Evaluate the collective function of references cited together in a given text segment.
Classify their combined role into one of the following categories: 'method', 'background', or 'result'.

Text:Similarly, we have recently found that coculture of pulmonary arterial ECs (PAECs) with pulmonary arterial SMCs (PASMCs) results in formation of myoendothelial gap junctions, which induce activation of TGF- signaling and differentiation of the PASMCs toward a contractile phenotype (21).
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