Sympathectomy aggravates subchondral bone changes during osteoarthritis progression in mice without affecting cartilage degeneration or synovial inflammation.

OBJECTIVE: Osteoarthritis (OA) pathogenesis involves the interaction of articular cartilage with surrounding tissues, which are innervated by tyrosine hydroxylase-positive (TH+) sympathetic nerve fibers suggesting a role of the sympathetic nervous system (SNS) during OA progression. We analyzed the effects of sympathectomy (Syx) in a murine OA model. METHODS: Peripheral Syx was generated by 6-hydroxydopamine (6-OHDA) injections in male C57BL/6 mice. OA was induced in wild-type (WT) and Syx mice by destabilization of the medial meniscus (DMM). TH+ fibers and splenic NE were analyzed to evaluate Syx efficiency. OA progression was examined by OARSI and synovitis scores and micro-CT. Expression of TH, α2A- and ß2-adrenergic receptors (AR), and activity of osteoblasts (ALP) and osteoclasts (TRAP) was investigated by stainings. RESULTS: Syx resulted in synovial TH+ fiber elimination and splenic NE decrease. Cartilage degradation and synovitis after DMM were comparably progressive in both WT and Syx mice. Calcified cartilage (CC) and subchondral bone plate (SCBP) thickness and bone volume fraction (BV/TV) increased in Syx mice due to increased ALP and decreased TRAP activities compared to WT 8 weeks after DMMWT and Syx mice developed osteophytes and meniscal ossicles without any differences between the groups. AR numbers decreased in cartilage but increased in synovium and osteophyte regions after DMM in both WT and Syx mice. CONCLUSION: Peripheral dampening of SNS activity aggravated OA-specific cartilage calcification and subchondral bone thickening but did not influence cartilage degradation and synovitis. Therefore, SNS might be an attractive target for the development of novel therapeutic strategies for pathologies of the subchondral bone.

Platelet-rich plasma stimulates dermal microvascular endothelial cells and adipose derived stem cells after external radiation.

BACKGROUND: Platelet-rich plasma (PRP) products are currently suggested in the treatment of chronic wounds due to possible pro-angiogenic effects. Microvascular compromise represents the major component in radiogenic wound healing complications. The effects of PRP on irradiated cells of the cutaneous wound healing process are still poorly understood. MATERIAL AND METHODS: Human dermal microvascular endothelial cells (HDMEC) and human adipose derived stem cells (hASC) were cultured and irradiated with doses of 2 to 12 Gy. PRP was activated, characterized and added to the incubation media in different concentrations after external radiation. Cell count was determined 48 h after radiation using a semi-automated cell counting system. Levels of interleukin-6 (IL-6), basic fibroblast growth factor (bFGF) and soluble intercellular adhesion molecule-1 (sICAM-1) in the supernatants of HDMEC and hASC co-cultures were determined by enzyme-linked immunosorbent assay (ELISA). Non-irradiated hASC and HDMEC served as controls. RESULTS: The employed PRP preparations were characterized and contained platelet derived growth factor (PDGF-AB), vascular endothelial growth factor (VEGF), bFGF and high levels of sICAM-1. Addition of PRP to irradiated cultures of HDMEC and hASC prevented profound radiation-induced decline in cell numbers. 10% PRP restored cell numbers to levels of untreated, non-irradiated cultures. Basic FGF expression was decreased significantly in hASC monocultures treated with 10% PRP without external radiation and after irradiation with 6 and 12 Gy. These inhibitory effects of PRP were also observed in HDMEC. In contrast, co-cultures of HDMEC-ASC showed a dose-dependent increase in bFGF expression when treated with 5 or 10% PRP. Doses of 6 and 12 Gy increased IL-6 expression in cultures stimulated with 5% PRP. CONCLUSIONS: Use of PRP in co-cultures of hASC and HDMEC restores proliferative defects caused by external radiation probably by induction of bFGF. Under irradiated conditions, PRP might induce pro-inflammatory stimuli which could be beneficial in treatment of chronic wounds where healing processes are defective. Combined use of hASC and PRP products might be helpful in the treatment of radiogenic wounds.