A subset of fibroblasts were enriched in 'mitotic cell cycle' and 'chromosome modification' associated processes and were termed 'proliferative mesenchymal progenitors (PMP)'. Their signature RNAs included transcription factors (Foxm1, Hoxb5, Sox11, and Tbx3), signaling molecules (Fgf7 and Pdgfra) and cell cycle/chromatin modifiers (Aurka, Bub1, Cdk1, Top2a, and Hmgb2).

 'Myofibroblasts (MyoF)' were identified by RNAs involved in 'actin binding', and 'smooth muscle contraction', as evidenced by the signature genes including: Hhip, Acta2, Actg2, Myh11, and Tagln.

'Pericyte' like cells (PC) co-expressed Pdgfrb, as evidenced by the signature genes including: Dlk1, Acta1, Rgs5, Cspg4, and Mcam. 

A transitional stage of fibrobalst.

'Matrix fibroblasts' (MFB) expressed RNAs associated with 'extracellular matrix' and 'cell adhesion', as evidenced by the signature genes including: Fn1, Eln, Vcam, and Fgf10, which is a growth factor essential for early lung morphogenesis and alveolarization. 

A transitional stage of fibrobalst.

 'Endothelial cells' (Endo) were readily identified by RNAs defining 'blood vessel development/morphogenesis', as evidenced by the signature genes including: Cav1/2, Cd34, Fli1/4, Kdr, Nrp1, Pecam1, Tek, Encm, Sox17, and Tie1.  

'Myeloid/immune cells' (ML) shared close similarity of 'immune/defense response', 'lysosome', and 'phagocytosis' related RNAs, as evidenced by the signature genes including: Fcgr1a/2b/3, Mpeg1, Mrc1, Ly86, and Cyba/b, RNAs expressed by macrophages and monocytes that are not abundant in the normal fetal lung.

'Epithelia cells' consisted of 28 out of 148 individual cells that were linked by large scale adoption of the transcriptional machinery critical for epithelial specialization, including formation of tight junctions, apical-basal orientations, and 'respiratory' tube formation, as evidenced by the signature genes including Epcam, Cdh1, Nkx2-1, Foxa2, Sftpa1, Sftpb, Sftpc, Abca3, Atp11a, Slc34a2, Id2, Sox9, Gata6, Pdgfa, Shh, Etv5, Ager, Clic3, Cldn18, Emp2, Pdpn, and Hopx.