Histomorphometry of fresh frozen iliac crest bone biopsies

Periosteal Sharpey's fibers: a novel bone matrix regulatory system?

Sharpey's "perforating" fibers (SF) are well known skeletally in tooth anchorage. Elsewhere they provide anchorage for the periosteum and are less well documented. Immunohistochemistry has transformed their potential significance by identifying their collagen type III (CIII) content and enabling their mapping in domains as permeating arrays of fibers (5-25 μ thick), protected from osteoclastic resorption by their poor mineralization. As periosteal extensions they are crucial in early skeletal development and central to intramembranous bone healing, providing unique microanatomical avenues for musculoskeletal exchange, their composition (e.g., collagen type VI, elastin, tenascin) combined with a multiaxial pattern of insertion suggesting a role more complex than attachment alone would justify. A proportion permeate the cortex to the endosteum (and beyond), fusing into a CIII-rich osteoid layer (<2 μ thick) encompassing all resting surfaces, and with which they apparently integrate into a PERIOSTEAL-SHARPEY FIBER-ENDOSTEUM (PSE) structural continuum. This intraosseous system behaves in favor of bone loss or gain depending upon extraneous stimuli (i.e., like Frost's hypothetical "mechanostat"). Thus, the birefringent fibers are sensitive to humoral factors (e.g., estrogen causes retraction, rat femur model), physical activity (e.g., running causes expansion, rat model), aging (e.g., causes fragmentation, pig mandible model), and pathology (e.g., atrophied in osteoporosis, hypertrophied in osteoarthritis, human proximal femur), and with encroaching mineral particles hardening the usually soft parts. In this way the unobtrusive periosteal SF network may regulate bone status, perhaps even contributing to predictable "hotspots" of trabecular disconnection, particularly at sites of tension prone to fatigue, and with the network deteriorating significantly before bone matrix loss.

Short-term delay of puberty causes a transient reduction in bone strength in growing female rats

Multiple factors affect the structural development of the skeleton; in particular, estrogen levels during growth are an important factor in the pathogenesis of bone fragility. The delay of menarche and infrequent menstrual cycles decrease estrogen levels during adolescence and decrease peak bone mass. The aim of this study was to determine if delayed puberty through administration of a GnRH antagonist initiated prior to the onset of the first estrus cycle would delay the increase in estrogen levels and impede bone strength development in female rats. Twenty-three-day-old female Sprague-Dawley rats were randomly assigned to one of four groups; 1) short-term control group (C-ST) (n = 12), 2) long-term control (C-LT) (n = 12), 3) short-term GnRH antagonist group (G-ST) (n = 12) and 4) long-term GnRH antagonist group (G-LT) (n = 12). Injections (0.2 ml) of either saline or GnRH antagonist (100 microg/day) (Cetrotide, Serono, Inc) were given intraperitoneally for a duration of 18 days. Pubertal and gonadal development was retarded as indicated by a delay in vaginal opening (an indicator of pubertal onset), lower ovarian and uterine weights and lower estradiol levels in the short-term experimental animals (G-ST). However, at maturity (G-LT), there were no significant differences found in these measures. A delay in the timing of puberty significantly attenuated the development of femoral bone strength at 6 weeks of age. Peak moment, yield moment and stiffness in the G-ST group were all significantly less than the C-ST group. Cortical width was significantly attenuated due to the increased percentage of marrow area per total bone area in the G-ST group. However, femoral bone strength was recovered at maturity (G-LT). In summary, a transient delay in pubertal timing has short-term effects on bone strength development. In the current animal model of delaying puberty through GnRH antagonist injections, there appears to be no long-term effects on bone strength.

The cryomicrotomy of rat dental tissues: a technique for histological and immunohistochemical analysis

We have applied a method developed for the cryomicrotomy of non-decalcified bone to the histological preparation of the tooth and related dental tissues. Cryosections of rat mandible have been cut on a heavy-duty freezing microtome. Both cellular and extracellular structure was well preserved and the sections of tooth and bone appeared to be suitable for optical and scanning electron microscopy and for immunohistochemical analysis. However, there was an overall strong non-specific binding of immunohistochemical reagents to enamel which was not evident in the other mineralized tissues of the mandible. This may relate to important differences in the nature of this tissue.

Producing frozen sections of calcified bone

We describe a procedure for the rapid production and maintenance of fresh frozen bone biopsies which can be used for a variety of immunohistochemical techniques. Within 5 min of excision, tissue is placed in cold 5% polyvinyl alcohol, surrounded with 3% carboxymethylcellulose in a hand made aluminum foil embedding mold and frozen by immersion in an absolute ethanol/dry ice slurry at -70 C. The tissue block is attached to the specimen stub with cryocompound and installed in a -32 C cryostat whose tungsten carbide D profile knife is maintained at -70 C. Automatic controls are set at a slow cutting speed and the "sectioning window" is adjusted to fit the biopsy size. Knife angle, thickness gauge and antiroll bar are changed to produce a complete section. The block face is smoothly "papered" with a polyvinylpyrrolidone (PVP) impregnated Ross lens paper strip. A single section is cut and positioned on a sequentially numbered, acid cleaned, double dipped chrome-alum gelatin coated slide; adhesion is aided by "press-blotting" with bibulous paper. Sections are stored at -20 C or in a desiccator at room temperature. A brief fixation followed by removal of the water soluble PVP and lens paper generates fresh frozen bone sections suitable for further analysis.

Relationship between the location of osteoblastic alkaline phosphatase activity and bone formation in human iliac crest bone

It is not feasible to use in vivo tetracycline double labeling to study bone formation in biopsies taken during the emergency fixation of fractures. We therefore compared the trabecular localization and extent of osteoblastic alkaline phosphatase (AP) perimeters with tetracycline and osteoid perimeters in iliac crest biopsies from 7 women with postmenopausal osteoporosis and 13 women without metabolic bone disease. Fresh biopsies were chilled to -70 degrees C, and triplicate serial unfixed undecalcified cryostat sections were cut and reacted for AP, stained for osteoid, or mounted unstained. At individual remodeling sites, the mineralizing perimeter (M.Pm) was measured as the extent of a double or single label accompanied by greater than or equal to 1 lamella of osteoid and greater than or equal to 1 lamella of mineralized matrix between the mineralization front and the adjacent label. Osteoid perimeters (O.Pm) and AP perimeters (AP.Pm) were also measured. In each biopsy there was good agreement between the location of AP and bone formation (kappa statistic, range 0.71-1.0). The overall sensitivity and specificity of AP as an indicator of the location of bone formation were 0.963 and 0.902, respectively. At the level of the basic multicellular unit, in those samples in which greater than 3 active BMUs were found, there was (1) significant positive correlation between the M.Pm and both AP.Pm and AP-positive O.Pm (except 1 patient) and (2) no significant difference between the M.Pm and AP-positive O.Pm (17 of 18 patients and 18 of 18 patients at the tissue level).(ABSTRACT TRUNCATED AT 250 WORDS)