Original source: Physics World
Normal bladder function in rats has been restored by researchers in the US, who have developed an implantable, closed-loop system that exploits optogenetics. Nerve cells in the rats’ bladders were modified to respond to the light emitted by implanted LEDs, which allowed bladder function to be controlled by an external wireless device. The technique could be used to develop sophisticated treatments for people suffering from bladder problems such as overactive bladder (OAB) syndrome and urinary incontinence – and could be extended to treating other organs.
Serious bladder-control problems can be treated with implanted bioelectronic devices that stimulate and control nerve cells in the bladder using electrical signals. While the signals can control bladder activity very precisely, they also affect the region surrounding the bladder and this can lead to unwanted side-effects including pain and inflammation.
The new control technique overcomes this problem and was developed by a team led by Robert Gereau at Washington University in St Louis and John Rogers at Northwestern University near Chicago. The team also included researchers at the University of Illinois at Urbana-Champaign. Their system uses light to control bladder activity, thereby eliminating the need for a disruptive electrical signal.
Team makes use of optogenetics, which involves using a virus to bind a protein called opsin to nerve cells in the bladders of live rats. Opsin converts light into electrochemical signals and the researchers hypothesized that the activity of these modified cells could be regulated precisely by developing shining light on them using a closed-loop control system.
The implantable system includes a stretchable, high-precision strain sensor that is placed around the rat’s bladder. The sensors measure bladder circumference continuously, while transmitting data on a wireless link to an external interface device. If the sensor data indicated that a rat’s bladder was emptying abnormally frequently, the external device would then send a signal back to the base station, which instructed microscopic LEDs attached to the sensor to turn on. Subsequently, activity in the surrounding light-sensitive nerve cells prevented the bladder from emptying.
Mickle and colleagues tested their device in rats injected with cyclophosphamide, which induces OAB. The frequency of bladder emptying was restored to normal and the rats displayed no significant inflammation or behavioural changes in response to the implant.
The team is confident that further improvements and the appropriate scaling could make their technique a ground-breaking treatment for OAB in the coming years. With additional adaptations, it could also be used to treat conditions related to other organs. Potential applications include influencing nerve cells in the bowels to reduce incontinence and also inducing a feeling of fullness in the stomach to combat obesity.
The research is described in Nature.