The metabolic heterogeneity of glycosaminoglycans of the different zones of the epiphyseal growth plate and the effect of ethane-1-hydroxy-1, 1-diphosphonate (EHDP) upon glycosaminoglycan synthesis in vivo

Pirfenidone reduces subchondral bone loss and fibrosis after murine knee cartilage injury

Pirfenidone is an anti-inflammatory and anti-fibrotic drug that has shown efficacy in lung and kidney fibrosis. Because inflammation and fibrosis have been linked to the progression of osteoarthritis, we investigated the effects of oral Pirfenidone in a mouse model of cartilage injury, which results in chronic inflammation and joint-wide fibrosis in mice that lack hyaluronan synthase 1 (Has1^-/- ) in comparison to wild-type. Femoral cartilage was surgically injured in wild-type and Has1^-/- mice, and Pirfenidone was administered in food starting after 3 days. At 4 weeks, Pirfenidone reduced the appearance, on micro-computed tomography, of pitting in subchondral bone at, and cortical bone surrounding, the site of cartilage injury. This corresponded with a reduction in fibrotic tissue deposits as observed with gross joint surface photography. Pirfenidone resulted in significant recovery of trabecular bone parameters affected by joint injury in Has1^-/- mice, although the effect in wild-type was less pronounced. Pirfenidone also increased Safranin-O staining of growth plate cartilage after cartilage injury and sham operation in both genotypes. Taken together with the expression of selected extracellular matrix, inflammation, and fibrosis genes, these results indicate that Pirfenidone may confer chondrogenic and bone-protective effects, although the well-known anti-fibrotic effects of Pirfenidone may occur earlier in the wound-healing response than the time point examined in this study. Further investigations to identify the specific cell populations in the joint and signaling pathways that are responsive to Pirfenidone are warranted, as Pirfenidone and other anti-fibrotic drugs may encourage tissue repair and prevent progression of post-traumatic osteoarthritis. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:365-376, 2018.

Effects of etidronate on calcification of scales and ribs in the goldfish, Carassius auratus

Effects of etidronate on the calcification of scales and ribs were investigated in goldfish. Daily intraperitoneal injections of etidronate at doses of 1 and 10 mgP/kg body weight for 2 weeks inhibited calcification of ontogenic scales and ribs without affecting the accretion of organic matrices. Removal of some scales induced their regeneration within the two-week period. Their newly formed organic matrix was fully uncalcified in fish treated with 10 mgP/kg, whereas in those treated with 1 mgP/kg, the regenerating scales were only partially calcified. Daily administration of etidronate 10 mgP/kg resulted in an increase of body weight. These results suggested that the inhibitory effect of etidronate on the calcification of osseous tissues in mammals can be expected also on comparable tissues in fishes. An appropriate dose of etidronate that inhibits hard tissue calcification but not affects the body growth in fish seemed to exist between 1 and 10 mgP/kg.

Effects of ethane-1-hydroxy-1,1-diphosphonate on ossification of the posterior longitudinal ligament in Zucker fatty rats

PURPOSE

Using Zucker fatty rats as an animal model, we evaluate the effectiveness of ethane-1-hydroxy-1,1-diphosphonate on ossification of the posterior longitudinal ligament by histopathologically investigating the prodromal, early, and advanced stages of ossification of the spinal ligaments.

METHODS

73 Zucker fatty rats were allocated to the ethane-1-hydroxy-1,1-diphosphonate group (n=33) and the control group (n=40). The former group was fed ethane-1-hydroxy-1,1-diphosphonate daily. The feed was given starting 2 months after birth and continued until the rats were killed at 3 to 18 months later. Chemical analysis of the blood, radiographic tests, and histopathological examination were then conducted for both groups.

RESULTS

The results showed that ossification of the spinal ligaments involved excessive cartilage cell proliferation around areas affected by enthesitis; enlargement of the fibrocartilage tissue layer; ligament thickening; calcification of the matrix around the cartilage cells; and ossification of the spinal ligaments through enchondral ossification. Radiographic examinations showed that osteoproliferation in vertebral bodies in rats receiving ethane-1-hydroxy-1,1-diphosphonate was generally suppressed compared with controls, whereas histopathological examinations found no clear difference in cartilage cell proliferation in areas affected by enthesitis between the two groups, indicating the absence of calcification or osteo-proliferation in areas affected by enthesitis for the rats receiving ethane-1-hydroxy-1,1-diphosphonate.

CONCLUSION

Ethane-1-hydroxy-1,1-diphosphonate is effective in suppressing progressive ligament ossification.

Autoradiographic investigation of the effect of 1-hydroxyethylidene-1, 1-bisphosphonate on matrix protein synthesis and secretion by secretory ameloblasts in rat incisors

Seven daily subcutaneous injections of 1-hydroxyethylidene-1, 1-bisphosphonate (HEBP) can induce enamel hypoplasia. Several enamel-free zones were observed along the crown-analogue side of rat incisors during the secretory stage of amelogenesis. Ameloblasts related to the enamel-free zones lay directly on the abnormally non-mineralized mantle dentine, whereas the adjacent ameloblasts, which were forming the enamel matrix layer, were associated with the region where mineralization of dentine was proceeding. The further purpose of this study was to investigate the synthetic and secretory activity of these two groups of ameloblasts and to trace the fate of the radioactively labelled proteins. [(3)H]-proline was administered to Wistar rats 12 h after the last injection of HEBP. Light-microscopic autoradiography was performed. Quantitative analysis indicated that the ameloblasts of the enamel-forming zones in the drug-treated group showed a distribution pattern of silver grains similar to that of the controls. The ameloblasts of the enamel-free zones also demonstrated incorporation of [(3)H]-proline at the same level. There was some labelling over the non-mineralized mantle dentine, which was supposed to indicate the penetration of ameloblast products. From these results, it is concluded that HEBP does not affect the ameloblast activity in protein synthesis. The complete failure of enamel-layer formation in some specific regions is probably due to the failure in protein secretion and protein deposition. This study provides additional evidence that the mineralization of dentine is an essential factor in successful enamel matrix secretion and deposition.

Scanning electron microscopy of final enamel formation in rat mandibular incisors following single injections of 1-hydroxyethylidene-1,1-bisphosphonate

A single, high dose of 1-hydroxyethylidene-1,1-bisphosphonate (HEBP) results in three different types of lesions along the enamel surface of the rat incisor, one of which is seen as a "bright band" crossing the final enamel surface in the scanning electron microscope (SEM). The present study presents the structural surface features of final enamel formation and its subsequent maturation in normal and HEBP-exposed rats. The position of the bright band is examined in relation to where the Tomes processes pits disappear (DTPP), where the boundary between "light" and "dark" enamel (LDB) as seen by SEM is located, and in particular, where the so-called opaque boundary (OB) is positioned. Groups of rats were given a subcutaneous dose of 0, 5, or 10 mg P/kg body wt of HEBP and killed at intervals of either 12 hours or 2 or 9 days. The mandibular incisors were processed for SEM after enzymatic digestion of enamel organ remains. Enamel surface nodules, 100-300 nm in diameter and composed of smaller units, were evident at the start of final enamel formation which was defined as the area from DTPP to LDB. With increasing maturation, the nodules merged to form a smooth surface. In HEBP-treated animals, growth and merging of these surface nodules became arrested at the time of injection resulting in an irreversible "porous" stage corresponding to that part of the surface enamel. This area--the bright band--developed corresponding to the start of the area of final enamel formation and was subsequently carried incisally during the eruption of the incisor.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of ethane-1-hydroxy-1, 1-diphosphonate on cell differentiation, and proteoglycan and calcium metabolism, in the proximal tibia of young rats

The effects of ethane-1-hydroxy-1, 1-diphosphonate(EHDP) on cell differentiation, and on the metabolism of proteoglycan and calcium in the epiphyseal plate and metaphysis of rats were investigated through histology and autoradiograms of [35S]-sulfate, 45Ca, and [3H]-thymidine. Suppression of bone resorption in the metaphysis due to low dose EHDP administration was associated with a proliferation of osteoclasts with an increased number of nuclei. High dose EHDP induced enlargement of the hypertrophic zone of the epiphyseal plate and suppression of calcification of the cartilage matrix. This change had a significant association not only with the suppression of chondroitin sulfate synthesis and the degradation in the cartilage matrix, but also with the suppression of growth and differentiation of chondrocytes. Calcification was also inhibited in the metaphysis, and growth and differentiation from undifferentiated mesenchymal cells to osteoblasts, osteocytes, and osteoclasts were also suppressed by high dose EHDP.

Effects of single doses of 1-hydroxyethylidene-1,1-bisphosphonate on the mineralizing front of rat incisor enamel: a microradiographic and scanning electron microscopic study

The effects of a single dose of HEBP were examined by injecting rats subcutaneously with various doses (0.5, 1, 2.5, 5 and 10 mg P/kg body wt) and killing them either 2 or 9 days after injection. The maxillary incisors were processed for microradiography and the mandibular incisors for scanning electron microscopy after enzymatic digestion of the enamel organ remains. All doses resulted in a hypomineralized incremental band corresponding to the position of the mineralizing front at the time of injection. At 5 and 10 mg P/kg body wt, a hypomineralized lesion was found throughout the whole thickness of the enamel in an area which corresponded to the stage of late enamel secretion at the time of injection. The surface layer covering this lesion was elevated or disrupted. By scanning electron microscopy, there were three different types of lesions along the enamel surface: a "demarcation groove" corresponding to the initial enamel formation at the time of injection; an "area containing mineral globules" and a "bright band" corresponding to the stages of late secretory and final enamel formation, respectively, at the time of injection. A single injection of HEBP thus interferes with different stages of enamel formation. The findings may be explained as of the physico-chemical effects of HEBP on the mineral phase alone, but a direct effect of the drug on ameloblast function cannot be excluded.

Association of collagenase and tissue inhibitor of metalloproteinases (TIMP) with hypertrophic cell enlargement in the growth plate

In the transition from proliferating to hypertrophic cell zones in the growth plate, there is an increased in chondrocyte cell volume and a corresponding decrease in collagen content to allow for cell enlargement. To substantiate our hypothesis that collagenase is responsible for these changes, growth plates from rats treated with bisphosphonate (HEBP) were compared histologically and biochemically with growth plates from normal and vitamin D and phosphate deficient (-VDP) rats. HEBP-treated rats developed an expanded hypertrophic cell zone (HCZ) characterized by the presence of two distinct populations of hypertrophic cells. The proximal hypertrophic cells were only 2-fold enlarged compared to the proliferating cells, whereas 1/6 of the distal hypertrophic cells were enlarged almost 5-fold and appeared morphologically identical with hypertrophic cells from normal and -VDP rats. The HEBP growth plates were divided into cross-sectional thirds and analyzed for active and latent collagenase. The juxta-metaphyseal (lower 1/3) cartilage contained 100% of the fully enlarged hypertrophic cells and appeared identical to those found in normal and -VDP growth plates, along with 81% of the active and 77% of the total collagenase. Collagenase and tissue inhibitor of metalloproteinases (TIMP) were measured in extracts of similarly divided tissues. The presence of true collagenas was confirmed by using [3H]-telopeptide-free collagen. TIMP levels were inversely related to the presence of active collagenase and cellular hypertrophy. Substantial levels of latent collagenase were found in the extracellular fluid at sites of active collagenolysis, but not in the fluid phase surrounding the 2-fold enlarged hypertrophic cells. It is postulated that increased amounts of active collagenase and insufficient levels of TIMP may account for the reduced collagen content seen in the lower HCZ of both -VDP and HEBP rickets. Unlike active collagenase, which remains localized by binding to collagen, latent enzyme is probably restricted in its mobility throughout the extracellular space by diffusion, itself, or the interstices of the extracellular matrix.

1-Hydroxyethylidene-1,1-bisphosphonate (HEBP) simultaneously induces two distinct types of hypomineralization in the rat incisor dentine

Effects of 1-hydroxyethylidene-1,1-bisphosphonate (HEBP) on the dentinogenesis of the rat maxillary incisor were microradiographically examined 96 hours after a single subcutaneous injection. HEBP produced hypomineralized incremental bands in the enamel (HPOe) and in the dentine (outer HPO1 and inner HPO2) in a dose-dependent manner. In the labial dentine, both HPO1 and HPO2 did not extend apically beyond the apical limit of the HPOe and were thus located in the circumpulpal dentine. The two lesions in the labial dentine fully developed with a dosage of 10 mg/ P/kg or larger, and with 15 mg P/kg or larger, gross hypoplastic lesions developed. Therefore, histological analysis at shorter postinjection intervals was carried out on the labial dentine with 10 mg P/kg of HEBP. The HPO1 appeared along the dentine-predentine junction by 24 hours and was characterized by reduced numbers of inorganic crystals and 10 nm particles which invested the collagen fibrils. Therefore, the HPO1 was judged to be produced by the disturbance of transformation of the predentine to dentine. The precursor lesion of HPO2 appeared in the proximal predentine by 4 hours, and was characterized by reduced number of collagen fibrils and unusually coarse interfibrillar stippled material. This lesion migrated to the dentine by 96 hours and became the HPO2, which was characterized by reduced number of collagen fibrils. Individual collagen fibrils in the HPO2 were invested by as many inorganic crystals and 10 nm particles as in the normal dentine. The HPO2 is considered to be produced by the disturbance of organic matrix formation.

Bisphosphonates: a new class of drugs in diseases of bone and calcium metabolism

The geminal bisphosphonates are characterized by a PCP bond and are therefore analogs of pyrophosphate. They bind strongly to hydroxyapatite crystals and in vitro inhibit both crystal formation and dissolution. In vivo they inhibit soft tissue calcification and when given in large amounts also normal calcification. This effect is due to the inhibition of calcium phosphate crystal growth. Furthermore, the bisphosphonates are very potent inhibitors of bone resorption. The mechanism(s) of action is not yet known but is likely to be at a cellular level. The extent of the biological activity of each compound depends on the specific chemical structure, so that each individual bisphosphonate must be considered as a separate compound. The only common characteristic is the PCP group, which gives the compound its high affinity to bone. The individual effects, however, are determined by the side groups on the carbon atom. This opens interesting possibilities for the development of new compounds. No bisphosphonate analyzed so far can be degraded in vivo; all are either deposited in the skeleton, where they remain for years until the bone is destroyed, or are excreted in the urine. The high affinity for bone explains the specificity of the compounds for bone and the fact that they have relatively few nonosseous effects. Bisphosphonates are used in man to inhibit ectopic calcification, including dental tartar and ectopic ossification. Furthermore, they are used to inhibit bone resorption, especially in diseases such as Paget's disease and tumoral osteolysis. Finally, when linked to 99nTc, bisphosphonates are employed as bone scanning agents.

EHDP-induced rachitic syndrome in rats is not reversed by vitamin D metabolites

To examine whether either of the two known active vitamin D metabolites 1,25(OH)2D3 or 24,25(OH)2D3 could reverse the mineralization defect induced by 1-hydroxyethylidene-1,1-bis phosphonate (EHDP), a model of EHDP-induced rickets was used. Rats at the age of 31 days were injected for 10 consecutive days with EHDP (10 mg/kg). Other littermates were treated with a combination of EHDP and either 1,25(OH)2D3 or 24,25(OH)2D3 or were treated following 10 days of EHDP, with either of the vitamin D metabolites for an additional 72 hr. Samples of cartilage fluid (Cfl) and of blood were removed prior to sacrifice for biochemical studies of some parameters of calcification. These parameters were correlated with the results of light and electron microscope studies of growth plate cartilage and bone. EHDP-treated rats revealed signs of typical rickets, manifested by widened growth plates and impaired bone mineralization. Transmission electron microscope (TEM) examination revealed matrix vesicles distributed throughout the growth plate; however, there appeared to be an arrest of the spread of the crystals at the provisional zone of calcification. Treatment with either 1,25(OH)2D3 or 24,25(OH)2D3 failed to reverse the rachitic condition of the animals. Serum calcium blood levels were elevated in the 1,25(OH)2D3 and EHDP-treated group. 1,25(OH)2D3 and 24,25(OH)2/D3 further increased the already elevated serum alkaline phosphatase levels observed in EHDP rats, although the increase observed with 1,25(OH)2D3 was not statistically significant.(ABSTRACT TRUNCATED AT 250 WORDS)

Cell fractions from rat rib growth cartilage. Biochemical characterization of matrix molecules

In an attempt to isolate and characterize the putative target cells for growth hormone, chondrocytes were isolated from rat rib growth cartilage and fractionated by centrifugation in a discontinuous Percoll gradient. This resulted in three cell fractions with differing properties. The fraction with the lowest density consisted mainly of large, lipid-containing cells which became flattened in subsequent culture. The cells in this fraction were fair collagen producers but synthesized only minor amounts of proteoglycans and apparently no proteoglycan aggregates. These cells probably originate in the hypertrophy zone of the growth plate. The fraction with highest density, on the other hand, consisted of small cells which upon cell culture became polygonal and surrounded with refractile matrix. They synthesized less collagen, but more proteoglycans than the low-density fraction. The proportion of proteoglycan aggregates was rather low (10-20%) but otherwise the proteoglycans were similar to those synthesized by other chondrocytes. This cell fraction was tentatively identified as cells from the upper part of the growth plate. Finally, the middle fraction was heterogeneous, consisting of cells of varying shape. This fraction synthesized large amounts of both collagen and proteoglycans. In all three cell fractions, type II collagen predominated. There were also minor amounts of (1a, 2a, 3a) collagen, and, in the two denser fractions, of type I collagen.

Effects of disodium ethane-1-hydroxy-1, 1-diphosphonate (EHDP) in adult normal and selectively parathyroidectomized rats. I. Effects on plasma calcium, bone tissue, and adrenal glands at low or normal calcium intake

One-year-old intact and selectively parathyroidectomized rats were given a normal or low calcium diet for 8 months and, during the last 3 weeks, diphosphonates (EHDP) at a low dose level of 1.0 mg EHDP/kg body weight/day intraperitoneally. The administration of EHDP impaired the animals' ability to maintain the blood calcium level during a low calcium intake. Calcium-deficient intact animals had significantly reduced plasma calcium during EHDP treatment, while calcium-deficient parathyroidectomized animals showed no further reduction. Calcium deficiency alone resulted in osteoporosis which was prevented by parathyroidectomy. The short period of EHDP treatment had no significant effect on the bone mass in control, osteoporotic, and parathyroidectomized animals. The calcium accretion rate by bone became significantly increased upon a low calcium intake in intact rats but not in parathyroidectomized ones. This increase was counteracted by EHDP which gave rise to reduced accretion in both parathyroidectomized and osteoporotic animals. In addition EHDP caused hypertrophy of the adrenal cortex in all treated groups.

Diphosphonates: history and mechanisms of action

The history of diphosphonates began with studies of inorganic pyrophosphate. This compound was found to occur in many biological fluids and inhibited the precipitation of calcium phosphates. It also slowed the transformation of amorphous calcium phosphate to its crystalline form, and inhibited crystal aggregation and dissolution. These observations suggested that it might be a compound of physiological or pathophysiological significance, perhaps in hypophosphatasia and in renal lithiasis. Diphosphonates are compounds where the P-O-P bond of pyrophosphate is replaced by a P-C-P bond. Many diphosphonates have been synthesized and tested and some relationship of their structure to the spectrum of biological effects has been observed. These analogues have similar properties to pyrophosphate, but unlike pyrophosphate they are resistant to enzymic degradation. Their experimental properties have led to their clinical development as bone scanning agents and in the treatment of disorders of ectopic mineralization and increased bone resorption.

The use of brominated toluidine blue O in X-ray microanalysis for proteoglycan

Toluidine blue O, a cationic dye has been used for visualizing proteoglycan by light and electron microscopy. Toluidine blue O has now been brominated and incorporated into epiphyseal cartilage during its fixation. Using energy dispersive X-ray microanalysis, bromine has been measured from area to area and compared to measurements of sulphur, a naturally occurring element of proteoglycan. Since bromine has been combined mole for mole with toluidine blue O and it is already known that toluidine blue O combines approximately mole for mole with the glycosaminoglycans of proteoglycan, the measurement of bromine, presents an indirect measure of proteoglycan concentration. The X-ray spectral localization of sulphur presents problems in X-ray analysis which are overcome with bromine which makes this technique attractive for workers in this field.

Effect of ethane-1-hydroxy-1,1-diphosphonate and vitamin D on bone mineralization

Administration of large quantities of ethane-1-hydroxy-1,1-diphosphonate to growing chicks resulted in a decrease in percent bone ash and an increase in percent osteoid. The degree of inhibition of bone mineral accumulation was a function of both duration and quantity of ethane-1-hydroxy-1,1-diphosphonic acid administration. The inhibition of bone mineral accumulation could be partially corrected with administration of 1,25-dihydroxyvitamin D3. Administration of high levels of ethane-1-hydroxy-1,1-diphosphonate also resulted in inhibition of intestinal calcium absorption. This could be reversed or prevented by the administration of 1,25-dihydroxyvitamin D3.

Correlation of lysozyme activity with proteoglycan biosynthesis in epiphyseal cartilage

Pig epiphyseal cartilage (proximal ulna epiphysis) previously incubated into vitro in the presence of sodium [35S]sulfate or [3H]thymidine was either analyzed by autoradiography or separated into 9 morphologically defined consecutive layers and investigated for 35S-incorporation into the guanidinium chloride-extractable proteoglycans and for lysozyme activity. The lowest 35S incorporation and lysozyme activity were determined in the zone of resting cells, but there is a consecutive increase in the rate of proteoglycan synthesis and lysozyme activity toward the diaphyseal cartilage-bone junction, with the maximum at the lower columnar cell zone and a sharp reduction of both parameters at the hypertrophic zone. The maxima of 35S incorporation and [3H]thymidine incorporation do not coincide. The guanidinium chloride-soluble proteoglycans exhibit macromolecular polydispersity. Fractions excluded from as well as retarded by Sepharose 2B gel could be separated and were detected in all zones. The results indicate a correlation of proteoglycan biosynthesis and lysozyme activity in epiphyseal cartilage.

Effects of diphosphonates on glycosaminoglycan synthesis and proteoglycan aggregation in normal adult articular cartilage

The effects of disodium ethane-1-hydroxy-1,1-diphosphonate (EHDP) and disodium dichloromethylene diphosphonate (Cl2MDP) on glycosaminoglycan synthesis and macromolecular organization of proteoglycans have been examined in normal adult canine cartilage. One to 500 micron of either compound produced reversible inhibition of glycosaminoglycan synthesis to about 70% of control levels, whereas lower concentrations had no effect. Based on Sephadex G-200 chromatography, the average hydrodynamic size of glycosaminoglycans in diphosphonate-treated cartilage was similar to that of those in control cartilage. In most cases proteoglycan aggregates from diphosphonate-treated cartilage were smaller in hydrodynamic size than those from control cartilage, as judged by Sepharose 2B elution profiles. The size of purified proteoglycan subunits, obtained after dissociation of the aggregates with 4 M guanidinium chloride or after incubation of the aggregates with hyaluronic acid beta1 leads to 3 hydrolase, was not affected by the diphosphonates. Furthermore, proteoglycans from diphosphonate-treated cartilage did not interact in vitro with hyaluronic acid, suggesting that diminished proteoglycan aggregation may have resulted from an abnormality in the hyaluronate-binding region of the proteoglycan core protein.

The effects of ethylene-1-hydroxy-1, 1-diphosphonate on cellular transformation and organic matrix of the epiphyseal growth plate of the rat--a light microscopic and ultrastructural study

Ethylene-1-hydroxy-1, 1-diphosphonate (EHDP) was administered intraperitoneally to one-day-old rats. In the first experiment, each animal was given 4 injections of EHDP distributed over two consecutive days and corresponding to a total amount of EHDP of 100 mg/kg bwt/day. The animals were sacrificed 12 hours after the last injection. In the second experiment, each animal was given 3 injections, each containing 50 mg of EHDP/kg bwt, with an interval of 6 hours and were thereafter left to survive for 4 days. Animals in the first experiment showed in comparison to normal controls an increased width of the hypertrophic zone; lack of calcified septa within the zone of provisional calcification; persistent atypical chondrocytes in the calcification zone and a large number of matrix vesicles lacking in crystals. The ground substance showed an accumulation of fine precipitates apparently representing undegraded aggregates of proteoglycan macromolecules. Animals in the second experiment formed a new apparently normal epiphyseal growth plate, while the "old" epiphyseal cartilage formed under the influence of EHDP remained largely unresorbed within the metaphysis. Besides the previously described inhibitory effects of diphosphonates on the crystallization of matrix vesicles and the growth of hydroxyapatite crystals, EHDP, at the doses used, was found to have a profound inhibitory effect on the differentiation and migration of the epiphyseal chondrocytes as well as on the degradation of proteoglycan macromolecules. The observed inhibition of vascular invasion appears to be related to inhibition of enzyme degradation of the ground substance, as evidenced by the observation of extracellular lysosomelike bodies in the erosion zone.

Fibrodysplasia ossificans progressiva. Biochemical changes in blood serum, urine, skin, bone, and ectopic ossification

Increased urinary output of total hydroxyproline, hydroxylysine and uronic acid was found in two patients suffering from fibrodysplasia ossificans progressiva. Before treatment of one of the patients, the high molecular weight peptide fraction deriving from newly synthesised collagen was particularly increased. Treatment with disodium etidronate (diphosphonate) reduced the values. The urinary values of sodium, potassium and calcium were also depressed during treatment, and, in both patients, serum phosphate was high, while serum calcium was normal. The hydroxyproline and hydroxylysine contents in skin and bone of FOP patients did not differ from controls, while ectopic ossifications showed a considerable increase in hydroxylysine in relation to normal bone.

Light microscopic and ultrastructural observations on the short-term effects of ethylene-1-hydroxy-1, 1-diphosphonate (EHDP) on rat tibia epiphysis

Ethylene-1-hydroxy-1, 1-diphosphonate (EHDP) was administered intraperitoneally to one-day old rats at a concentration of 30 and 40 mg/kg body weight/injection. Two groups of animals received four doses, respectively, over a 44-hour-period and a third group received two high doses with a 15-hour interval, the total amounts corresponding to 30, 40 and 20 mg/P/kg body weight. Animals in the first two experimental groups showed increased width of the hypertrophic zone as compared with normal controls and lack of calcified septa within the zone of provisional calcification. In the calcification zone, persistent atypical chondrocytes were present and in the septa a large number of matrix vesicles which hardly ever contained any crystals. The ground substance of these septa contained fine precipitates, probably representing proteoglycan complexes which were not seen normally in this zone. In the third group, the septa of the calcification zone were calcified and the hypertrophic zone was not clearly widened. In the metaphysis, remnants of cartilage or osteoid were observed as "islands" covered with osteoblast-like cells which showed signs both of collagen and apatite formation, the latter evidenced by the appearance of crystals within the matrix vesicles. It is suggested that the complex effects observed in calcifying cartilage after administration of high doses of EHDP in vivo are not restricted solely to the stage of crystal formation.