In recent years, the possibility of creating tissues and organs by tissue engineering for research and therapy has generated increased interest in cells suitable for such use. However, working with young cells that have undergone a relatively small number of divisions and can renew themselves in the long term is challenging [1]. Therefore, the umbilical cord (UC) has become a popular target of scientific research [2,3] (see Fig. 7).

UC is yellowish-white in color tissue, has a gelatinous appearance, and is slightly twisted; in mammals, it forms a connection between the fetus and the placenta [4]. This structure is responsible for the exchange of nutrients and oxygen during gestation. The umbilical cord's macroscopic structure contains the vein and arteries surrounding the connective tissue [5].UC is of interest to researchers because it can be easily non-invasive obtained during parturition, and because it is considered a clinical waste, it has no ethical controversy [6]. In addition, it is a source of several types of cells. At least five cell types have already been described in the UC tissue and blood, including epithelial cells, mesenchymal stem/stromal cells (MSCs) [7], smooth muscle cells, endothelial cells [8] and progenitor blood cells [9]. UC-MSCs were isolated from veins, extra gelatinous tissue around the vessels, and Wharton's jelly [[10], [11], [12]]; The umbilical cord-originated cell lines present many advantages compared to MSCs from other adult tissues, as they commonly exhibit higher proliferation abilities. In addition, their genetic and phenotypic stability is maintained even after a long-term in vitro culture, suggesting they are primitive compared to adult tissue-derived MSCs [13].

The UC-MSCs morphology, proliferation, immunophenotyping, and multi-directional differentiation abilities are similar to bone marrow (BM) derived MSCs [14]. Therefore, they are an ideal alternative source for BM-MSCs. Furthermore, UC-MSCs are proposed as an essential option in immunotherapy and regenerative medicine due to their anticancer properties and capacity to secrete cytokines and growth factors [15].

In feline species, MSCs were isolated from amniotic membrane, adipose tissue, bone marrow, amniotic fluid, and fat; up to date, the adipose-derived MSCs were the most commonly used in therapy for some feline diseases [16]. Mainly kidney diseases [17,18], asthma [19], gingivostomatitis [20,21] and chronic enteropathy [22].

Numerous published works documented the UC-MSCs isolation, characterization, and differentiation potential, including humans and animals like horses, dogs, rats, pigs, and sheep [23]. On the other hand, there is a lack of studies carried out in feline species about the MSCs isolation from distinct parts of the umbilical cord. Therefore, the present study aimed to isolate and culture MSCs derived from cats, separately from two parts of the feline umbilical cord (fUC): Wharton's jelly (WJ), umbilical cord vessels (UCV), and the whole umbilical cord (WUC). Moreover, we aimed to characterize the MSCs derived from different compartments of fUC for the first time by their morphology, plastic adherence, expansion capacity, differentiation ability and phenotype to find out which part of the cord is the most suitable for MSCs isolation in this species basis on their basic characteristics.