Complex sentence: Several African American health workers and educators associated with Tuskegee Institute helped the PHS to carry out its experimentation and played a critical role in its progression, though the extent to which they were aware of methodology of the study is not clear in all cases.
Split into simpler sentences: Several African American health workers and educators associated with Tuskegee Institute helped the PHS to carry out its experimentation and played a critical role in the progress of the study. The extent to which they knew about the basis of the study is not clear in all cases.