Biological Equivalence of GGTA-1 Glycosyltransferase Knockout and Standard Porcine Pericardial Tissue Using 90-Day Mitral Valve Implantation in Adolescent Sheep

Objective There is growing interest in the application of genetically engineered reduced antigenicity animal tissue for manufacture of bioprosthetic heart valves (BHVs) to reduce antibody induced tissue calcification and accelerated structural valve degeneration (SVD). This study tested biological equivalence of valves made from Gal-knockout (GalKO) and standard porcine pericardium after 90-day mitral valve implantation in sheep. Methods GalKO (n = 5) and standard (n = 5) porcine pericardial BHVs were implanted in a randomized and blind fashion into sheep for 90-days. Valve haemodynamic function was measured at 30-day intervals. After explantation, valves were examined for pannus, vegetation, inflammation, thrombus, and tissue calcification. Results Nine of 10 recipients completed the study. There was no difference between study groups for haemodynamic performance and no adverse valve-related events. Explanted BHVs showed mild pannus integration and minimal thrombus, with no difference between the groups. Limited focal mineral deposits were detected by x-ray. Atomic spectroscopy analysis detected tissue calcium levels of 1.0 µg/mg ± 0.2 for GalKO BHVs and 1.9 µg/mg ± 0.9 for standard tissue BHVs (p = 0.4), considered to be both low and equivalent. Conclusions This is the first demonstration of biological equivalence between GalKO and standard pig pericardium. The GalKO mutation causes neither intrinsic detrimental biological nor functional impact on BHV performance. Commercial adaptation of GalKO tissue for surgical or transcatheter BHVs would remove the clinical disparity between patients producing anti-Gal antibody and BHVs containing the Gal antigen. GalKO BHVs may reduce accelerated tissue calcification and SVD, enhancing patient choices, especially for younger patients. Graphical Abstract

P065 A case of fibrodysplasia ossificans progressiva in Kenya

Background Fibrodysplasia Ossificans Progressiva (FOP) is an extremely rare and disabling disorder affecting 1 in 2 million individuals worldwide. It is caused by mutations in bone morphogenetic protein which leads to extra-skeletal ossification of soft tissues in a characteristic cranio-caudal pattern. Hallux valgus, episodic flares and progressive functional disability are characteristic features. The cause of death is often cardio-respiratory failure following thoracic insufficiency. The objective of our case study is to describe a rare but interesting case of fibrodysplasia ossificans progressiva (FOP) in an African setting. Methods This was a retrospective case review Results Two-year-old boy presented with painful firm masses of bony consistency over the axilla, neck, occiput and the forehead for seven months. He developed progressive inability to lift the arms, flex his neck and had a characteristic stiff posture while walking. The masses had a waxing and waning nature lasting about 4–5 days but with no complete resolution. He was previously treated with antibiotics for lymphadenitis which was diagnosed by biopsy of the neck mass at a different health facility. On examinationhe had bony masses on the posterior aspect of the neck tender on palpation and attached to the underlying subcutaneous tissue. Similar masses were found on his anterior and posterior chest wall measuring 1 cm by 1 cm anteriorly and larger masses- measuring 5 cm by 5 cm posteriorly. He had bilateral hallux valgus and both elbows held in fixed flexion. His fingers had varying degrees of fixed flexion. The lower limbs were unaffected. Laboratory evaluation within normal ranges. extensive dystrophic soft tissue calcification around both elbows outlining the joint capsules. dystrophic soft tissue calcification in the bilateral axillae extensive “sheet like” soft tissue dystrophic calcifications overlying the posterior elements of the vertebral column separate from the vertebrae. Histology showed muscle replacement by hyaline cartilage and bone with intervening fibromyxoid stroma. Discussion & Conclusions This case is meant to raise awareness of this rare disease across Africa. The misdiagnosis of FOP approaches 90% of cases worldwide. Definitive genetic testing of FOP is now available and can now confirm a diagnosis before the appearance of heterotopic ossifications. Clinical suspicion of FOP early in life on the basis of malformed great toes can lead to early clinical diagnosis. Current management focuses on early diagnosis, avoidance of trauma and optimization of function. A short course of oral steroids is beneficial in prevention of flares.

Transthyretin: From Structural Stability to Osteoarticular and Cardiovascular Diseases

Transthyretin (TTR) is a tetrameric protein transporting hormones in the plasma and brain, which has many other activities that have not been fully acknowledged. TTR is a positive indicator of nutrition status and is negatively correlated with inflammation. TTR is a neuroprotective and oxidative-stress-suppressing factor. The TTR structure is destabilized by mutations, oxidative modifications, aging, proteolysis, and metal cations, including Ca2+. Destabilized TTR molecules form amyloid deposits, resulting in senile and familial amyloidopathies. This review links structural stability of TTR with the environmental factors, particularly oxidative stress and Ca2+, and the processes involved in the pathogenesis of TTR-related diseases. The roles of TTR in biomineralization, calcification, and osteoarticular and cardiovascular diseases are broadly discussed. The association of TTR-related diseases and vascular and ligament tissue calcification with TTR levels and TTR structure is presented. It is indicated that unaggregated TTR and TTR amyloid are bound by vicious cycles, and that TTR may have an as yet undetermined role(s) at the crossroads of calcification, blood coagulation, and immune response.

CALCIFICATION OF ARTERIES IN PATIENTS WITH ATHEROSCLEROSIS: CAUSES AND MECHANISMS OF DEVELOPMENT

The paper shows analogies between the mechanisms of calcification of arteries, various tissues and bone mineralization. In calcification the same mechanisms are involved, as at ossification of an organic matrix of a bone, including participation of stem cells. In the arteries and capillaries of various organs found polypotent precursors – mesenchymal stem cells, presumably responsible for the pathological mineralization of the arterial wall. Circulating in the blood and present in the intima of the human atheromatous aorta colony-forming stem cells of the stromal line of differentiation. Adventitia cells or pericytes are considered as a pluripotent mesenchymal reserve for replenishment of some cellular forms of connective tissue. Bone marrow stem cells of the stromal line of differentiation with the presence of pluripotent stromal cells in the blood and granulomas (plaques) and their transformation into bone tissue cells are involved in atherogenesis. Smooth muscle cells (SMCs) and myofibroblasts of the arterial wall adventitia have an osteoblast-like phenotype. Collagen and elastic fibers are involved in the calcification of blood vessels and soft tissues. Calcification of granulomas (plaques) accompanies their inflammatory morphogenesis, accompanied by the development of scar tissue. It often accompanies and completes the inflammation in them. This process is observed with the gradual replacement of the parenchyma of some organs with connective tissue. The mineral phase in bones and soft tissues, represented by calcium (Ca) and phosphate (P), contacts with nucleators - specific areas of collagen fibers. Non-collagen proteins are also involved in arterial calcification. With the progression of atherosclerosis and calcification of granulomas/plaques by cells present in the arterial wall, osteonectin is expressed. Osteopontin content is associated with Ca deposits in them; in particular, it correlates with the Ca level in the coronary arteries. In the processes of ossification and calcification, phosphatases play a certain role. In areas of calcification of granulomas/plaques, osteoprotegerin is found, which inhibits the activity of alkaline phosphatase in the aorta and prevents calcification of the media. Arterial wall calcification and inflammation are inhibited by fetuin-A and matrix γ-carboxyglutaric protein (MGP). The rate of bone formation and tissue calcification depends on the concentration of Ca and P in plasma and extracellular fluid. With their high concentration in the extracellular fluid, the mineral phase appears where it normally does not exist. Lipids are among the initiators of granuloma / plaque calcification in the arteries. The role of inflammation and necrosis in the calcification of the arteries is confirmed by experiments on animals with repeated intravenous injections of adrenaline, which causes focal necrosis of the middle membrane, which then undergoes calcification. In arterial walls, heart muscle, bone and cartilage tissue, osteonectin, osteocalcin, osteopontin, bone sialoprotein are often formed. In general, the mechanisms of arterial and soft tissue calcification are poorly understood. There are no effective remedies for calcification.

Spinal Stenosis Caused by Calcinosis in a Patient With Systemic Sclerosis

Calcinosis or dystrophic soft-tissue calcification occurs in damaged/devitalized tissues in the presence of normal calcium/ phosphorus metabolism.1 It is a known complication of connective tissues diseases, especially juvenile dermatomyositis and systemic sclerosis (SSc), and may be localized or widespread.2

Calcinosis cutis in limited cutaneous systemic sclerosis

Soft tissue calcification is seen in some rheumatological diseases, including systemic sclerosis. We herein present a clinical image of calcinosis cutis of finger pulps and its characteristic radiographic image in a patient with limited cutaneous systemic sclerosis.

Systemic sclerosis skin is a primed microenvironment for soft tissue calcification—a hypothesis

Calcinosis cutis, defined as sub-epidermal deposition of calcium salts, is a major clinical problem in patients with SSc, affecting 20–40% of patients. A number of recognized factors associated with calcinosis have been identified, including disease duration, digital ischaemia and acro-osteolysis. Yet, to date, the pathogenesis of SSc-related calcinosis remains unknown, and currently there is no effective disease-modifying pharmacotherapy. Following onset of SSc, there are marked changes in the extracellular matrix (ECM) of the skin, notably a breakdown in the microfibrillar network and accumulation of type I collagen. Our hypothesis is that these pathological changes reflect a changing cellular phenotype and result in a primed microenvironment for soft tissue calcification, with SSc fibroblasts adopting a pro-osteogenic profile, and specific driving forces promoting tissue mineralization. Considering the role of the ECM in disease progression may help elucidate the mechanism(s) behind SSc-related calcinosis and inform the development of future therapeutic interventions.