ALDHs consist of 24 families in the eukaryotic ALDH gene superfamily. Nineteen of them are found in the human genome and belong to the ALDH1-9, ALDH16, and ALDH18 families. 1 There are six isotype genes in the ALDH1 family (ALDH1A1, ALDH1A2, ALDH1A3, ALDH1B1, ALDH1L1, and ALDH1L2). Among them, ALDH1A1, ALDH1A2, and ALDH1A3 encode cytosolic enzymes that oxidize retinal and aliphatic aldehydes. ALDH1A1 protein binds to retinaldehyde in great affinity and has been considered a major retinoid acid-metabolizing enzyme. 2 Cytosolic ALDH1A1 also plays a role in acetaldehyde oxidation and alcohol preference

The liver has an inherent regenerative capacity via hepatocyte proliferation after mild‐to‐modest damage. When hepatocytes exhaust their replicative ability during chronic or severe liver damage, liver progenitor cells (LPC), also termed oval cells (OC) in rodents, are activated in the form of ductular reaction (DR) as an alternative pathway. LPC is often intimately associated with hepatic stellate cells (HSC) activation to promote liver fibrosis. The Cyr61/CTGF/Nov (CCN) protein family consists of six extracellular signaling modulators (CCN1–CCN6) with affinity to a repertoire of receptors, growth factors, and extracellular matrix proteins. Through these interactions, CCN proteins organize microenvironments and modulate cell signalings in a diverse variety of physiopathological processes. In particular, their binding to subtypes of integrin (αvβ5, αvβ3, α6β1, αvβ6, etc.) influences the motility and mobility of macrophages, hepatocytes, HSC, and LPC/OC during liver injury. This paper summarizes the current understanding of the significance of CCN genes in liver regeneration in relation to hepatocyte‐driven or LPC/OC‐mediated pathways. Publicly available datasets were also searched to compare dynamic levels of CCNs in developing and regenerating livers. These insights not only add to our understanding of the regenerative capability of the liver but also provide potential targets for the pharmacological management of liver repair in the clinical setting.