Aim: We hypothesized that anabolic steroid, combined with substrate strain upregulates expression of gap junction protein Connexin 43 (Cnx43) and increases cell-to-cell communication in human supraspinatus tendon cells.

Methods: Human supraspinatus cells were isolated and cultured in nutrient media arranged into 4 groups: 1) non-load, non-steroid (NLNS, n=12); 2) non-load, steroid (NLS, n=12); 3) load, non-steroid (LNS, n=12); and 4) load, steroid (LS, n=12). Steroid and load groups were cultured in 100Nm nandrolone decanoate and loaded at 1% elongation daily for 5 days, respectively. On day five of treatment, cells examined for immunocytochemistry. Cells were also subjected to mechanical stimulation by micro-pipette indentation and the intracellular calcium concentration ([Ca2+]ic) was quantitated using fluorescence microscopy. Numerous parameters were calculated: a) mean average response to stimulation, b) mean peak [Ca2+]ic, c) time of Ca2+ wave propagation, d) spontaneously responding cells prior to stimulation, and e) cell oscillation after stimulation (an indicator of cell toxicity).

Results: The LS group demonstrated the greatest density of Cnx43 in comparison to the other groups. Also, the LS group cells showed a significantly greater mean peak [Ca2+]ic and a significantly decreased propagation time, compared to the values of the other groups (p< 0.05).

Conclusions: Anabolic steroid, when combined with passive stretch, upregulates gap junction protein Cnx 43 and significantly increases calcium signalling in human supraspinatus tendon cells. When carefully prescribed and monitored, anabolic steroids may increase intercellular calcium signalling and may enhance the healing process of deficient rotator cuff tendons. More research will be necessary to fully evaluate the safety and efficacy of anabolic steroids for this application.