Static Osteogenesis versus Dynamic Osteogenesis: A Comparison between Two Different Types of Bone Formation

In contrary to what has traditionally been believed, bone formation can occur through two different types of osteogenesis: static (SO) and dynamic (DO) osteogenesis, which are thus named because the former is characterized by pluristratified cords of unexpectedly stationary osteoblasts which differentiate at a fairly constant distance from the blood capillaries and transform into osteocytes without moving from the onset site, while the latter is distinguished by the well-known typical monostratified laminae of movable osteoblasts. The two types of osteogenesis differ in multiple aspects from both structural and functional viewpoints. Besides osteoblast arrangement, polarization, and motion, SO and DO differ in terms of time of occurrence (first SO and later DO), conditioning factors to which they are sensitive (endothelial-derived cytokines or mechanical loading, respectively), distribution of osteocytes to which they give rise (haphazard or ordered in planes, respectively), the collagen texture resulting from the different deposition types (woven or lamellar, respectively), the mechanical properties of the bone they form (poor for SO due to the high cellularity and woven texture and good for DO since osteocytes are located in more suitable conditions to perceive loading), and finally the functions of each, i.e., SO provides a preliminary rigid scaffold on which DO can take place, while DO produces bone tissue according to mechanical/metabolic needs

Role of Phytoestrogen Ferutinin in Preventing/Recovering Bone Loss: Results from Experimental Ovariectomized Rat Models

In the Chapter 35 of the book are reported observations of recent pubblications on the effect of ferutinin in preventing/recovering severe osteoporosis secondary to ovariectomy in rats. On the basis of the results so far obtained, the authors suggest to enumerate ferutinin among the osteoprotective substances. This fact acquires a more relevant importance in the light of recent tenable evidences reported from various authors concerning the absence of negative side effects by some phytoestrogens (particularly genistein, 8-prenylnaringenin, reveratrol and red clover extract) on the tropism of various organs commonly targeted by estrogens. In conclusion, the results reported not only provide evidence that ferutinin can significantly prevent/recover ovariectomy-induced bone loss in rats, but also that it could protect against the onset of uterus cancer. Although the putative undesired estrogenic-like side effects on uterus of such phytoestrogen have not yet been fully investigated, ferutinin could be an interesting safer alternative new candidate for HRT in treatment of post-menopausal symptoms, since it seems to protect from bone loss induced by ovariectomy (Palumbo et al., 2009; Ferretti et al., 2010) and in part to mime the ovarian endocrine function during menopause

Bone texture modifications during bone regeneration and osteocyte cell-signaling changes in response to treatment with Teriparatide

Bone texture modifications during bone regeneration and osteocyte cell-signaling changes in response to treatment with Teriparatid

Effect of PTH (1-34) on trabecular bone of rat vertebral body in induced-biochemical osteoporosis by calcium- deprived diet

Rats fed calcium-deprived diet were used as experimental model for studying bone modelling alterations during biochemical osteoporosis and recovery of bone loss. Such model is suitable to evaluate the possible effects exerted by PTH(1-34) in preventing as well as in recovering metabolic osteoporosis. Three-month-old Sprague Dawley male rats were divided in different groups: some fed normal diet or calcium-deprived diet with/without 40µg/Kg/day PTH(1-34), provided by Eli Lilly-USA, for 4 weeks and some with restoration of normal diet with/without PTH (1-34) for further 4 weeks. To evaluate the occurrence of osteogenesis during the first 4 weeks of the experimental period, rats received three labels of bone deposition at 1st, 20th and 27th day (and then were sacrificed); during the successive 4 weeks (in which those rats previously fed with calcium-deprived diet had restoration of normal diet), animals received three labels of bone deposition at 1st, 7th and 14th day. Histomorphometrical analyses were performed on cortical and trabecular bone taken from the central level of the 5th lumbar vertebral body, transversely sectioned. The results showed that differences among the groups were observed mainly in trabecular bone with respect to cortical one, thus underlining the different role of the two types of bone architecture in mineral and skeletal homeostasis. Concerning trabecular bone, the observations showed that administration of PTH (1-34) during calcium-deprived diet and/or during the restoration of normal diet induces higher deposition of trabecular bone with respect to that recorded in rats that never received PTH(1-34), neither during calcium-deprived diet nor during restoration of normal diet. Since increments of trabecular bone are detectable only after the period of diet restoration (but not before), the authors suggest that a chronic administration of PTH (1-34) is necessary to achieve appreciable results on bone mass recovery

Effects of PTH(1-34) during fracture healing after experimental bone drilling in rat femur: novel aspects

The study concerns the role of PTH(1-34) during bone lesion repair. 3-month-old male Sprague-Dawley rats, in which trans-cortical holes were drilled at femur middiaphysis, were divided in groups with/without Teriparatide administration (40g/ Kg/day), and sacrificed at different times (10, 28, 45 days). In 2002 (1) we demonstrated the occurrence of two successive bone forming processes during both skeletal organogenesis and bone repair, i.e. static (SO) and dynamic (DO) osteogenesis: the former (due to stationary osteoblasts, haphazardly grouped in cords) producing preliminary bad quality trabecular bone, the latter (due to typical polarized osteoblasts organized in ordered movable laminae) producing mechanically valid bone tissue. In brief, the primary function of SO is to provide a rigid scaffold, containing osteocytes (i.e. mechano-sensors), to DO-osteoblastic laminae; therefore, in DO mechanical factors can play a crucial role in transduction of mechanical stresses into biological signals. In the present work, histomorphometric analysis showed that, already after 10 days from drilling, notwithstanding the holes are temporarily filled by the same amount of newly-formed trabecular bone (produced by SO) independently from the treatment, the number of movable osteoblast laminae (typical of DO), covering the trabecular surface, is statistically higher in animals submitted to PTH(1-34) administration than in the control ones; this suggests that the mere effect of Teriparatide is to anticipate the occurrence of dynamic osteogenesis involved in the production of good quality bone more suitable to loading. These findings are also supported by the higher values of microhardness as well as the more ordered-fibered texture (observed by polarized light) in treated animals with respect to control ones that strongly indicates the qualitative (instead of quantitative) effect of PTH (1-34) in improving bone healing. The present investigation could be of crucial importance in further translational clinical research in humans to define the best therapeutic strategies in recovering skeletal lesions, particularly in terms of time of administration of PTH(1-34)

Induced Biochemical osteoporosis: Effects of 1-month calcium–deprived diet on rat bone remodelling with/without contemporary administration of PTH(1-34)

It is known that rats fed calcium-deprived diet develop osteoporosis due to en-hanced bone resorption secondary to parathyroid overactivity resulting from nutritional hypocalcemia. Therefore, rats provide a good experimental animal model for studying bone remodelling alterations during biochemical osteoporosis. This preliminary study is performed in 3 month-old Sprague Dawley male rats, divided into 4 groups (5 rats each): 1) base line, 2) normal diet for 4 weeks, 3) calcium-deprived diet for 4 weeks; 4) calcium-deprived diet for 4 weeks plus contemporary administration of PTH(1-34) 40µg/kg/day. Three labels of osteogenesis were performed at 1st , 20th and 27th day of experimental period in order to evaluate bone formation during animal treatment. His-tomorphometrical analyses were performed on cortical bone of femoral diaphyses, as well as on trabecular bone of distal femoral metaphyses, both transversely sectioned. The preliminary results showed that at femur mid-diaphyseal level the diet induced a reduction of cortical bone area (even if not significant) with enlargement of the medul-lary canal due to endosteal resorption, while periosteal neo-deposition is similar in all groups and particularly abundant in those periosteal regions mainly devoted in answering the mechanical demands. PTH(1-34) treatment seems to reduce endosteal resorption only in those surfaces where periosteal mechanical loading are less consistent. Conversely, PTH(1-34) treatment doesn't seem to affect osteoblast activity. Moreover, in distal femoral metaphyses, diet induced osteoclast activity, with a decrease in the amount of trabecular bone volume, confirming that this architecture is mainly devoted in answering the metabolic demands. The novelty of the proposed model Is the contemporary administration of PTH(1-34) together with calcium deprived diet to evaluate induced-biochemical osteoporosis. This model seems a good starting point for successive studies in order to study bone alterations during unbalanced calcium metabolism frequently occurring in aging and to define time and manner of bone mass recovery

PRELIMINARY FINDINGS OF A POTENZIATED PIEZOSURGERGICAL DEVICE AT THE RABBIT SKULL

The number of available ultrasonic osteotomes has remarkably increased. In vitro and in vivo studies have revealed differences between conventional osteotomes, such as rotating or sawing devices, and ultrasound-supported osteotomes (Piezosurgery®) regarding the micromorphology and roughness values of osteotomized bone surfaces. Objective: the present study compares the micro-morphologies and roughness values of osteotomized bone surfaces after the application of rotating and sawing devices, Piezosurgery Medical® and Piezosurgery Medical New Generation Powerful Handpiece. Methods: Fresh, standard-sized bony samples were taken from a rabbit skull using the following osteotomes: rotating and sawing devices, Piezosurgery Medical® and a Piezosurgery Medical New Generation Powerful Handpiece. The required duration of time for each osteotomy was recorded. Micromorphologies and roughness values to characterize the bone surfaces following the different osteotomy methods were described. The prepared surfaces were examined via light microscopy, environmental surface electron microscopy (ESEM), transmission electron microscopy (TEM), confocal laser scanning microscopy (CLSM) and atomic force microscopy. The selective cutting of mineralized tissues while preserving adjacent soft tissue (dura mater and nervous tissue) was studied. Bone necrosis of the osteotomy sites and the vitality of the osteocytes near the sectional plane were investigated, as well as the proportion of apoptosis or cell degeneration. Results and Conclusions: The potential positive effects on bone healing and reossification associated with different devices were evaluated and the comparative analysis among the different devices used was performed, in order to determine the best osteotomes to be employed during cranio-facial surgery

Biocompatibility Analyses of Al₂O₃-Treated Titanium Plates Tested with Osteocyte and Fibroblast Cell Lines

Osseointegration of a titanium implant is still an issue in dental/orthopedic implants durable over time. The good integration of these implants is mainly due to their surface and topography. We obtained an innovative titanium surface by shooting different-in-size particles of Al₂O₃ against the titanium scaffolds which seems to be ideal for bone integration. To corroborate that, we used two different cell lines: MLO-Y4 (murine osteocytes) and 293 (human fibroblasts) and tested the titanium scaffolds untreated and treated (i.e., Al₂O₃ shot-peened titanium surfaces). Distribution, density, and expression of adhesion molecules (fibronectin and vitronectin) were evaluated under scanning electron microscope (SEM) and confocal microscope (CM). DAPI and fluorochrome-conjugated antibodies were used to highlight nuclei, fibronectin, and vitronectin, under CM; cell distribution was analyzed after gold-palladium sputtering of samples by SEM. The engineered biomaterial surfaces showed under SEM irregular morphology displaying variously-shaped spicules. Both SEM and CM observations showed better outcome in terms of cell adhesion and distribution in treated titanium surfaces with respect to the untreated ones. The results obtained clearly showed that this kind of surface-treated titanium, used to manufacture devices for dental implantology: (i) is very suitable for cell colonization, essential prerequisite for the best osseointegration, and (ii) represents an excellent solution for the development of further engineered implants with the target to obtain recovery of stable dental function over time

Ultrastructural aspects of articular cartilage and subchondral bone in patients affected by post-traumatic shoulder instability: preliminary observations

Post traumatic shoulder instability is a frequent condition in young active population. Notwithstanding a lot of data have been collected on capsular-legament lesions and gleno-humeral defects, no data are available on early ultrastructural ostheo-condral damages that are known to be highly associated with the onset of invalidating pathologies, like osteoarthritis (OA). Thus, the mechanisms of joint instability and the identification of which components in the articular complex are primarily affected in instability are of clinical significance, particularly in the light of deepening knowledge on the onset/development of OA. In the present study, biopsies of the articular cartilage and sub-chondral bone were taken from 10 patients (aged 26-40) underwent surgery in Policlinico of Modena. The withdrawals were immediately fixed and embedded for Transmission Electron Microscopy (TEM). The observations were performed in tangential, arcuate, and radial layers of the articular cartilage as well as in sub-chondral bone. TEM observations showed that chondrocytes in the superficial layers (i.e. tangential and arcuate) display normal and very well preserved ultrastructure, probably due to synovial liquid supply; otherwise, chondrocytes in the radial layer (not only in calcified but also in the un-calcified one) show various degrees of degeneration, with cytoplasm partially coerced and variously-sized vacuoles, both signs of suffering; occasionally, in the radial layer, chondrocytes with morphological signs of apoptosis or autophagy were also observed. As far as sub-chondral bone is concerned, osteocytes next the deeper calcified cartilage (within 80-100 micra from the cement line) also show evidences of degeneration, while osteocytes more distant from the osteo-chondral border display normal ultrastructure probably due to the vascular bone supply. In all patients of the study, the ultrastructural features of osteo-chondral complex are not depending on age. The present study represents the first ultrastructural investigation of the articular osteo-chondral complex in shoulder instability, evaluating the state of preservation/viability of both chondrocytes and osteocytes throughout the successive layers of the articular cartilage and sub-chondral bone. These preliminary observations are the basis to understand if the early surgical treatment in shoulder instability could avoid the onset of OA

Role of osteocyte apoptosis in peculiar ossicles of the hearing sense organ: preliminary observations on hearing loss and osteoporosis

Starting point of the present study is the osteocyte role in bone remodelling that allows bone adaptation to mechanical load [1-3]. Bone remodelling has been investigated in relation to the occurrence of apoptosis [4] to understand if and how the process of programmed cell death interferes with bone turnover. In 1998, in a study on human middle ear, Marotti et al. [5] demonstrated that: 1) over 40% of osteo-cytes are dead within the 2nd year of age (but the authors were not able to demonstrate if osteocyte death occurred by degeneration or apoptosis); 2) bone remodelling occurs only occasionally. Recently [6], we showed that: 1) osteocytes of human auditory ossicles die by apoptosis; 2) also osteocytes located inside scleral ossicles of lower vertebrate eye (reptiles and birds) phylogenetically so far from human auditory ossicles are widely affected by apoptosis (about 60%); 3) in scleral ossicles bone turnover never occur. It is to be noted that both auditory ossicles of human ear and scleral ossicles of vertebrate eye are peculiar bony segments continuously submitted to stereotyped stresses and strains, with specialized func-tions: the first are involved in sound wave transmission and the latter protect the eyeball against deformation during the movement and have a role in visual accomodation, providing attachment for the ciliary muscles. In both cases, bone remodelling might severely impair, by resorption, the mechanical resistance of these extremely small specialized bony segments. Thus, we suggested that in auditory and scleral ossicles, submitted to stereotyped loading for all life, bone mechanical adaptation is not needed and osteocyte programmed death could represent the mechanism to avoid bone remodelling and to make stable, when necessary, bone structure and mechanical resistance. More recently, to confirm this hypothesis, clinical data were collected from a cohort of patients aged 55-85 years affected by hearing loss. The main target of the present study is to exclude any correlation between hearing loss and osteoporosis. During osteoporosis, unbalanced bone turnover causes the bone depletion in skeletal segments; such condition, in the peculiar ossicles of human middle ear, should imply hearing impairment. Our preliminary observations indicate, instead, that osteoporotic patients do not show higher percentage of hearing loss with respect to non osteoporotic ones. This evidence is ascribable to osteocyte apoptosis of auditory ossicles that avoid bone remodelling, thus assuring the integrity of such bony segments also in osteoporotic conditions. References [1] Turner (1991) Omeostatic control of bone structure: an application of feed-bach theory. Bone 12: 203-217. [2] Turner and Forwood (1995) What role does the osteocyte network play in bone adaptation? Bone 16: 283-285. [3] Marotti (1996) The structure of bone tissue and the cellular control oftheir deposition. IJAE 101(4): 26-79. [4] Noble et al. (1997) Identification of apoptotic changes in osteocytes in normal and pathological human bone. Bone 20: 273-282. [5] Marotti et al. (1998) Morphometric investigation on osteocytes in human auditory ossicles. Ann Anat 180: 449-453. [6] Palumbo et al. (2012) Osteocyte apoptosis in human auditory ossicles and scleral ossicles of lower ver-tebrates: a mere coincidence or linked processes? Calcif. Tissue Int. 90: 211-218