Incidence and Costs of Clinically Significant Events with Systemic Therapy in Patients with Unresectable Hepatocellular Carcinoma: A Retrospective Cohort Study

INTRODUCTION

Systemic therapies have been associated with clinically significant events (CSEs) in patients with unresectable hepatocellular carcinoma (uHCC). We evaluated the incidence of CSEs (bleeding, clotting, encephalopathy, and portal hypertension), and their impact on healthcare resource utilization (HCRU) and costs, in patients with uHCC treated with first-line (1L) atezolizumab plus bevacizumab (A + B), lenvatinib (LEN), or sorafenib (SOR) in the USA.

METHODS

A retrospective cohort study was performed using medical/pharmacy claims from Optum® Clinformatics® Data Mart. Patients diagnosed with HCC who initiated 1L A + B between June 01, 2020 and December 31, 2020 or LEN/SOR between January 01, 2016 and May 31, 2020 were included. Outcomes included incidence rates of CSEs, HCRU, and costs. Subgroup analysis was performed in patients with no CSEs or ≥ 1 CSE.

RESULTS

In total, 1379 patients were selected (A + B, n = 271; LEN, n = 217; SOR, n = 891). Clotting (incidence rate per 100 patient-years [PY] 94.9) and bleeding (88.1 per 100 PY) were the most common CSEs in the A + B cohort. The most common CSEs in the LEN cohort were clotting (78.6 per 100 PY) and encephalopathy (66.3 per 100 PY). Encephalopathy (73.0 per 100 PY) and portal hypertension (72.3 per 100 PY) were the most common CSEs in the SOR cohort. Mean total all-cause healthcare costs per patient per month (PPPM) were $32,742, $35,623, and $29,173 in the A + B, LEN, and SOR cohorts, respectively. Mean total all-cause healthcare costs PPPM were higher in patients who had ≥ 1 CSE versus those who did not (A + B $34,304 versus $30,889; LEN $39,591 versus $30,621; SOR $31,022 versus $27,003).

CONCLUSION

Despite improved efficacy of 1L systemic therapies, CSEs remain a concern for patients with uHCC, as well as an economic burden to the healthcare system. Newer treatments that reduce the risk of CSEs, while improving long-term survival in patients with uHCC, are warranted.

Incentivizing COVID-19 Vaccination in a Polarized and Partisan United States

CONTEXT

As COVID-19 vaccines were rolled out in early 2021, governments at all levels in the United States experienced significant difficulty in consistently and efficiently administering injections in the face of vaccination resistance among a public increasingly politically polarized on vaccination preferences before the beginning of mass vaccinations.

METHODS

Using an original conjoint experiment fielded to a nationally representative sample before the mass proliferation of COVID-19 vaccines, the authors examined how different incentives (e.g., employer mandates, state-organized or health care provider-organized vaccination clinics, and financial incentives) affect the public's preference to get vaccinated. They also tested how financial incentive preferences correlated with self-reported vaccination intention using observational data from the June 2021 Kaiser Family Foundation Health Tracking Poll.

FINDINGS

The authors found financial incentives positively influenced vaccine preferences among the mass public and all partisan groups, including Republicans who were initially "unlikely" to be vaccinated. The authors used the observational data to replicate their experimental findings, showing positive financial incentive attitudes positively correlated with self-reported vaccination disclosures.

CONCLUSIONS

These results provide support for direct financial incentives, rather than other incentives, as being a valuable tool for policy makers tasked with alleviating vaccination resistance among a US mass public increasingly polarized along partisan lines.

Durvalumab Treatment Patterns for Patients with Unresectable Stage III Non-Small Cell Lung Cancer in the Veterans Health Administration (VHA): A Nationwide, Real-World Study

BACKGROUND

Durvalumab is approved for the treatment of adults with unresectable stage III non-small cell lung cancer (NSCLC) post-chemoradiotherapy (CRT). This real-world study describes patient characteristics and durvalumab treatment patterns (number of doses and therapy duration; treatment initiation delays, interruptions, discontinuations, and associated reasons) among VHA-treated patients.

METHODS

This was a retrospective cohort study of adults with unresectable stage III NSCLC receiving durvalumab at the VHA between 1 January 2017 and 30 June 2020. Patient characteristics and treatment patterns were presented descriptively.

RESULTS

A total of 935 patients were included (median age: 69 years; 95% males; 21% Blacks; 46% current smokers; 16% ECOG performance scores ≥ 2; 50% squamous histology). Durvalumab initiation was delayed in 39% of patients (n = 367). Among the 200 patients with recorded reasons, delays were mainly due to physician preference (20%) and CRT toxicity (11%). Overall, patients received a median (interquartile range) of 16 (7-24) doses of durvalumab over 9.0 (2.9-11.8) months. Treatment interruptions were experienced by 19% of patients (n = 180), with toxicity (7.8%) and social reasons (2.6%) being the most cited reasons. Early discontinuation occurred in 59% of patients (n = 551), largely due to disease progression (24.2%) and toxicity (18.2%).

CONCLUSIONS

These real-world analyses corroborate PACIFIC study results in terms of the main reasons for treatment discontinuation in a VHA population with worse prognostic factors, including older age, predominantly male sex, and poorer performance score. One of the main reasons for durvalumab initiation delays, treatment interruptions, or discontinuations was due to toxicities. Patients could benefit from improved strategies to prevent, identify, and manage CRT and durvalumab toxicities timely and effectively.

Twenty-four Hour Hormone Profiles of TSH, Free T3 and Free T4 in Hypothyroid Patients on Combined T3/T4 Therapy

The benefits of using thyroxine (T4) plus triiodothyronine (T3) in combination in thyroid hormone replacement are unproven but many individuals continue to be treated with this regime. When T3 is used alone for hypothyroidism, it results in wide fluctuations of thyroid hormone levels. However, only limited data exists on combined T3/T4 therapy. In this study, we have compared 24-hour profiles of thyroid stimulating hormone (TSH), free T4 (fT4) and free T3 (fT3) and cardiovascular parameters in 10 hypothyroid patients who had been on once daily combined T3/T4 therapy for more than 3 months with 10 patients on T4 alone. Twenty patients, who were part of a larger study, investigating the long-term benefits of combined T3/T4 therapy, were recruited into this sub-study. Over 24-hours, 12 samples were taken for thyroid hormones. Their 24-hour pulse and BP is also monitored on a separate occasion. On T4 alone, a modest 16% rise in fT4 with no change in fT3 was seen in the first 4-hours post-dose. In contrast, on combined treatment, fT3 levels showed a marked rise of 42% within the first 4-hours post-dose (T3/T4:T4=6.24: 4.63 mU/L, p<0.001). Mean exposure to fT3 calculated by area under the curve (AUC) was higher (T3/T4:T4=1148:1062, p<0.0001) on T3. Circadian rhythm of TSH was maintained on both treatments. No difference in pulse or blood pressure over the 24-hours was seen between the groups. Our data suggests that despite chronic combined T3/T4 therapy, wide peak-to-trough variation in fT3 levels persists. Although no immediate cardiovascular effects were seen, the long-term consequences for patients on combined therapy are unknown.

Plaster of Paris as bone substitute in spinal surgery

In order to assess the effectiveness of calcium sulphate (plaster of Paris; POP) as a substitute for autologous bone graft, we performed lumbar intervertebral fusion in mature sheep using POP and a variety of other graft materials, and reviewed the literature. The osteoconductivity of the POP grafts was compared to that of grafts carried out with autogenous iliac crest, frozen allogeneic bone, and ProOsteon 500 coralline bone. We also compared the osteogenicity of POP to admixtures of autogenous iliac crest bone with POP and coralline bone, and to an osteoinductive demineralized sheep bone preparation (DBM). The substrates were loaded into tubular titanium mesh, implanted into excavated disc spaces and recovered after a period of 4 months. Fusion mass segments tested in flexion and tension showed that POP was equal to autogenous bone and most other substrates. The POP fusions were significantly tougher than the DBM fusions, even though histomorphometry failed to reveal differences in the amount of trabecular bone. We conclude that POP can be used to achieve a biomechanically stable interbody lumbar vertebral fusion. In addition, our literature review indicated that POP can be used as a vehicle for local delivery of antibiotics in bone infections.

Comparative morphology of the marrow sac

Electron microscopic techniques have been used to profile the morphologies of marrow sacs in different laboratory species. These structures all comprise a condensed layer of overlapping fibroblast-like stromal cells and apparently confine the medullary and endosteal osteoblast/lining cells to separate histiotypic compartments. There were some variations in the morphology of the sac cells in the different species. In rats, cats, and sheep, scanning electron microscopy (SEM) showed a seamless arrangement of marrow sac cells which resembled a thin, flat simple squamous epithelium; they displayed few intercellular cytoplasmic processes. In the rabbit and pigeon, the sac comprised a more woven, multilayered fabric of broadly elongate flat fibroblast-like cells which displayed numerous intercellular processes. Transmission electron microscopy (TEM) showed that all marrow sac cells were attenuated with elongated nuclei, a few small round mitochondria, and a sparse rough endoplasmic reticulum. In the majority of animals, the sac was one to two cell layers thick. The rabbit and pigeon sacs were multilayered, and never less than three to four cells deep. The cell layers were not closely apposed. Tight or gap junctions were absent at the points of intercellular contact. These morphological results suggest that marrow sacs are common elements of the vertebrate skeleton with species specific morphologies.

Endogenous parathyroid hormone-related peptide enhances proliferation and inhibits differentiation in the osteoblast-like cell line ROS 17/2.8

To investigate potential effects of endogenous parathyroid hormone-related peptide (PTHrP) on osteoblast function, ROS 17/2.8 cells were transfected with full-length PTHrP cDNA in a sense or antisense orientation to alter PTHrP production. Compared with vector-transfected control cells, PTHrP-overproducing (sense-transfected) cells showed increased DNA synthesis ([(3)H]-thymidine incorporation) and increased growth (cell number). The extent of apoptosis was compared for the different clones using the terminal deoxynucleotide-mediated dUTP nick-end-labeling assay (TUNEL) and Hoechst staining. No differences in percentages of apoptotic cells were found under basal culture conditions or after 3 days of serum deprivation, which, itself, markedly increased numbers of apoptotic cells. The effect of PTHrP on osteoblast differentiation was assessed by examining two protein markers of differentiation, alkaline phosphatase, and bone morphogenetic protein (BMP)-2. Alkaline phosphatase activity was decreased in sense-transfected cells and increased in antisense-transfected cells, compared with cells transfected with empty vector. PTHrP-overproducing cells also showed decreased numbers of BMP-2-positive cells, whereas antisense-transfected cells showed no difference compared with vector control. The results indicate that: (a) endogenously produced PTHrP can increase growth of these osteoblastic cells by stimulating proliferation while not affecting apoptosis; and (b) the increased cell proliferation produced by PTHrP was accompanied by a reduction in activity or amount of two proteins normally expressed by differentiated osteoblasts.

Compartment syndrome complicating metastatic malignant melanoma

Compartment syndrome is well documented in the literature. Neoplasia as a cause is a rare. We report a patient with known metastatic malignant melanoma presenting with a compartment syndrome of the arm caused by a relatively slow growing, non-invasive metastatic deposit. This was excised and the patient made an uneventful recovery.

Plaster of Paris as an osteoconductive material for interbody vertebral fusion in mature sheep

STUDY DESIGN

In adult female sheep, histologic and biomechanical criteria were used to determine whether the osteoconductive performance of plaster of paris would promote the incorporation of the tubular titanium mesh implants used for interbody vertebral fusions.

OBJECTIVES

To compare the osteogenicity of plaster of paris with that of autogenous iliac crest bone and bone marrow 6 months after they were loaded into tubular titanium mesh cages and implanted as L3-L5 bridges after L4 corpectomies.

SUMMARY OF BACKGROUND DATA

One of the aims of surgery for vertebral pathology is to stabilize the spine by interbody fusions. The morbidity associated with the use of iliac crest autograft bone for fusion grafts prompted trials using plaster of paris as an osteoconductive substrate.

METHODS

The total volume of bone that invested the L3-L5 mesh cages after 6 months was quantitated by computed tomography scans. All specimens subsequently were cut into fusion mass segments for biomechanical testing in flexion, extension, compression, and torsion, and then embedded in plastic for sectioning and histomorphometry to determine the trabecular bone volume within the titanium mesh.

RESULTS

In each experimental model, implants of plaster of paris were the osteoconductive equal of autogenous iliac crest bone/marrow preparations. The volumes of bone formed around and within the titanium mesh were identical, and the tissues were biomechanically indistinguishable. A partial mechanism was determined by modifying the system for midshaft femoral defects.

CONCLUSIONS

In the sheep, a tubular titanium mesh packed with plaster of paris forms an osteoconductive conduit to achieve a biomechanically stable interbody lumbar vertebral fusion.

Functional oxytocin receptors discovered in human osteoblasts

Undifferentiated or differentiated human trabecular bone cells with osteogenic capacity in primary culture express oxytocin receptors (OTRs). OTR expression then persists upon differentiation to an osteoblast phenotype. A human epithelial osteosarcoma cell line, Saos-2, also expresses OTRs. Expression was determined both at mRNA and protein levels. Functional OTRs are evidenced by an increase in intracellular calcium concentration, [Ca2+]i, in response to 10 nM oxytocin (OT). An oxytocin antagonist (OTA) blocked this effect, demonstrating specificity for OT. OT also stimulated prostaglandin E2 (PGE2) synthesis in both confluent undifferentiated and differentiated human trabecular bone cells. This is the first report of OTR mRNA and protein expression and of prescribed OT signal pathways in osteoblastic cells. Since PGE2 has been shown to increase bone turnover in favor of bone formation, OT may be a new class of a bone anabolic agent.

Transforming growth factor-beta2 mRNA level in unloaded bone analyzed by quantitative in situ hybridization

The effects of tail suspension hypokinesia on the gene expression for TGF-beta2 at different sites within bone were evaluated. TGF-beta2 mRNA signal levels were determined quantitatively by an image analysis system. The osteopenia induced by tail suspension was verified by histomorphometry. In the periosteum of nonsuspended control rats, TGF-beta2 mRNA was highly expressed in the preosteoblasts and osteoblast-rich cambial layers; very little signal was present within the middle and outer fibroblastic layers. Gene expression was significantly reduced in suspended rats, and this was evident both in terms of the number of silver grains in unit area or length of tissue and in each osteoblast and preosteoblast. Hypokinesia also reduced the expression of TGF-beta2 mRNA level in cortical and trabecular bone osteocytes, but did not adversely affect the mRNA level in chondrocytes in growth plate. The results affirm the site-specific response of TGF-beta2 gene expression in rats, and suggest that the cortical and trabecular bone osteopenia associated with hypokinesia in rats may be associated with a deficit in osteoblastic and osteocytic TGF-beta2 level.

Long-term remodeling of vascularized and nonvascularized onlay bone grafts: a macroscopic and microscopic analysis

The present study was performed to compare vascularized and nonvascularized onlay bone grafts to investigate the potential effect of graft-to-recipient bed orientation on long-term bone remodeling and changes in thickness and microarchitectural patterns of remodeling within the bone grafts. In two groups of 10 rabbits each, bone grafts were raised bilaterally from the supraorbital processes and placed subperiosteally on the zygomatic arch. The bone grafts were oriented parallel to the zygomatic arch on one side and perpendicular to the arch on the contralateral side. In the first group, vascularized bone grafts were transferred based on the auricularis anterior muscle, and in the second group nonvascularized bone grafts were transferred. Fluorochrome markers were injected during the last 3 months of animal survival, and animals were killed either 6 or 12 months postoperatively. The nonvascularized augmented zygoma showed no significant change in thickness 6 months after bone graft placement and a significant decrease in thickness 1 year after graft placement (p < 0.01). The vascularized augmented zygoma showed a slight but statistically significant decrease in thickness 6 months after graft placement (p < 0.003), with no significant difference relative to its initial thickness 1 year after graft placement. In animals killed 6 months after bone graft placement, both the rate of remodeling and the bone deposition rate measured during the last 3 months of survival were significantly higher in the vascularized bone grafts compared with their nonvascularized counterparts (p < 0.02). By 1 year postoperatively, there were no significant differences in thickness, mineral apposition rate, or osteon density between bone grafts oriented perpendicular and parallel to the zygomatic arch. These findings indicate that the vascularity of a bone graft has a significant effect on long-term thickness and histomorphometric parameters of bone remodeling, whereas the direction of placement of a subperiosteal graft relative to the recipient bed has minimal effect on these parameters. In vascularized bone grafts, both bone remodeling and deposition are accelerated during the initial period following graft placement. Continued bone deposition renders vascularized grafts better suited for the long-term maintenance of thickness and contour relative to nonvascularized grafts.

Expression of BMP-2 by rat bone marrow stromal cells in culture

To investigate the role of bone morphogenetic protein (BMP-2) in ossifying rat bone marrow stromal cell cultures, we determined the population of fibroblast-like stromal cells that expressed BMP-2 immunocytochemically (anti-rhBMP-2 monoclonal antibody), and compared that to alkaline phosphatase (AP) and collagen synthesis formed in culture over a 4-week period in control and dexamethasone-supplemented mineralizing media. In control media, the percentage of BMP-2-positive stromal cells (BMP-2(+)) increased from 12 to 25% within the first 4 days of culture. In mineralizing media, the level of BMP-2(+) cells was significantly increased (43-44%). The intensity of immunostaining gradually increased with time. The levels of AP were undetectable at 1 week in both control and mineralizing media, but increased gradually over the next 2 weeks and peaked at 3 weeks. ALP levels were significantly greater in cultures grown in mineralizing medium (P < 0.05 at 3 weeks, P < 0.01 at 4 weeks). Collagen synthesis peaked and was significantly greater at 3 weeks (P < 0.05) in cultures grown in mineralizing medium. The levels of AP and collagen synthesis most closely reflected the changes in the percentage of BMP-2(+) cells from 7 to 28 days. Though these changes may reflect a primary action of BMP-2 on marrow osteoprogenitor-like stromal cells, they do not exclude a mechanism that involves the induction of other members of the BMP family known to stimulate AP and collagen synthesis. We conclude that BMP-2 expression in cultures of fibroblast-like marrow stromal cells is enhanced when those cells are induced to become osteoblasts by exposure to dexamethasone.

Torsional injury resulting in disc degeneration: I. An in vivo rabbit model

Torsional injuries may be a precursor to intervertebral disc degeneration, but published rabbit models indicate a latent time of 6 months. We describe a rabbit model in which instability and disc degeneration appear within 3 months. Sixty-five male New Zealand rabbits underwent presurgical irradiation to inhibit heterotopic bone formation. Control animals then underwent either a soft-tissue release or facetectomy and capsulotomy, whereas experimental animals received surgery and an acute 30 degrees torsional lumbar injury. Capsulotomy, as well as facetectomy without torsion, failed to effect disc degeneration. However, the rabbits that received torsion exhibited clear indications of degenerative disc changes (thinning, increased PLA2 levels, and decreased nucleus pulposus volume) within 60-90 days. The observations associate disc degeneration with a destabilizing acute torsional injury.

Torsional injury resulting in disc degeneration in the rabbit: II. Associative changes in dorsal root ganglion and spinal cord neurotransmitter production

The mechanism mediating the chronic pain associated with lumbar disc degeneration may involve neurotransmitters elaborated by dorsal root ganglion (DRG). This hypothesis has been tested in an applicable rabbit model of disc degeneration. Twenty control male rabbits underwent a soft-tissue release; 20 experimental rabbits sustained a facetectomy and capsulotomy and received an acute torsional lumbar injury. The levels of calcitonin gene-related peptide, vasoactive intestinal peptide, and substance P were measured in the DRG, spinal cord, and disc at 10, 30, 60, and 90 days postoperatively. Torsional injury was associated with a statistically significant increase in most DRG and spinal cord neurotransmitter values after 60-90 days. These points in time marked the periods of maximum biomechanical instability and disc narrowing. Such data support concepts about the association between chronic lumbar spinal instability, disc degeneration, and pain.

Positively charged dextran resin inhibits trabecular bone repair in the rabbit tibial physis

Because exposure to positively charged dextran resin (PCDR) inhibits the growth of cultured rat and human bone cells, we tested the hypothesis that PCDR might inhibit bone repair in vivo. Central physeal defects were created by drilling 3.0-mm holes from the proximal tibial plateau into the metaphysis. The defects in left tibiae were packed with neutral resin (control); those in right tibiae were filled with PCDR. At the end of the 1st, 2nd, 3rd, and 10th postoperative weeks, the outcomes were quantitated by documenting the percent trabecular bone volume within the defect. The PCDR-filled defects showed a significant decrease in trabecular bone formation as early as the 2nd week. By the 10th postoperative week, formation of trabeculae had been reduced by nearly 40%. The inhibition conferred by PCDR suggests that the resin could be used as a suppressive interpositional material.

Winner of the AlbertTrillat Young Investigator Award. The effects of aggressive notchplasty on the normal knee in dogs

We assessed the possible association between an aggressive intercondylar notchplasty and histopathologic, radiographic, and gait changes to the knee. Three groups of six adult greyhounds were observed for 6 months. Group I dogs had a sham operation. Group II dogs had a 4-mm notchplasty of the lateral femoral condyle where it articulates with the lateral tibial spine. Group III dogs had a 7- to 8-mm notchplasty of the lateral femoral condyle to simulate the long-term effects of an overly aggressive notchplasty. Force plate gait analyses were not significantly different for any dogs at 3 and 6 months. Histopathologic studies (hematoxylin and eosin and safranin O stains) revealed notchplasty area remodeling with a thin layer of lamellar bone covered by fibrous connective tissue. Both Group II and III dogs had significant loss of lateral femoral condyle and trochlear groove articular surface proteoglycans. The radiographic notch width index remained unchanged throughout the study for Group I; the indexes increased immediately after surgery in Groups II and III because of the notchplasty, but after 6 months these values returned to near-preoperative measurements. An aggressive intercondylar notchplasty caused articular cartilage histopathologic changes at 6 months consistent with those found in knees with early degenerative arthritis. Significant refilling of a non-impinged notchplasty occurred by 6 months after surgery. Our results raise concern about the effects of aggressive intercondylar notch widening in humans.

Prevention of corticosteroid-induced bone loss with alendronate

The putitive bone-sparing effect of alendronate was tested in two animal models of osteopenia: estrogen-deficient female rats and glucocorticoid-treated male rats. In the first study, 18 female Sprague-Dawley rats, 4 months of age, were ovariectomized (OVX), and an additional 6 rats were sham-operated. The OVX rats were treated with either vehicle, 17beta-estradiol (E2) (100 microg/rat/week, s.c.), or alendronate (1 mg/kg/day, on alternate days, orally). In the second study, 24 8-month-old male Wistar rats were treated with either vehicle, methyl prednisolone (7 mg/kg once a week, s.c.), prednisolone plus testosterone (16 mg/kg once every 3 weeks, i.m.), or prednisolone plus alendronate (20 microg/kg twice a week, s.c.). Prior to treatment and at the end of the 6-week treatment period, bone mineral density (BMD) of the lumbar spine was measured by dual energy x-ray absorptiometry, and mean femur weights were calculated. The OVX rats had subnormal BMD (-3.91 +/- 1.0% vs control +5.19 +/- 3.92%, P < 0.05) and femur weights (720 +/- 6 mg vs %; 746 +/- 11 mg, P < 0.05). OVX-induced bone loss was completely abolished by the administration of E2 (7.01 +/- 2.32%, P < 0.005; 748 +/- 6 mg, P < 0.01), or alendronate (24.2 +/- 2.73%, P < 0.0001; 779 +/- 11 mg, P < 0.001). In the second study in older male rats, glucocorticoids significantly decreased BMD (-9.70 +/- 3.44% vs -1.10 +/- 1.75%, P < 0.05), and femur weight (1070 +/- 14 mg vs 1180 +/- 24 mg, P < 0.01). Concomitant administration of testosterone (BMD 4.23 +/- 1.84%, P < 0.005; femur weight 1260 +/- 56 mg, P < 0.02), or alendronate (BMD 8.18 +/- 1.36%, P < 0.001; femur weight 1360 +/- 50 mg) with prednisolone, abolished the corticosteroid-induced bone loss. Bone histomorphometry showed a 34% loss of trabecular bone volume in glucocorticoid-treated rats (P < 0.05), which was prevented with both testosterone and alendronate therapies. However, at the doses used in both models, alendronate was more efficacious than either E2 or testosterone in increasing BMD and femur weight. In summary, this study demonstrated that alendronate therapy is highly effective in counteracting the osteopenia of OVX and glucocorticoid therapy.

The origin of bone formed by heterotopic periosteal autografts

PURPOSE

This study tested the hypothesis that a significant amount of the new bone produced by heterotopic periosteal autografts is derived osteoinductively because proliferating periosteal cells express the bone morphogenetic protein (BMP).

MATERIALS AND METHODS

Rabbit ulnar and radial periosteum were autografted as free grafts (FGs) to the forelimb musculature, and as millipore diffusion chambers grafts (MDCGs) to the rectus abdominus muscle. The grafts were recovered at 3, 5, 7, 14, and 28 days postoperation, fixed in 4% paraformaldehyde, demineralized in 0.6N HCL, and 4.0 microns paraffin-embedded sections were immunostained with monoclonal antibody against recombinant human (rh) BMP-2.

RESULTS

Sections from FGs recovered 5 to 28 days postoperatively exhibited cartilage and bone; fibrous tissue, cartilage, bone, and osteochondroid differentiated within MDCGs. Although BMP-2 was expressed by mesenchymal cells, osteoblasts, osteocytes, and osteoclasts, none of the MDCGs produced the osteoinductive signature of transmembrane bone formation.

CONCLUSIONS

These observations indicated that the larger fraction of the new bone produced by heterotopic periosteal autografts is derived from the graft cells.

Prevention of corticosteroid-induced bone loss with nitric oxide donor nitroglycerin in male rats

Nitric oxide (NO) has been reported to inhibit osteoclastic bone resorption. We examined the bone sparing effect of NO on prevention of corticosteroid-induced bone loss in older male rats. Recently, we demonstrated that NO donor nitroglycerin (NG) can alleviate ovariectomy-induced bone loss, and the protective effects of estrogens on bone are mediated through NO [Bone 18(4):301-304; 1996]. Therefore, we chose to study a different model (i.e., steroid-induced osteoporosis in males) to evaluate whether NG can inhibit the bone loss associated with corticosteroid therapy. Twenty-five 32-week-old male Wistar rats were randomly assigned to five groups (n = 5/group). They received either vehicle, methylprednisolone (7 mg/kg per week), NO synthase inhibitor L-NAME (25 mg/kg per day), NO donor nitroglycerin (NG, 0.2 mg twice daily), a combination of prednisolone+NG, or prednisolone plus L-NAME, respectively. Prior to treatment and at the end of the 6 week treatment period, bone mineral density (BMD) of the lumbar spine was measured by dual energy X-ray absorptiometry scanning. Administration of prednisolone significantly decreased BMD (-9.50%, p < 0.05). The group receiving NG with prednisolone (-2.34%) and the group treated with NG alone (-0.36%) were not statistically different from the control group (-0.11%). Similar to the changes in BMD, femur weights were also significantly lower in prednisolone-treated rats (1.09 +/- 0.01 g vs. 1.17 +/- 0.03 in controls; p < 0.05). However, the rats receiving prednisolone together with NG were able to maintain their femur weights (1.13 +/- 0.02). There was a reduction of 9.5% of BMD (p < 0.05) and 7.8% of femoral weight (p < 0.05) in rats treated with L-NAME. A 50%-70% reduction of the percentage trabecular bone volume in the proximal tibia and distal femur and a 50% reduction of the midshaft cortical area was seen after corticosteroid therapy, and these too were prevented by administration of NG. Here, we demonstrate, for the first time, that supplementation with a NO donor compound can counteract prednisolone-induced bone loss.

Antitumor effect of positively charged resin in the hamster cheek pouch model

Following the signal observation that contact with positively charged dextran resin (PCDR) inhibited the growth of cultured mammary (Hs578T and MDA-MB-231), pancreatic (H2T), and myeloma (RR-658) tumor cell lines, studies were developed in the hamster cheek pouch model using hamster H2T pancreatic tumor cells to determine if the antiproliferative effect of PCDR could inhibit tumorigenesis. In these studies, the control population represented groups injected with H2T cells alone or in combination with either neutral or negatively charged resin. When cells (5 x 10(2) to 1 x 10(5)) and PCDR were administered simultaneously, the tumor incidence (percent engraftment) and growth of tumors that already had been established were significantly reduced. When PCDR was injected into already established 1-35-mm2 H2T tumors (engraftment for 21 days = 96%), the resin suppressed the growth of the smallest tumors (< 10 mm2). In none of these trials was the somatic growth of the host hamsters affected. PCDR contact with H2T cells in vitro for 4 days or used to treat growing solid tumors for 72 days significantly reduced cellular ornithine decarboxylase activity. While the mechanism of PCDR action has not been established, the observations have implications for in vivo tumor therapeutic models.

Burn-associated bone disease in sheep: roles of immobilization and endogenous corticosteroids

To determine the role of immobilization in the pathogenesis of burn-associated bone disease, we selected the sheep as a model to study the effects of burn injury compared with a sham-burned control group. Seven of the sheep were subjected to controlled 40% flame burn, and seven underwent anesthesia with arterial and venous cannulation but without burn. After labeling newly formed bone with tetracycline and calcein, the sheep were killed 2 weeks after burn or sham burn, and the iliac crest and lumbar vertebrae were analyzed for histomorphometry. Analysis failed to demonstrate a significant reduction of bone formation rate in the burned sheep. Osteoid area and surface and osteoblast surface, which correlated significantly with bone formation rate (r = 0.49, p < 0.025), were reduced in the burned sheep. Results suggest that immobilization may play a primary role in the pathogenesis of burn-associated bone disease, but the presence of differences in other histomorphometric features indicates the bone disease is multifactorial.

Negatively charged beads and transforming growth factor-beta1 stimulate bone repair in rabbits

Previous studies have shown the osteogenic potential of negatively charged Sephadex beads when used to heal osseous defects in an animal model. The present study examined the effect of adding the growth factors transforming growth factor-beta1 and basic fibroblast growth factor to negatively charged Sephadex beads and neutral (non-osteogenic) Sephadex beads in a critical size calvarial defect in rabbits. New Zealand White rabbits were divided into six groups of five rabbits; 15 mm parietal defects were created and filled with either negatively charged Sephadex beads (three groups) or neutral Sephadex beads (three groups). Each group received either 2 microg of transforming growth factor-beta1, 1 microg of basic fibroblast growth factor, or buffer (control). Animals were killed at 5 weeks, and their calvaria were submitted to plain radiographic and histomorphometric analyses. Defects treated with negatively charged Sephadex beads produced significantly more new trabecular bone than neutral Sephadex beads (p < 0.01), whereas the neutral beads treated with transforming growth factor-beta1 formed significantly more bone than controls. The addition of transforming growth factor-beta1 to negatively charged beads resulted in near closure of the craniotomy defect. The application of transforming growth factor-beta1 to this model resulted in significantly more ectopic bone (p < 0.01) outside the defect on the dural and periosteal surfaces. Basic fibroblast growth factor, in the dose used, appeared to have an inhibitory effect on new bone formation fostered by negatively charged Sephadex beads. This study suggests that the addition of transforming growth factor-beta1 to the known osteoconductive matrix of negatively charged Sephadex beads may be therapeutically useful in nonhealing bony defects.

The histomorphologic changes in vascularized bone transfer and their interrelationship with the recipient sites: a 1-year study

In 13 New Zealand White rabbits with a mean age of 6 months, vascularized bone transfers incorporated as paired auricular anterior myo-osseous flaps were harvested; they were placed in either an inlay or an onlay position relative to the zygomatic arch. The onlay bone transfers were placed either in full contact or in partial contact with the zygomatic arch. The animals were sacrificed 1 year after transfer. At 1 year, the inlay transfer simulated the adjacent zygoma in width and thickness. Onlay full contact transfers maintained significant aug mentation in thickness of the zygoma, while the onlay partial contact transfers did not; the thickness of the augmented zygoma in the onlay full contact subgroup was significantly greater than that in the onlay partial contact transfers. The onlay partial contact grafts had remodeled into the zygoma in bone contact, where the orientation of mismatched osteons within the bone transfers had transformed to match that of the native zygoma. In areas of bone contact between the onlay and the host bone, full-thickness conversion from a cortical to a trabecular architecture had occurred in both the transfer and host bones. These findings have numerous implications regarding mechanisms that could be exploited clinically to optimize the survival of a bone transfer; they also raise questions regarding alteration of the recipient bed after placement of an onlay bone transfer.

Expression of selected osteogenic markers in the fibroblast-like cells of rat marrow stroma

The fibroblast-like cells in the marrow stromal system were separated from endothelial cells and macrophages by negative selection of magnetic beads. Immunocytochemistry confirmed that these fibroblast-like cells expressed fibronectin and collagen Type III, but not Factor VIII and epithelial membrane antigen (endothelial cell markers) or Mac I (macrophage marker). The fibroblast-like stromal cells (FSC) synthesized the insulin-like growth factors (IGF)-I and -II in amounts equivalent to that produced by unfractionated marrow stromal cells (UMSC); in both, the concentration of IGF-II was 10 times higher than that of IGF-I. Northern analysis revealed that FSC and UMSC expressed identical patterns of mRNAs for IGF-I and transforming growth factor (TGF) -beta 2, for osteopontin, and for procollagen Types I and III (Type I > Type III). Type II procollagen mRNA was not expressed in both cell populations. The TGF-beta 2 gene mRNA was expressed at a lower level by the FSC than UMSC. The pattern of gene expression in these cells is consistent with an osteoprogenitor phenotype. Both FSCs and UMSCs express parathyroid hormone (PTH) and estrogen receptor genes (rtPCR technique). The study provides additional evidence that fibroblast-like marrow stromal cells have an osteoblast signature, and that they are largely responsible for the osteogenic performance of cells in unfractionated marrow.

Rat tail suspension reduces messenger RNA level for growth factors and osteopontin and decreases the osteoblastic differentiation of bone marrow stromal cells

We previously reported that bone marrow stromal cells produce insulin-like growth factors (IGF-I and -II), and that medium conditioned by marrow stromal cells stimulates osteoblast proliferation in vitro. The present study employed the rat tail-suspension model to unload the hindlimbs. It was designed to test the hypothesis that the development of osteopenia or osteoporosis could be due to a deficit in the osteogenic function of marrow stromal cells. Although tail suspension suppressed body weight during the first 3 days of an 11-day pair-fed study, the overall weight gain recorded by these animals was normal. Nevertheless, bone growth was inhibited by suspension. Similarly, the total adherent marrow stromal cell population harvested from the femurs and tibias was decreased by tail suspension, and only half the normal number of fibroblastic stromal cell colonies grew when they were cultured. The proliferation of alkaline-phosphatase-positive cells in the stroma was also inhibited. Northern hybridization revealed that the messenger RNA level for transforming growth factor-beta 2 and IGF-II in stromal cell was reduced by tail suspension. The production of IGF-II by marrow stromal cells was also decreased. The steady-state level of five different transcript sizes of IGF-I mRNA was altered differentially by tail suspension. Osteopontin mRNA was also reduced in marrow stromal cells from tail-suspended rats compared with the normal rats. These data suggest that skeletal unloading not only alters the mRNA level for growth factors and peptide production, but also affects the proliferation and osteogenic differentiation of marrow stromal cells. These changes may be responsible for the reduced bone formation in osteopenia and osteoporosis.

Effects of C-terminal parathyroid hormone-related peptide on osteoblasts

A C-terminal analog of parathyroid hormone-related peptide (PTHrP), PTHrP(107-139), was found to stimulate cAMP production in three osteoblast cell preparations. The effect was studied most extensively in ROS 17/2.8 cells. The effect was dose-related and comparable in magnitude to that produced by PTHrP(1-34), but potency was lower. The functional significance of the cAMP effect is unknown, but preliminary findings indicated that PTHrP(107-139) also inhibited osteopontin mRNA levels in ROS 17/2.8 cells treated with peptide for 48 h. The results suggest that the carboxy-terminal region of PTHrP may play a role in bone metabolism by influencing osteoblast activity.

The healing of grafts combining freeze-dried and demineralized allogeneic bone in rabbits

The adjunctive role of demineralized bone matrix (DBM) in enhancing the incorporation of segmental freeze dried (FD)-allogeneic bone grafts has been studied in the rabbit ulna and fibula. The studies compared the healing patterns of fresh segmental autografts, FD-allografts, DBM-allografts, and FD-allografts supplemented at the graft-host junctions with FD- or DBM-allografts as particulates (ulna) or as segmental struts (fibula). The outcome was evaluated at five and ten weeks by a radiologic score, by biomechanical properties (breaking strength, energy to failure, stiffness), and histology. The ulnar autografts healed most rapidly (ten weeks = 100%), followed by DBM allografts (60%). By all criteria, FD-allografts were poorly incorporated (20-40%), and the process was not improved by supplements of FD- or DBM-particulate/strut bone. Histologically, the DBM component of composite fibular strut grafts was osteoinductive and united with host tissues within 35 days. The contiguous FD-allograft struts were not incorporated, showing fibrocartilaginous nonunions and resorptive foci. While the addition of DBM does not protect FD-allograft integrity in the rabbit, segmental mineralized FD-allografts could provide mechanical support for some intervals until, in such composite grafts, osteoinductive processes produced biomechanically competent new bone.

Negatively charged resins stimulate bone formation in subperiosteal sites in rats. The effect of age

The osteogenic response to subperiosteal injection of negatively charged ion exchange resins was compared in the tibiae of one-month and 16- to 22-month-old rats. The resins were administered either in the form of beads (CM Sephadex) or as particles (CM cellulose, carboxymethylcellulose), and the animals were killed at two weeks and at one month after injection. Histologically, the resins did not produce an inflammatory response. Periosteal bone formation was observed wherever resin was in contact with bone, and in the resin bed the connective tissues that invested the charged materials ossified within the first month. Marrow spaces commonly formed where periosteal growth was most rapid. The osteogenic effect was independent of resin conformation, and it was more pronounced in the younger rats.

Periosteal attachment fibers in the rat calvarium

The anatomical relationships between the fiber tracts and bone lining cells within the rat calvarial periosteum have been studied by electron microscopy. Classical Sharpey's fibers were not observed in this location. Rather, thin unmineralized fibers originating from the periosteum traversed the cambial layer and passed to the bone surface between individual osteoblasts or groups of osteoblasts. The organizational relationship suggests that the osteogenic calvarial cell populations are compartmentalized into domains that might be particularly sensitive and responsive to the biomechanical forces of masticatory muscles.

Effects of aluminum on rat bone cell populations

Aluminum (Al) loading is associated with reduced bone formation and osteomalacia in human and certain animal models. However, uncertainty exists as to the cellular effect(s) of Al as both inhibition and stimulation of osteoblast proliferation have been reported. Furthermore, the extent to which Al affects osteoprogenitor cell populations is unknown. To determine the cellular effects of Al in the rat, an animal model in which Al bone disease has been produced, we compared the in vitro effect of 10-50 microns Al on the proliferation and hydroxyproline collagen formation of marrow osteoprogenitor stromal cell populations and perinatal rat calvarial osteoblasts. In subconfluent cultures, Al suppressed proliferation of both marrow fibroblast-like stromal cells and calvarial osteoblasts. In confluent cultures, however, Al selectively stimulated periosteal fibroblast and osteoblast DNA synthesis and collagen (hydroxyproline) production, both in the presence or absence of 1,25-dihydroxyvitamin D. Osteocalcin was not detected in osteoblast-conditioned media or extracellular matrix. These observations suggest that the bone formation defect associated with Al toxicity in growing rats may be a function of impaired patterns of osteoprogenitor/osteoblast proliferation. Furthermore, the Al-stimulated increase in collagen formation is consistent with the development of osteomalacia in Al-toxic humans and animals. The mechanism by which Al stimulated DNA synthesis and collagen production in more mature cultures awaits further study.

Rat tail suspension causes a decline in insulin receptors

Decreased muscular activity results in weakness and muscular atrophy. Coincident with this protein catabolic state is glucose intolerance and hyperinsulinemia. Rats were tail suspended for 7 to 14 days to accomplish unloading of the hindlimbs. Insulin resistance was documented in these animals by a 14 day tail suspension-related 26% increase in serum glucose in spite of a 253% increase in serum insulin concentration. Microsomal membranes were prepared from hindlimb muscles and specific binding of insulin and insulin-like growth factor I (IGF-I) were determined in these membranes. Insulin binding was decreased by 27% at 7 days and by 21% at 14 days. In contrast, IGF-I binding was unchanged at 7 days and was increased by 24% at 14 days. Liver membrane insulin receptors also had declined by 14 days of suspension, suggesting that the change in insulin receptors was a generalized, humorally-mediated phenomenon. These data suggest that tail suspension in rats results in insulin resistance, hyperinsulinemia, a decline in insulin receptors in liver and muscle, and a relative increase in muscle membrane IGF-I receptors. These data are consistent with the hypothesis that resistance to insulin's effects on protein metabolism in skeletal muscle may contribute to the protein catabolism associated with decreased muscular activity.

Nutritional rickets: thoughts about pathogenesis

The pathogenesis of nutritional rickets is not well-understood. While the etiologies include deficiencies of vitamin D, calcium (Ca) or phosphate (PO4), and perhaps aluminium toxicity, the role these nutrients play in the development of tissue level anomalies characteristic of rachitic cartilage and bone has yet to be defined. Reported alterations in the biochemistry of rachitic bone and cartilaginous matrix which could adversely affect mineralization and endochondral ossification are of questionable significance since the tissues mineralize rapidly when exposed to Ca and PO4 salts in vivo and in vitro. The low Ca and PO4 concentrations of the extracellular fluid (ECF) bathing rachitic cartilage and bone matrix suggest that local mechanisms operate to impair mineralization. In healing rickets, the Ca and PO4 content of these tissue fluids increases in the same time-frame it takes to experimentally remineralize the matrices. However, it is not certain what determines the Ca and PO4 content of the ECF. Cytokines which may play a role in the cellular regulation of Ca and PO4 and maintain processes which contribute to normal patterns of endochondral ossification could provide a mechanism common to the pathogenesis of rickets from a variety of causes.

Fetal fracture healing in a lamb model

A large animal model to assess fetal fracture repair and the ability to close excisional bony defects is presented. Incisional and excisional ulnar fractures were made in 14 midgestation fetal lambs, harvested at serial time points, and subjected to high-resolution low-kilovolt magnification radiographs, magnetic resonance imaging scans, and histologic analysis. Fetal fracture healing was characterized by early closure of excisional defects and rapid fracture healing with minimal or no soft-tissue inflammation or callus formation. Magnetic resonance imaging scans of the fractures revealed a characteristic pattern compatible with the histologic findings, namely, minimal inflammation in soft tissue adjacent to the fracture site. Histologic and magnification radiographic findings indicated that complete bony repair occurred within 21 days in incisional defects and within 40 days in excisional defects. In both cases, healed fetal bone resembled normal bone matrix. Excisional defects, including periosteum, of greater than three times the width of the bony cortex closed rapidly with virtually normal-appearing bony matrix and with minimal or no callus formation.

T-lymphocyte control of HLA-DR blood monocyte differentiation into neo-fibroblasts. Further evidence of pluripotential secreting functions of HLA-DR monocytes, involving not only collagen but also uromodulin, amyloid-beta peptide, alpha-fetoprotein and carcinoembryonic antigen

Previous studies led us to demonstrate in pathological situations that the fibroblast, not the macrophage, was the terminal maturation step of the HLA-DR monocyte and that the entire process came under T-lymphocyte control. Fibrosis which developed under immunosuppressive treatment (cyclosporin) after organ transplantation is an illustration of these in vitro observations. The present in vitro study was undertaken in order to investigate whether or not this transformation process takes place under physiological conditions and if so, the nature of the T-lymphocyte control. We report that normal HLA-DR monocytes/macrophages are able to secrete type 1 collagen and to differentiate into neo-fibroblasts. However, contrarily to what happened in pathology, only a few neo-fibroblasts developed transiently. The addition of conditioned medium (CM) from activated T-lymphocytes greatly enhanced the transformation process. Counteracting this CM effect, cell-to-cell contact between neo-fibroblasts and T-cells resulted in the loss of fibroblastic shape. The 'end-result' macrophage engulfed numerous lymphocytes giving rise to a multinucleated cell. This giant cell no longer adhered to the slide and died. The question is raised as to whether the process observed in vitro is involved in vivo in tissue repair. We also report that HLA-DR monocytes and the neo-fibroblasts which derive from them are able to secrete, in addition to type 1 collagen, a variety of proteins such as uromodulin, amyloid-beta peptide, alpha-fetoprotein and carcinoembryonic antigen. In cystic fibrosis we previously reported a high level of uromodulin production by HLA-DR monocytes differentiating towards the fibroblastic phenotype. Pathologies characterized by excessive production of either alpha-feto-protein, carcinoembryonic antigen, beta-amyloid protein (Alzheimer's disease) should be investigated, taking into account the involvement of HLA-DR monocytes and their possible uncontrolled differentiation into neo-fibroblasts.

Contribution of marrow stromal cells to the regulation of osteoblast proliferation in rats: evidence for the involvement of insulin-like growth factors

Fibroblast-like marrow stromal cells are believed to play a role in the maintenance of osteoblast populations at the marrow-bone interface. We now report that this interaction may be very specific. Stromal cell conditioned medium (SC-CM) stimulated DNA synthesis and proliferation in culture of neonatal rat calvarial osteoblasts at low concentrations (1.25-5%), but was inhibitory at 10%. At growth promoting effective concentrations, the activity of osteoblast alkaline phosphatase was decreased. This action was selective since SC-CM failed to promote the growth of rat calvarial fibroblasts. Characterization of the SC-CM indicated the cells produced IGF-I and -II and a wide range of molecular weight fractions with putative stimulatory action (FPLC analysis using Superose 12 and 6 gel permeation columns). HPAE-PAD analysis showed that some elements were glycosylated, and the composition suggested the presence of N- and O-linked oligosaccharide chains. Because rat marrow stromal fibroblast-like cells produce a number of osteotropic factors which affect calvarial osteoblast growth, these interactions may be important to considerations about the etiology of the osteoporoses.

Partial characterization of rat marrow stromal cells

Fibroblast-like rat marrow stromal cell (CFU-F) cultures have been characterized in terms of their responsiveness to calciotropic hormones, metal ions, the nonsteroidal antiinflammatory drug, and by their putative paracrine role in the maintenance of active populations of osteoblasts at the marrow-bone interface. These studies indicate that CFU-Fs lack a complete osteoblast signature. Subconfluent CFU-Fs grown in the presence or absence of 10(-7) M dexamethasone lack receptors for PTH and calcitonin, and fail to show enhanced cAMP or cGMP responses to 10(-7) M 1-34 PTH (rat), or any evidence of osteocalcin production [+/- 10(-9) M 1,25-(OH)2D3]. Low concentrations of fluoride [10(-12) and 10(-9) M] stimulated CFU-F grown in vitro in serum-free media, though higher levels (10(-7) and 10(-6) M), inhibited growth in vivo and in vitro. Aluminum (10(-12)-10(-7) M) and ibuprofen (10(-7) M) did not alter normal growth patterns, indicating an action on bone cells more differentiated than CFU-Fs. Serum-free conditioned medium (CM) from control and ovariectomized (OVX)/OVX+ dihydrotachysterol-Rx rat CFU-F cultures was mitogenic for neonatal rat calvarial osteoblasts in vitro, but not for ROS 17/2.8 cells. The studies affirm the mesenchymal-like character of CFU-Fs and project their significant role in sustaining functional endosteal osteogenic cell populations.

Monocytic origin of fibroblasts: spontaneous transformation of blood monocytes into neo-fibroblastic structures in osteomyelosclerosis and Engelmann's disease

We describe here two pathological situations, osteomyelosclerosis and Engelmann's disease, in which HLA-DR blood monocytes modulate to the fibroblastic class, in long-term culture. Monocytes/macrophages were identified by immunofluorescence, using monoclonal antibodies against surface markers (Leu M3, CD 68, and HLA-DR) and the neo-fibroblasts by electron microscopy and immunofluorescence using monoclonal antibodies against a cytoplasmic enzyme specifically involved in the synthesis of collagen (5B5). Macrophages makers were found on the neo-fibroblasts, whereas HLA-DR macrophages expressed the cytoplasmic marker 5B5. Since osteoblasts are classically derived from fibroblasts, the significance of the in vitro differentiation of monocytes/macrophages into fibroblasts to the in vivo mechanism leading to excessive osteoblastic proliferation in both osteomyelosclerosis and Engelmann's disease, is discussed. The possible involvement of this pathway leading from monocytes to fibroblasts and osteoblasts in the normal process of bone modeling and remodeling in questioned.

Calcium metabolism and bone mineralization in female rats fed diets marginally sufficient in calcium: effects of increased dietary calcium intake

Experiments were carried out to determine the ability of female rats with poorly mineralized skeletons to increase bone mineralization in response to increased dietary Ca consumption. We specifically addressed this question with regard to two different periods of the life cycle: the period of sexual maturation (6-9 weeks of age), and in animals that had attained adult rates of skeletal mineralization (100 days of age). We found that at both stages, increased dietary Ca consumption resulted in increased trabecular bone volume and total bone Ca. In the younger animals, it was found that dietary history influenced the disposition of bone mineral. Animals that were initially Ca-deprived exhibited increased trabecular bone and decreased cortical thickness compared to animals continuously fed 0.5% Ca. Ovariectomy of mature animals reduced but did not eliminate the response to increased Ca intake.

Skeletal effects of sodium fluoride during hypokinesia

This study tested the capacity of fluoride (F) to prevent the disuse-associated reduction in bone formation/growth. Suspending young male Wistar rats by the tail for 2-2.5 weeks reduced femoral cortical (P less than 0.05) and trabecular (P less than 0.01) bone areas. Tetracycline labelling showed that the decrement in cortical area was largely due to a reduction in the percent periosteal mineralizing surface (PsMS). Periosteal mineral apposition rate (PsMAR) was not affected. Endosteal mineralizing surface (EsMS) and mineral apposition rate (EsMAR) were significantly stimulated spontaneously during the second week of suspension. F treatment (5 mg/kg/day i.p.) prevented the loss in bone area, and established a trend toward increased PsMS without affecting EsMS and EsMAR. None of these changes are associated with alterations in serum Ca, P or osteocalcin. F treatment in hypokinetic animals caused a decrease in serum PTH (-21% compared to control; P = 0.001). We conclude that F prevents the development of hypokinetic osteopenia in rats.

Long-term effects of tissue expansion on cranial and skeletal bone development in neonatal miniature swine: clinical findings and histomorphometric correlates

Progressive tissue expansion induces significant gross, histologic, and bony changes in skulls and long bones of neonatal miniature swine. These bony changes consist of erosion underlying tissue expanders, with bony lipping and bone deposition at the periphery of the expander. Cranial suture lines underneath expanders appear effaced and convoluted. Serial CT scans reveal decreased bone thickness and volume (p less than 0.02) but identical bone density (p = 0.60) beneath expanders. Increased bone volume and thickness occur at the periphery of expanders (p less than 0.02). Bone density (CT number) is unaffected by tissue expansion in both cranial and long bones. These findings have histomorphometric correlates: Osteoclastic bone resorption occurs underneath expanders with periosteal reaction at the periphery of expanders. Cranial sutures are similarly affected, but no cranial synostosis results. No changes to the inner table of the skull or stigmata of increased intracranial pressure were observed either in CT scans or in behavioral changes in long-term animals. The pathophysiology of bony changes is a remodeling effect, not one of simple pressure deformation. Increased bone resorption and complete inhibition of bone formation occur until the pressure is removed. Cranial bone is significantly more affected than long bone. After removal of the expanders, reparative bone remodeling begins within 5 days and nearly complete healing of the cranial defects occurs within 2 months (p less than 0.02). No plagiocephaly results despite early coronal suture changes. On the basis of this study, we conclude that tissue expansion causes significant but reversible effects, readily monitored by high-resolution CT scans, on neonatal and infant cranial and long bones.

Effect of cortisone on cells at the bone-marrow interface

A study of the association between the rate of proliferation of marrow fibroblast-like stromal cells (in vitro) and the rate of endosteal bone mineralization (EsMR) (in vivo) was undertaken in an osteopenic rat model. We report that 200 g male rats treated with cortisone acetate (5 mg/day for 7 days) exhibit decreases in marrow fibroblast colony-forming units (FCFU) and tetracycline-based measurements of EsMR at the level of the femoral midshaft. In cortisone-treated rats recovering for 1-3 weeks, the FCFU census and EsMR normalized during the first posttreatment week, remained at control levels after 2-3 weeks, and exhibited a relapse in the third week which signified only partial recovery. These changes were unrelated to patterns of body weight gain. The data indicate that the FCFU census can serve to index endosteal osteoblast vigor.

Maturation of bone and dentin matrices in rats flown on the Soviet biosatellite Cosmos 1887

We have studied the chemistry, hydroxyapatite crystal size, and maturational changes in bone and dentin from rats exposed to microgravity for 12 days in a Soviet biosatellite (Cosmos 1887). Bone ash was reduced in vertebrae (L5) but not in the non-weight-bearing calvaria or mandibles. All tissues had a relatively normal percentage composition of Ca, P, and Mg. Nevertheless, flight rat calvaria and vertebral tissues tended to exhibit lower Ca/P and higher Ca/Mg ratios that any of their weight-matched controls groups, and gradient density analysis (calvaria) indicated a strong shift to the fractions lower specific gravity that was commensurate with impaired rates of matrix-mineral maturation. X-ray diffraction data were confirmatory. Bone hydroxyapatite crystal growth in the mandibles of flight rats was preferentially altered in such a way as to reduce their size (C-axis dimension). But in the mandibular diastemal region devoid of muscle attachments, flight rat bone and dentin were normal with respect to the Ca, P, Mg, and Zn concentrations and Ca/P and Ca/Mg ratios of age-matched controls. These observations affirm the concept that while microgravity most adversely affects the maturation of newly formed matrix and mineral moieties in weight-bearing bone, such effects occur throughout the skeleton.

Effect of dihydrotachysterol on bone induction in ovariectomized rats

We have demonstrated via marrow stromal cell cultures and the osteoinductive response to demineralized bone grafts (DBM) that the cortical bone deficit in the ovariectomized (OVX) rat (6 weeks postop) is primarily due to impaired osteoprogenitor cell proliferation, and that dihydrotachysterol (DHT) treatment can be protective. In cultured marrow stromal cells from OVX rats, short-term DHT-Rx exaggerated the already subnormal pattern of marrow stromal cell proliferation. However, in DBM grafts, DHT treatment benefited the time-course of mesenchymal cell DNA synthesis as measured by tritiated thymidine incorporation and osteogenic cell maturation as measured by alkaline phosphatase concentration, and established a suggestive trend toward normalization of bone formation/mineralization (24 h 45Ca incorporation). The data from this animal model infer that DHT could moderate the bone loss normally seen in ovariectomized rats via an activation of the osteoprogenitor cell population.

Correlation of MRI images with histology in avascular necrosis in the hip. A preliminary study

The role of MRI in identifying the tissue level changes in the femoral head was investigated in five patients diagnosed as having avascular necrosis by radiology, scintigraphy, and MRI (0.35 Telsa). Radiographic scoring by the Ficat and Arlet system showed one hip with stage I, one stage II, two stage III, and one stage IV changes. The histologic features of core biopsy specimens obtained during decompression of the femoral heads were compared to the preoperative T1 and mixed T1/T2-weighted MR images. The cores varied with respect to their distance from the subchondral bone (7-23 mm) and length (19-45 mm). At the subchondral end of the core tract, low T1-weighted images corresponded to marrow fibrosis (5 cases) and in three of five cases to increased trabecular bone volume (TBV = 44-50%). Subjacent areas of diffusely decreased MR signal corresponded to marrow fibrosis and necrosis, with a relatively normal TBV (17-28%). The distal ends of the core tracts showed normal fatty marrow and a normal MR signal. The observations affirm that the MR signal intensity is largely reduced as a function of marrow degeneration and loss of fat content, but the signal is not predictive of particular histotypic morphologic patterns.

Bone cell populations and histomorphometric correlates to function

A circadian context has been used to develop information about the proliferative and functional behavior of the cell populations that function to model the long bones of growing rats. We asked: Are the proliferating cells in the growth cartilages and diaphyseal bone of young adult growing rats distributed within single or multiple populations? Can cytomorphometry (TEM-C) be used to determine ultrastructural correlates to the well-defined circadian rhythm of matrix formation displayed by functionally synchronous populations of metaphyseal osteoblasts? Can TEM-C reveal changes in osteoclast ultrastructure that could index a biological rhythm for osteoclastic bone mineralysis/resorption? Kinetic results derived from multiple radiothymidine labeling (DNA synthesis) support the single population model for chondrocytes and diaphyseal osteoprogenitor cells. TEM-C studies at the midpoints of the daily light and dark spans show that osteoblast RER-membrane development and cysternal volumes are maximal at the recorded daytime peak of net collagen synthesis. The extent of metaphyseal osteoclast surface ruffling (mineralysis) is also twofold greater during the day than the night--an observation supporting the concept that bone formation and resorption activities are coupled.