In the field of regenerative medicine, new ventures face unformed markets and inconsistent industry practices. We study two university-centric regenerative medicine ecosystems to explore the characteristics of venturing activity and ecosystem development under irreducible uncertainty. The situational analysis reveals multi-level effects. At the micro-level, entrepreneurial coping strategies are significantly affected by cultural artifacts generated by the ecosystem university. At the macro-level, entrepreneurial ecosystems may develop along different paths, generating idiosyncratic contexts for venturing activity. A model of entrepreneurial ecosystem development is presented, with implications for theories of entrepreneurial behavior as well as policy practice in developing technology sectors.