heterotopic ossification of skeletal muscle and deep connective tissue. Occasional reports of mild heterotopic ossification in Albright's hereditary osteodystrophy (AHO) and a recent report of two patients with AHO who had atypically extensive heterotopic ossification suggested a common genetic basis for the two disorders. AHO is caused by heterozygous inactivating mutations in the GNAS1 gene that result in decreased expression or function of the alpha subunit of the stimulatory G protein (Gsalpha) of adenylyl cyclase.

METHODS

We tested the hypothesis that GNAS1 mutations cause POH, using the polymerase chain reaction to amplify GNAS1 exons and exon-intron boundaries in 18 patients with sporadic or familial POH.

RESULTS

Heterozygous inactivating GNAS1 mutations were identified in 13 of the 18 probands with POH. The defective allele in POH is inherited exclusively from fathers, a result consistent with a model of imprinting for GNAS1. Direct evidence that the same mutation can cause either POH or AHO was observed within a single family, in which the phenotype correlated with the parental origin of the mutant allele.

CONCLUSIONS

Paternally inherited inactivating GNAS1 mutations cause POH. This finding extends the range of phenotypes derived from haplo insufficiency of GNAS1, provides evidence that imprinting is a regulatory mechanism for GNAS1 expression, and suggests that Gsalpha is a critical negative regulator of osteogenic commitment in nonosseous connective tissues.

Mast cell involvement in fibrodysplasia ossificans progressiva

Fibrodysplasia ossificans progressiva (FOP) is a catastrophic genetic disorder of progressive heterotopic ossification associated with dysregulated production of bone morphogenetic protein 4 (BMP4), a potent osteogenic morphogen. Postnatal heterotopic ossification in FOP is often heralded by hectic episodes of severe post-traumatic connective tissue swelling and intramuscular edema, followed by an intense and highly angiogenic fibroproliferative mass. The abrupt appearance, intense size, and rapid intrafascial spread of the edematous preosseous fibroproliferative lesions implicate a dysregulated wound response mechanism and suggest that cells and mediators involved in inflammation and tissue repair may be conscripted in the growth and progression of FOP lesions. The central and coordinate role of inflammatory mast cells and their mediators in tissue edema, wound repair, fibrogenesis, angiogenesis, and tumor invasion prompted us to investigate the potential involvement of mast cells in the pathology of FOP lesions. We show that inflammatory mast cells are present at every stage of the development of FOP lesions and are most pronounced at the highly vascular fibroproliferative stage. Mast cell density at the periphery of FOP lesional tissue is 40- to 150-fold greater than in normal control skeletal muscle or in uninvolved skeletal muscle from FOP patients and 10- to 40-fold greater than in any other inflammatory myopathy examined. These findings document mobilization and activation of inflammatory mast cells in the pathology of FOP lesions and provide a novel and previously unrecognized target for pharmacologic intervention in this extremely disabling disease.

Fibrodysplasia ossificans progressiva

Fibrodysplasia ossificans progressiva (FOP) is an extremely rare and disabling genetic disorder of connective tissue. The condition is characterized by congenital malformation of the great toes and by progressive heterotopic ossification of the tendons, ligaments, fasciae, and striated muscles. Fibrodysplasia ossificans progressiva occurs sporadically and is transmitted as a dominant trait with variable expression and complete penetrance. Reproductive fitness is low. There are fewer than 150 known patients with the disorder in the United States. A point prevalence of one affected patient in every 2 million of population has been observed. There is no sexual, racial, or ethnic predilection. The disease presents in early life; its course is unavoidably progressive. Most patients are confined to a wheelchair by the third decade of life and often succumb to pulmonary complications in the 5th/6th decade of life. At present there is no effective prevention or treatment. The recent discovery of overproduction of bone morphogenetic protein-4 in lesional cells and lymphocytic cells of affected patients provides a clue to both the underlying pathophysiology and potential therapy. The FOP gene has recently been mapped to human chromosome 4q 27-31.

Bone formation and inflammation in cardiac valves

BACKGROUND

For nearly a century, the mechanical failure of calcified heart valves was attributed to a passive degenerative process. Recently, several case reports described bone formation in surgically excised heart valves and suggested an unexpected process of tissue repair.

METHODS AND RESULTS

We studied the prevalence and pathology of heterotopic ossification in 347 surgically excised heart valves (256 aortic, 91 mitral) in 324 consecutive patients (182 men, 142 women; mean age 68 years) who underwent cardiac valve replacement surgery between 1994 and 1998. The valves were examined microscopically to determine the prevalence and features of bone formation and remodeling. Two hundred eighty-eight valves (83%) had dystrophic calcification. Mature lamellar bone with hematopoietic elements and active bone remodeling were present in 36 valves (13%) with dystrophic calcification. Endochondral bone formation, similar to that seen in normal fracture repair, was identified in 4 valves. Microfractures were present in 92% of all valves with ossification. Neoangiogenesis was found in all valves with ossification. Bone morphogenetic proteins 2 and 4 (BMP 2/4), potent osteogenic morphogens, were expressed by myofibroblasts and preosteoblasts in areas adjacent to B- and T-lymphocyte infiltration in valves where ossification was identified. Mast cells were present in calcified and ossified valves and were especially prominent in atheromatous regions.

CONCLUSIONS

Heterotopic ossification consisting of mature lamellar bone formation and active bone remodeling is a relatively common and unexpected finding in end-stage valvular heart disease and may be associated with repair of pathological microfractures in calcified cardiac valves.

Progressive osseous heteroplasia

Progressive osseous heteroplasia (POH) is a recently described genetic disorder of mesenchymal differentiation characterized by dermal ossification during infancy and progressive heterotopic ossification of cutaneous, subcutaneous, and deep connective tissues during childhood. The disorder can be distinguished from fibrodysplasia ossificans progressiva (FOP) by the presence of cutaneous ossification, the absence of congenital malformations of the skeleton, the absence of inflammatory tumorlike swellings, the asymmetric mosaic distribution of lesions, the absence of predictable regional patterns of heterotopic ossification, and the predominance of intramembranous rather than endochondral ossification. POH can be distinguished from Albright hereditary osteodystrophy (AHO) by the progression of heterotopic ossification from skin and subcutaneous tissue into skeletal muscle, the presence of normal endocrine function, and the absence of a distinctive habitus associated with AHO. Although the genetic basis of POH is unknown, inactivating mutations of the GNAS1 gene are associated with AHO. The report in this issue of the JBMR of 2 patients with combined features of POH and AHO--one with classic AHO, severe POH-like features, and reduced levels of Gsalpha protein and one with mild AHO, severe POH-like features, reduced levels of Gsalpha protein, and a mutation in GNAS1--suggests that classic POH also could be caused by GNAS1 mutations. This possibility is further supported by the identification of a patient with atypical but severe platelike osteoma cutis (POC) and a mutation in GNAS1, indicating that inactivating mutations in GNAS1 may lead to severe progressive heterotopic ossification of skeletal muscle and deep connective tissue independently of AHO characteristics. These observations suggest that POH may lie at one end of a clinical spectrum of ossification disorders mediated by abnormalities in GNAS1 expression and impaired activation of adenylyl cyclase. Analysis of patients with classic POH (with no AHO features) is necessary to determine whether the molecular basis of POH is caused by inactivating mutations in the GNAS1 gene.

GNAS1 mutation and Cbfa1 misexpression in a child with severe congenital platelike osteoma cutis

We evaluated a 7-year-old girl with severe platelike osteoma cutis (POC), a variant of progressive osseous heteroplasia (POH). The child had congenital heterotopic ossification of dermis and subcutaneous fat that progressed to involve deep skeletal muscles of the face, scalp, and eyes. Although involvement of skeletal muscle is a prominent feature of POH, heterotopic ossification has not been observed in the head, face, or extraocular muscles. The cutaneous ossification in this patient was suggestive of Albright hereditary osteodystrophy (AHO); however, none of the other characteristic features of AHO were expressed. Inactivating mutations of the GNAS1 gene, which encodes the alpha-subunit of the stimulatory G protein of adenylyl cyclase, is the cause of AHO. Mutational analysis of GNAS1 using genomic DNA of peripheral blood and of lesional and nonlesional tissue from our patient revealed a heterozygous 4-base pair (bp) deletion in exon 7, identical to mutations that have been found in some AHO patients. This 4-bp deletion in GNAS1 predicts a protein reading frameshift leading to 13 incorrect amino acids followed by a premature stop codon. To investigate pathways of osteogenesis by which GNAS1 may mediate its effects, we examined the expression of the obligate osteogenic transcription factor Cbfa1/RUNX2 in lesional and uninvolved dermal fibroblasts from our patient and discovered expression of bone-specific Cbfa1 messenger RNA (mRNA) in both cell types. These findings document severe heterotopic ossification in the absence of AHO features caused by an inactivating GNAS1 mutation and establish the GNAS1 gene as the leading candidate gene for POH.

Deficiency of the alpha-subunit of the stimulatory G protein and severe extraskeletal ossification

Progressive osseous heteroplasia (POH) is a rare disorder characterized by dermal ossification beginning in infancy followed by increasing and extensive bone formation in deep muscle and fascia. We describe two unrelated girls with typical clinical, radiographic, and histological features of POH who also have findings of another uncommon heritable disorder, Albright hereditary osteodystrophy (AHO). One patient has mild brachydactyly but no endocrinopathy, whereas the other manifests brachydactyly, obesity, and target tissue resistance to thyrotropin and parathyroid hormone (PTH). Levels of the alpha-subunit of the G protein (Gsalpha) were reduced in erythrocyte membranes from both girls and a nonsense mutation (Q12X) in exon 1 of the GNAS1 gene was identified in genomic DNA from the mildly affected patient. Features of POH and AHO in two individuals suggest that these conditions share a similar molecular basis and pathogenesis and that isolated severe extraskeletal ossification may be another manifestation of Gsalpha deficiency.

Linkage exclusion and mutational analysis of the noggin gene in patients with fibrodysplasia ossificans progressiva (FOP)

Fibrodysplasia ossificans progressiva (FOP) is an extremely rare and disabling genetic disorder characterized by congenital malformation of the great toes and by progressive heterotopic endochondral ossification in predictable anatomical patterns. Although elevated levels of bone morphogenetic protein 4 (BMP4) occur in lymphoblastoid cells and in lesional cells of patients with FOP, mutations have not been identified in the BMP4 gene, suggesting that the mutation in FOP may reside in a BMP4-interacting factor or in another component of the BMP4 pathway. A powerful antagonist of BMP4 is the secreted polypeptide noggin. A recent case report described a heterozygous 42-bp deletion in the protein-coding region of the noggin gene in a patient with FOP. In order to determine if noggin mutations are a widespread finding in FOP, we examined 31 families with 1 or more FOP patients. Linkage analysis with an array of highly polymorphic microsatellite markers closely linked to the noggin gene was performed in four classically-affected multigenerational FOP families and excluded linkage of the noggin locus to FOP (the multipoint lod score was -2 or less throughout the entire range of markers). We sequenced the noggin gene in affected members of all four families, as well as in 18 patients with sporadic FOP, and failed to detect any mutations. Single-strand conformation polymorphism (SSCP) analysis of 4 of these patients plus an additional 9 patients also failed to reveal any mutations. Among the samples analyzed by SSCP and DNA sequencing was an independently obtained DNA sample from the identical FOP patient previously described with the 42-bp noggin deletion; no mutation was detected. Examination of the DNA sequences of 20 cloned noggin PCR products, undertaken to evaluate the possibility of a somatic mutation in the noggin gene which could be carried by a small subset of white blood cells, also failed to detect the presence of the reported 42-bp deletion. We conclude that mutations in the coding region of noggin are not associated with FOP.

Treatment of osteoporosis: are physicians missing an opportunity?

BACKGROUND

Medical treatment of women with established osteoporosis may decrease the incidence of future fractures. Postmenopausal women who have sustained a distal radial fracture have decreased bone-mineral density and nearly twice the risk of a future hip fracture. The purpose of this study was to evaluate the adequacy of diagnosis and treatment of osteoporosis in postmenopausal women following an acute fracture of the distal part of the radius.

METHODS

A retrospective cohort study was performed with use of a claims database that includes more than three million patients, from thirty states, enrolled in multiple health plans. All women, fifty-five years of age or older, who sustained a distal radial fracture between July 1, 1994, and June 30, 1997, were identified in the database. Only patients with at least six months of continuous and complete medical and pharmaceutical health-care coverage from the date of the fracture were enrolled, to ensure that all health-care claims would be captured in the database. This cohort of patients was then evaluated to determine the proportion who had undergone either a diagnostic bone-density scan or treatment with any recommended medication for established osteoporosis (estrogen, a bisphosphonate, or calcitonin) within six months following the fracture.

RESULTS

A search of the database identified 1,162 women, fifty-five years of age or older, who had a distal radial fracture. Of these 1,162 patients, thirty-three (2.8 percent) underwent a bone-density scan and 266 (22.9 percent) were treated with at least one of the medications approved for treatment of established osteoporosis. Twenty women had both a bone-density scan and drug treatment. Therefore, only 279 (24.0 percent) of the 1,162 women who sustained a distal radial fracture underwent either diagnostic evaluation or treatment of osteoporosis. There was a significant decrease in the rate of treatment of osteoporosis with increasing patient age at the time of the fracture (p < 0.0001).

CONCLUSIONS

Current physician practice may be inadequate for the diagnosis and treatment of osteoporosis in postmenopausal women who have sustained a distal radial fracture.

Fibrodysplasia ossificans progressiva, a heritable disorder of severe heterotopic ossification, maps to human chromosome 4q27-31

Fibrodysplasia ossificans progressiva (FOP) is a severely disabling, autosomal-dominant disorder of connective tissue and is characterized by postnatal progressive heterotopic ossification of muscle, tendon, ligament, and fascia and by congenital malformation of the great toes. To identify the chromosomal location of the FOP gene, we conducted a genomewide linkage analysis, using four affected families with a total of 14 informative meioses. Male-to-male transmission of the FOP phenotype excluded X-linked inheritance. Highly polymorphic microsatellite markers covering all human autosomes were amplified by use of PCR. The FOP phenotype is linked to markers located in the 4q27-31 region (LOD score 3.10 at recombination fraction 0). Crossover events localize the putative FOP gene within a 36-cM interval bordered proximally by D4S1625 and distally by D4S2417. This interval contains at least one gene involved in the bone morphogenetic protein-signaling pathway.

Surgical management of Paget's disease

Orthopedic complications of Paget's disease occur commonly and arise as a result of chronically accelerated bone remodeling in focal regions of the skeleton. Complications include pathologic fractures with delayed union, progressive skeletal deformity, chronic bone pain and pagetic arthritis. The new bisphosphonates have transformed the treatment of Paget's disease in the past decade but have not yet been studied in depth for their ability to prevent orthopaedic complications. Although few patients with Paget's disease ever require surgical intervention, successful operative management of orthopaedic complications has dramatically improved the quality of life for many sufferers. Selected modalities with promising results include total hip replacement for end-stage pagetic arthritis of the hip, total knee replacement for end-stage pagetic arthritis of the knee, proximal tibial osteotomy for painful malalignment of the knees, internal fixation for pathological fractures, and decompressive laminectomy for spinal stenosis. Complications of surgery on pagetic bone include hemorrhage, infection, pathologic fracture, delayed union, nonunion, and aseptic loosening of hardware. Medical, surgical, and rehabilitative modalities provide a wide array of options in managing orthopaedic complications of Paget's disease and are useful in improving quality of life for sufferers of the condition. Prospective studies are needed to assess the ability of antipagetic medications to prevent severe long-term complications such as deformity, arthritis, and malignancy. Localization of susceptibility genes for Paget's disease may accelerate identification of targets for gene therapy and disease prevention.

Phenotypic and molecular heterogeneity in fibrodysplasia ossificans progressiva

Fibrodysplasia (myositis) ossificans progressiva (FOP) is an extremely rare inherited disorder in which progressive ossification of major striated muscles, often following injury, is associated with abnormal skeletal patterning. Altered expression of bone morphogenetic proteins may be a contributory cause. To examine this hypothesis, we compared the patterns of expression of bone morphogenetic proteins (BMPs) mRNAs from lymphoblastoid cell lines from two small multigenerational families with autosomal dominant transmission of FOP. Although affected members of both families showed the characteristic phenotype of FOP, one family was more severely affected than the other. Expression of mRNAs for BMP-1, 2, 3, 5, and 6 mRNAs were not detected within the more severely affected family, but BMP-4 mRNA was expressed in affected but not unaffected members of this family. The results of linkage exclusion analysis using a highly polymorphic microsatellite marker near the BMP-4 gene were consistent with linkage of FOP and BMP-4 in this family. Within the less severely affected family, affected and unaffected members showed similar levels of mRNA expression of BMPs 1, 2, 4, and 5, and linkage of FOP to the BMP-4 gene was excluded. It is concluded that clinical, radiographic, and biochemical data in these two families with FOP establish clinical and molecular heterogeneity and also suggest the possibility of genetic heterogeneity.

Body mass and fracture risk. A study of 330 patients

Low body mass is a major risk factor for low energy hip fractures among women. The purpose of this study was to ascertain whether normal body mass also protects against low energy wrist fractures. A retrospective analysis of body mass indices of 330 women who sustained hip or wrist fractures from falls was performed. Data were grouped by race and age. The mean body mass index for white patients with wrist fractures was 26.4, compared with a mean body mass index of 22.3 in white patients with hip fractures. For black patients, those with wrist fractures had a mean body mass index of 28.5, compared with a mean body mass index of 22.9 for those with hip fractures. Using data from The National Health and Nutrition Examination Surveys, the mean body mass index of patients with wrist fractures was seen to be equal to or greater than the national mean body mass index, whereas that of patients with hip fractures was substantially below average. Accordingly, normal body mass was protective against hip fractures but not against wrist fractures. Because adipose tissue more typically is distributed about the hip than the wrist, the protective mechanism of normal body mass against osteoporotic fractures may promote better preventative interventions against this disease.

Conductive hearing loss in individuals with fibrodysplasia ossificans progressiva

Fibrodysplasia ossificans progressiva (FOP) is a very rare genetic disorder that is characterized by progressive heterotopic ossification of soft tissues and congenital malformation of the great toes. Although previous case studies have reported hearing loss in individuals with FOP, there have been no large-scale studies regarding the nature or cause of the hearing loss. Here, we report the findings of a two-part study. In Part I, we report the findings of a postal survey regarding hearing loss that was sent to 102 individuals with FOP. In Part II, we report the findings of on-site hearing evaluations of eight individuals with FOP. The findings of both studies indicate that individuals with FOP are at risk for hearing loss and that the type of loss is predominantly conductive in nature, similar to that seen in individuals who have otosclerosis.

Illustrative disorders of ectopic skeletal morphogenesis: a childhood parallax for studies in gravitational and space biology

Heterotopic ossification is a key feature of at least three distinct genetic disorders of osteogenesis in humans: fibrodysplasia ossificans progressiva, progressive osseous heteroplasia, and Albright's hereditary osteodystrophy. All three conditions are genetic disorders of childhood, but the pathobiology of osteogenic induction, the histopathology of osteogenesis, the anatomic distribution of heterotopic lesions, and the developmental patterns of disease progression differ among the three conditions. The phenotypic distinction of these disorders is critically important in counselling patients and families as well as in advancing research to define the molecular pathophysiology of heterotopic osteogenesis in these disabling genetic disorders. Genetic disorders of tissue modeling and morphogenesis provide an important parallax to disturbances of tissue re-modeling that are of paramount importance to gravitational and space biologists as humans begin to explore and live in environments beyond the planet on which they evolved. Disorders of osteogenesis are of particular concern to space biologists due to the dramatic changes in skeletal biology in altered gravitational fields.

The human bone morphogenetic protein 4 (BMP-4) gene: molecular structure and transcriptional regulation

Bone morphogenetic protein 4 (BMP-4) is a vital regulatory molecule that functions throughout human development in mesoderm induction, tooth development, limb formation, bone induction, and fracture repair and is overexpressed in patients who have fibrodysplasia ossificans progressiva. The human gene encoding bone morphogenetic protein 4 (BMP-4) has been isolated and its structural organization characterized. The complete DNA sequence of an 11.2 kb region has been determined. BMP-4 mRNA is transcribed from four exons, although there is evidence that alternate first exons may be used. Transcript initiation occurs at variable positions within a GA-rich region of the DNA. The promoter region is GC-rich with no obvious TATA or CAAT consensus sequences, and contains both positive and negative transcriptional regulatory elements within the 3 kb 5' flanking region of the RNA start site. Comparison of the human and murine BMP-4 genes reveals highly conserved sequences not only in the exon-coding regions but also within the introns and 5' flanking regions. BMP-4 localizes to human chromosome 14q21 by fluorescence in situ hybridization, a location more centromeric than that recently reported. These studies provide a foundation for understanding the genetic regulation of this important gene in human development.

Progressive osseous heteroplasia. Report of a family

We report a case of progressive osseous heteroplasia in a female infant who had progressive ossification of the skin and deep connective tissues. Isolated dermal ossification is present in her father and younger sister suggesting an autosomal dominant mode of inheritance with variable expressivity or possible somatic mosaicism. This report of a family with progressive osseous heteroplasia contributes to the understanding of this uncommon genetic disorder, which must be distinguished from fibrodysplasia ossificans progressiva and Albright's hereditary osteodystrophy. The paucity of familial cases of progressive osseous heteroplasia currently limits the use of a genome-wide linkage analysis, but linkage exclusion analysis with promising candidate genes is a possibility.

Encrypted morphogens of skeletogenesis: biological errors and pharmacologic potentials

Bone morphogenetic proteins (BMPs) are members of a class of ancient, highly conserved signalling molecules that play major roles in embryonic axis determination, organ development, tissue repair, and regeneration throughout the animal kingdom. The bone morphogenetic proteins are potent developmental morphogens that act in a concentration-dependent manner to specify cell fates in developing and regenerating systems. Complementary DNAs have been cloned for approximately twenty BMPs, and recombinant proteins have been produced for many of these genes. Transgenic and naturally occurring animal models demonstrate a wide variety of potential functions for BMP genes during development and tissue regeneration, and a wide range of pharmacologic effects are predicted from knock-out or over-expression of the BMP genes. Fibrodysplasia ossificans progressiva (FOP), a rare and devastating genetic disease of ectopic osteogenesis in humans, is associated with over-expression of at least one of the BMPs. The BMPs, their transmembrane receptors, their intracellular signal transducers, and their secreted antagonists hold great promise as pharmacologic agents in modulating a vast array of developmental and regenerative pathways in human diseases.

Pulmonary and cardiac function in advanced fibrodysplasia ossificans progressiva

Fibrodysplasia ossificans progressiva is a rare genetic disease characterized by heterotopic ossification in soft tissues. Severe disability results from progressive immobilization of the limbs, jaw, and chest wall. To determine whether cardiac function is altered in this disease, 25 patients ranging in age from 5 to 55 years (disease duration 1-51 years) were studied. History, physical examination, pulmonary functions, electrocardiography, and echocardiography were performed on each patient. Physical examination of the lungs and heart was unrevealing; no right sided ventricular gallops were heard, and no patient was found to have neck vein distention or peripheral edema. The patients had extremely limited chest expansion (1.9 +/- 0.8 inches), suggesting dependence on diaphragmatic breathing. Lung volumes were severely reduced (mean forced vital capacity 44% +/- 14% of predicted), but flow rates were relatively normal. All patients had normal capillary oxygen saturation. Echocardiography was technically difficult, but no abnormalities of left or right ventricular function were seen. Ten (40%) patients had electrocardiographic evidence of right ventricular dysfunction. Compared with patients without such evidence, these patients were older, had significantly longer disease duration, higher hemoglobin, and more impaired pulmonary function. The results of this study suggest that the presence of severely restrictive chest wall disease is associated with a high incidence of right ventricular abnormalities on electrocardiogram. Whether cor pulmonale will eventually occur remains to be determined.

Differential expression of bone and cartilage related genes in fibrodysplasia ossificans progressiva, myositis ossificans traumatica, and osteogenic sarcoma

Fibrodysplasia ossificans progressiva, myositis ossificans traumatica, and osteogenic sarcoma are representative genetic, traumatic, and neoplastic disorders of osteogenesis, respectively. However, the pathology, pathophysiology, and natural history of the disorders differ substantially. Gene expression related to bone induction was studied in these disorders. Primary cell lines established from lesional tissues derived from each of these disorders expressed different patterns of protooncogenes, bone morphogenetic protein genes, and bone phenotype specific genes. The osteogenic sarcoma cell line expressed the entire repertoire bone morphogenetic proteins 1 to 7, c-fos and c-jun messenger ribonucleic acids. Myositis ossificans traumatica cells expressed phenotype markers similar to those of the osteogenic sarcoma cells, and expressed bone morphogenetic proteins 1, 4, and 6 and c-fos messenger ribonucleic acids, but not c-jun messenger ribonucleic acid. Fibrodysplasia ossificans progressiva early lesional cells demonstrated specific over-expression of bone morphogenetic protein 4 messenger ribonucleic acid. Differential expression of genes related to osteogenesis have important implications for understanding the earliest molecular events in normal and dysregulated osteogenesis in humans.

Pseudomalignant heterotopic ossification

Pseudomalignant heterotopic ossification is a rare, self limited connective tissue disorder of unknown origin that may occur atypically during childhood and can simulate either soft tissue sarcoma or fibrodysplasia ossificans progressiva. A complex constellation of diagnostic features usually enable the differentiation of pseudomalignant heterotopic ossification from extraosseous osteosarcoma and fibrodysplasia ossificans progressiva during a time span of approximately 8 to 12 weeks. Orthopaedic surgeons who treat children with connective tissue tumors should be familiar with pseudomalignant heterotopic ossification and its differential diagnosis. The occasional mild and variable expression of fibrodysplasia ossificans progressiva rarely may make it more difficult to distinguish from pseudomalignant heterotopic ossification. It is possible that pseudomalignant heterotopic ossification is a form fruste of fibrodysplasia ossificans progressiva.

Characterization of bone morphogenetic protein 4 receptor in fibrodysplasia ossificans progressiva

Bone morphogenetic protein 4, a potent osteogenic morphogen, has been implicated in fibrodysplasia ossificans progressiva because it is uniquely overexpressed in lymphoblastoid cells and preosseous fibroproliferative lesional cells of patients with fibrodysplasia ossificans progressiva. Bone morphogenetic protein 4 signals through a heteromeric complex of serine/ threonine kinase receptors (type I and type II) on the surface of responding cells. Semi-quantitative competitive reverse transcription polymerase chain reaction was used to quantitate steady state levels of messenger ribonucleic acid expression for bone morphogenetic protein 4 and the bone morphogenetic protein receptors. These data confirmed the previous finding of elevated steady state levels of bone morphogenetic protein 4 messenger ribonucleic acid in lymphoblastoid cell lines of affected individuals in a family that exhibited autosomal dominant inheritance of fibrodysplasia ossificans progressiva. There were no differences in the steady state levels of messenger ribonucleic acid for either the Type I or Type II bone morphogenetic protein 4 receptors between affected and unaffected individuals in that same family. The presence of bone morphogenetic protein 4 receptor messenger ribonucleic acid in fibrodysplasia ossificans progressiva lesional tissue and unaffected muscle tissue and demonstrates the deregulation of bone morphogenetic protein 4 messenger ribonucleic acid in fibrodysplasia ossificans progressiva. These data support the hypothesis that the molecular basis of bone morphogenetic protein 4 signaling is abnormal in fibrodysplasia ossificans progressiva.

Catastrophic falls in patients who have fibrodysplasia ossificans progressiva

There have been numerous anecdotal reports of catastrophic falls in patients with fibrodysplasia ossificans progressiva. To determine the incidence of serious morbidity and mortality associated with falls in this patient population, the authors surveyed the 135 patient members of the International Fibrodysplasia Ossificans Progressiva Association and an age and gender matched control group. Eighty-one percent of the fibrodysplasia ossificans progressiva population suffered a fall resulting in injury compared with 44% of the controls. Sixty-seven percent of the falls initiated a painful flareup of fibrodysplasia ossificans progressiva leading to permanent loss of movement in almost all patients. Fifty-four percent of all falls suffered by the fibrodysplasia ossificans progressiva group led to permanent disability compared with 4% of all falls in the control group. Although trauma to the head was a common site of injury in both groups, the injury profile in the fibrodysplasia ossificans progressiva group included traumatic brain injuries, intracranial hemorrhage and death whereas the control group suffered mostly minor soft tissue lacerations. Deficiencies in coordinate gait and protective function likely accounted for the severity of injuries especially to the head in the fibrodysplasia ossificans progressiva population. Precautions are recommended that are intended to minimize the risk of injury without compromising a patient's functional level and independence. These recommendations include limitation of high risk activities, protective head gear, safety improvements in living environments, and augmentation of stabilizing and protective functions.

Embryonic overexpression of the c-Fos protooncogene. A murine stem cell chimera applicable to the study of fibrodysplasia ossificans progressiva in humans

Murine embryonic overexpression of the c-fos protooncogene leads to early postnatal heterotopic chondrogenesis and osteogenesis with phenotypic features similar to those seen in children who have the disabling heritable disease fibrodysplasia ossificans progressiva. The overexpression of Fos in embryonic stem cell chimeras leads to heterotopic endochondral osteogenesis at least in part through a bone morphogenetic protein 4 mediated signal transduction pathway. In contrast, early fibrodysplasia ossificans progressiva lesions express abundant bone morphogenetic protein 4, without abundant expression of c-Fos, suggesting that the primary molecular defect in fibrodysplasia ossificans progressiva may be independent of the sustained Fos effects on chondrogenesis and osteogenesis. Comparisons of the clinical, molecular, and pathogenetic features of the c-Fos embryonic stem cell chimeras with those of fibrodysplasia ossificans progressiva provide insight into the earliest events in the molecular pathogenesis of genetically induced heterotopic chondrogenesis and osteogenesis. The relevance of the c-Fos embryonic stem cell chimera to the study of the currently untreatable human disease fibrodysplasia ossificans progressiva demonstrates the power of using embryonic stem cell technology for generating gain of function mutations in the study of human bone disease.

Acute lymphocytic infiltration in an extremely early lesion of fibrodysplasia ossificans progressiva

A 2-year-old child with fibrodysplasia ossificans progressiva underwent a muscle biopsy of a very early lesion, and had findings that showed the earliest stage ever seen in the histopathology of fibrodysplasia ossificans progressiva. This very early stage consisted of intense perivascular lymphocytic infiltration into normal appearing skeletal muscle. A nearly identical histopathologic sequence was noted in a cat with phenotypic features similar to those of fibrodysplasia ossificans progressiva in humans. These new findings represent the earliest documented changes that have ever been noted in fibrodysplasia ossificans progressiva, and provide further histopathologic support for the recent discovery that lymphocytes may play a role in the pathogenesis of heterotopic ossification in fibrodysplasia ossificans progressiva.

Treatment of patients who have fibrodysplasia ossificans progressiva with isotretinoin

Retinoids are a plausible family of therapeutic agents for fibrodysplasia ossificans progressiva due to their ability to inhibit differentiation of mesenchymal tissue into cartilage and bone. A prospective study was conducted to assess the efficacy of isotretinoin (13-cis-retinoic acid) in the prevention of heterotopic ossification in patients who had fibrodysplasia ossificans progressiva. Eleven anatomic regions were assessed in each of 21 patients by clinical examination, radiographs, and bone scans. An anatomic region was considered to be involved if there was clinical, radiographic, or radionuclide evidence of orthotopic or heterotopic ossification anywhere in the region. There were 143 involved anatomic regions and 88 uninvolved anatomic regions at the beginning of the study. Only one of the 88 anatomic regions that was completely uninvolved at the beginning of the study became involved during isotretinoin therapy. However, 16 of the 21 patients (76%) had major flare ups develop in 38 of 143 (27%) previously involved anatomic regions while administered isotretinoin therapy. Isotretinoin at steady state doses of 1 to 2 mg/kg per day decreased the incidence of heterotopic ossification at uninvolved anatomic regions compared with an external control group, as long as the medication was started before the appearance of any orthotopic or heterotopic ossification in that anatomic region. The data did not allow the determination of whether isotretinoin was effective or detrimental in preventing disease flareups in regions that had even minimal orthotopic or heterotopic ossification at the time the therapy began. Extreme caution should be exercised when using this medication in patients who have fibrodysplasia ossificans progressiva.

Osteoporosis. Definition and clinical presentation

Osteoporosis is a skeletal condition characterized by decreased density (mass/volume) of normally mineralized bone. The reduced bone density leads to decreased mechanical strength, thus making the skeleton more likely to fracture. Postmenopausal osteoporosis (Type I) and age-related osteoporosis (Type II) are the most common primary forms of bone loss seen in clinical practice. Secondary causes of osteoporosis include hypercortisolism, hyperthyroidism, hyperparathyroidism, alcohol abuse, and immobilization. In the development of osteoporosis, there is often a long latent period before the appearance of the main clinical manifestation, pathologic fractures. The earliest symptom of osteoporosis is often an episode of acute back pain caused by a pathologic vertebral compression fracture, or an episode of groin or thigh pain caused by a pathologic hip fracture. In the diagnostic process, the extent and severity of bone loss are evaluated and secondary forms of bone loss are excluded. A careful diagnostic work-up that includes clinical history, physical examination, laboratory evaluation, bone densitometry, and radiographic imaging will allow the clinician to determine the cause of osteoporosis and to institute medical interventions that will stabilize and even reverse this frequently preventable condition.