Mesenchymal stem cells (MSCs) show great promise in blood vessel restoration and vascularization enhancement in many therapeutic situations. Typically, the co-implantation of MSCs with vascular endothelial cells (ECs) is effective for the induction of functional vascularization in vivo, indicating its potential applications in regenerative medicine. The effects of MSCs-ECs-induced vascularization can be modeled in vitro, providing simplified models for understanding their underlying communication. In this article, a contact coculture model in vitro and an RNA-seq approach were employed to reveal the active crosstalk between MSCs and ECs within a short time period at both morphological and transcriptional levels. The RNA-seq results suggested that angiogenic genes were significantly induced upon coculture, and this prevascularization commitment might require the NF-κB signaling. NF-κB blocking and interleukin (IL) neutralization experiments demonstrated that MSCs potentially secreted IL factors including IL1β and IL6 to modulate NF-κB signaling and downstream chemokines during coculture. Conversely, RNA-seq results indicated that the MSCs were regulated by the coculture environment to a smooth muscle commitment within this short period, which largely induced myocardin, the myogenic co-transcriptional factor. These findings demonstrate the mutual molecular mechanism of MSCs-ECs-induced prevascularization commitment in a quick response.