Cardiovascular diseases remain the leading cause of death worldwide. Mechanisms of disease genesis and progression are therefore of great clinical interest, but yet to be fully understood. The heart consists of many different cell types that contribute to homeostasis and disease. Being the most abundant immune cell in the human heart, cardiac resident macrophages (crMΦs) were only recently identified as a crucial cell population and have since come into focus. LncRNAs, a class of regulatory molecules, sought attention in the last years with the discovery of their importance in regulation of gene expression and cellular development. LncRNAs are transcripts longer than 200 nucleotides with no apparent coding potential. The intervention with lncRNAs offers the possibility to manipulate molecules that are expressed in a very tissue-specific manner. Therefore, potential side-effects after lncRNA depletion are avoided in other cell types or organs. The aim of this work is to elucidate the importance and function of long non-coding RNAs (lncRNAs) in crMΦs in health and disease.

We used RNA sequencing and single cell sequencing data to identify promising lncRNA candidates based on their expression and dysregulation during pressure overload of the left ventricle (transverse aortic constriction, TAC). Out of over 10,000 lncRNAs identified, we first picked the ones dysregulated during disease. We subsequently analyzed the remaining 356 candidates based on their enrichment in cardiac resident macrophages. One of the remaining 18 candidates is a lncRNA that is an antisense transcript to a transcription factor known to play an important role in the development and survival of tissue-resident macrophages. Recent studies could show that the absence of this transcription factor (TF) leads to the disappearance of tissue-specific macrophages from their respective tissues. Analysis of publicly available data (GEO data) shows a synergistic effect between this lncRNA and the TF. Also, different previous studies suggest a regulation of the TF via its antisense transcript lncRNA. 

We used different in vitro macrophage models including cell lines like BMDMs and J774A.1, a mouse macrophage cell line, to further characterize this lncRNA. We applied different specific knockdown methods (siRNA, CRISPR/Cas-systems) and in vitro methods including chemotaxis and wound healing assays. Experiments showed that loss of function of the lncRNA had an impact on the migration of macrophages and on chemotaxis.  
In our project we could find first hints suggesting that this lncRNA plays a role in maintaining the pool of functional macrophages. Therefore it represents potential for further studies and could be an interesting candidate for future usage in therapeutic intervention.