Ryan had left the Warriors during the previous season to join Worcester Warriors.
He originally joined Glasgow in 2010 following three years in Edinburgh.
Ryan, who played 14 games for Edinburgh, is a former Scotland age-grade internationalist who went on to win Scotland A honours and who has also represented the Army.
He went on to gain full,Scotland honours and toured with the British and Irish Lions in 2013.
He joined Edinburgh from Border Reivers in 2007. Following up under-21 international honours in 2006 he made his Scotland A debut in the victory against their Italian counterparts at McDiarmid Park, Perth, in February 2007. He had joined Reivers on an apprentice contract the previous summer and made his competition debut in starting at loose head in the Magners League match against Ulster the following November.
The Scotland under-21 forward scored the clinching try for the Army in their 23-13 victory against the Royal Navy at Portsmouth in December 2005, a result that secured the Inter-Services Under-21 Championship for his team. Ryan, who has served in the Royal Signals, has played also for the Combined Servicesí under-21 team, and he stepped up to Scotlandís under-21 team in making his international debut against France at Falkirk in February 2006 as well as playing in all four subsequent matches in the championship as loose head in an ever-present front five. Later in the year he played in all five matches in the under-21 world championship in France, and when he subsequently signed for Reivers he also joined Heriotís.
In addition to playing rugby, he is also an RADI adventure diver.