Section 5. A professional corporation may render professional services in the commonwealth only through its officers, employees and agents who are duly licensed to render such professional services in the commonwealth; provided, however, that nothing in this chapter shall be construed (a) to require any person who is employed by a professional corporation to be licensed to perform services for which no license is otherwise required, (b) to prohibit the rendering of professional services by a licensed natural person acting in his individual capacity, notwithstanding that such person may be a shareholder, director, officer, employee or agent of a professional corporation, or (c) to prohibit unlicensed persons employed by a professional corporation from rendering professional services under the supervision of licensed officers, employees or agents of such professional corporation, to the extent permitted by law or the regulations of the applicable regulating board.