Effects of hormone replacement therapy on connective tissue: why is this important?

Strontium ranelate retards disc degradation and improves endplate and bone micro-architecture in ovariectomized rats with lumbar fusion induced - Adjacent segment disc degeneration

Objectives

Adjacent segment disc degeneration (ASDD) is one of the long-term sequelae of spinal fusion, which is more susceptible with osteoporosis. As an anti-osteoporosis drug, strontium ranelate (SR) has been reported to not only regulate bone metabolism but also cartilage matrix formation. However, it is not yet clear whether SR has a reversal or delaying effect on fusion-induced ASDD in a model of osteoporosis.

Materials and methods

Fifth three-month-old female Sprague-Dawley rats that underwent L4-L5 posterolateral lumbar fusion (PLF) with spinous-process wire fixation 4 weeks after bilateral ovariectomy (OVX) surgery. Animals were administered vehicle (V) or SR (900 mg/kg/d) orally for 12 weeks post-PLF as follows: Sham+V, OVX + V, PLF + V, OVX + PLF + V, and OVX + PLF + SR. Manual palpation and X-ray were used to evaluate the state of lumbar fusion. Adjacent-segment disc was assessed by histological (VG staining and Scoring), histomorphometry (Disc Height, MVD, Calcification rate and Vascular Bud rate), immunohistochemical (Col-II, Aggrecan, MMP-13, ADAMTS-4 and Caspase-3), and mRNA analysis (Col-I, Col-II, Aggrecan, MMP-13 and ADAMTS-4). Adjacent L6 vertebrae microstructures were evaluated by microcomputed tomography.

Results

Manual palpation and radiographs showed clear evidence of the fused segment's immobility. After 12 weeks of PLF surgery, a fusion-induced ASDD model was established. Low bone mass caused by ovariectomy can significantly exacerbate ASDD progression. SR exerted a protective effect on adjacent segment intervertebral disc with the underlying mechanism possibly being associated with preserving bone mass to prevent spinal instability, maintaining the functional integrity of endplate vascular microstructure, and regulating matrix metabolism in the nucleus pulposus and annulus fibrosus.

Discussion

Anti-osteoporosis medication SR treatments not only maintain bone mass and prevent fractures, but early intervention could also potentially delay degenerative conditions linked to osteoporosis. Taken together, our results suggested that SR might be a promising approach for the intervention of fusion-induced ASDD with osteoporosis.

Effect of hormone replacement therapy on intervertebral disc height

OBJECTIVE

Intervertebral discs act as shock absorbers, thereby helping to reduce the risk of vertebral body fractures. Previous studies have shown that estrogen loss following menopause is associated with disc height reduction whereas treatment with hormone replacement therapy (HRT) helps to maintain disc height. This study reports the effect of HRT on disc height from a post hoc analysis of a prospective randomized clinical trial of the effect of HRT on bone density.

METHODS

A total of 355 healthy postmenopausal women aged (mean ± standard deviation) 55.4 ± 4.8 years were randomized to HRT with oral 1 mg or 2 mg estradiol plus dydrogesterone or placebo. Dual-energy X-ray absorptiometry measurements (Lunar DPX) were obtained at baseline and following 2 years of treatment. Intervertebral disc height was measured in discs between T12 and L3 using the bone densitometer ruler.

RESULTS

Compared with baseline, treatment with HRT resulted in a significant increase in total disc height with 1 mg estradiol (0.16 ± 0.65 cm, p = 0.015) and with 2 mg estradiol (0.21 ± 0.86 cm, p = 0.006) whilst there was no significant increase with placebo (0.13 ± 0.65 cm, p = 0.096). Between-group differences were not statistically significant.

CONCLUSIONS

These results are consistent with previous findings of a beneficial effect of estrogen on discs. This may be in part responsible for the anti-fracture efficacy of HRT on vertebral fractures.

Comparison of static and dynamic balance during early follicular and ovulation phases in healthy women, using simple, clinical tests: a cross sectional study

Balance may be influenced by several factors. The menstrual cycle can be considered as an important factor which may affect postural control. This study was aimed to investigate the influence of early follicular and ovulation phases on static and dynamic balance indices. Thirty non-athlete healthy women with a regular menstrual cycle aged between 18 and 25 years participated in the study. Static balance was evaluated through single-leg stance test and dynamic balance was investigated with posteromedial direction of Y- balance test during early follicular and ovulation (24-48 hours after the peak of estrogen) phases of menstrual cycle. The balance tests were performed in a randomized order in each session. A paired t-test analysis was performed to compare the data during the early follicular and ovulation phases. The results indicated that both static and dynamic balance scores were higher in ovulation phase in comparison to early follicular phase (p < .001). It is worth noting to consider the balance fluctuations during different phases of menstrual cycle when prescribing exercise programs for healthy women or when they participate in sport or recreational activities.

Estrogen deficiency does not decrease the in vitro osteogenic potential of rat adipose-derived mesenchymal stem cells

Osteoporosis due to estrogen deficiency is an increasing bone health issue worldwide: new strategies are being studied for regenerative medicine of bone pathologies in these patients. The most commonly used cells for tissue engineering therapy are the bone marrow mesenchymal stem cells (BMSCs), but they might be negatively affected by aging and estrogen deficiency. Besides the general advantages of adipose-derived mesenchymal stem cells (ADSCs) over BMSCs, ADSCs also seem to be less affected by aging than BMSCs, but in the literature, little is known about ADSCs in estrogen deficiency. The present study investigated the in vitro behavior of ADSCs, isolated from healthy (SHAM) and estrogen-deficient (OVX) rats. Phenotype, clonogenicity, viability, and osteogenic differentiation, at both cellular and molecular levels, were evaluated with or without osteogenic stimuli. Pro-inflammatory cytokines, growth factors, and adipogenic differentiation markers were also analyzed. There were no significant differences between OVX and SHAM ADSCs in some analyzed parameters. In addition, clonogenicity, osteopontin (Spp1) gene expression, alkaline phosphatase (ALP) activity at 2 weeks of culture, total collagen (COLL), osteocalcin (Bglap) gene expression and production, and matrix mineralization were significantly higher in OVX than in SHAM ADSCs. Besides the increase in some osteogenic markers, peroxisome proliferator-activated receptor gamma (Pparg) gene was also more expressed in OVX in osteogenic medium, with a concomitant estrogen receptor 1 (Esr1) gene expression decrease. These results underlined that ADSCs were not affected by estrogen deficiency in an osteogenic microenvironment.

Stem cell and extracellular matrix-related molecules increase following melatonin treatment in the skin of postmenopausal rats

The menopause has a negative effect in the skin. Melatonin affects skin functions and structures through actions mediated by cell-surface and putative-nuclear receptors expressed in skin cell. We have therefore determined the effects of melatonin treatment on stem cell in the epidermis and extracellular matrix related molecules in the dermis the skin of postmenopausal rats. A total of 45 female rats were divided into 5 groups: control group, group A [ovariectomy (OVX)], group B (OVX +10 mg/kg/day melatonin), group C (OVX +30 mg/kg/day melatonin), group S (sham operated + 10 mg/kg/day melatonin). Ventral skin samples were excised at 12th week after ovariectomy. Hematoxylin-eosin, periodic acid- methylamine silver, elastic van Gieson staining techniques were used to measure histomorphometrically the thickness of elastic fibers and basement membrane, depths of the epidermis, dermis, and subcutaneous fat layer. Immunohistochemical staining methods were used for fibroblast growth factor β (FGF β), collagen type I, fibronectin, β-catenin, c-kit, c-Myc evaluation. Epidermal thickness, subcutaneous fat layer, and elastic fibers were significantly decreased in group C, and there was a significant increase after melatonin treatment. Although there was no difference in dermal thickness of group C, melatonin also significantly increased the dermal thickness. High FGF β, type I collagen, fibronectin, β-catenin, c-Myc immunoreactivity developed following melatonin in all groups. Thus melatonin treatment of postmenopausal rats was mostly due to the decrease of stem cell and extracellular matrix-related molecules in the skin.