Irradiation induces bone injury by damaging bone marrow microenvironment for stem cells

Radiation therapy can result in bone injury with the development of fractures and often can lead to delayed and nonunion of bone. There is no prevention or treatment for irradiation-induced bone injury. We irradiated the distal half of the mouse left femur to study the mechanism of irradiation-induced bone injury and found that no mesenchymal stem cells (MSCs) were detected in irradiated distal femora or nonirradiated proximal femora. The MSCs in the circulation doubled at 1 week and increased fourfold after 4 wk of irradiation. The number of MSCs in the proximal femur quickly recovered, but no recovery was observed in the distal femur. The levels of free radicals were increased threefold at 1 wk and remained at this high level for 4 wk in distal femora, whereas the levels were increased at 1 wk and returned to the basal level at 4 wk in nonirradiated proximal femur. Free radicals diffuse ipsilaterally to the proximal femur through bone medullary canal. The blood vessels in the distal femora were destroyed in angiographic images, but not in the proximal femora. The osteoclasts and osteoblasts were decreased in the distal femora after irradiation, but no changes were observed in the proximal femora. The total bone volumes were not affected in proximal and distal femora. Our data indicate that irradiation produces free radicals that adversely affect the survival of MSCs in both distal and proximal femora. Irradiation injury to the vasculatures and the microenvironment affect the niches for stem cells during the recovery period.     

The Emerging Picture of the Mouse Mammary Stem Cell

The isolation and characterisation of mammary stem cells is an important step towards elucidating the hierarchy of epithelial cell development in the mammary gland and identifying cells that are targets of breast carcinogenesis. Mammary stem cells have recently been prospectively isolated through the identification of specific cell surface markers and in vivo transplantation into cleared fat pads. These cells were demonstrated to reconstitute an entire mammary gland comprising all mature epithelial cell types and to be capable of self-renewal on serial transplantation, thus possessing the defining features of stem cells. Notably, mouse mammary stem cells were found to share the hallmark properties of the basal subtype of breast cancer. This review will summarize the strategy used in the identification of mouse mammary stem cells and their characterisation.     

Simply produced closed-head, focal lesions for study of repair in immature rat cerebral cortex

Multiple electroconvulsive shocks consistently and rapidly produce uniform, bilaterally symmetrical lesions in the immature rat's cerebral cortex, without the incidental damage that accompanies other experimental injuries to the central nervous system. The terminal lesion, devoid of nerve cells, is a narrow, laminar band of numerous myelinated axons, unaccompanied by a glial scar. Insofar as the initially damaged area becomes occupied by nerve fibers, the healing process may be thought of as involving a regeneration. A variety of studies for which the electroshock lesions might be used is suggested.     

Mitomycin C in combination with radiotherapy as a potent inhibitor of tumour cell repopulation in a human squamous cell carcinoma

The potential of Mitomycin C in combination with fractionated irradiation to inhibit tumour cell repopulation of a fast growing squamous cell carcinoma after fractionated radiotherapy was investigated in vivo. A rapidly growing human squamous cell carcinoma (FaDu(dd)) was used for the study. For experiments, NMRI (nu/nu) mice with subcutaneously growing tumours were randomly allocated to no treatment, Mitomycin C, fractionated irradiation (ambient: 11 x 4.5 Gy in 15 days), or fractionated irradiation combined with Mitomycin C. Graded top up doses (clamped blood flow: 0-57 Gy) were given at day 16, 23, 30 or 37. End point of the study was the time to local tumour progression. Data were examined by multiple regression analysis (Cox). Mitomycin C alone resulted in a median time to local tumour progression of 23 (95% confidence limits: 17-43) days, fractionated irradiation in 31 (25-35) days and combined Mitomycin C plus fractionated irradiation in 65 (58-73) days (P=0.02). Mitomycin C decreased the relative risk of local recurrence by 94% (P<0.001) equivalent to 31.7 Gy top up dose. Repopulation accounted for 1.33 (0.95-1.72) Gy per day top up dose after fractionated irradiation alone and for 0.68 (0.13-1.22) Gy per day after fractionated irradiation+Mitomycin C (P=0.018). Mitomycin C significantly reduces the risk of local recurrence and inhibits tumour cell repopulation in combination with fractionated irradiation in vivo in the tested tumour model.     

人鼻咽癌细胞USPF及其放射效应

目的探讨未能被５－溴－２′－脱氧尿苷（ＢｒｄＵ）标记的，具有Ｓ期细胞ＤＮＡ含量的时相比例（ＵＳＰＦ）存在的另一种可能机制，即所谓“半成品库”机制。方法运用ＢｒｄＵ／ＤＮＡ双参数流式细胞计量术分析了不同培养状况下人鼻咽癌ＣＮＥ细胞放射前后有关细胞增殖特性参数的变化情况，并进行统计学处理。结果（１）ＵＳＰＦ和ＬＳＰＦ之间存在可逆性；（２）可逆性ＵＳＰＦ存在可以不伴有Ｓ期时间的变化；（３）上述可逆性与放射引起的细胞再增殖速率有关。结论除了ＢｒｄＵ弥散不均和Ｓ期阻滞（流产）机制外，还可能存在“半成品库”机制。后者存在的合理性在放射效应试验中已得到证实。     

The role of PET imaging in overcoming radiobiological challenges in the treatment of advanced head and neck cancer

Purpose

Despite the large variety of treatment methods available for the management of advanced head and neck carcinomas, these tumours remain highly challenging due to their aggressiveness and complex anatomical location. Among the treatment challenges associated with head and neck cancers, hypoxia and tumour repopulation during treatment are, most likely, the main reason for locoregional treatment failure. Whilst the number of techniques and predictive assays designed to assess the oxygenation status or the proliferative ability of tumours is rather large, they all come with drawbacks which limit their implementation as routine clinical procedures. Latest developments in the field of nuclear medicine have opened the road to new possibilities in functional imaging, thus overcoming some of the confines imposed by the more conventional techniques.

Materials and methods

The current paper presents the role of PET imaging as a quantitative evaluation tool for hypoxia status and proliferative ability of advanced head and neck tumours. Traditional as well as novel radioisotopes with high affinity towards hypoxia and proliferative tumour activity are presented and their pre-clinical/clinical results analysed.

Results

While the number of clinical studies which aimed to validate novel radiotracers for head and neck cancer is limited, a number of results show promising correlation between uptake/marker activity and treatment outcome.

Conclusion

There is need for further studies and well designed clinical trials to obtain more conclusive results.     

Liver regeneration in response to partial hepatectomy in rats treated with retrorsine: a kinetic study

BACKGROUND/AIM: We have designed an experimental model in which transplantation of normal hepatocytes into rats previously treated with retrorsine (a naturally-occurring pyrrolizidine alkaloid) results in near-complete replacement of the recipient liver by donor-derived cells. Two/thirds partial hepatectomy was found to be essential for this process to occur. To probe this finding, in the present study we describe the kinetics of liver regeneration in response to partial hepatectomy in rats given retrorsine. METHODS: Six-weeks-old male Fisher 344 rats received retrorsine (2 injections of 30 mg/kg each, i.p., 2 weeks apart), or the vehicle. Four weeks after the last injection, partial hepatectomy was performed and rats were killed at 1, 2, 3, 6, and 15 days thereafter. RESULTS: At time zero, i.e. prior to partial hepatectomy, liver weight and total liver DNA content were significantly lower in retrorsine-treated animals compared to controls (DNA content: 19.2+/-1.7 vs. 25.7+/-1.1 mg/liver). Diffuse megalocytosis (enlarged hepatocytes) was present in the group exposed to retrorsine. By day 3 post-partial hepatectomy liver DNA content in control animals had more than doubled compared to day 1 values (20.2+/-1.5 vs. 8.8+/-1.2), while very little increase was seen in retrorsine-treated rats at the same time points (7.6+/-0.4 vs. 6.1+/-0.2). At 2 weeks after partial hepatectomy, total DNA content returned close to normal levels in the control group (26.9+/-1.0 mg/liver); however, the value was still very low in animals receiving retrorsine (9.1+/-0.7). Data on BrdU labeling were consistent with this pattern and indicated that DNA synthesis following partial hepatectomy was largely inhibited in the retrorsine group. Similarly, no mitotic response was observed in hepatocytes following partial hepatectomy in animals exposed to retrorsine. CONCLUSIONS: These results clearly indicate that retrorsine exerts a strong and persistent cell cycle block on hepatocyte proliferation. Further, these results are in agreement with the hypothesis that selective proliferation of transplanted hepatocytes in retrorsine-treated animals is dependent, at least in part, on the persistent cell cycle block imposed by the alkaloid on endogenous parenchymal cells.     

Correction of T cell deficiency in ZAP‐70 knock‐out mice by simple intraperitoneal adoptive transfer of thymocytes

The tyrosine kinase zeta chain‐associated protein of 70 kDa (ZAP‐70) plays a key role in T cell development and signalling. In the absence of ZAP‐70, T cell development is arrested in the CD4⁺CD8⁺ double‐positive stage, thus ZAP‐70 homozygous knockout (ZAP‐70^–/–) mice have no mature T cells in their peripheral lymphoid organs and blood, causing severe immunodeficiency. We investigated the early kinetics and long‐term effects of wild‐type thymocyte transfer on T cell repopulation in ZAP‐70^–/– mice. We used a single intraperitoneal (i.p.) injection to deliver donor thymocytes to the recipients. Here, we show that after i.p. injection donor thymocytes leave the peritoneum through milky spots in the omentum and home to the thymus, where donor‐originated CD4^–CD8^– double‐negative thymocytes most probably restore T cell development and the disrupted thymic architecture. Subsequently, newly developed, donor‐originated, single‐positive αβ T cells appear in peripheral lymphoid organs, where they form organized T cell zones. The established chimerism was found to be stable, as donor‐originated cells were present in transferred ZAP‐70^–/– mice as late as 8 months after i.p. injection. We demonstrate that a simple i.p. injection of ZAP‐70^+/+ thymocytes is a feasible method for the long‐term reconstitution of T cell development in ZAP‐70‐deficient mice.