Communication, Communication, Communication. Clarity and transparity. These are the keys to great company culture, and what great leaders understand and execute. Hyper-growth is tough on a million levels, having a team that loses cohesion, collaboration and togetherness is one more problem you really don't need. Much changes as you move from start-up to scale-up, and often that includes people and/or their responsibilities and sense of place in the organisation. Culture is complex because humans are complex. One simple, but not always easy, rule, is to be open to everybody about what is going on and why.
High performing teams, and talented individuals are much more likely to stay on your bus, if they feel you are not keeping things from them.