Radiation-induced reduction of BMP-induced proteoglycan synthesis in an embryonal mesenchymal tissue equivalent using the chicken "limb bud" test

Surgical treatment of anterior cervical osteophytes causing dysphagia

PURPOSE

Dysphagia due to anterior cervical osteophytes is a rare condition. However, it can become serious enough to permanently impair the quality of life up to making normal food intake impossible. If conservative treatment fails, there is the option of surgical resection of the osteophytes. The objective of this study was to assess the outcomes of resections of anterior cervical osteophytes causing spondylogenic dysphagia, taking literature into consideration.

METHOD

Resection of anterior cervical osteophytes using a standard anterior approach was performed in 14 consecutive patients with spondylogenic dysphagia between 2009 and 2015. Indomethacin or radiation was used to prevent recurrence. Imaging and clinical data were collected in follow-up examinations over an average of 50 months.

RESULTS

The osteophytes were sufficiently resected in all cases. Anterior plates were placed in three patients due to pronounced segmental mobility. Five patients were given recurrence prevention in the form of indomethacin, nine with radiation. One patient required revision surgery for a hematoma. No other serious complications were observed. All patients had significant improvement of their symptoms. No recurrences or signs of increasing instability were found during the follow-up period.

CONCLUSION

When conservative treatment fails, surgical resection of cervical osteophytes is a sufficient method for treating spondylogenic dysphagia. High patient satisfaction and improvement of the quality of life are achieved with a low complication rate. Routine additional stabilization has been discussed as recurrence prevention. Prophylaxis using indomethacin or radiation, known primarily from hip replacement, also appears to be an option.

The effects of low dose X-irradiation on osteoblastic MC3T3-E1 cells in vitro

BACKGROUND

It has been indicated that moderate or high dose of X-irradiation could delay fracture union and cause osteoradionecrosis, in part, mediated by its effect on proliferation and differentiation of osteoblasts. However, whether low dose irradiation (LDI) has similar roles on osteoblasts is still unknown. In this study, we investigated whether and to what extent LDI could affect the proliferation, differentiation and mineralization of osteoblasts in vitro.

METHODS

The MC3T3-E1 cells were exposed to single dose of X-irradiation with 0, 0.1, 0.5, 1.0 Gy respectively. Cell proliferation, apoptosis, alkaline phosphatase (ALP) activity, and mineralization was evaluated by methylthiazoletetrazolium (MTT) and bromodeoxyuridine (BrdU) assay, flow cytometry, ALP viability kit and von Kossa staining, respectively. Osteocalcin (OCN) and core-binding factor α1 (Cbfα1) expressions were measured by real time-PCR and western blot, respectively.

RESULTS

The proliferation of the cells exposed to 2.0 Gy was significantly lower than those exposed to ≤1.0 Gy (p < 0.05) from Day 4 to Day 8, measured by MTT assay and BrdU incorporation. For cells exposed to ≤1.0 Gy, increasing dosages of X-irradiation had no significant effect on cell proliferation and apoptosis. Importantly, LDI of 0.5 and 1 Gy increased ALP activities and mineralized nodules of MC3T3-E1 cells. In addition, mRNA and protein expressions of OCN and Cbfα1 were also markedly increased after treatment with LDI at 0.5 and 1 Gy.

CONCLUSIONS

LDI have different effects on proliferation and differentiation of osteoblasts from those of high dose of X-irradiation, which might suggest that LDI could lead to promotion of fracture healing through enhancing the differentiation and mineralization of osteoblasts.

The effects of various irradiation doses on the growth and differentiation of marrow-derived human mesenchymal stromal cells

Mesenchymal stromal cells (MSC) are progenitors of mesenchymal tissues including bones. Irradiation can damage the osteogenic activity of human marrow by suppressing osteoblasts leading to post-irradiation osteoporosis. However, the effect of therapeutic irradiation on MSC remains unexplored. We investigated the effects of various doses of X-ray irradiation on human MSC (hMSC) by measuring its post-irradiation proliferation and differentiation activities. Standard immunophenotypes and differentiating functions of the MSC were determined. Irradiation inhibited proliferation of hMSC up to two wk post-irradiation but thereafter, those residual surviving cells regained their normal proliferation rate. Bone forming activity as reflected by alkaline phosphatase (ALP) and calcium deposition were both reduced in a dose-dependent fashion. Maximum suppressive effect on osteogenic activity was noted in MSC treated with high-dose irradiation (12 Gy). Adipocyte percentage was also reduced by 50% in cultures that received >4 Gy. Attempts to protect the irradiated cells with 1 microM all-trans retinoic acid did not show any beneficial effect on MSC proliferation and differentiation. The direct impairment of proliferation and osteogenic differentiation potential of MSC by irradiation may contribute partly to the post-transplant osteoporosis.

Wertigkeit einer kombinierten Ossifikationsprophylaxe mit Indometacin und Bestrahlung bei Azetabulumfrakturen

BACKGROUND

Heterotopic ossification is a complication in patients with surgically treated acetabular fractures. The incidence is related to the surgical approach (extended iliofemoral, posterior or a combined approach). The objective of this study was to evaluate the incidence of heterotopic ossification in patients with acetabular fractures who received a combined prophylaxis with both a single dose of radiation and indomethacin compared to those who received only a prophylaxis with radiation or indomethacin.

PATIENTS AND METHODS

A total of 24 patients with a combined prophylaxis after surgery were examined retrospectively 24 months after trauma. A systematic literature review was performed and our own results were compared with different methods for prophylaxis of heterotopic ossification from the literature.

RESULTS

Only one patient developed a heterotopic ossification. In accordance with the literature, combined prophylaxis showed the least incidence of ossification compared to the other methods. Differences in incidence frequencies were significant between the different prophylaxis methods.

CONCLUSION

A combined prophylaxis for heterotopic ossification in surgically treated acetabular fractures seems to be a better alternative than a prophylaxis with radiation or indomethacin alone.

Expression of bone morphogenic protein 2/4, transforming growth factor-β1, and bone matrix protein expression in healing area between vascular tibia grafts and irradiated bone—experimental model of osteonecrosis

PURPOSE

For the surgical treatment of osteoradionecrosis after multimodal therapy of head-and-neck cancers, free vascular bone grafts are used to reconstruct osseous structures in the previously irradiated graft bed. Reduced, or even absent osseous healing in the transition area between the vascular graft and the irradiated graft bed represents a clinical problem. Inflammatory changes and fibrosis lead to delayed healing, triggered by bone morphogentic protein 2/4 (BMP2/4) and transforming growth factor (TGF)-beta(1). Given the well-known fibrosis-inducing activity of TGF-beta(1), an osteoinductive effect has been reported for BMP2/4. However, the influence of irradiation (RT) on this cytokine expression remains elusive. Therefore, the aim of the present in vivo study was to analyze the expression of BMP2/4, TGF-beta(1), collagen I, and osteocalcin in the transition area between the bone graft and the graft bed after RT.

METHODS AND MATERIALS

Twenty Wistar rats (male, weight 300-500 g) were used in this study. A free vascular tibia graft was removed in all rats and maintained pedicled in the groin region. Ten rats underwent RT with 5 x 10 Gy to the right tibia, the remainder served as controls. After 4 weeks, the previously removed tibia grafts were regrafted into the irradiated (Group 1) and nonirradiated (Group 2) graft beds. The interval between RT and grafting was 4 weeks. After a 4-week osseous healing period, the bone grafts were removed, and the transition area between the nonirradiated graft and the irradiated osseous graft bed was examined histomorphometrically (National Institutes of Health imaging program) and immunohistochemically (avidin-biotin-peroxidase complex) for the expression of BMP2/4, TGF-beta(1), collagen I, and osteocalcin.

RESULTS

Absent or incomplete osseous healing of the graft was found in 9 of 10 rats after RT with 50 Gy and in 1 of 10 of the rats with nonirradiated osseous grafts. Histomorphometrically, the proportion of osseous healing in the transition area was 17% in Group 1 and 48% in Group 2 (p = 0.001). Compared with the nonirradiated rats, reduced enchondral and perichondral ossification was found in the healing area after RT, with a reduction of BMP2/4 and osteocalcin expression. TGF-beta(1) and collagen I expression in the transition area to the irradiated osseous graft bed was significantly increased compared with that in the nonirradiated osseous graft bed.

CONCLUSION

After RT, osseous healing of vascular bone grafts is significantly reduced and may be a result of radiation-induced inhibition of BMP2/4 and osteocalcin expression. In addition, induction of TGF-beta(1) and collagen I expression occurs. Because the effects of the TGF-beta superfamily are manifold and partially unknown, additional research directions could be in the exogenous application of BMP2/4 and inhibition of TGF-beta(1) by antibody treatment to search for appropriate therapeutic approaches for improving osseous healing in the irradiated graft bed.

Radiation-induced suppression of the Bmp2 signal transduction pathway in the pluripotent mesenchymal cell line C2C12: an in vitro model for prevention of heterotopic ossification by radiotherapy

Heterotopic ossification is a common complication after total hip replacement. Clinical studies showed the effectiveness of radiation for prevention of heterotopic ossification. The mechanism of radiotherapy responsible for the reduction of heterotopic ossification is unclear. The purpose of this study was to study an analogue model showing a time- and dose-dependent effect of radiation. Using cells of the defined embryonic mouse cell line C2C12, the influence of ionizing radiation on the Bmp-induced signal cascade leading to osteogenic differentiation was analyzed. Binding of iodinated Bmp2 to the receptors, Smad1 activation, and alkaline phosphatase (ALP) activity were determined in cells with or without irradiation. The cytotoxic effect of radiotherapy was evaluated using viability tests. Radiotherapy reduced formation of the Bmp2/Bmp receptor complex. This effect was dependent on dose. The phosphorylation (activation) of Smad1 decreased after irradiation in a time-dependent manner, whereas the level of total Smads was not influenced by radiotherapy. The ALP activity decreased after radiotherapy. A dose of 7 Gy delivered 6 h before or after incubation with Bmp resulted in about a 30% decrease in ALP activity. No signs of cytotoxic effects were observed within the time window studied using doses of 0 to 20 Gy. The time- and dose-dependent effect of radiotherapy for prevention of heterotopic ossification known from the results of clinical studies has an analogue in the C2C12 cell model. The primary mechanism of radiotherapy seems to be an influence on cellular responsiveness to the Bmp2-induced osteoblastic differentiation. The results suggest a down-regulation of the Bmp2/receptor complex.