Effect of bound phosphoproteins and other organic phosphates on alkaline phosphatase-induced mineralization of collagenous matrices in vitro

The aim of the present study was to determine to what extent the rate at which collagen mineralizes correlates with the amount and nature of bound phosphate groups. Sheets of collagen prepared from demineralized bovine dentin or cortical bone were complexed with various concentrations of phosphoserine [(P)Ser] or rat dentin phosphoproteins (PP; lowly or highly phosphorylated PP, LPP or HPP). Alternatively, phosphate groups were removed from the collagenous carrier material by treatment with phosphatases. Mineralization was achieved by incubation in culture medium supplemented with 45Ca, alkaline phosphatase and 10 mM beta-glycerophosphate. The sheets were monitored for uptake of 45Ca and lag times calculated and plotted against the amount of bound phosphate. It was observed that dephosphorylation of the carrier causes an increase in lag time and that rat PP decreases lag times in a concentration-dependent way. HPP were more effective than LPP. (P)Ser or other small organic P-containing molecules had hardly any influence on lag time. It is concluded that next to the amount of bound phosphate, the nature of phosphorylated substances has considerable influence on the rate of mineralization of a collagenous carrier.

[Tendinosis calcarea--results of treatment with needling]

In a prospective study, 33 patients with calcifying tendinitis had a needling in local anaesthesia performed under control of an image converter. There was at least a one year follow-up period. Resorption of the hydroxyapatite deposits was seen in 23 instances; 75% of all patients were free of symptoms or had considerably improved (Table 3). For better assessment of these results we embarked on an additional retrospective study observing the spontaneous evolution of 235 hydroxyapatite deposits for 3 years on average. On the x-ray, these deposits had a characteristic appearance and could be classified into one of three types: either sharply outlined and densely structured (type I), or with cloudy limitations and transparent in structure (type III). In addition we saw deposits combining the features of both of the above named types (type II) (Table 5, Fig. 6). Based on this classification, a clear correlation was revealed to exist between initial x-ray findings and the frequency of resorption after needling: with type I, complete resorption was seen in 33% of the cases, with type II in 71%, and with type III in 85% of the cases (Table 6). With type II, however, only half of the patients were free of symptoms. Surgical removal of the hydroxyapatite deposits became necessary in 3 patients because of persisting heavy pains. As complication we observed intraoperatively an incomplete tear of the rotator cuff, the relation of which to the needling remained unsure. In this context, the question is discussed whether calcifying tendinitis and rupture of the rotator cuff may represent two disease entities of identical origin.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of 1alpha,25-dihydroxyvitamin D3 receptor in cell extracts with low protein concentration

An unacceptable loss of tritiated 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] to the wall of the reaction tubes constituted an obstacle when examining C3H/10T1/2 Cl 8 cells for 1,25-(OH)2D3 receptor. The loss of tracer in low protein cell extracts could be strongly reduced by incubating the cell extracts in polyethylene tubes and in the presence of inert peptides prepared by digestion of gluten proteins. When incubated in buffer the recovery of tracer increased from 3 to 45% by using polyethylene tubes instead of sodium-glass tubes. However, the presence of a sufficient amount of inert peptides in the buffer significantly increased the recovery of tracer to 89%. This procedure improved the saturation binding analysis of the 1,25-(OH)2D3 receptor in the C3H/10T1/2 Cl 8 cells using the hydroxylapatite assay.

Acute calcific periarthritis of the hand and elbows in women. A study and review of the literature

OBJECTIVE

To study the clinical and radiological features of acute calcific periarthritis (ACP) of the hand and elbow in women and to review the literature.

METHODS

A retrospective study of ACP of the hand and elbow was conducted in 10 women, and the literature since 1970 reviewed, using Medline data.

RESULTS

Ten women fulfilled the criteria of a single focus ACP. Mean age was 36.5 years (range 25-53). X-ray diffraction in 3 patients who underwent aspiration biopsy showed a pattern of calcium hydroxyapatite. The clinical course was short and self-limited. Most cases mimicked septic conditions and were initially misdiagnosed. All patients demonstrated gradual resolution of calcific deposits after 1-3 weeks.

CONCLUSIONS

We conclude that calcific tendinitis of the hand and elbow is a self-limiting disease affecting mainly pre or perimenopausal women.

Effect of basic fibroblast growth factor on the growth and differentiation of adult stromal bone marrow cells: enhanced development of mineralized bone-like tissue in culture

Rat stromal bone marrow cells (SBMC) were shown to produce mineralized bone-like tissue in culture in the presence of dexamethasone, ascorbic acid, and beta-glycerophosphate. The addition of 3 ng/ml of basic fibroblast growth factor (bFGF) resulted in a significant increase in formation of mineralized tissue. The present study was aimed at assessing the effect of bFGF on the proliferation and differentiation of SBMC and on the sequential development of mineralized bone-like tissue in culture. Transmission electron microscopy of bFGF-treated cultures demonstrated the development of a multilayered structure resembling mineralized bone tissue consisting of cell layers embedded within a heavy extracellular matrix. The matrix was rich in bundles of collagen fibers associated with extensive mineral deposits consisting of hydroxyapatite as determined by infrared spectrophotometry. The addition of 3 ng/ml of bFGF resulted in significant enhancement of [3H]thymidine and [3H]proline incorporation and protein accumulation by 12-, 2.5-, and 2.5-fold, respectively. bFGF treatment increased cAMP responsiveness, alkaline phosphatase activity, osteocalcin level, 45Ca2+ deposition, and mineralized-like tissue formation and induced the earlier expression of these markers in the treated culture. A biphasic sequence of events was observed during the development of mineralized bone-like tissue in bFGF-treated and control cultures. The first phase is characterized by cell proliferation and matrix accumulation and is reflected by a progressive increase in [3H]thymidine and [3H]proline incorporation until day 11. The second phase, which follows, is characterized by a sharp decline in cell proliferation and matrix accumulation and a concomitant expression of osteoblast differentiation as reflected by the progressive increase in alkaline phosphatase activity, mineral deposition, and osteocalcin expression. Treatment of cultures with bFGF accentuated this biphasic sequence of events. These results indicate that bFGF has the capacity to stimulate both the growth and the biochemical functions of SBMC obtained from a young adult animal.

Osteopontin-hydroxyapatite interactions in vitro: inhibition of hydroxyapatite formation and growth in a gelatin-gel

Osteopontin is a phosphorylated bone matrix sialoprotein, postulated to play a regulatory role in biomineralization. The effects of a crude preparation of rat bone osteopontin and a more highly purified bovine bone osteopontin were evaluated using a gel diffusion system to measure effects of 0.1-100 micrograms/ml of this matrix protein on hydroxyapatite formation and crystal proliferation. Bovine osteopontin at concentrations greater than 25 micrograms/ml inhibited both hydroxyapatite formation and growth in a dose-dependent manner. Osteopontin at concentrations lower than 25 micrograms/ml had no detectable effect on the amount of mineral accumulated in experiments with and without pre-formed hydroxyapatite seed crystals either when initial mineral deposition was assessed at 3.5 days, or when mineral formation and growth were assessed at 5 days. There was a statistically significant dose-dependent decrease in crystal length at all concentrations tested. The rat osteopontin preparation had similar inhibitory abilities. Partial dephosphorylation of bovine osteopontin with alkaline phosphatase removed its inhibitory ability, and reduced its ability to bind calcium. The affinity of bovine osteopontin for hydroxyapatite was determined based on a Langmuir adsorption isotherm, with values of K (binding affinity) and N (number of binding sites) being 0.026 ml/microgram and 1084 micrograms/m2, respectively. The data suggest that, in this system, osteopontin is an effective inhibitor of hydroxyapatite formation and growth due to its affinity for the hydroxyapatite crystals. In this system, osteopontin, distinct from other phosphoproteins which both promote and inhibit hydroxyapatite deposition, did not enhance mineral formation at any concentration tested.

Concentration and hydroxyapatite binding capacity of plasma osteocalcin in chronic alcoholic men: effect of a three-week withdrawal therapy

Plasma concentrations of osteocalcin (OC) were studied in 40 chronic alcoholic men (age range: 21-56 years) before and after 3 weeks of ethanol withdrawal therapy and in 50 non-alcoholic controls selected in respect to age and sex. Plasma OC level in alcoholic subjects was significantly lower than in the controls (3.0 +/- 2.6 micrograms/l and 4.7 +/- 2.8 micrograms/l, respectively). After 21 days of withdrawal therapy, plasma OC level was significantly higher than at the day of admission (5.8 +/- 3.5 micrograms/l, P < 0.001). This level was not statistically different from that of the controls. We also demonstrated that the hydroxyapatite binding capacity of plasma OC before as well as after the withdrawal period was not different from that of the controls. The acetaldehyde adduction of purified bovine OC in vitro did not change any of its immunoactivity and hydroxyapatite binding capacity. The results emphasize the fact that the decrease of plasma osteocalcin in chronic alcoholics is reversible within 3 weeks of alcohol withdrawal and that the circulating protein seems to be similar to that present in controls.