Effect of Some Gut Hormones in Generation of Insulin Producing Cells from Mesenchymal Stem Cells

Abstract

Diabetes mellitus (DM) is an incurable metabolic disease constituting a major threat to human health. The number of patients suffering from this disease is growing in an alarming rate. The major goal of future diabetes therapy is to promote β-cell regeneration through stem cell therapy. Mesenchymal stem cells (MSCs) have already made their mark in the young field of regenerative medicine. Being easily derived from many adult tissues, their therapeutic worth has already been validated for a number of conditions. Recently, the umbilical cord (UC) has been proved to be a good source of MSCs especially from Wharton’s Jelly (WJ), the connective tissue surrounding the umbilical vessels. However, generation of insulin producing cells (IPCs) from WJ-MSCs is still a challenge. Thus, it is urgently demanding a highly efficient protocol for IPCs generation using novel differentiation factors. Glucagon like-peptide-1 (GLP-1) a gut hormone has been implicated in the differentiation of MSCs into IPCs. Obestatin, another gut hormone, has been recently shown to improve generation of functional β-cells from pancreatic MSCs. In the current study we aimed to isolate, propagate and characterize MSCs from the WJ, as non-invasive and readily available source of stem cells as well as to examine the effect of gut hormones including GLP-1 and obestatin in the generation of IPCs in-vitro from WJ-MSCs in comparison to exendin-4. To fulfill the aims of the current study, the following experiments were performed: 1- Characterization of the isolated WJ-MSCs according to the criteria defined by the International society for cellular therapy (ISCT).

- This was done through: a) Morphological examination b) Immunophenotyping c) Mesengenic (adipogenic) differentiation 2- The Effect of gut hormones on the isolated cells was investigated under proliferation conditions as well as during short and long differentiation protocols. Assessment of each experiment was done through: a) Morphological examination b) Gene expression assay for both stem cells markers as well as β-cells markers c) Functional assessment by measuring the glucose stimulated insulin secretion (GSIS). Results of the current study can be summarized as follows: • The WJ represents a source of MSCs which yields homogenous population that can be easily isolated and possess all MSCs characteristics including plastic adherence, expression of MSCs specific cluster of differentiation (CD) surface markers and MSCs adipogenic differentiation.

• Under proliferation conditions, gut hormones; GLP-1 and obestatin, together with exendin-4, induced exit of WJ-MSCs from stemness state.

• The WJ-MSCs can be differentiated to IPCs using exendin-4, GLP-1 and obestatin.

• Under short and long differentiation protocols, obestatin, as well as exendin-4, induced expression of β-cell markers, while GLP-1 failed to show similar effect. • As for GSIS, IPCs generated with GLP-1 and obestatin showed higher secretion of insulin, while those generated by exendin-4 showed more glucose responsiveness than both and this was more evident during short differentiation protocol. In conclusion, our results showed that WJ-MSCs represent a readily available, non-invasive, highly promising source of stem cells for β-cells regeneration. However, many factors such as induction protocols and mechanisms of differentiation should be further explored. Most importantly the novel finding of the current study is that gut hormones including GLP-1 and obestatin can generate IPCs from WJ-MSCs. Obestatin is an effective differentiating factor comparable to exendin-4 and may be better than GLP-1. This implies that obestatin should be considered a novel differentiating marker for optimization protocols. Mechanism of obestatin on generation of IPCs from MSCs should be elucidated and this warrants further investigations.