[Principles of biological aging]

Effects of aging on the histology and biochemistry of rat tendon healing

INTRODUCTION

Tendon diseases and injuries are a serious problem for the aged population, often leading to pain, disability and a significant decline in quality of life. The purpose of this study was to determine the influence of aging on biochemistry and histology during tendon healing and to provide a new strategy for improving tendon healing.

METHOD

A total of 24 Sprague-Dawley rats were equally divided into a young and an aged group. A rat patellar tendon defect model was used in this study. Tendon samples were collected at weeks 2 and 4, and hematoxylin-eosin, alcian blue and immunofluorescence staining were performed for histological analysis. Meanwhile, reverse transcription-polymerase chain reaction (RT-PCR) and western blot were performed to evaluate the biochemical changes.

RESULTS

The histological scores in aged rats were significantly lower than those in young rats. At the protein level, collagen synthesis-related markers Col-3, Matrix metalloproteinase-1 and Metallopeptidase Inhibitor 1(TIMP-1) were decreased at week 4 in aged rats compared with those of young rats. Though there was a decrease in the expression of the chondrogenic marker aggrecan at the protein level in aged tendon, the Micro-CT results from weeks 4 samples showed no significant difference(p>0.05) on the ectopic ossification between groups. Moreover, we found more adipocytes accumulated in the aged tendon defect with the Oil Red O staining and at the gene and protein levels the markers related to adipogenic differentiation.

CONCLUSIONS

Our findings indicate that tendon healing is impaired in aged rats and is characterized by a significantly lower histological score, decreased collagen synthesis and more adipocyte accumulation in patellar tendon after repair.

Ginsenoside Rg3 inhibits the senescence of prostate stromal cells through down-regulation of interleukin 8 expression

Senescent stromal cells support the development of prostate cancer and are considered potential therapeutic targets. This research evaluated the regulatory effects of ginsenoside Rg3 on the senescence of prostatic stromal cells pre-incubated in medium supplemented with 0.5% fetal bovine serum. The results revealed that ginsenoside Rg3 decreased the number of stromal cells positively stained with a senescent cell marker (senescence-associated β-galactosidase). Ginsenoside Rg3 also increased the viability of stromal cells and promoted cell cycle transition from G0/G1 to S phase, as well as inhibited the carcinoma-associated fibroblast-like phenotype in prostate stromal cells, through the up-regulation of smooth muscle cell markers SM22 and smooth muscle myosin heavy chain. Conditioned medium collected from stromal cells treated with ginsenoside Rg3 exhibited an attenuated effect on the promotion of prostate cancer cell migration compared with conditioned medium from stromal cells without Rg3 treatment. Down-regulation of interleukin 8 (IL-8) in a dose- and time-dependent manner was observed in ginsenoside Rg3-treated stromal cells, and over-expression or addition of IL-8 reversed the anti-senescence role of Rg3 in prostate stromal cells. Furthermore, ginsenoside Rg3 down-regulated IL-8 expression by decreasing the reactive oxygen species level in prostatic stromal cells and reducing the transcriptional activity of IL-8 promoter by damping the transcription factors C/EBP β and p65 binding to IL-8 promoter. Our research revealed that ginsenoside Rg3 was able to inhibit prostate stromal cell senescence by down-regulating IL-8 expression. The results suggest a potential value for ginsenoside Rg3 in prostate cancer treatment through the targeting of pro-carcinogenic senescent stromal cells.

Moderate treadmill running exercise prior to tendon injury enhances wound healing in aging rats

The effect of exercise on wound healing in aging tendon was tested using a rat moderate treadmill running (MTR) model. The rats were divided into an MTR group that ran on a treadmill for 4 weeks and a control group that remained in cages. After MTR, a window defect was created in the patellar tendons of all rats and wound healing was analyzed. We found that MTR accelerated wound healing by promoting quicker closure of wounds, improving the organization of collagen fibers, and decreasing senescent cells in the wounded tendons when compared to the cage control. MTR also lowered vascularization, increased the numbers of tendon stem/progenitor cells (TSCs) and TSC proliferation than the control. Besides, MTR significantly increased the expression of stem cell markers, OCT-4 and Nanog, and tenocyte genes, Collagen I, Collagen III and tenomodulin, and down-regulated PPAR-γ, Collagen II and Runx-2 (non-tenocyte genes). These findings indicated that moderate exercise enhances healing of injuries in aging tendons through TSC based mechanisms, through which exercise regulates beneficial effects in tendons. This study reveals that appropriate exercise may be used in clinics to enhance tendon healing in aging patients.