Stress-strain analysis of contractility in the ileum in response to flow and ramp distension in streptozotocin-induced diabetic rats--association with advanced glycation end product formation

CD44 fucosylation on bone marrow-derived mesenchymal stem cells enhances homing and promotes enteric nervous system remodeling in diabetic mice

Background

Diabetes can cause extensive enteric nervous system (ENS) injuries and gastrointestinal motility disorder. In developing possible treatments, researchers have engaged in tissue regeneration engineering with the very promising bone marrow-derived mesenchymal stem cells (BMSCs). However, BMSCs have poor homing ability to the targeted tissues after intravenous injection. Thus, we aimed to investigate whether enhancing the expression of E-selectin ligand on BMSCs could improve their homing ability and subsequently influence their role in ENS remodeling in diabetic mice.

Methods

First, we constructed the fucosylation modification of CD44 on BMSCs through a fucosyltransferase VII (FTVII) system to generate a Hematopoietic Cell E-/L-selectin Ligand (HCELL) property, a fucosylated sialyllactosaminyl glycovariant of CD44 that potently binds E-selectin. Next, FTVII-modified and unmodified BMSCs labeled with green fluorescent protein (GFP) were injected into diabetic mice through the tail vein to compare their homing ability to the gastrointestinal tract and their effect on ENS remodeling, respectively. A bioluminescent imaging system was used to evaluate the homing ability of GFP-labeled BMSCs with and without FTVII modification, to the gastrointestinal tract. Gastrointestinal motility was assessed by gastrointestinal transient time, defecation frequency, stool water content and colon strips contractility. Immunofluorescence staining and western blotting were used to assess the expression levels of protein gene product 9.5 (PGP9.5), glial fibrillary acidic protein (GFAP) and glial cell line-derived neurotrophic factor (GDNF).

Results

The FTVII-mediated α(1,3)-fucosylation modification of CD44 on BMSCs generated a HCELL property. Bioluminescent imaging assays showed that FTVII-modified BMSCs had enhanced homing ability to gastrointestinal tract, mainly to the colon, 24 h after injection through the tail vein. Compared with diabetic mice, FTVII-modified BMSCs significantly promoted the gastrointestinal motility and the ENS remodeling, including intestinal peristalsis (P < 0.05), increased feces excretion (P < 0.05) and the water content of the feces (P < 0.05), restored the spontaneous contraction of the colon (P < 0.05), and upregulated the protein expression levels of PGP9.5 (P < 0.01), GFAP (P < 0.001), and GDNF (P < 0.05), while unmodified BMSCs did not (P > 0.05).

Conclusions

CD44 fucosylation modification on murine BMSCs promotes homing ability to the gastrointestinal tract and ENS remodeling in diabetic mice.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13578-021-00632-2.

Diabetes and the Small Intestine

OPINION STATEMENT

Diabetes mellitus (DM) and its associated complications are becoming increasingly prevalent. Gastrointestinal symptoms associated with diabetes is known as diabetic enteropathy (DE) and may manifest as either diarrhea, fecal incontinence, constipation, dyspepsia, nausea, and vomiting or a combination of symptoms. The long-held belief that vagal autonomic neuropathy is the primary cause of DE has recently been challenged by newer theories of disease development. Specifically, hyperglycemia and the resulting oxidative stress on neural networks, including the nitrergic neurons and interstitial cells of Cajal (ICC), are now believed to play a central role in the development of DE. DE occurs in the majority of patients with diabetes; however, tools for early diagnosis and targeted therapy to counter the detrimental and potentially irreversible effects on the small bowel are lacking. Delay in diagnosis is further compounded by the fact that DE symptoms overlap with those of gastroparesis or can be confused with side effects from diabetes medications. Still, early recognition of the presence of DE is essential to mitigating symptoms and preventing further progression of complications including dysmotility and malabsorption. Current diagnostic modalities include manometry, wireless motility capsule (SmartPill™), and scintigraphy; however, these are not regularly utilized in clinical practice due to limited availability. Several medications are available for symptom relief in DE patients including rifaximin for small intestinal bacterial overgrowth (SIBO) and somatostatin analogues for diarrhea. While rodent models on stem cell therapy and alteration of the microbiome are promising, there is still a great need for further research on the pathologic underpinnings and development of novel treatment modalities for DE.

Diabetes-induced mechanophysiological changes in the small intestine and colon

The disorders of gastrointestinal (GI) tract including intestine and colon are common in the patients with diabetes mellitus (DM). DM induced intestinal and colonic structural and biomechanical remodeling in animals and humans. The remodeling is closely related to motor-sensory abnormalities of the intestine and colon which are associated with the symptoms frequently encountered in patients with DM such as diarrhea and constipation. In this review, firstly we review DM-induced histomorphological and biomechanical remodeling of intestine and colon. Secondly we review motor-sensory dysfunction and how they relate to intestinal and colonic abnormalities. Finally the clinical consequences of DM-induced changes in the intestine and colon including diarrhea, constipation, gut microbiota change and colon cancer are discussed. The final goal is to increase the understanding of DM-induced changes in the gut and the subsequent clinical consequences in order to provide the clinicians with a better understanding of the GI disorders in diabetic patients and facilitates treatments tailored to these patients.

Advanced glycation end products interfere with gastric smooth muscle contractile marker expression via the AGE/RAGE/NF-κB pathway

Excessive production of advanced glycation end products (AGE) has been implicated in the pathogenesis of diabetic complications. Smooth muscle (SM) phenotype transition is involved in diabetes-associated gastric motility dysfunction. We investigated whether AGE interfere with gastric antral SM contractile marker expression. Sixteen Sprague-Dawley rats were randomly divided into control and streptozotocin-induced diabetic groups. Sixteen weeks after streptozotocin administration, gastric antral SM strip contractility in the groups were measured. The gastric tissue expression of AGE was tested. Primary cultured gastric smooth muscle cells (SMCs) were used in complementary in vitro studies. In the presence and absence of AGE, SMCs were transfected with myocardin plasmid or treated with nuclear factor-κB (NF-κB) inhibitor or anti-RAGE antibody. Diabetic rats showed weakness of SM strip contractility and decreased expression of SM contractile marker genes (myosin heavy chains [MHC], α-actin, calponin) as compared with the control group. Gastric antral SM layer Nε-(carboxymethyl) lysine (CML) level, the major AGE compound, were increased in the diabetic rats. AGE downregulated SM contractile markers and myocardin expression in a concentration-dependent manner. Myocardin overexpression prevented these results. AGE treatment activated NF-κB in SMCs. The NF-κB inhibitor BAY 11-7082 and anti-RAGE antibody blocked the effects of AGE on myocardin downregulation. AGE may induce the development of gastric dysmotility by downregulating SM contractile proteins and myocardin expression via the AGE/RAGE/NF-κB pathway.