Parathyroid Hormone, Its Fragments and Their Analogs for the Treatment of Osteoporosis

Fracture healing on non-union fracture model promoted by non-thermal atmospheric-pressure plasma

Non-thermal atmospheric-pressure plasma (NTAPP) is attracting widespread interest for use in medical applications. The tissue repair capacity of NTAPP has been reported in various fields; however, little is known about its effect on fracture healing. Non-union or delayed union after a fracture is a clinical challenge. In this study, we aimed to investigate how NTAPP irradiation promotes fracture healing in a non-union fracture model and its underlying mechanism, in vitro and in vivo. For the in vivo study, we created normal and non-union fracture models in LEW/SsNSlc rats to investigate the effects of NTAPP. To create a fracture, a transverse osteotomy was performed in the middle of the femoral shaft. To induce the non-union fracture model, the periosteum surrounding the fracture site was cauterized after a normal fracture model was created. The normal fracture model showed no significant difference in bone healing between the control and NTAPP-treated groups. The non-union fracture model demonstrated that the NTAPP-treated group showed consistent improvement in fracture healing. Histological and biomechanical assessments confirmed the fracture healing. The in vitro study using pre-osteoblastic MC3T3-E1 cells demonstrated that NTAPP irradiation under specific conditions did not reduce cell proliferation but did enhance osteoblastic differentiation. Overall, these results suggest that NTAPP is a novel approach to the treatment of bone fractures.

Peptide-Based Biomaterials for Bone and Cartilage Regeneration

The healing of osteochondral defects (OCDs) that result from injury, osteochondritis, or osteoarthritis and bear lesions in the cartilage and bone, pain, and loss of joint function in middle- and old-age individuals presents challenges to clinical practitioners because of non-regenerative cartilage and the limitations of current therapies. Bioactive peptide-based osteochondral (OC) tissue regeneration is becoming more popular because it does not have the immunogenicity, misfolding, or denaturation problems associated with original proteins. Periodically, reviews are published on the regeneration of bone and cartilage separately; however, none of them addressed the simultaneous healing of these tissues in the complicated heterogeneous environment of the osteochondral (OC) interface. As regulators of cell adhesion, proliferation, differentiation, angiogenesis, immunomodulation, and antibacterial activity, potential therapeutic strategies for OCDs utilizing bone and cartilage-specific peptides should be examined and investigated. The main goal of this review was to study how they contribute to the healing of OCDs, either alone or in conjunction with other peptides and biomaterials.

A pre-market interventional, single-arm clinical investigation of a new topical lotion based on hyaluronic acid and peptides, EGYFILTM, for the treatment of pain and stiffness in soft tissues

BACKGROUND

Muscle pain and stiffness are strictly interconnected. Injuries frequently occur during sport activities, causing muscle pain, with or without stiffness, and require effective as well as fast-acting treatments. Topical products can be ideal for the treatment of such physical alterations as they are convenient and simple to use. In this study, it was investigated the application of a novel topical formulation, EGYFIL™, for the treatment of pain and stiffness due to muscle contracture, trauma, and/or overtraining. The lotion is composed of hyaluronic acid, a well-known ingredient for the pain alleviation, mixed with skin conditioning SH-Polypeptide-6 and SH-Oligopeptide-1, embedded in it.

METHODS

Twenty-six patients with pain and/or stiffness were enrolled. After a screening visit (Time 0, t0), patients were treated for the first time with the IP. The treatment consisted of topical application of the pain lotion. Level of pain and stiffness were measured with Numerical Rating Scale (NRS). Patients' pain and/or stiffness were evaluated at t0 (prior to using the product), after three hours (t1), and after three days (t2) of treatment. Participants were free to apply and re-apply the product ad libitum over the course of the study period (3 days). Potential adverse events (AE) and tolerance were evaluated during each visit.

RESULTS

There was a 22% decrease in pain in the first three hours (p < 0.001), followed by an additional 20% decrease after three days (p=0.0873). Overall, there was a 42% decrease in pain over the three days of the study (p =0.001). Furthermore, a 24% reduction in stiffness in the first three hours (p=0.025) and a 38% decrease in stiffness over three days (p < 0.001) were observed. Reduction in pain and stiffness were neither age, nor sex dependent. No adverse effects were reported during the study.

CONCLUSION

EGYFIL™ is safe and seems to reduce pain and stiffness in patients during the 3 days of treatment, already after 3 h from the first application.

TRIAL REGISTRATION

ClinicalTrials.gov ID: NCT05711953. This trial was registered on 03/02/2023.

Bioactive Materials for Bone Regeneration: Biomolecules and Delivery Systems

Novel tissue regeneration strategies are constantly being developed worldwide. Research on bone regeneration is noteworthy, as many promising new approaches have been documented with novel strategies currently under investigation. Innovative biomaterials that allow the coordinated and well-controlled repair of bone fractures and bone loss are being designed to reduce the need for autologous or allogeneic bone grafts eventually. The current engineering technologies permit the construction of synthetic, complex, biomimetic biomaterials with properties nearly as good as those of natural bone with good biocompatibility. To ensure that all these requirements meet, bioactive molecules are coupled to structural scaffolding constituents to form a final product with the desired physical, chemical, and biological properties. Bioactive molecules that have been used to promote bone regeneration include protein growth factors, peptides, amino acids, hormones, lipids, and flavonoids. Various strategies have been adapted to investigate the coupling of bioactive molecules with scaffolding materials to sustain activity and allow controlled release. The current manuscript is a thorough survey of the strategies that have been exploited for the delivery of biomolecules for bone regeneration purposes, from choosing the bioactive molecule to selecting the optimal strategy to synthesize the scaffold and assessing the advantages and disadvantages of various delivery strategies.

A Novel Prenylflavonoid Icariside I Ameliorates Estrogen Deficiency-Induced Osteoporosis via Simultaneous Regulation of Osteoblast and Osteoclast Differentiation

Regulation of osteoblast-mediated bone formation and osteoclast-mediated bone resorption is crucial for bone health. Currently, most clinical drugs for osteoporosis treatment such as bisphosphonates are commonly used to inhibit bone resorption but unable to promote bone formation. In this study, we discovered for the first time that icariside I (GH01), a novel prenylflavonoid isolated from Epimedium, can effectively ameliorate estrogen deficiency-induced osteoporosis with enhancement of trabecular and cortical bone in an ovariectomy (OVX) mouse model. Mechanistically, our in vitro results showed that GH01 repressed osteoclast differentiation and resorption through inhibition of RANKL-induced TRAF6-MAPK-p38-NFATc1 cascade. Simultaneously, we also found that GH01 dose-dependently promoted osteoblast differentiation and formation by inhibiting adipogenesis and accelerating energy metabolism of osteoblasts. In addition, both in vitro and in vivo studies also suggested that GH01 is not only a non-toxic natural small molecule but also beneficial for restoration of liver injury in OVX mice. These results demonstrated that GH01 has great potential for osteoporosis treatment by simultaneous regulation of osteoblast and osteoclast differentiation.

Multipotential Role of Growth Factor Mimetic Peptides for Osteochondral Tissue Engineering

Articular cartilage is characterized by a poor self-healing capacity due to its aneural and avascular nature. Once injured, it undergoes a series of catabolic processes which lead to its progressive degeneration and the onset of a severe chronic disease called osteoarthritis (OA). In OA, important alterations of the morpho-functional organization occur in the cartilage extracellular matrix, involving all the nearby tissues, including the subchondral bone. Osteochondral engineering, based on a perfect combination of cells, biomaterials and biomolecules, is becoming increasingly successful for the regeneration of injured cartilage and underlying subchondral bone tissue. To this end, recently, several peptides have been explored as active molecules and enrichment motifs for the functionalization of biomaterials due to their ability to be easily chemically synthesized, as well as their tunable physico-chemical features, low immunogenicity issues and functional group modeling properties. In addition, they have shown a good aptitude to penetrate into the tissue due to their small size and stability at room temperature. In particular, growth-factor-derived peptides can play multiple functions in bone and cartilage repair, exhibiting chondrogenic/osteogenic differentiation properties. Among the most studied peptides, great attention has been paid to transforming growth factor-β and bone morphogenetic protein mimetic peptides, cell-penetrating peptides, cell-binding peptides, self-assembling peptides and extracellular matrix-derived peptides. Moreover, recently, phage display technology is emerging as a powerful selection technique for obtaining functional peptides on a large scale and at a low cost. In particular, these peptides have demonstrated advantages such as high biocompatibility; the ability to be immobilized directly on chondro- and osteoinductive nanomaterials; and improving the cell attachment, differentiation, development and regeneration of osteochondral tissue. In this context, the aim of the present review was to go through the recent literature underlining the importance of studying novel functional motifs related to growth factor mimetic peptides that could be a useful tool in osteochondral repair strategies. Moreover, the review summarizes the current knowledge of the use of phage display peptides in osteochondral tissue regeneration.

Recent advances in design and applications of biomimetic self-assembled peptide hydrogels for hard tissue regeneration

Abstract

The development of natural biomaterials applied for hard tissue repair and regeneration is of great importance, especially in societies with a large elderly population. Self-assembled peptide hydrogels are a new generation of biomaterials that provide excellent biocompatibility, tunable mechanical stability, injectability, trigger capability, lack of immunogenic reactions, and the ability to load cells and active pharmaceutical agents for tissue regeneration. Peptide-based hydrogels are ideal templates for the deposition of hydroxyapatite crystals, which can mimic the extracellular matrix. Thus, peptide-based hydrogels enhance hard tissue repair and regeneration compared to conventional methods. This review presents three major self-assembled peptide hydrogels with potential application for bone and dental tissue regeneration, including ionic self-complementary peptides, amphiphilic (surfactant-like) peptides, and triple-helix (collagen-like) peptides. Special attention is given to the main bioactive peptides, the role and importance of self-assembled peptide hydrogels, and a brief overview on molecular simulation of self-assembled peptide hydrogels applied for bone and dental tissue engineering and regeneration.

Graphic abstract

Teriparatide and Abaloparatide Have a Similar Effect on Bone in Mice

Three bone anabolic pharmaceuticals are currently approved for treatment of osteoporosis, teriparatide (PTH (1-34)), the parathyroid hormone-related protein analog abaloparatide (ABL), and romosozumab. The present study compared the effect of intermittent PTH (1-34) and ABL on bone tissue directly mole-to-mole in female mice. Forty-seven C57BL/6 mice were randomly allocated to the following groups: Baseline (n = 11), Control (Ctrl) (n = 12), PTH (n = 12), and ABL (n = 12). The mice were injected s.c. with PTH (100 µg/kg), ABL (96 µg/kg), or saline (Ctrl) five days a week for three weeks. To assess the effect of PTH and ABL, the hindlimb bones were analyzed with DXA, µCT, mechanical testing, dynamic bone histomorphometry, and histological quantification of bone cells. In addition, serum calcium concentration was determined. PTH and ABL significantly increased femoral areal bone mineral density (aBMD) (borderline significant p = 0.06 for PTH), femoral mid-diaphyseal bone strength, femoral metaphyseal and epiphyseal and vertebral bone volume fraction (BV/TV), connectivity density, volumetric bone mineral density (vBMD), and bone formation rate (BFR/BS) compared to Ctrl. In addition, ABL also significantly increased mid-diaphyseal cortical thickness and bone area compared to Ctrl. Neither PTH nor ABL significantly increased bone strength at the femoral neck. In conclusion, abaloparatide and PTH have similar bone anabolic properties when compared directly mole-to-mole in mice.

Spinal Cord Injury as a Model of Bone-Muscle Interactions: Therapeutic Implications From in vitro and in vivo Studies

Spinal cord injuries (SCIs) represent a variety of conditions related to the damage of the spinal cord with consequent musculoskeletal repercussions. The bone and muscle tissues share several catabolic pathways that lead to variable degrees of disability in SCI patients. In this review article, we provide a comprehensive characterization of the available treatment options targeting the skeleton and the bone in the setting of SCI. Among the pharmacological intervention, bisphosphonates, anti-sclerostin monoclonal antibodies, hydrogen sulfide, parathyroid hormone, and RANKL pathway inhibitors represent valuable options for treating bone alterations. Loss phenomena at the level of the muscle can be counteracted with testosterone, anabolic-androgenic steroids, and selective androgen receptor modulators. Exercise and physical therapy are valuable strategies to increase bone and muscle mass. Nutritional interventions could enhance SCI treatment, particularly in the setting of synergistic and multidisciplinary interventions, but there are no specific guidelines available to date. The development of multidisciplinary recommendations is required for a proper clinical management of SCI patients.

Effects of Teriparatide and Vibration on Bone Mass and Bone Strength in People with Bone Loss and Spinal Cord Injury: A Randomized, Controlled Trial

Spinal cord injury (SCI) is associated with marked bone loss and an increased risk of fracture. We randomized 61 individuals with chronic SCI and low bone mass to receive either teriparatide 20 μg/d plus sham vibration 10 min/d (n = 20), placebo plus vibration 10 min/d (n = 20), or teriparatide 20 μg/d plus vibration 10 min/d (n = 21). Patients were evaluated for 12 months; those who completed were given the opportunity to participate in an open-label extension where all participants (n = 25) received teriparatide 20 μg/d for an additional 12 months and had the optional use of vibration (10 min/d). At the end of the initial 12 months, both groups treated with teriparatide demonstrated a significant increase in areal bone mineral density (aBMD) at the spine (4.8% to 5.5%). The increase in spine aBMD was consistent with a marked response in serum markers of bone metabolism (ie, CTX, P1NP, BSAP), but no treatment effect was observed at the hip. A small but significant increase (2.2% to 4.2%) in computed tomography measurements of cortical bone at the knee was observed in all groups after 12 months; however, the magnitude of response was not different amongst treatment groups and improvements to finite element-predicted bone strength were not observed. Teriparatide treatment after the 12-month extension resulted in further increases to spine aBMD (total increase from baseline 7.1% to 14.4%), which was greater in patients initially randomized to teriparatide. Those initially randomized to teriparatide also demonstrated 4.4% to 6.7% improvements in hip aBMD after the 12-month extension, while all groups displayed increases in cortical bone measurements at the knee. To summarize, teriparatide exhibited skeletal activity in individuals with chronic SCI that was not augmented by vibration stimulation. Without additional confirmatory data, the location-specific responses to teriparatide would not be expected to provide clinical benefit in this population. © 2018 American Society for Bone and Mineral Research.

A vitronectin-derived peptide reverses ovariectomy-induced bone loss via regulation of osteoblast and osteoclast differentiation

Osteoporosis affects millions of people worldwide by promoting bone resorption and impairing bone formation. Bisphosphonates, commonly used agents to treat osteoporosis, cannot reverse the substantial bone loss that has already occurred by the time of diagnosis. Moreover, their undesirable side-effects, including osteonecrosis of the jaw, have been reported. Here, we demonstrated that a new bioactive core vitronectin-derived peptide (VnP-16) promoted bone formation by accelerating osteoblast differentiation and activity through direct interaction with β1 integrin followed by FAK activation. Concomitantly, VnP-16 inhibited bone resorption by restraining JNK-c-Fos-NFATc1-induced osteoclast differentiation and αvβ3 integrin-c-Src-PYK2-mediated resorptive function. Moreover, VnP-16 decreased the bone resorbing activity of pre-existing mature osteoclasts without changing their survival rate. Furthermore, VnP-16 had a strong anabolic effect on bone regeneration by stimulating osteoblast differentiation and increasing osteoblast number, and significantly alleviated proinflammatory cytokine-induced bone resorption by restraining osteoclast differentiation and function in murine models. Moreover, VnP-16 could reverse ovariectomy-induced bone loss by both inhibiting bone resorption and promoting bone formation. Given its dual role in promoting bone formation and inhibiting bone resorption, our results suggest that VnP-16 could be an attractive therapeutic agent for treating osteoporosis.

The use of bioactive peptides to modify materials for bone tissue repair

It has been well recognized that the modification of biomaterials with appropriate bioactive peptides could further enhance their functions. Especially, it has been shown that peptide-modified bone repair materials could promote new bone formation more efficiently compared with conventional ones. The purpose of this article is to give a general review of recent studies on bioactive peptide-modified materials for bone tissue repair. Firstly, the main peptides for inducing bone regeneration and commonly used methods to prepare peptide-modified bone repair materials are introduced. Then, current in vitro and in vivo research progress of peptide-modified composites used as potential bone repair materials are reviewed and discussed. Generally speaking, the recent related studies have fully suggested that the modification of bone repair materials with osteogenic-related peptides provide promising strategies for the development of bioactive materials and substrates for enhanced bone regeneration and the therapy of bone tissue diseases. Furthermore, we have proposed some research trends in the conclusion and perspectives part.

The role of peptides in bone healing and regeneration: a systematic review

BACKGROUND

Bone tissue engineering and the research surrounding peptides has expanded significantly over the last few decades. Several peptides have been shown to support and stimulate the bone healing response and have been proposed as therapeutic vehicles for clinical use. The aim of this comprehensive review is to present the clinical and experimental studies analysing the potential role of peptides for bone healing and bone regeneration.

METHODS

A systematic review according to PRISMA guidelines was conducted. Articles presenting peptides capable of exerting an upregulatory effect on osteoprogenitor cells and bone healing were included in the study.

RESULTS

Based on the available literature, a significant amount of experimental in vitro and in vivo evidence exists. Several peptides were found to upregulate the bone healing response in experimental models and could act as potential candidates for future clinical applications. However, from the available peptides that reached the level of clinical trials, the presented results are limited.

CONCLUSION

Further research is desirable to shed more light into the processes governing the osteoprogenitor cellular responses. With further advances in the field of biomimetic materials and scaffolds, new treatment modalities for bone repair will emerge.

Osteoporosis in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a lifestyle-related chronic inflammatory pulmonary disease associated with significant morbidity and mortality worldwide. COPD is associated with various comorbidities found in all stages of COPD. The comorbidities have significant impact in terms of morbidity, mortality, and economic burden in COPD. Management of comorbidities should be incorporated into the comprehensive management of COPD as this will also have an effect on the outcome in COPD patients. Various comorbidities reported in COPD include cardiovascular disease, skeletal muscle dysfunction, anemia, metabolic syndrome, and osteoporosis. Osteoporosis is a significant comorbidity in COPD patients. Various risk factors, such as tobacco smoking, systemic inflammation, vitamin D deficiency, and the use of oral or inhaled corticosteroids (ICSs) are responsible for its occurrence in patients with COPD. This review will focus on the prevalence, pathogenesis, risk factors, diagnosis, and treatment of osteoporosis in COPD patients.

Critical size defect regeneration by rhPTH-collagen membrane as a new tissue engineering tool

Recombinant Human Parathyroid Hormone (rhPTH 1-34) administration is an effective treatment to improve bone mass in osteoporosis. The aim of this study was to develop a Tissue Engeenering Tool for bone regeneration. We evaluated the efficacy of a freeze dried rhPTH membrane in calvarial critical size defect (CSD). Forty-four Wistar female rats (body weight 150 ± 50 g) with CSD (5 mm) were divided into four groups: group 1: rhPTH membrane (rhPTHm); group 2: atelocollagen membrane (Cm); group 3: rhPTH and atelocollagen I (CrhPTHm); group 4: without any treatment (CG). All samples were evaluated on the 1st, 3rd, and 6th weeks (weeks) post-surgery by soft X-ray, histological and histometric studies. Soft X-ray results showed a radiolucent image with many irregular radiopaque areas. Histologically, rhPTHm was replaced by reticular bone (7%) since 3rd week, and lamellar bone ossicles (30%) at 6th week. Cm showed bone formation like composite bone type on week 1st, 3rd, and 6th (2%, 44%, and 41%, respectively). With CrhPTHm, bone formation was observed in all periods (2.4%, 48%, and 53%), showing statistical difference with CG in the 3rd and 6th wks (p = 0.03 and 0.01). Our results demonstrated the effectiveness of a new biomaterial called CrhPTHm because its ability to regenerate calvarial CSD. Moreover, the membrane represents a new local intermittent delivery system allowing rhPTH slow release.

Pharmacogenomics of osteoporosis: a pathway approach

Osteoporosis is frequent in postmenopausal women and old men. As with other prevalent disorders, it is the consequence of complex interactions between genetic and acquired factors. Candidate gene and genome-wide association studies have pointed to several genes as determinants of the risk of osteoporosis. Some of them were previously unsuspected and may help to find new therapeutic targets. Several drugs already available are very effective in increasing bone mass and decreasing fracture risk. However, not all patients respond properly and some of them suffer fragility fractures despite therapy. Investigators have tried to identify the genetic features influencing the response to antiosteoporotic therapy. In this article we will review recent data providing insight into new genes involved in osteoporosis and the pharmacogenetic data currently available.

Sustained release of PTH(1-34) from PLGA microspheres suppresses osteoarthritis progression in rats

We previously reported that PTH(1-34) inhibits the terminal differentiation of articular chondrocytes and, in turn, suppresses the progression of osteoarthritis (OA). However, this treatment requires an injection of PTH(1-34) once every 3 days over the treatment period. In this study, we studied the effect of sustained administration of PTH(1-34) in a papain-induced OA rat model. We developed an effective controlled-release system for prolonging the treatment duration of an intra-articular injection for OA treatment in rats. The effects of released PTH(1-34) from PLGA(65:35)-encapsulated PTH(1-34) microspheres (PTH/PLGA) on papain-induced OA in rat knees were studied. Microsphere morphology was observed in vitro by scanning electron microscopy, and microsphere size was determined with a particle size analyzer. The PTH(1-34) encapsulation efficiency and release profile, as well as the toxicity of PTH/PLGA, were examined. The bioactivity of released PTH(1-34) was tested by examining cAMP levels in MC3T3E1 cells. In vivo, we evaluated the changes of localized GAG, Col II, and Col X in the articular cartilage of rat knees. Our results demonstrated that the surface of the PLGA microspheres was smooth, and the size of the microspheres was in the range of 51-127 μm. PTH/PLGA microspheres sustainably released PTH(1-34) for 19 days with a concentration range of 0.01-100 nM that covered the expected concentration of 10nM at 37°C. The cAMP levels of MC3T3E1 cells were elevated in the response to released PTH(1-34) from PTH/PLGA microspheres, indicating that the released PTH(1-34) is bioactive. Most importantly, intra-articular treatment with either PTH(1-34) (0.1-100 nM) 3 days/injection or PTH/PLGA microspheres (15 days/injection) for 5 weeks revealed the similar effect on suppressing papain-induced OA changes (decreasing GAG and Col II and increasing Col X) in rat knee cartilage. The effect of PTH/PLGA microspheres on suppressing OA progression was similar to that of a once-every-three-day injection of PTH(1-34), indicating that both the sustained and intermittent action of PTH(1-34) effectively suppress OA progression. The developed PLGA microspheres with sustained release and long-term effect may be potent carriers for PTH(1-34) used to treat early OA.

Parathormone--25(OH)-vitamin D axis and bone status in children and adolescents with type 1 diabetes mellitus

BACKGROUND

Skeletal involvement in patients with type 1 diabetes mellitus (T1DM) has complex pathogenesis and despite numerous researches on this problem, many questions remain unanswered.

OBJECTIVE

This study aimed to assess bone status by measurement parathormone (PTH), 25-hydroxy vitamin D [25(OH)D] serum levels in children and adolescents with T1DM and its relation to insulin-like growth factor-1 (IGF-1), disease duration, puberty stage, and metabolic control.

PATIENTS AND METHODS

This study included 36 children and adolescents with T1DM and 15 apparently healthy controls. Serum levels of 25(OH)D, PTH, IGF-1 measured using enzyme-linked immunosorbent assay (ELISA), while glycosylated hemoglobin (HbA1c), calcium (Ca), inorganic phosphorus (PO(4) ) using autoanalyzer. Bone quality assessed using dual energy X-ray absorptiometry (DEXA).

RESULTS

Diabetic patients showed significant increase in PO(4) and PTH levels, while significant decrease in Ca, IGF-1, and 25(OH)D serum levels. As much as 52.8% of patients showed reduced 25(OH)D, and 30.65% showed elevated PTH serum levels. In diabetic patients, abnormal bone status (osteopenia-osteoporosis) found mostly in total body (94.40%) then lumber-spine (88.90%), ribs (88.90%), pelvis (86.10%), thoracic-spine (80.60%), arms (80.60%) and legs (77.80%), while head bones showed no abnormalities. Long diabetic duration had negative; meanwhile PTH, onset age, and puberty age had positive impact on bone status.

CONCLUSIONS

Children and adolescent with T1DM have abnormal bone status mostly in axial skeleton which may be contributed to impairment of formation of 25(OH)D and IGF-1. Physical activity, calcium and vitamin D supplement seem important in T1DM. Elevated serum PTH level in diabetic patients is not uncommon and its positive correlation with bone status needs further investigations.

Effect of teriparatide on induced tooth displacement in ovariectomized rats: a histomorphometric analysis

INTRODUCTION

The aim of this study was to evaluate morphologically the effect of teriparatide on induced orthodontic movement of the maxillary first molars in ovariectomized rats.

METHODS

Ovariectomized Wistar rats (n = 16), ovariectomized rats treated with teriparatide (n = 16), and nonovariectomized rats (n = 16) had orthodontic tooth movement for 5 and 7 days. The group treated with teriparatide received a subcutaneous injection (Forteo, Eli Lilly, Indianapolis, Ind; 30 μg/kg/day) for 90 days after the ovariectomy. Histologic sections obtained from the maxilla were prepared for the morphometric analysis of dental movement, the thickness of the periodontal ligament, and the number of osteoclasts in the pressure and tension areas of the apex of the root and alveolar crest in the distal root of the maxillary first molars.

RESULTS

The ovariectomized rats treated with teriparatide had similar responses at 5 and 7 days after the induced dental movements compared with the untreated ovariectomized group. Both ovariectomized groups had greater molar movement on day 7 day compared with the controls (P <0.05). There were no statistically significant differences between groups in the spacing of the periodontal ligament or the number of osteoclasts in the areas studied.

CONCLUSIONS

These data suggest that the treatment of osteoporosis with teriparatide is a good alternative for patients undergoing orthodontic treatment.

Antifracture efficacy of currently available therapies for postmenopausal osteoporosis

Osteoporosis is a systemic bone disease characterized by low bone mass and bone mineral density, and deterioration of the underlying structure of bone tissue. These changes lead to an increase in bone fragility and an increased risk for fracture, which are the clinical consequences of osteoporosis. The classical triad for consideration in osteoporosis is morbidity, mortality and cost. Vertebral fracture is an important source of morbidity in terms of pain and spinal deformity. On the other hand, hip fracture is associated with the worst outcomes and is widely regarded as a life-threatening event in the elderly; it is the source of the bulk of the cost of the disease in contemporary healthcare. The prevention of osteoporosis-associated fracture should include fall prevention, calcium supplementation and lifestyle advice, as well as pharmacological therapy using agents with proven antifracture efficacy. The most commonly used osteoporosis treatments in Europe are the bisphosphonates alendronate, risedronate, ibandronate and zoledronic acid; the selective estrogen receptor modulator (SERM) raloxifene; teriparatide; and strontium ranelate. Recent additions include the biological therapy denosumab and the SERM bazedoxifene. In this review, we explore the antifracture efficacy of these agents with the aim of simplifying treatment decisions. These treatments can be broadly divided according to their mode of action. The antiresorptive agents include the bisphosphonates, the SERMs and denosumab, while the bone-forming agents include parathyroid hormone and teriparatide. Strontium ranelate appears to combine both antiresorptive and anabolic activities. We collated data on vertebral and hip fracture efficacy from the pivotal 3-year phase III trials, all of which had a randomized, double-blind, placebo-controlled design. The relative reductions in risk in the osteoporosis trials range from 30% to 70% for vertebral fracture and 30% to 51% for hip fracture. This translates into 3-year number needed to treat values of between 9 and 21 for vertebral fracture and from 48 upwards for hip fracture. International guidelines agree that agents that have been shown to decrease vertebral, nonvertebral and hip fractures should be used preferentially over agents that only demonstrate vertebral antifracture efficacy. This is the case for alendronate, risedronate, zoledronic acid, denosumab and strontium ranelate. Finally, therapeutic decisions should be based on a balance between benefits and risks of treatment, which must be carefully considered in each particular case both by the physician and the patient. Indeed, no single agent is appropriate for all patients and, therefore, treatment decisions should be made on an individual basis, taking into account all measures of treatment effect and risk before making informed judgments about the best individual treatment option.

Intermittent PTH1-34 causes DNA and chromosome breaks in osteoblastic and nonosteoblastic cells

Toxicological studies have demonstrated that intermittent PTH1-34 treatment is associated with an increased incidence of osteosarcoma in Fischer 344 rats. Comet and micronucleus (MN) tests, standard methods to evaluate genotoxic potential of drugs, were used to detect DNA and chromosome breaks, respectively, after PTH1-34 treatment. MC3T3 cells, primary osteoblast calvarial cells, and human osteoblasts were treated with PTH1-34 (50 and 100 nM) for 6 h/day for 21 days to mimic intermittent administration. Genotoxic assays were performed at 6 h and 7, 14, and 21 days. Osteoblasts extracted from bone marrow of mice treated with daily subcutaneous PTH1-34 injections (20 and 40 μg/kg) for 10 weeks as well as Hep-2, HeLa, and Hep-G2 cells were also tested. We observed a significant increase in DNA lesions and MN prevalence in human and murine osteoblasts treated with PTH1-34 compared to controls (P < 0.01). The effect observed in vitro and confirmed in vivo was time- and dose-dependent. For nonosteoblastic Hep-2 and HeLa cells we observed increased DNA damage and MN prevalence only later in the course of the protocol, after 21 days of treatment (P < 0.01). In Hep-G2 cells intermittent PTH1-34 did not induce DNA damage or chromosome breaks. Our results demonstrated that intermittent PTH increases DNA and chromosome breaks in osteoblasts. This genotoxic effect is attenuated in nonosteoblastic cells, and the ability to induce DNA damage is lost in cells with detoxification properties (HepG2 cells) tested in vitro.

Secreted frizzled related protein 1 is a target to improve fracture healing

Genetic studies have identified a high bone mass of phenotype in both human and mouse when canonical Wnt signaling is increased. Secreted frizzled related protein 1 (sFRP1) is one of several Wnt antagonists and among the loss-of-function mouse models in which 32-week-old mice exhibit a high bone mass phenotype. Here we show that impact fracture healing is enhanced in this mouse model of increased Wnt signaling at a physiologic level in young (8 weeks) sFRP1(-/-) mice which do not yet exhibit significant increases in BMD. In vivo deletion of sFRP1 function improves fracture repair by promoting early bone union without adverse effects on the quality of bone tissue reflected by increased mechanical strength. We observe a dramatic reduction of the cartilage callous, increased intramembranous bone formation with bone bridging by 14 days, and early bone remodeling during the 28-day fracture repair process in the sFRP1(-/-) mice. Our molecular analyses of gene markers indicate that the effect of sFRP1 loss-of-function during fracture repair is to accelerate bone healing after formation of the initial hematoma by directing mesenchymal stem cells into the osteoblast lineage via the canonical pathway. Further evidence to support this conclusion is the observation of maximal sFRP1 levels in the cartilaginous callus of a WT mouse. Hence sFRP1(-/-) mouse progenitor cells are shifted directly into the osteoblast lineage. Thus, developing an antagonist to specifically inhibit sFRP1 represents a safe target for stimulating fracture repair and bone formation in metabolic bone disorders, osteoporosis and aging.

Lipoxygenase metabolites are mediators of PTH-dependent human osteoblast growth

PTH-induced osteoblast proliferation may contribute to its anabolic effects in bone. Since PTH-dependent osteoblast-like cell (Ob) growth is mediated via protein kinase C (PKC) and MAP kinase-kinase (MEK) and since lipoxygenase (LO) products activate PKC in a number of cell types, we assessed the expression of LO pathways in primary human cultured Ob. Ob from pre- or post-menopausal women were cultured and were treated with PTH and assayed for the expression of 12-LO and both type I and type II 15-LO mRNA and for the release their enzymatic products, 12- and 15-hydroxyeicosatetraenoic acid (HETE). Cells were also treated with PTH for stimulation DNA synthesis. First, Ob express platelet type- 12-LO and both type I and type II 15-LO mRNA and release their enzymatic products, 12- and 15-hydroxyeicosatetraenoic acid (HETE). Second, in female Ob, PTH induced a rapid increase in 12-HETE (50 fold increase) and 15-HETE (80 fold increase) and increased the expression of 12-LO mRNA but not of the two isoforms of 15-LO. PTH as well as 12 and 15-HETE stimulated DNA synthesis in Ob. The LO inhibitor baicalein inhibited PTH-stimulated DNA synthesis, which was reversed in the presence of either 12- or 15-HETE. A PKC inhibitor (bisindolylmaleimide I) as well as a MEK inhibitor (PD 98059) completely inhibited the stimulation of DNA synthesis by PTH, 12-HETE and the combination of PTH and 12-HETE. In contrast, 15-HETE-induced DNA synthesis was not abolished by these inhibitors. Further, 15-HETE partially restored the stimulatory effect of PTH on DNA synthesis in cells treated with PKC or MEK inhibitors. Finally, PTH- induced ERK1/2 phosphorylation, was blocked by a MEK inhibitor. These results demonstrate a novel mechanism of PTH-induced human bone cell proliferation operating through LO enzymes.

Evidence that treatment with risedronate in women with postmenopausal osteoporosis affects bone mineralization and bone volume

Risedronate is used in osteoporosis treatment. Postmenopausal women enrolled in the Vertebral Efficacy with Risedronate Therapy trial received either risedronate (5 mg/day) or placebo for 3 years. Subjects received calcium and vitamin D supplementation if deficient at baseline. Lumbar spine bone mineral density (BMD) was measured at baseline and at 3 years. Quantitative back-scattered electron imaging (qBEI) was performed on paired iliac crest biopsies (risedronate, n = 18; placebo, n = 13) before and after treatment, and the mineral volume fraction in the trabecular bone was calculated. Combining dual-energy X-ray absorptiometric values with the mineral volume fraction for the same patients allowed us to calculate the relative change in trabecular bone volume with treatment. This showed that the effect on BMD was likely to be due partly to changes in matrix mineralization and partly due to changes in bone volume. After treatment, trabecular bone volume in the lumbar spine tended to increase in the risedronate group (+2.4%, nonsignificant) but there was a significant decrease (-3.7%, P < 0.05) in the placebo group. Calcium supplementation with adequate levels of vitamin D led to an approximately 3.3% increase in mineral content in the bone material independently of risedronate treatment. This increase was larger in patients with lower matrix mineralization at baseline and likely resulted from correction of calcium/vitamin D deficiency as well as from reduced bone remodeling. Combining BMD and bone mineralization density distribution data show that in postmenopausal osteoporosis 3-year treatment with risedronate preserves or may increase trabecular bone volume, unlike placebo. This analysis also allows, for the first time, separation of the contributions of bone volume and matrix mineralization to the increase in BMD.

Roles of epidermal growth factor family in the regulation of postnatal somatic growth

Ligands of the epidermal growth factor receptor (EGF-R), known to be important for supporting tissue development particularly in the gut and brain, have also been implicated in regulating postnatal somatic growth. Although optimal levels of both milk-borne and endogenous EGF-R ligands are important for supporting postnatal somatic growth through regulating gastrointestinal growth and maturation, supraphysiological levels of EGF-R ligands can cause retarded and disproportionate growth and alter body composition because they can increase growth of epithelial tissues but decrease masses of muscle, fat, and bone. Apart from their indirect roles in influencing growth, possibly via regulating levels of IGF-I and IGF binding proteins, EGF-R ligands can regulate bone growth and modeling directly because they can enhance proliferation but suppress maturation of growth plate chondrocytes (for building a calcified cartilage scaffold for bone deposition), stimulate proliferation but inhibit differentiation of osteoblasts (for depositing bone matrix), and promote formation and function of osteoclasts (for resorption of calcified cartilage or bone). In addition, EGF-like ligands, particularly amphiregulin, can be strongly regulated by PTH, an important regulatory factor in bone modeling and remodeling. Finally, EGF-R ligands can regulate bone homeostasis by regulating a pool of progenitor cells in the bone marrow through promoting proliferation but suppressing differentiation of bone marrow mesenchymal stem cells.

Picking a bone with contemporary osteoporosis management: Nutrient strategies to enhance skeletal integrity

Epidemic rates of osteoporosis in the western world have yielded intense efforts to develop management approaches to combat this potentially devastating disorder; recent research has unveiled innovative strategies which hold considerable promise for prevention of skeletal compromise and amelioration of suboptimal bone health. According to many algorithms and practice directives, the contemporary assessment and management of osteoporosis focuses heavily on determination of fracture risk and pharmaceutical intervention for those patients deemed to be at high risk. While routine recommendations for calcium and vitamin D have been incorporated into most regimens, disproportionately little attention has been given to recent research elucidating improved bone health and diminution in fracture rates experienced by patients receiving specific nutrients. In mainstream medical practice, clinical analysis and management of nutritional or dietary issues is sometimes perceived as unconventional, primitive or unsophisticated health care. Recent evidence-based research, however, supports intervention with adequate amounts of specific nutrients including vitamin D, strontium, vitamin K, and essential fatty acids in the prevention and primary management of osteoporosis.

Recombinant full-length parathyroid hormone (1-84)

Full-length parathyroid hormone (PTH) 1-84 is a recombinant version of human PTH. It is approved in the EU for the treatment of postmenopausal women with osteoporosis who have a high risk of fractures. Once-daily subcutaneous administration of PTH(1-84) stimulates new bone formation and increases bone mass. In the pivotal, randomised, double-blind, multicentre, 18-month TOP trial in 2532 postmenopausal women with osteoporosis, subcutaneous PTH(1-84) 100 microg/day significantly reduced the incidence of new or worsened vertebral fractures relative to placebo (primary endpoint). Moreover, the increase from baseline in bone mineral density (BMD) at the lumbar spine, total hip, femoral neck and trochanter was also significantly greater than in the placebo group. In another well designed study (PaTH; n = 238), 1 year of subcutaneous PTH(1-84) 100 microg/day followed by 1 year of alendronate 10 mg/day resulted in significantly greater increases in total spine, femoral neck and total hip BMD at 24 months compared with patients who received placebo for the second year. During the first year, PTH(1-84) in combination with alendronate was no more effective than PTH(1-84) monotherapy in terms of increasing areal lumbar spine BMD. PTH(1-84) is generally well tolerated, although patients should be monitored for elevated serum calcium.

Over-expression of TIMP-1 in osteoblasts increases the anabolic response to PTH

Intermittent PTH treatment induces structural changes that affect cancellous bone mass and have led to its indication for the treatment of osteoporosis. PTH is also known to upregulate the expression of matrix metalloproteinases (MMP) in osteoblasts. We wanted to find out whether inhibiting osteoblastic MMPs can affect the anabolic action of PTH in vivo. We had shown previously that mice over-expressing TIMP-1 (tissue inhibitor of MMPs) specifically in osteoblasts display an increase in bone mineral density and bone mass combined with an overall decrease in bone turnover. In the present study, 10-week-old wild-type (WT) and transgenic (TG) mice were treated with PTH at 40 microg/kg/day for 1.5 months. DEXA analysis was performed before and after treatment, and histomorphometric and molecular analysis were carried out at the end of the experiment. Our findings indicate that the transgene boosted the anabolic action of PTH. The femurs of PTH-treated TG mice displayed a greater increase in bone mineral density and trabecular bone volume than treated WT mice. Interestingly, the positive effect of the transgene on the action of PTH resulted from both reduced bone resorption activity and an increase in the bone formation rate. Osteoclastic surfaces that were increased in PTH-treated WT mice remained unchanged in TG mice, suggesting a decrease in osteoclastic differentiation. Histomorphometric data also indicate that PTH administration increased osteoblast activity in TG mice and affected the number of osteoblasts in WT mice. In conclusion, we demonstrate that inhibiting osteoblastic MMPs can potentiate the anabolic effect of PTH by decreasing osteoclast activity and increasing osteoblast activity. Our data also suggest that osteoblastic MMPs have some role in mediating the anabolic effects of PTH in vivo and indicate that inhibitors of MMPs could constitute a new therapy for degenerative diseases.

Parathyroid hormone and leptin--new peptides, expanding clinical prospects

There are three injectable and one oral bone-building (i.e., bone anabolic) parathyroid hormone (PTH) peptides. One of the four, Lilly's injectable teriparatide (Forteo), is currently being used, and the other three are in clinical trials. They are being used or assessed only for treating postmenopausal osteoporosis. However, their potential clinical targets now extend far beyond osteoporosis. They can accelerate the mending of even severe non-union fractures; they will probably be used to strengthen the anchorage of pros-theses to bone; they have been shown to treat psoriasis that has resisted other treatments; they can increase the size of haematopoietic stem cell proliferation and accelerate the endogenous repopulation or repopulation by donor transplants of bone marrow depleted by chemotherapeutic drugs; and they may prevent vascular ossification. Leptin, a member of the cytokine superfamily has a PTH-like osteogenic activity and may even partly mediate PTH action. But leptin has two drawbacks that cloud its therapeutic future. First, apart from directly stimulating osteoblastic cells, it targets cells in the hypothalamic ventromedial nuclei and through them it reduces oestrogenic activity by promoting osteoblast-suppressing adrenergic activity. Second, it stimulates vascular and heart valve ossification, which leads to such events as heart failure and diabetic limb amputations.

Osteogenic PTHs and vascular ossification—Is there a danger for osteoporotics?

Inflammation in vascular (mostly arterial) walls and heart valves triggered by the trans-endothelial influx of LDL particles and the action of subsequently modified (e.g., by oxidation) LDL particles can trigger true bone formation by valvar fibroblasts, by a subpopulation of re-differentiation-competent VSMCs (vascular smooth muscle cells) or by vascular pericytes. Vascular ossification can lead to heart failure and death. Elderly osteoporotic women who need osteogenic drugs to restore their lost skeletal bone are paradoxically prone to vascular ossification-the "calcification paradox." The recent introduction into the clinic of a potently osteogenic parathyroid hormone peptide, Lilly's rhPTH-(1-34)OH (Forteotrade mark), to reverse skeletal bone loss raises the question of whether this and other potently osteogenic PTHs still in clinical trial might also stimulate vascular ossification in such osteoporotic women. Indeed the VSMCs in human and rat atherosclerotic lesions hyperexpress PTHrP and the PTHR1 (or PTH1R) receptor as do maturing osteoblasts. And the evidence indicates that endogenous PTHrP with its NLS (nuclear/nucleolar localization sequence) does stimulate VSMC proliferation (a prime prerequisite for atheroma formation and ossification) via intranuclear targets that inactivate pRb, the inhibitory G1/S checkpoint regulator, by stimulating its hyperphosphorylation. But neither externally added full-length PTHrP nor the NLS-lacking PTHrP-(1-34)OH gets into the VSMC nucleus and instead they inhibit proliferation and calcification by only activating the cell's PTHR1 receptors. No PTH has an NLS and, as expected from the observations on the externally added PTHrPs, hPTH-(1-34)OH inhibits calcification by VSMCs and cannot stimulate vascular ossification in a diabetic mouse model. Encouraging though this may be for osteoporotics with their "calcification paradox," more work is needed to be sure that the skeletally osteogenic PTHs do not promote vascular ossification with its cardiovascular consequences.

The effects of parathyroid hormone fragments on bone formation and their lack of effects on the initiation of colon carcinogenesis in rats as indicated by preneoplastic aberrant crypt formation

The parathyroid hormone (PTH) and some of its fragments and analogs stimulate bone growth in various animal models and humans and one of them (hPTH-(1-34)) has been approved by the USFDA for treating osteoporosis. However, there are reports that PTH can stimulate the PI-3 kinase/mitogen-activated protein kinases-mediated proliferation of rat enterocytes and that primary hyperparathyroidism in humans is associated with an increased incidence of colon cancer. Here we have investigated the ability of two PTH fragments, hPTH-(1-34)NH(2) and [Leu(27)]cyclo(Glu(22)-Lys(26))hPTH-(1-31)NH(2) to initiate colon carcinogenesis or increase the initiatory activity of the widely used colon carcinogen azoxymethane (AOM). The initiation of colon carcinogenesis by AOM was indicated by the very early appearance of aberrant crypt foci. While both PTH peptides strongly stimulated femoral bone formation, they did not cause the appearance of ACFs or affect the number or the distribution along the colon of AOM-induced ACFs. Nor did AOM affect the PTHs' ability to stimulate bone formation. Thus, a relatively short PTH treatment that is long enough to strongly stimulate bone formation does not initiate colon carcinogenesis in rats.

How to grow bone to treat osteoporosis and mend fractures

The growing number of patients with osteoporosis in our aging population need "anabolic" drugs to stimulate bone growth, improve bone microarchitecture, and accelerate fracture healing. Potent anabolic agents such as parathyroid hormone (PTH) and some of its adenylyl cyclase-stimulating fragments are either on their way, or have just now reached the clinic. This article discusses how PTHs might stimulate bone growth. The controversial bone anabolic activities of the widely used cholesterol-lowering lipophilic statins and how they might stimulate bone growth are also probed. Also, evidence is presented for leptin, a controller of body fat stores and the ovarian cycle. It has the remarkable property of being an anabolic and antianabolic that uses a hypothalamic factor to restrain osteoblast activity but by itself stimulates osteoblasts and inhibits osteoclasts.